Building Pathology Flashcards

Question

What indicators would you look out for if you suspect dry rot ?

Answer 1

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 2

Ait can pass through masonry

Answer 3

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 4

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. Refer to BRE digest 251

Answer 5

Vertical, larger at the top than the bottom

Answer 6

BRE Digest 251 - Assessing cracks in houses. This defines the inspection and cracking sizes to reference

Answer 7

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

Answer 8

Elm Oak Willow Poplar Hawthorn - NHBC

Answer 9

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

Answer 10

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 11

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 12

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

Answer 13

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 14

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 15

Slipped slates * blocked gutters * failed tanking systems

Answer 16

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 17

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. Concrete carbonation is a chemical process in which carbon dioxide (CO₂) from the air reacts with calcium hydroxide (Ca(OH)₂) in the concrete to form calcium carbonate (CaCO₃), reducing the concrete's alkalinity. The lowered pH can lead to corrosion of the steel reinforcement within the concrete, as the protective oxide layer on the steel is compromised.

Answer 18

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 19

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

Answer 20

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 21

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 22

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 23

Assessment of damage in low-rise buildings

Answer 24

Installing wall tie in existing construction

Answer 25

Replacing wall ties

Answer 26

Oak Willow

Answer 27

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 28

It is remedied by removing the delaminated concrete, cleaning the re-bar and patching the concrete.

Answer 29

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 30

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 31

BRE444 Hammer testing (Tests compressive strength ) Visual inspection Magnet cover testing (detects the steel ) Phenolphthalein test (High PH =Pink, low PH = no colour change - carbonated concrete)

Answer 32

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. 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 33

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 34

The extent of the defect, when the existing roof was recovered, the approximate life span, the cost, timing, clients intentions for the building. Significant roof repairs will trigger the need to comply with regulations - 50% rule.

Answer 35

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 36

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

Answer 37

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 38

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 39

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 40

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 41

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 42

Speedy carbide meter or protimeter.

Answer 43

Penetrating Rising Condensation ( + interstitial condensation)

Answer 44

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

Answer 45

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

Answer 46

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 47

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 48

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 49

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 50

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

Answer 51

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 52

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 53

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 54

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 55

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 56

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 57

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

Answer 58

Insect attack Dry rot Wet rot Structural defects

Answer 59

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 60

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

Answer 61

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 62

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 63

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 64

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

Answer 65

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 66

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

Answer 67

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

Answer 68

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 69

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 70

Chrysolite - white - most common asbestos in buildings, Corrugated asbestos cement sheets. Amosite - brown - found in fire retardant materials Crocidolite - blue - pipe insulation, plastics and cement products.

Answer 71

Horizontal cracking every 5 or so brick courses. Corrosion of old steel ties causes 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 72

Loss in colour, caulking and delamination

Answer 73

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 74

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 75

Herbaceous perennial plant.

Answer 76

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

Answer 77

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 78

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

Answer 79

Injected with herbicide or excavated with the roots and disposed.

Answer 80

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 81

- asbestos - concrete defects - cold roof - wood wool slabs

Answer 82

- failed on lack of DPC - insufficient foundations - poor ventilation to floor voids - damp penetration - lead pipework

Answer 83

- Cut edge corrosion - plastisol degradation - Asbestos use in insulation

Answer 84

- Sulphate attack - defective flashing - removal of stack below

Answer 85

Erosion, acid attack, salt crystallisation could all cause the stack to lean. BRE good repair 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 86

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 87

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 88

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 89

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 90

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 91

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 92

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 93

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 94

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 95

clay expands = heave like., sand washes away

Answer 96

Concrete Carbonation Symptoms: Color change (phenolphthalein test) Surface dusting Fine cracking Corrosion of reinforcement (rust staining, spalling) Tests: Phenolphthalein test Depth of carbonation measurement Sulphate Attack Symptoms: Expasion and cracking (map cracking) Surface scaling Loss of strength White efflorescence Tests: Visual inspection Chemical analysis (XRD, SEM) Core sampling and testing Alkali-Silica Reaction (ASR) Symptoms: Network cracking Gel exudation Discoloration Expansion Tests: Petrographic analysis Chemical tests (SEM-EDS) Expansion testing (concrete prisms, mortar bars)

Answer 97

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 98

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 99

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

Answer 100

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 101

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 102

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

Answer 103

Cathodic protection Corrosion inhibitors Epoxy resin repairs

Answer 104

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 105

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 106

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 107

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 108

Refer to approved document H section one and look at table 1 = for the calculation of drained area and then table 2 = Gutter sizes and outlet sizes

Answer 109

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 110

Fix the specific issue relating to the water ingress

Answer 111

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 112

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 113

Spore Hyphae Mycelium Fruiting Body

Answer 114

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 occu

Answer 115

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 116

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 117

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 118

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 119

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 120

Refer to BRE Gidence Subsidence damage to domestic buildings. 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 121

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 122

Cracks occur at the junction between new elements - Differential movement between two elements

Answer 123

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 124

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 125

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 126

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 127

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 128

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

Answer 129

Roof and wall abutment

Answer 130

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 131

Asbestos, brick slips, Raac, lead paint, wood wool, horse hair plaster, silica dust , Polyurethane foam, high alumina cement

Answer 132

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 133

- horizontal cracks in bed joints of brickwork every 6- 8 courses (usually external ) long with some diagonal cracking - Damp patches internally where there may be cold bridging in the tie position - Walls leaning or bulging (typically gable walls ) - Upward movement can result in an upturning of the roof, particular 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 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 134

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 135

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 136

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 137

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 138

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 139

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 140

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

Answer 141

A 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 142

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 143

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

Answer 144

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

Answer 145

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 146

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

Answer 147

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

Answer 148

Interstitial condensation Wood boring insect attack Roof spread Water ingress

Answer 149

Concrete Carbonation HAC Alkali Silica Reaction Chloride Attack Sulphate Attack

Answer 150

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

Answer 151

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 152

Water ingress

Answer 153

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 154

Moisture, food, fungi

Answer 155

Cut back 1000mm from affected area

Answer 156

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

Answer 157

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 158

Pourous Silica containing Shallow rebar

Answer 159

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

Answer 160

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 161

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

Answer 162

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

Answer 163

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

Answer 164

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

Answer 165

Thermal bridging or water ingress

Answer 166

They produce toxins which can be harmful to health

Answer 167

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

Answer 168

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

Answer 169

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 170

Eroded holes, typically in concrete

Answer 171

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

Answer 172

Min 150mm size.

Answer 173

Weep holes

Answer 174

Specify a protection cream like stormdry

Answer 175

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

Answer 176

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 177

Lead Rigid plastic Bitumen

Answer 178

Part A Building Regulations: Structure. Table 5

Answer 179

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 180

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 181

o prohibit vertical and horizontal planes from moving

Answer 182

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 183

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

Answer 184

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

Answer 185

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 186

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

Answer 187

Burnt clay brick Engineering brick Concrete brick Sand lime brick

Answer 188

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 189

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

Answer 190

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

Answer 191

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

Answer 192

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 193

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 194

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

Answer 195

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 196

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 197

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

Answer 198

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 199

Heave Settlement Subsidence

Answer 200

Identifies rebar in concrete

Answer 201

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

Answer 202

Doc H - table 1 and 2 - and BRE guides/BS

Answer 203

To ensure there is not a build up of gases