13 - Building Pathology Flashcards

Question

Can you give me a examples of deleterious materials ?

Answer 1

* Asbestos * RAAC planks * Calcium silicate bricks * HAC (High Alumina Cement)

Answer 2

The term 'deleterious materials' is a broad one, encompassing not only materials that are dangerous to health or which are the causes of failures in buildings, but increasingly, materials which are environmentally damaging.

Answer 3

Dry rot can penetrate masonry, different humidity, One of the main differences between wet rot and dry rot is that wet rot needs a higher moisture content to grow. Wet rot fungus likes to grow on timber with a high moisture content of around 50% and above while for dry rot to grow it will germinate at a lower timber moisture content of around 20% to 30%.

Answer 4

Dry Rot – Wood shrinks and splits into cuboidal cracks. Wood is light in weight and crumbles under fingers. Usually mycelium on the surface which is grey when wet and yellow/purple when dry. Fruiting body usually brown/red in colour. Indoors only.

Answer 5

* Consider the affected area * Remove affected timbers * introduction additional ventilation * rapidly dry out the area * trat area with a pesticide - probor10 * replaced timber if splicing go 500mm past affected areas * protect joist ends form moisture ingress

Answer 6

As it can pass through masonry.

Answer 7

* Wood wall slabs * snapped headers * Stone defects * sulphate attack in concrete or chimney stack * damp penetration * timber attacks * lead paint * asbestos * shallow foundations to bays - differential movement

Answer 8

Regular Horizontal cracking at regular intervals - wall tie failure Stepped or diagonal cracking - Movement, location dependant Horizontal cracking - Differential movement Cracking larger at top than bottom - Subsidence 0 - Hairline cracks: Less than 0.1 mm in width. No repair action required. 1 - Fine cracks: Up to 1 mm in width. Generally restricted to internal wall finishes. Easily treated using normal decoration. 2 - Cracks easily filled: Up to 5 mm in width. Not necessarily visible externally, but doors and windows may require adjusting to prevent sticking. Can be masked by suitable linings. 3 - Cracks that require opening up: Widths of 5-15 mm. Weather-tightness and service pipes may be affected. External brickwork may need repointing or, in some cases, to be replaced. 4 - Extensive damage: Widths of 15-25 mm. Windows and door frames become distorted, walls lean or bulge noticeably. Requires breaking-out and replacement of wall sections. 5 – Structural damage: Widths greater than 25 mm. Beams lose their bearing, walls require shoring, and the structure is generally unstable. May require major repair works.

Answer 9

Vertical, larger at the top than the bottom

Answer 10

BRE Digest 251 - Assessment of damage in low-rise budlings - This defines the inspection and cracking sizes to reference

Answer 11

BRE Digest 298 - Low-rise building foundations - the influence of trees in clay soil

Answer 12

``` Elm Oak Willow Poplar Hawthorn - NHBC ```

Answer 13

You can only see a limited inspection, if the cavity has been filled your inspection will be poor

Answer 14

* Replacement and or removal. * Replacement via remedial replacement resin set wall ties installed into the brick centre * Can also sleeve existing wall tie to limit further expansion * Treat existing wall ties with anti corrosion paint

Answer 15

* Dependant on the outbreak, a lack of ventilation. You would see damage or cuboidal cracking to the affected timber if visible then * Spores the dust presence of the rot * Hyphae 0 fine what strands * Mycelium - a collection of mass of hyphae * fruiting body - mushroom like appearance 0 dark red - releases the spores and the cycle starts again

Answer 16

* Common Furniture Beetle. * House Longhorn Beetle. * Deathwatch Beetle. * Wood Boring Weevil.

Answer 17

Design and calibrated for timber, foil backed plaster board, black ash mortar will give inaccurate readings, it should be used to back up visual identification

Answer 18

Consider the location and presence of damp, normally is low air flow/changes area, behind furniture, corners of room, near or adjacent to bathrooms and kitchens. Normally black spots.

Answer 19

• Slipped slates • blocked gutters • failed tanking systems q

Answer 20

That as a roof ages the fixings which are often nails start to fail resulting in tile or slate slippage especially in windy weather conditions.

Answer 21

The carbon dioxide being absorbed into the concrete to cause calcium carbonate which lowers the concrete ph., which can affect the protective coating on the steel reinforcement.

Answer 22

* The extent and depth can be confirmed using a phenolphthalein solution. Phenolphthalein solution reacts with the concrete – changes to pink if uncarbonated concrete and remains colourless on carbonated concrete * Carbonation depth is assessed using a solution of phenolphthalein indicator that appears pink in contact with alkaline concrete with pH values in excess of 9 and colourless at lower levels of pH * The test is most commonly carried out by spraying the indicator on freshly exposed surfaces of concrete broken from the structure or on split cores * Cover meter can detect reinforcement positions, cover depth and bar diameters * Structural assessment may be required

Answer 23

* Cracking * Bulging * Movement on the walls above or below DPC * Unevenness to the floor

Answer 24

As they are not protected with a DPM when they comes into contact with a water source they expand and can transfer this up into the slab above

Answer 25

Dry rot is the most serious form of fungus decay in a building, spreads onto and destroys much of the timber. On the other hand, the wet rot fungus occurs more frequently but is less serious, the decay is usually detained to where the timber becomes and stays wet. The Wet rot fungus tends to grow on porous surfaces, for example, timber with a high moisture content of around 50% while for dry rot to grow moisture of around 20% needs to be present. If left untreated wet rot can cause major structural problems as it can lead to weakened timbers.

Answer 26

* Tell tale sign 1 - Small round exit holes. * Tell tale sign 2 - fine, powdery dust. * Tell tale sign 3 - Crumbly edges to boards and joists. * Tell tale sign 4 - Tunnels within the timber. * Tell tale sign 5 - Weak or damaged timbers or flooring.

Answer 27

* Adult * Eggs * Lava * Pupa Adult • The cycle begins with the mating of two beetles. Woodworm beetles only have a short lifespan as a mature adult between 10-14 days. Eggs • The female beetle will then lay her eggs into the cracks of the timber so that the eggs are protected and don’t become dislodged. Larva • After a few days, the eggs then begin to hatch and the new born larva burrow downwards into the timber producing frass – bore dust as they tunnel into the timber. This is the worm stage of an infestation. • This is the lengthy part of the cycle, as larvae can live from anywhere between two to five years. • During this time, the larvae will feed its way up and down through the timber (which can lead to structural damage). • This is also the part of the cycle when woodworm can be detected through the frass being produced. The frass can help us identify the species of woodworm and confirm the woodworm infestation is active. Pupa • The woodworm’s lifecycle is almost at an end now. The larvae form a pupal chamber where it ‘pupates’ and changes from the larva into an adult beetle just below the surface of the wood. • Adult Beetle emerges • These now adult beetles will eat their way through the timber to create exit holes which can be seen on the surface of the timber. From here the beetles will ‘flee the nest’ and start the whole process again. • Visit our woodworm page to find out more about these tiny creatures and how we can treat the damage they cause to your home if left untreated.

Answer 28

* Oak * Willow

Answer 29

Occurs in steel framed buildings with covering masonry or stone. Often found in early 20th century buildings. The porous cladding allows moisture to come into contact with the steel which then corrodes, expands and causing cracking to the facing around the steel frame. Repairs can include removal of the facework, clean the steel work, apply protective paint. OR Cathodic protection whereby a current is passed through. It does not make good existing corrosion but prevents continuation of process

Answer 30

* Carbonation occurs when the alkaline elements of the concrete react with carbon dioxide creating calcium carbonate which lowers the PH level of the concrete. The carbon dioxide can react with the protective coating on the steel and corrode it. Levels of carbonation impacted by compaction, temperature, humidity, carbon dioxide levels. Overtime the concrete will weaken and crack It is remedied by removing the delaminated concrete, cleaning the re-bar and patching the concrete.

Answer 31

* Calcium chloride additive was used as an accelerator until it was banned in 1977. The calcium chloride increase the conductivity of the concrete and speed of reaction. Eventually, it will cause the rebar to corrode and expand. Chlorides are also found in poorly washed marine aggregates or being exposed or sea water. The chloride is absorbed into the body of the concrete.

Answer 32

* Chemical reaction affecting concrete causing it to expand and crack. This is due to penetration of sulphates into the concrete from external sources such as rainwater or the materials mixed in. * Can lead to large cracks and potential heave. * Remedy is to break out and replace the concrete. * Generally occurs in houses built between 45-70’s in areas with mining or close to the sea. Occurs as soon as concrete comes into contact with moisture with sulphate but the cracks vary in the time they show up, depends on factors such as slab thickness, moisture content etc.

Answer 33

* BRE444 * Hammer testing * Visual inspection * Magnet cover testing * Phenolphthalein test

Answer 34

* Crazing - Surface crazing caused by lack of protection from UV exposure. No treatment is required if in small localised patches but should be monitored. * Ponding - If the gradient is not sufficient and there are dips in the roof finish, it can lead to pools of water. It can lead to water ingress if there is a gap in the roof finish. * Thermal Movement * Cracks and splits can occur when there is thermal movement between the substrate and membrane. Usually requires localised repair to the area around the crack. * Blistering - Caused when water vapour beneath the roof finish increases. The source of moisture should be traced and the blister opened and allowed to dry before patch repairing. * Flashing and Falls around openings- Defective lead from deterioration or poor workmanship around openings causing water ingress. Depending on the issue with the lead, there are different repairs. * People - Punctures caused by people from impact damage. * Cracks and tears along the line of joists - Caused by thermal movement or saturation of insulation or sagging decking. Repaired by cutting felt back and allowing it to dry before patching over."

Answer 35

Firstly, visually inspect the roof for any defects and then use a thermographic camera to identify colder areas that may identify areas of leaks.

Answer 36

The extent of the defect, when the existing roof was recovered, the approximate life span, the cost, timing, clients intentions for the building

Answer 37

Decay to the timber forming the structure, inadequate supports or alterations carried out to the structure. Change of roof coverings. Secondary problems may be slipped tiles or opening joints at the ridge allowing water ingress.

Answer 38

Any material that is harmful to health, safety, environment, not suitable for their purpose or pose a risk for where it is used.

Answer 39

* Asbestos – Fiberous material used for a variety of reasons from roof sheets to insulation and fire stopping. It is carcinogenic and needs to be removed if there is a risk of release of fibres. * Wood Wool Slabs – When used as permanent shuttering for concrete, it may lead to grout loss and inadequate coverage of steels which leads to inadequate fire protection. If used for roof decking, it is not considered deleterious. * Calcium Silicate Bricks – Shrinks after construction with further movement from wetting. Thermal movement more likely than with clay bricks. Construction details must allow for movement and if designed and used correctly, performs well. * High Alumina Cement – Gives high early strength and used in maritime buildings. Porosity is increased and resistance to chemical attack is reduced. Where water and chemicals are present in the mix, it can lead to the concrete becoming friable and lead to loss of strength.

Answer 40

The concern comes from the potential for movement that have given calcium silicate bricks the label of deleterious otherwise the bricks actually increase in strength when exposed to atmospheric carbon dioxide although does shrink it too. In highly polluted areas, sulphur dioxide in damp conditions causes the calcium silicate to decompose to form a gypsum crust.

Answer 41

Used in buildings between 1954 and 1974. Precast pre-stressed concrete beams particularly in maritime buildings. Leaves concrete friable and sometimes browns it. Usually found in roof beams.

Answer 42

When used as permanent shuttering for concrete, it may lead to grout loss, honeycombing or voids which can reduce fire resistance, corrosion protection and loss of strength. It is adequate for use in flat roof decking.

Answer 43

A building is considered damp if moisture becomes visible through discoloration of finishes or causes mould growth, sulphate attack, frost damage or puddles and drips.

Answer 44

Speedy carbide meter or protimeter.

Answer 45

* Penetrating * Rising * Condensation ( + interstitial condensation)

Answer 46

Measures the electrical resistance between two electrodes. Generally used for moisture in wood.

Answer 47

Measures moisture in masonry through adding masonry dust into a container with calcium carbide which releases a gas in proportion to the moisture present.

Answer 48

It is caused by a lack/failure of DPC or bridging. The remedies can be injecting DPC, removing the cause of bridging which may involve reducing the ground level.

Answer 49

Identify what the building is exposed to. Is there a leak, overflowing gutter etc. Identified by discolouration or damp patches which can darken and grow if left for long time. Remedies can be unblocking a gutter, fixing roof tiles, flashing, faulty pointing, lack of dpc below the parapet.

Answer 50

A cold bridge is created when poor thermal insulators come into contact allowing heat to flow through the path. E.g. at the junction of a concrete slab and external walls.

Answer 51

Generally occurs in top corners of rooms where warm air rises and collects and due to the change in temperature, the warm air releases vapour onto the colder surface. It is an issue in poorly vented and cold buildings where there is high moisture volume. It can be remedied by venting the property better and maintaining regular internal temperature.

Answer 52

Generally should be left for 3-4 months but this is not practical.

Answer 53

Lateral damp ingress from defected cavity ties. Due to mortar dropping onto the cavity tie which allows moisture to penetrate through the brick. Remedy is to remove the wall tie and replace it.

Answer 54

Rising damp generally only occurs to the bottom 1m of the wall. Test the moisture in the wall at 300mm intervals. If it is closer to the ceiling, odds are that it is condensation particularly if there is a mildew on the surface.

Answer 55

* Penetrating – Enters via a porous bridge transferring moisture through capillary action or there might be a hole in the building fabric. * Rising – Moisture rising up from the ground through capillary action normally up to 1m high with tide marks. Usually from bridging of DPC or lack/failure of DPC. * Condensation – Warm moist air comes into contact with cold surfaces which releases the moisture. Generally at high level.

Answer 56

Firstly, what is the building made from and what is the construction method? Are there local factors such as trees or high water tables? Have any alterations been carried out? Are there any nearby drains where the cracking is. What is the age of the building?

Answer 57

* Subsidence – shrinkage of clay * Heave – saturated clay * Settlement – Movement from increased load. * Differential settlement – when parts of a building are constructed off different foundations or the ground has different soils, they move at different speeds. * Lintel failure – Usually leads to triangular cracking to the brickwork above the window to drop. * Internal alterations – drying of timbers or installation of steel beams without consideration of impact.

Answer 58

* BRE Digest 251 * Up to 2mm – very slight/aesthetic * 2-5mm – slight / aesthetic * 5-15mm – moderate/ serviceable * 15-20mm – severe/ serviceable * Over 25mm – very severe / stability issues"

Answer 59

General rule of thumb is that it is caused by differential settlement due to different foundation types. It could also be because windows were swapped and the new window is not strengthened and causes the bay to drop.

Answer 60

Cohesive soils such as clay. Could be because of trees or high water table, leaking drains etc.

Answer 61

* Insect attack * Dry rot * Wet rot * Structural defects

Answer 62

Dry Rot – Wood shrinks and splits into cuboidal cracks. Wood is light in weight and crumbles under fingers. Usually mycelium on the surface which is grey when wet and yellow/purple when dry. Fruiting body usually brown/red in colour. Indoors only. Wet Rot – Wood shrinks and splits. Wood darkens. Mycelium grows on surface which can be white, brown, green or amber in colour. Fruiting bodies can be different colours and occurs internally or externally.

Answer 63

* Locate and remove the source of moisture and dry out the timber * Remove rotten wood plus 450mm * Apply fungicidal fluid and strengthen joists if required

Answer 64

* 50-60% for Wet Rot. Will not survive below 44%. | * 25% for dry rot

Answer 65

* Features include shrunken wood with cuboidal shapes. Cotton wool type mycelium on the surface. Timber crumbles under finger. Fruiting bodies are red/brown in colour and pancake shaped. * Identify the rot and where it is at its worst. Remove the cause and strengthen the joists as required or fully replace. If the dry rot has passed through the masonry, this will need sterilisation too.

Answer 66

* Spores – with dry rot, it is a fine orange brown dust. The spores activate when in contact with timber. * Hyphae – Timber and moisture are present, the spores will produce fine white strands which allows the rot to grow by feeding on timber. * Mycelium – Hyphae mass is known as mycelium. It grows on various materials and over vast distances which allows it to progressively destroy the structural timber. * Fruiting Body – Mushroom like form pumps spores into the air which is transferred by air currents and germinates it to create a new attack. Repeat the process

Answer 67

* Category A (insecticidal treatment) – common furniture beetle, death watch, house longhorn beetle. * Category B (treatment of rotten area only) – wood boring weebills. * Category C (No treatment required) Bark borers * Remedial methods – study flight holes to identify beetles and determine if it is still active or dormant. Apply boron based treatment to affected areas

Answer 68

Holes in wooden item with frass around the holes. Typically 1-1.5mm holes.

Answer 69

Adult beetles lay eggs on the timber. The grubs feed on the timber, hatch into beetles which breed, lay eggs and the process repeats.

Answer 70

Most woodworm requires high moisture. May indicate an issue with the structure and damp.

Answer 71

Chemical insecticides. Resolve damp issue as damp wood may be re-infected

Answer 72

* Furniture beetles and longhorn – 2-5 years | * Death-watch beetle – up to 10 years

Answer 73

Confirm why the floor is deflecting. Notching to joists, not adequate for spans? Inadequate support? Can the issue be remedied without destroying the floor? Supplement the joists, overboard or remove it and replace.

Answer 74

Poor or inadequate curing – environmental conditions being conducive to evaporation and lack of protection. If the mixture is too wet or excessive floating which causes aggregate to sink, the cement paste on top will start to crack.

Answer 75

* Chrysolite – most common asbestos in buildings. Corrugated asbestos cement sheets. * Amosite – found in fire retardant materials * Crocidolite – pipe insulation, plastics, cement products.

Answer 76

Horizontal cracking every 5 or so brick courses. Corrosion of old steel ties causes the cracks. Remedy – use a borescope to determine the defect. Locate the wall ties and isolate and remove. Install replacement stainless steel mechanically fixed ties.

Answer 77

Common with slates or tiles. Nails have rusted and expanded which cracks the tile allowing them to slip. Generally, if one nail has failed, several are likely to fail too.

Answer 78

* Plastisol degradation * Cut edge corrosion * Defective fastenings

Answer 79

Loss in colour, caulking and delamination

Answer 80

When cut edge of coated metal are exposed to elements, delamination may occur in the form of peel back of factory coating. The unprotected metal then rusts and corrodes. Can be remedied by applying a silicone paint/elastomeric coating. If the corrosion is bad, may be better to replace the panel.

Answer 81

Plastisol is a PVC coating. Usually has a leather effect. Or use PVF2 which is a thinner material with a smooth finish. These are both effected by temperature, UV exposure which can lead to caulking and delamination.

Answer 82

Herbaceous perennial plant.

Answer 83

Hallow stems with raised nodes. Similar appearance to bamboo. Can reach 3-4m per year. Broad leaves with small white flowers

Answer 84

Invasive species which forms thick colonies that crowd and kill over species. Extend 7m horizontally and 3m deep making excavations difficult. Plant is resilient to normal weed killers and cutting. Needs herbicide application to kill it over a period of months.

Answer 85

Offence to plant or grow it. Illegal to cause spread. Classed as controlled waste and requires a licence to dispose at licensed sites.

Answer 86

Injected with herbicide or excavated with the roots and disposed.

Answer 87

* Inherent characteristics – some stones have layers with different erosion rates. Small cracks in the stone can cause problems. * Salt crystallisation – salts in solutions pass into the stonework. As the stone dries, the salt crystallises which expands and blows the stone. Damage usually shows ass a powder on surface but can split the stone. * Frost Attack – General freeze thaw particularly if the stone has large pores. * Incorrect bedding – Stones should be laid in natural bedding position as it is stronger like this. If laid vertically, the layers are vertical making them more vulnerable to damage. * Incorrect pointing – inappropriate mortar mixes can cause issues with the mortar and stone. If it is too strong, the mortar will crack with movement or shrinkage which may allow water penetration. Strong mortar may also prevent moisture evaporating out and will instead go through the stone and potentially cause salt crystallisation. * Expansion of Metal – Iron and steel cramps have been used as fixings for stone. When they rust, they expand and can fracture the stone

Answer 88

* Asbestos * Concrete defects * Cold roof * Wood wool slabs

Answer 89

* Failed on lack of DPC * Insufficient foundations * Poor ventilation to floor voids * Damp penetration * Lead pipework.

Answer 90

* Cut edge corrosion * Plastisol degradation * Asbestos use in insulation

Answer 91

* Sulphate attack * Defective flashing * Removal of stack below

Answer 92

Erosion, acid attack, salt crystallisation could all cause the stack to lean. BRE Guide states any lean of the stack of more than 1 in 100mm is unsafe. Consider lining the flue with a liner and replace broken bricks and pots. Relaunch the top if needed. Worst case scenario rebuild the stack.

Answer 93

* Water paths through parapets, hidden valleys and gutters * Springy floors resulting from decaying timber floor joists. mainly caused by poor cross-ventilation. heel drop test to test the springy floor. * Rotten or stuck sash windows * Blocked internal gutters. * Damp penetration in solid walls * Corroded cast iron railings bursting stonework * Bowed brick walls, caused by the practice of lightly bonding high-quality facing bricks in with poorer quality bricks of the main wall, unbonded party walls and front walls and decaying coursed timbers buried in walls * Failure in roof trusses caused when roof ties rot and begin to spread. Dislodged joists and ridges caused by bomb blast damage. * Leaning chimneys/over-tall stacks/damp penetration via stacks * Perforated lead work or splitting caused by over-beating or poor maintenance * Missing or badly altered load-bearing timber partitions * Damp basements * Failure of timber lintels * Poorly applied or painted stucco limiting water evaporation from walls * Downpipes decanting on to lower roofs from roofs above, causing temporary flooding in heavy rainfall

Answer 94

* Blocked air vents to ground floors, causing dry rot * Failed or lack of damp proof course – rising dampness, penetrating damp, efflorescence on plaster, decay to skirtings * Delamination of brick skins – bulging of brickwork * Over notching of floor joists for retrofit of services – deflection of floors, reduction in load bearing capacity * Poorly fitting sash windows, risk of decay within window reveals, water penetration beneath sub-sills, draughty or dangerous operation, decay in concealed areas, lack of security * Roof covered with concrete interlocking tiles – overloading of roof structure, bowing of rafters and purlins, roof spread * Settlement of bay windows – internal cosmetic damage, distortion in load-bearing elements * Wall tie failure (particularly in black ash mortar) * Heave or subsidence of shallow foundations * Nail sickness – ferrous nails corroded

Answer 95

Blocked air vents to ground floors, causing dry rot • Failed or lack of damp proof course – rising dampness, penetrating damp, efflorescence on plaster, decay to skirtings • Delamination of brick skins – bulging of brickwork • Over notching of floor joists for retrofit of services – deflection of floors, reduction in load bearing capacity • Poorly fitting sash windows, risk of decay within window reveals, water penetration beneath sub-sills, draughty or dangerous operation, decay in concealed areas, lack of security • Roof covered with concrete interlocking tiles – overloading of roof structure, bowing of rafters and purlins, roof spread • Settlement of bay windows – internal cosmetic damage, distortion in load-bearing elements • Wall tie failure (particularly in black ash mortar) • Heave or subsidence of shallow foundations • Nail sickness – ferrous nails corroded

Answer 96

* Occurs to reinforced concrete buildings and structures – it is inevitable * Fine cracks appear in the concrete causing the reinforcement to corrode * Hairline cracks appear along the reinforcement line * The reinforcement expands due to the rusting * Concrete spalls and cracks exposing the reinforcement

Answer 97

* Replacement – this involves removing defective concrete and cutting out the reinforcement to damaged members. New reinforcement is fixed but welding to existing and new concrete is cast. This is the simplest method and completed by specialist contractors. * Gunting – a propriety process in which fine concrete is sprayed onto a concrete surface under repair of high velocity. * Coating – coatings, sealants and membranes can be effective in reducing the carbonation process. however, if chloride is present at rebar depth then the coating will not prevent carbonation. * Electrochemical re-alkalisation – the cathodic reaction around rebars produce hydroxyl ions. The steel cathodes also attack alkali metal ions towards its surface, so high alkalinity is restored around rebar. A temporary anode (steel mesh) is attached to concrete, the electrolyte penetrates the concrete and raises the alkalinity at the cover. An anti-carbonation coating is applied. * Cathodic protection – this is a permanent and very expensive technique. an anode system (coating or mesh) are sprayed or fixed to the whole surface of concrete. A current is applied which passes to the reinforcement, which is then made cathode preventing corrosion of the reinforcement.

Answer 98

High Alumina Cement was used in the production of pre-cast concrete sections. This has very high strength at an early stage, however, loses strength as it ages and is susceptible to chemical attack in damp conditions. Introduced in 1925, cement producer Lafarge commenced the UK manufacture of High Alumina Cement to provide concrete that would resist chemical attack, particularly for marine applications.Used in the UK from 1950-1976 in the manufacture of pre-stressed concrete beams

Answer 99

HAC concrete was banned in 1976 for structural use although new uses are now becoming established under the name Calcium Aluminate Cement (CAC).

Answer 100

HAC concrete undergoes a mineralogical change known as conversion. During this process the concrete increases in porosity which in turn results in a loss of strength and reduction in resistance to chemical attack. The higher the temperature during the casting of the concrete the more quickly conversion takes place.

Answer 101

* An investigation should be undertaken consisting: * Sample testing * Collect details of construction materials used – the local authorities hold records of HAC buildings * If the strength has been reduced – reduce the live loads or strengthen * In the case of reinforcement corrosion – localised repairs can slow further deterioration

Answer 102

* Sulphate attack can cause serious damage to brickwork and concrete by creating expansive force that are, or can be, sufficient to disrupt mortar and create significant expansion, bowing and cracking of concrete floor slabs together with related collateral damage. * In some subsoil there can be a problem with sulphate attack. It occurs when the fill material (hardcore) beneath the slab contains sulphates and these migrate into the concrete. The sulphates react with the concrete causing it to expand. * Calcium, magnesium and sodium sulphates occur naturally in some clays and other sub soils * The sulphates dissolve in the groundwater and permeate the concrete. * This leads to an aggressive chemical reaction between the sulphates in solution and one of the chemicals in the cement. * The resulting compound expands rapidly as it forms and this can crack the foundation concrete. * If sulphate attack is a possibility it is wise to use sulphate resisting cement.

Answer 103

* Located in brickwork, blockwork, render and concrete. * Heave in concrete slabs and displacement of adjacent masonry * In dwellings with timber floors, the sleeper walls may become displaced causing deflection in floors * Cracking * Spalling * Loss of strength * Increase surface area for further attack * Friable * Edges and corners susceptible * Upwards bowing coupled with map pattern cracking and possibly displacement of brickwork at slab level are common indicators. Visual indicators of affected concrete may be the existence of flaky or crumbly concrete

Answer 104

Must be a high level of water-soluble sulphates within the adjacent ground. To affect concrete buried in the ground, the concrete must be of low density and there must be a large amount of moisture movement through the concrete. Common cause is contaminated hardcore beneath the concrete floor slab. The sulphates become mobile due to a broken drain or high-water table. The process of sulphate attack is: • sulphate enters concrete (solution form) • water evaporates leaving the sulphates • sulphates react with calcium hydroxide and calcium aluminates causing expansion • the concrete deteriorates causing cracking and heave

Answer 105

* BS 1881-124:2015 provides method of testing concrete samples * Assuming that concrete contains 15% by mass of cement, sulphate content can be expressed as a percentage of the mass of cement with anything over 5% likely to be harmful. In severe cases, 10-15% has been identified. * Visual indicators of affected concrete may be the existence of a flaky or crumbly concrete and in the case of thaumasite, a white mush.

Answer 106

* Remove affected concrete and start again with DPM * Remediate the ground * Investigate sulphate levels

Answer 107

Occurs where the chemical within the cement react with silica forms a gel substance which absorbs water and expands creating cracks where water can enter. Further cracking may occur as a result of water freezing within the cracks. * Cracking * Small pop outs * Map cracking * Tensile strength reduced * Gel absorbs water causing further cracking * Cracks run parallel to reinforcement bars

Answer 108

* Chlorides may either ingress (from penetration of de-icing salts) or cast insitu as sea dredged aggregates or calcium chloride additive. * Chloride ions attack the reinforcement can cause: * In certain circumstances ‘pitting’ corrosion can occur – when the steel is effectively eaten away without the formation of expansive rust * Corrosion of steel reinforcement is localised compared to carbonation and much more rapid. * Spalling of concrete * Significant loss of cross-sectional area * Pit in bar surface – rebars could be completely eaten away * Visual sign of cracking and spalling following expansive rusting

Answer 109

* Removal of cores for analysis in the lab * Petrographic analysis * Drilling dust, disregard 5mm * Profile grinder to remove dust

Answer 110

* Cathodic protection * Corrosion inhibitors * Epoxy resin repairs

Answer 111

Upward movement of moisture through permeable building materials such as brick by capillary action. It rises up the wall often to a height no more than 1.5m and usually leaves a characteristic horizontal tide mark.

Answer 112

* Damp patches * Peeling and blistering of wall finishes * Tide mark up to 1.5m above floor level * Sulphate action * Corrosion of edge beads * Musty smell * Condensation / mould growth * Rotting timbers – skirting boards, frames, linings and doors * Hydroscopic salts (nitrates and chlorides from ground water) absorb moisture which can be dissolved and moved to the surface of a material and cause extensive staining and disruption of finishes.

Answer 113

* Failure of DPC * DPC bridged – raised external soil levels or pathways of rubbish / debris * Mortar droppings within cavity * DPC not laid correctly – lap minimum 150mm * If suspended timber floor has been replaced by a solid floor, check for a difference in level of DPC’s * Rain penetration * Leaking gutters * Plumbing defect * Persistent spillages * Water trapped in building fabric

Answer 114

Resolve all water ingress – gutter, leaks etc. • Let the building dry naturally – promote ventilation • Hack-off and remove affected plaster area internally • Re-plaster (using renovation plaster) and redecorate. Renovation plaster stops salts and controls damp passing through the walls • Ensure all timbers are replaced as required • If the DPC is damaged – renew

Answer 115

Penetrating damp (or moisture ingress horizontally through the wall fabric) is an issue that can affect all buildings. Defined as roughly circular area on internal fabrics.

Answer 116

Fix the specific issue relating to the water ingress.

Answer 117

Moisture in the air (water vapour) is held in high temperature air and when it comes into contact with a cold surface it is cooled, and excess vapour condenses (dew point).

Answer 118

* Coldest internal surfaces - external walls, corners, windows, wall/floor junctions, lintels and window reveals. * Water droplets on glazing * Rooms with a lot of water vapour * Concentrates in areas where air movement is restricted. * ‘Black spots’ mould AKA Stachybotrys Chartarum.

Answer 119

* It is condensation within the structural elements. * It has less immediate impact on the occupation as it occurs within or between the layers of the building envelope, where the dew point exists at depth within a building element, component or material. * Building at risk from interstitial condensation: * Structural components liable to rot e.g. timber framed walls of timber deck cold flat roof * Structural components liable to corrode e.g. steel framed walls * Impermeable out layers e.g. walls with impermeable cladding * Metal reinforcements e.g. reinforced concrete framed buildings * Buildings likely to have high internal vapour pressures e.g. swimming pools or textile factories

Answer 120

* These can cause severe decay in timber. The timber cracks in cubes during the decaying process, brown rots cause decay and as a result, the timber loses strength quickly. * The wood becomes darker in colour and dry i.e. it can crumble between the fingers * White covering over the affected area – initial stages of a fruiting body * Fruiting body grows which is brown * Starts to spread across the timber – affects the structural integrity of the timber

Answer 121

* The timber develops a fibrous consistency, similar to lint. * The cracking that appears is often along the grain. * The wood becomes lighter in colour i.e. looks bleached. * Generally white rot prefers high moisture within timber than brown rots

Answer 122

* Spore * Hyphae * Mycelium * Fruiting Body

Answer 123

The fungi will only survive and thrive in certain conditions: • FOOD (TIMBER) - Sapwood is attacked as it contains nutrients • MOISTURE - moisture must be present for decay to occur and moisture content of timber is key • TEMPERATURE - Fungi growth can be killed off by low or high temperatures • AIR - Fungi require oxygen, if air is excluded, decay will not occur.

Answer 124

Fungal timber decay occurring in poorly ventilated conditions in buildings, resulting in the timbers becoming dry and crumbly. There are typical symptoms of dry rot which are cuboidal cracking, hyphae, mycelium and fruiting body.

Answer 125

* Timber becomes dry and crumbly. * Timber becomes lightweight and has a dull brown colour. * Cuboidal cracking - more pronounced that wet rot * The strands are grey or white and 2-8mm thick. * Mycelium may be leathery or look like cotton wool balls. * Spore cannot be distinguished but “en mass” appear like rust red dust. * The fruiting body is often pancake shaped with white margin and red spores on the surface

Answer 126

* These conditions are usually found where water is coming into contact with the timber directly. * The most common defects allowing water entry are: * Failure of roof covering or rainwater goods * Defective rendering * Inadequate ventilation * Defective DPC * Plumbing leaks

Answer 127

* Detailed and extensive survey should be undertaken to identify the areas of timber and masonry affected. * If structural timbers have been damaged it may be necessary to get a structural engineer to assess * Determine the full extent of outbreak: * Cut out decayed timber to 0.5m beyond decayed wood, remove and burn. * Hack off plaster / rendering and remove skirting, architraves and other joinery from area to be treated to 2m beyond. * Remove surface mycelium from exposed masonry and wire brush. * Surface application of fungicidal fluid - water based surface biocide by brush or coarse spray. * Fungicidal rendering - fungicidal barrier to a greater depth * Preservative plug / paste inserted in holes * Irrigation - large quantities of water based fungicidal solution. Only to localised areas. * Treat sound, damp timber with organic preservative - preservative to sloping holes drilled into the wood or pressure injection OR proprietary paste treatment * Use preservative treated replacement timbers: pressure impregnated or organic solvent type of preservative.

Answer 128

A fungal rot affecting timber with a high moisture content usually around 40%. Mostly isolated to in one particular area.

Answer 129

* Cuboidal cracking * Dark brown colour * Crack run longitudinally with the grain * Fruiting bodies are rarely found in buildings

Answer 130

* Measures for controlling an outbreak of wet rot: * Primary measures: * Locate and eliminate sources of moisture * Promote rapid drying of the structure * Secondary measures * Establish size and significance of attack * Remove rotted wood; consider the need to apply localised preservative treatment in situ * Use preservative-treated replacement timbers * Introduce support measures

Answer 131

* Establish size and significance of the outbreak. * Remove rotted wood 450mm past affectede area, apply localised preservative treatment in situ * Use preservative-treated replacement timbers. * Introduce support measures (if required)

Answer 132

A generic term that is used to commonly describe the larva stage of wood boring beetles. A number of insects, mainly beetles, are able to use wood as a food source and some of them can cause serious damage to building timbers.

Answer 133

• COMMON FURNITURE BEETLE (WOODWORM) 3-5m long, dull brown Lines of pits on wings Found on or around damaged timber LATE MARCH – EARLY AUGUST (particularly warm weather. Softwood, European hardwoods 1-2mm dia. Circular flight holes Flight holes random orientation, mainly in direction of grain. Bore dust, cream coloured, lemon shaped pellets. Life cycle 2-5 years • LONG HORN BEETLE Adult 10-12mm, black or dull brown. Sapwood or softwoods particularly roof timbers. South-west of London mainly surrey. Flight holes, few large oval, 6-10mm largest dimension. JULY to OCTOBER Cream coloured, sausage shaped. ``` • DEATHWATCH 6-9mm long, chocolate brown MARCH to JUNE Bore dust, disc shaped cream pellets Flight holes circular 3mm diameter Mostly oak and elm (hardwoods) ``` • WEEVIL 3-5mm long, brownish black. Distinctive long snout. All year around. Flight holes, small ragged, 1mm diameter. Decayed softwood and hardwoods in damp conditions. Mostly found in below ground conditions.

Answer 134

Downward movement of the ground and any building on it, due to changes within the subsoil.

Answer 135

Identified by diagonal cracking which is usually tapered (of uneven width) in the buildings structure/façade and verified by leaning or pulling of the building. Subsidence usually shows up as cracks that are typically wider at the top than the bottom. They commonly appear around windows, doors and other weaker areas. Doors and windows may stick when opening them, walls and floors may show signs of distortion.

Answer 136

* Usually localised to certain areas of foundation- not distributed across the whole foundation * Therefore ground movement within these area will cause rotational movement on the foundation, which generates rotational forces within the building structure * Common in building built up clay * If the soil becomes dry due to water being sucked out by trees or a drought, the clay contracts and pulls the foundation causing deflection and structural damage. * It can occur when excess water leaks into the soil with high sand / gravel content and washes soil away from foundation, may be due to a leaking drain. * It can be a consequence of mining where the effect can be sudden, the extent of this depends on the method used for mining i.e. dredging, mining or pumping

Answer 137

* Refer to BRE guidance to understand how to assess damage. * Remedying the source of the problem can be effective, however it can sometimes make things worse i.e. removing a tree causes moisture to return = heave * Underpinning is an option but it is expensive and disruptive * Use pneumatic jacks to lift the building and reverse the movement

Answer 138

Downward movement of the ground or any structure on it, due to soil consolidation as a result of the load applied by the structure of the building.

Answer 139

* Cracks occur at the junction between new elements. | * Differential movement between two elements

Answer 140

* Occurs due to the pressure applied to the subsoil by a new building * Water contained within the sub soil squeezed out by new load * Amount of settlement depends on soil type

Answer 141

Expansion of the soil due to climatic and other factors (e.g., frost or removal of trees). The mass upwards movement of material as a result of expansion.

Answer 142

* Expansion of the corner of the building causing lifting. * Can be measured on a site over a period of time. * Check shrinkage potential of clay soil using industry data

Answer 143

The felling of trees in the vicinity of existing buildings stops the removal of moisture from the soil and the soil soaks up the water that the tree would have removed. Heave generally occurs in clay soils.

Answer 144

In the event that removing a tree is unavoidable, it is advised pollarding be carried out to slowly reduce the trees capacity to remove water from soil. Potentially necessary to seek advice from a geotechnical engineer

Answer 145

It is a weak spot in the insulation surrounding a house. Cold bridges (also known as thermal bridges) occur whenever there is a break in the continuity, or a penetration of the insulation.

Answer 146

Roof and wall abutment

Answer 147

The term 'deleterious materials' is a broad one, encompassing not only materials that are dangerous to health or which are the causes of failures in buildings, but increasingly, materials which are environmentally damaging

Answer 148

* Asbestos * Calcium chlorides * Calcium silicate bricks * CFC’s * Formaldehyde * Hair plaster * HAC (High Alumina Cement) * Hollow clay pot floors * Lead * Nickel sulphides

Answer 149

Cavity wall ties were introduced around 1920’s where external walls were changed from solid 225mm thick to cavity walls. Wall ties have undergone change from ferrous metal through to zinc coated, bituminised, galvanised plastic and ceramic to stainless steel. It is used to connect the two skins of the cavity wall together.

Answer 150

* Horizontal cracks in bed joints of brickwork every 6-8 courses (usually external skin) along with some diagonal cracking. * Damp patches internally where there may be cold bridging in the tie position. * Walls leaning or bulging (typically gable walls exhibit a pronounced effect). * Upward movement can result in an upturning of the roof, particularly at the gable end to alleviate pressure following expansion of wall ties due to corrosion, known as the Pagoda effect. * Internal wall cracking and lifting of walls and roof structured in extreme severe cases. * Increasing problem with cavity wall ties made from stainless steel. It arises when the galvanising is not of sufficient quality and the outer leaf of the cavity walls allows penetration, usually due to porous brick/blockwork. If ties rust the swelling effect may cause horizontal external cracks to appear in the wall.

Answer 151

* Age of ties, poor quality of coatings * Insufficient wall ties * Badly fitted ties, upside down or not 50mm embedment in the leaf * Poor quality mortar * Sea dredged aggregate in mortar * Corrosion due to failure in joints

Answer 152

* Replace existing wall ties with new stainless steel wall ties, min. 3per sqm * Additional remedial wall ties at vertical centres to jamb openings and at roof and corners * Remove or isolate existing defective ties * Clean cavity debris

Answer 153

Used as a permanent shuttering. Formwork is used to contain concrete in order to mould it to the required dims and to support it until it can support itself. It may be left in place for the lifetime of the building.

Answer 154

* Concrete does not adequately get compacted. * Risk of poor cover to the steel and hence loss of durability, possible reduction in strength, and loss of fire resistance. * Voiding and honey combing due to vibrations. Poor bond or failed bond between the wood wool and the hardened concrete. * Buildings constructed from 1950 to the mid-1970s are most likely to be affected by this form of construction. * If permanent shuttering is discovered, intrusive investigations may be needed to determine the adequacy of concrete cover to the steel reinforcement. If voiding is present, the affected area can be exposed and repaired using hand-fixed concrete repair methods or, if over a larger area, sprayed concrete.

Answer 155

Steel edge sheets are exposed to oxygen which are prone to corrosion which is exacerbated by water and pollutants. Consequently, the factory coating can peel off from these edges causing them to corrode. Tough cut edge corrosion usually begins around edges it gathers speed through capillary water action and can spread.

Answer 156

* Area must be first cleaned and prepared for treatment. * Depending on the severity of the corrosion, loose paint, rust and corroded areas are often removed manually, to which a high-quality weatherproof sealant is then applied to the effective areas. * Painting the cut edges and periodic re-painting where access is possible may provide a solution. If sheets with corroded edges are not repaired or replaced, further damage to the sheet may result, with increased risk of water penetration. Delamination of decorative coating may also be associated with cut-edge corrosion.

Answer 157

The presence of mycelium, fruiting body and the damage to the timber suspended floor.

Answer 158

Brown rots cause the wood to become darker in colour and to crack along and across the grain ;when dry, very decayed wood will crumble to dust. Many common wet rots are brown rots; dry rot is also in this group. White rots cause the wood to become lighter in colour and lint-like in texture, without cross cracks.All white rots are wet rots. wet rot green fruiting body.

Answer 159

* Cuboidale cracking * moisture content around 20% * temp mid 20% * Visual identification of spores, hypahe mycelium and fruiting body * Damage to timbers * Musty/mushroom smell * Lack of ventilation

Answer 160

Can be used however the source of moisture should be eradicated and the drying out and rapid heating of the space should be encouraged

Answer 161

Using the weather, wind, etc to assist in removing the moisture and the conditions that are not suitable for rot.

Answer 162

Via an initial inspection from removing a floor boards to confirm extents

Answer 163

Full removal of the flooring in the affected rooms due to widespread deuteriation of the timber floor

Answer 164

Wall tie failure can happen where there has been corrosion of the existing wall ties or when insufficient or incorrect wall ties have been installed. When a mild steel or galvanised steel wall tie corrodes, there is a build up of rust (also known as iron oxide), which causes the tie to expand in size.

Answer 165

* I would expect wall ties to be steel fish tail wall tie. * Cavity were widespread introduced 1920

Answer 166

Steel and Iron, now made of stainless steel to reduce the chance of corrosion.

Answer 167

I advised to review the extents and damage as a result of the expansion of wall tie, consideration was given to removal or replacement wall ties.

Answer 168

* Interstitial condensation * Wood boring insect attack * Roof spread * Water ingress

Answer 169

* Concrete Carbonation * HAC * Alkali Silica Reaction * Chloride Attack * Sulphate Attack

Answer 170

* Consider the location * Recent works * Construction of the building * Type of the cracking * Opening up works * Further investigations

Answer 171

Thermography uses specially designed infrared video or still cameras to make images (called thermograms) that show surface heat variations. Energy assessors use thermography as a tool to help detect heat losses and air leakage in building envelopes.

Answer 172

Water ingress

Answer 173

Reinforced Autoclaved Aerated Concrete is a lightweight form of concrete used in roof, floor, cladding and wall construction in the UK from the mid-1950s to the mid-1980. They have a strict lifespan and can fail dramatically without warning.

Answer 174

As it was a condition survey, the method of remediation was out the scope of my instruction. However I was further instructed to advise on the remediation, and I recommended treating and lapping would be required.

Answer 175

I used NBS Source to find an approproate manufacturer and product, and specified that installation should be in line with manufactuer's guidance.

Answer 176

Moisture, food, fungi

Answer 177

- Dry rot starts off-white while fruiting body is rusty brown - Wet rot is dark grey/black or white while the fruiting body is brilliant white skin or mushroom like

Answer 178

Cut back 1000mm from affected area

Answer 179

They are simplified - does not consider if it is active or historic movement.

Answer 180

Initially a steel ruler, then either a tell tale or screws and callipers. If it was internal I would use a magnified graticule. In a hard to access location I would use a displacement transducer.

Answer 181

- Pourous - Silica containing - Shallow rebar

Answer 182

Its a general term to describe the corrosion of rebar that often leads to the cracking of concrete.

Answer 183

- Dead load (constant load, e.g. building itself) - Live load (not constant, e.g. snow/rain, occupants) - Transient load (sudden changes e.g. wind)

Answer 184

A type of resin used in construction materials that has to be monitored as it is carcinogenic.

Answer 185

A type of natural gas which in high quantities and consumed in enclosed spaces is carcinogenic

Answer 186

Part L of the Building Regulations BS6229

Answer 187

There was discolouration to the edges of the sheets and bubbling to PVC finish. The discolouration extended past the first fixing so I therefore deemed that cleaning and applying an elastomeric coating would be insufficient. I recommended replacing the roof sheet in its entirety.

Answer 188

I undertook a ground level visual inspection externally and internally prior to using the pole camera, this allowed me to identify any areas requiring closer investigation such as where I noted some internal water ingress

Answer 189

As the joists affected were structural members, I consulted a structural engineer as it is out the scope of my competence to advise on structural repairs.

Answer 190

I measured the crack at a few different points including the widest point, and referred to the table in BRE 251. On identifying

Answer 191

Typically at brief/fee agreement we will identify any services that are definitely required, and what circumstances may require us to instruct specialists. Management of these sub-consultants is included in the fee proposal so it is not misleading.

Answer 192

Where the sheets have been cut in manufacturing creates an exposed untreated metal edge. Lacking a protective layer of coating, this edge is particularly vulnerable to corrosion caused by weathering

Answer 193

Degradation of the sheet leading to water ingress and loss of integrity of the sheet

Answer 194

- Clean and applying protection - Clean and apply elastometic coating - Replacement, if gone past the first fixing

Answer 195

Propping is generally necessary as a precaution when the joist requires repair or replacement. In this instance due to the rot I had concerns about its load bearing capacity and as it was being actively used by the public. The propping also allowed more time to specify the method of repair and assited with undertaking those repairs.

Answer 196

It would depend on the structural engineers design, but things i would consider are: - Compatible and suitable replacement - Suitably fixed/bound eg fasteners, dowels and adhesives - Testing prior to removing the props

Answer 197

Where there is a source of moisture - Defective roof coverings - Thermal bridging - Interstitial condensation ('between layers of construction')

Answer 198

I referred to bre 504. As the step flashing was missing in areas, in order to bring the entire element into the same lifecycle to save on costs i proposed replacing the entire flashing

Answer 199

It helps you identify the implications, such as aestetic, serviceability (e.g moisture ingress) and structural

Answer 200

- Defective finish - Lifecycle replacement - Defective rainwater goods overdoing the exposure to water increasing rate of corrosion.

Answer 201

I would recommend a sub-consultant that has undergone a pre-qualification to vet their experience and capability and ensure they have the capacity to undertake the service

Answer 202

BRE 504 and 297

Answer 203

Firstly I undertook a visual inspection - I noted - Damp musty smell - Darkened wood - Cracking along the grain lines due to shrinking

Answer 204

Remove the source of moisture Identify the stage and progression Identify the locality of the issue Recommend replacement (carcassing timber)

Answer 205

This prevented any further deterioration which may reduce the effectiveness of the specified repair, and also allowed the timber to dry out to take an accurate observation of the area affected

Answer 206

- Measuring at its widest parts - Look for any obvious causes - Identify when people first became aware of the crack

Answer 207

5mm-15mm. Weather tightness is often impared but can be remediated locally through repointing and limited opening up

Answer 208

ROC = Stay within my competence Strutural = safety implications

Answer 209

- Specialist viewpoint - Can be actioned quicker by taking authority - Access to tools - Allows BS and SE to work alongside eachother and create action for the client quicker

Answer 210

An aluminium step flashing. It was secured with flashing strips and chased into the mortar 25mm at each step.

Answer 211

Thermal bridging or water ingress

Answer 212

porulation germination hyphal growth (vegetative growth) reproduction

Answer 213

They produce toxins which can be harmful to health

Answer 214

Mould requires four factors for growth: Mould spores - always freefloating Food - anything that contains carbon Appropriate temperature - very wide Moisture - 70% humidity

Answer 215

cement, sand, stone, and water 1 : 2: 3

Answer 216

* Identified by noting rust staining and delamination of concrete. Examining the rebar will show localised breakdown where there is pitting. * Can carry out localised repairs however, if the chlorides are in the body of the concrete, it will continue to deteriorate. Better solution which costs more is cathodic protection where an external anode is connected to the metal and the passage of the current stops corrosion.

Answer 217

Erroded holes, typically in concrete

Answer 218

protection of a metal structure from corrosion from water by making it act as a cathode (negatively charged)

Answer 219

Single ply

Answer 220

Tapered insulation

Answer 221

Timber furrings but this is mainly used in primary construction

Answer 222

Min 150mm size.

Answer 223

Weep holes

Answer 224

Specify a protection cream like stormdry

Answer 225

- DPC level* - Openings and penetrations - Roof/wall junctions - Intermediate levels

Answer 226

The cavity below the DPC should be filled with concrete up to a level of 225 mm below it. Failing to add concrete properly can make the blockwork collapse inward. After filling the cavity with concrete, you can add a cavity tray to the wall.

Answer 227

- Lead - Rigid plastic - Bitumen

Answer 228

1 part cement, 2 parts sand, 3 parts gravel, and 0.5 part water.

Answer 229

To fix cracking

Answer 230

Part A Building Regulations: Structure. Table 5

Answer 231

50mm to 75mm = 200mm tie 76mm to 100mm = 225mm tie 101mm to 125mm = 250mm tie Typically you take the nominal length, add 125mm and select the nearest stock length

Answer 232

Type A - heavy duty Type B - general purpose Type C - basic duty Type D - light duty Above to BS 6697 Selected on the basis of design loading and cavity width.

Answer 233

To prohibit vertical and horizontal planes from moving

Answer 234

Its helical shape is designed for installing into existing structures. There are more heavy duty and affordable alternatives for use in a base build.

Answer 235

Type 1 as it can be used in any building of any size

Answer 236

2.5 per m2. 900mm (H) x 450mm (V) centres. Evenly distributed and around openings (V=225mm).

Answer 237

Due to increased expansion action seasonally in timber, more wall ties should be used. 4.4 pm2 for wind speeds up to 25m/s (90km/h), increase centres if wind loading is to be more severe.

Answer 238

Non-ferrous= iron. Steel is an iron alloy.

Answer 239

I specified an aluminium step flashing as it was like-for-like with what was existing.

Answer 240

I considered a lead stepped flashing but as lead is heavier than the existing aluminium I considered it to have compatibility risks.

Answer 241

- Burnt clay brick - Engineering brick - Concrete brick - Sand lime brick

Answer 242

- Lime mortar is more gentle and is more flexible once cured. It also intrinsically has better waterproofing. It is therefore more sympathetic to softer masonry like sandstone. - Cement mortar is stronger and may be used on more indsustrial high rise buildings or brick slips.

Answer 243

1:3 cement sand. More sand = weaker. Ratio of water depends on volume but for 1kg you would want 0.4 parts water.

Answer 244

External metal sheet, fixed to a support rail, insulation embedded within spacer framework, VCL, deck or purlin

Answer 245

A cesspit does not have an outlet and is required to be drained periodically eg once a month

Answer 246

It is designed to support external masonry façades above openings and at horizontal movement joints. They are generally fixed to concrete or steel frames and adjustment is provided in every direction to allow for tolerance in the structural frame.

Answer 247

The recesses allow mortar to seep through for extra binding capabilities. They also have a higher compressive strength as well as are less water absorbing

Answer 248

BS EN1996 design of masonry structures. This recommends a maximum of 12m of spacing.

Answer 249

A contraction joint is formed, sawed, or tooled groove in a concrete structure to create a weakened plane to regulate the location of cracking resulting from the dimensional change of different parts of the structure. A construction joint is naturally formed when old concrete is poured next to new concrete

Answer 250

- The sub-base - The visqueen dpm - If reinforcement was required - Movement joints

Answer 251

-protect the underside of the slab from attack by dampness and aggressive salts -prevents the poured concrete from de-watering and drying out too quickly, affecting strength and cracking

Answer 252

Propping is a system of structural members used temporarily to support loads during construction.

Answer 253

Most commonly associated with - foundation issues - differential movement: different building materials expand or contract differently in reaction to changes in temperature and moisture moisture - bowing walls .

Answer 254

- Heave - Settlement - Subsidence

Answer 255

Identifies rebar in concrete

Answer 256

- If walls on floors follow the same path - Refer to as built drawings - Thicker (300mm?)

Answer 257

Doc H and BRE guides/BS

Answer 258

Had we not installed a DPC, I might have expected sulphate attack

Answer 259

Carcassing timber

Answer 260

A gypsum plaster. I would specify a lime plaster in a historic property or a poorly ventilated property