Building Pathology Flashcards Preview

General Knowledge > Building Pathology > Flashcards

Flashcards in Building Pathology Deck (71)
Loading flashcards...
1
Q

What are the types of timber decay?`

A

Rot (occurring due to damp timbers)

Wood boring insects (subsequently occurring due to damp timbers)

2
Q

What are the Dry Rot Stages and What moisture Content cannot it form?

A

Its the most serious form of fungal decay in buildings. It can spread through a complete building and destroy the fabric of the property, it can start affecting timber at a moisture content above 20-40%.

Has Four Stages

Stage 1 - Spores - Present everywhere - Dry rot begins its life as tiny spores, these spores remain inactive until they come in contact with timber and enough moisture to make them active. Typically 20 percent moisture content is enough to make the fungus spores start to attack timber.

Stage 2 - Hyphae - A hypha is a long branching structure of a fungus – typically what fungus spores will grow into if left untreated. Dry rot hyphae are identifiable by the white fine stringy strands that become visible both inside and outside the timber. These strands allow the fungus to grow rapidly inside the timber.

Stage 3 - Mycelium The mycelium is the name given to a collection or mass of hyphae. Mycelium’s are the vegetative part of fungi and can spread very far in masonry and behind wall plaster in search of timber to attack, so you should be sure to treat any infected timber quickly. If left untreated for too long mycelium will grow and spread-out into a thick mass, before turning into its fourth and final stage

Stage 4 - Fruiting Body - The fruiting body is the final stage of the Dry Rot fungus’s life cycle. The fruiting body takes on a mushroom like appearance and it produces Dry Rot spores that it emits from the surface to be carried along by air currents out into the air. Fruiting bodies are formed by the fungi when it detects changes in its conditions. The fruiting body is created as an attempt to preserve the lifespan of the fungus by emitting spores to other areas of the property, effectively starting the Dry Rot fungus life cycle all over again.

3
Q

Tell me about wet rot?

A

Identification:

Dark brown staining on the timber.
Splitting or longitudinal cracking along the grain of the timber. Cuboidal cracking can occur but not as deep as dry rot.

Fruiting body rarely found though can be a honeycomb or knobbly, thin and olive in colour.

A damp, musty smell.
Timber that is damp to touch.
Hyphae is thin brown/black thread-like
Mycelium rarely occurs.
May have turned into shredded weat.

Moisture content of 45%-60% and between temperatures of -30 to 40oC

Wet rot stays to the damp area and does not spread like dry rot.

If the timbers are in reasonable condition they should be left to dry out in accordance with BRE Good Repair 12.

4
Q

What are the wood boring insects?

A

They are species, including certain beetles (‘woodworm’), that feed on wood, usually which is damp/moist and may seriously damage building timbers. In the UK, they include:

The common furniture beetle
Death watch beetle
House longhorn beetle
Powder post beetle.

Can be identified based on their flight holes and frass, refer to BRE guide or Hollis Surveying Building’s to identify.

5
Q

Why do insects attack timber?

A

Wood-boring insects only establish themselves where dampness exists. Beetle damage in buildings is usually confined to sapwood, although heartwood is vulnerable too if fungus is present. (usually over 18%)

Good preventative maintenance and moisture monitoring can avert dampness and, therefore, ensuing damage caused by wood-borers. However, over-reliance should not be placed on surface readings from electrical moisture meters. False readings may occur, for instance, because of surface deposits or past chemical treatments.

6
Q

How do you identify wood boring insect attack on timber?

A

Boreholes - Different sizes/shapes for different infestations

  • If active infestations have sharp rather than round edges
  • If active the interiors and bore dust (‘frass’) are not dark but the colour of freshly-cut timber.

Where signs of beetle activity are ambiguous, this can be resolved by monitoring for a year. Water-soluble glue is used to cover a group of holes with acid-free tissue paper, through which beetles will punch their way if present. Alternatively, holes can be clogged with wax polish.

7
Q

What are the types of water ingress/dampness?

A

Rising Damp
Penetrating Damp
Condensation

8
Q

What is rising damp?

A

Water rise’s upwards due to capillary action between the pores of porous building materials such as brickwork.

Natural osmosis also occurs which causes water to move from materials of lower to higher salt concentrations.

The movement of water is therefore dependant on the size and distribution of the pores within the wall and the presence of soluble salts.

9
Q

What are the effects of rising dampness to a building?

A
  • Rotten skirtings etc.
  • Damaged suspended timbers lead to ultimate failure.
  • Rot
  • Increased vapour levels may pose a risk of condensation.
  • External walls may be compromised through this saturation by frost action and efflorescence (salt crystallisation).
10
Q

Common reasons for the presence of rising damp?

A

Absence or failure of DPC

The 1875 Public Health Act introduced DPC as mandatory. Therefore property’s prior to then may not have a DPC.

Older houses may have used a slate DPC which may have cracked/failed. Bitumen or lead DPC’s may have flattened/become brittle. Injected DPC’s may have failed due to in-continuous banding.

Bridged DPC’s from raised ground levels externally

Hard exterior surfaces will not allow evaporation of water from the ground and may cause surface water to run back towards the house.

11
Q

What is Penetrating Damp?

A

Penetrating damp is caused by water leaking/penetrating a building’s envelope this can be\through walls, roofs, windows, openings or breaches etc.

It tends to happen as a result of failures to a buildings envelope.

The rate of which the dampness occurs will depend on the severity of the conditions such as the internal pore structure of the material, how much will evaporate into the air prior to reaching its internal surface.

12
Q

Common reasons for the presence of penetrating damp?

A
  • Absence or failures in damp-proof trays in cavity’s
  • Direct entry through open joints in construction
  • Absence or failure of flashings
  • Absence or failure of drip
  • Damaged service/plumbing pipes.
  • Bridged cavities.
13
Q

Tell me about condensation

A

When air becomes saturated at 100% RH, water vapour will condense on cold surfaces creating water droplets which is known as condensation.

Ideal conditions: 50% alongside sufficient heating to minimise saturating the air.

Humidity:
Humidity is the concentration of water vapour in the atmosphere.

Relative humidity is the amount of water vapour present in air expressed as a percentage against the the amount needed for saturation at the same temperature.

Colder air can hold less water vapor than hotter air. Therefore heating the property is critical.

Absolute humidity is termed as the pure amount of water in the atmosphere.

14
Q

So how does condensation affect buildings?

A

Mould growth and water vapor condenses on cold surfaces forming droplets.

High levels of vapour are increased from day to day activities such as cooking, washing, bathing etc.

Modern standards such as double glazing, draught proofing will disable some ventilation within the building which will aid condensation.

Human factors including not heating the property will also aid condensation.

15
Q

What is radon?

A

Radioactive gasses emitted from the earths surface which can adhere to dust particles and once breathed can cause respiratory issues such as lung cancer.

Usually found most in basements or underfloor voids where the building has been built on areas underlain with granite.

16
Q

Tell me about corrosion?

A

Corrosion is a chemical reaction between the environment and a ferrous metal. Direct oxidation of the metal occurs which leads to the formation of Hydrated Iron Oxide which gives the known red layer of rust.

The rust offer some protection but when it flakes off, the metal is exposed more resulting in further corrosion. The oxidation also results in the volumetric expansion of the metal. (wrought iron is capable of expanding 7x)

Direct oxidation:

  • Electrochemical reaction that occurs when the metal is in the presence of either:
    1. Water
    2. Oxygen
    3. Electrolyte (Electrically conducting solution, can be iron)
17
Q

Tell me about Sulphate Attack?

A

Sulphate salts (typically in calcium, magnesium or sodium) are naturally present in the ground, ground water and various building materials such as hardcore/brickwork etc.

When these salts come in contact with cementitious materials such as renders, mortars, concrete etc under damp conditions, these will react and cause expansion of the cementitious product and cause spalling, cracking, displacement.

Steps can be taken to reduce the likelihood of this through using sulphate resisting Portland cement, DPC’s, Coatings, Minimising contact etc.

Sulphate attack is common within older properties due to the lack of damp proofing and the use of ordinary Portland cement, which is vulnerable to sulphate attack. Also, the use of recycled ashes from burnt fossil fuels / industrial furnaces, as hardcore fill can be very high in sulphate content, causing a reaction with the cement when used beneath the floor slab.

A chemical analysis of soil borings should be undertaken during the design phase of any project involving concrete in contact with the soil to check for the presence of sulphates and determine if they’re aggressive.

18
Q

What is carbonation, how would you investigate and treat it?

A

Concrete is naturally alkaline (pH 13) due to the presence of calcium hydroxide, this alkalinity offers a protection to the embedded steel reinforcement from corrosion by acting as a passive layer.

As soon as concrete is poured, it is under attack from pollutants and acidic gasses in the atmosphere (carbon dioxide, sulphur dioxide or sulphur trioxide) enter the pores, cracks or breaches of concrete.

The gasses react with the alkaline material which creates acidic solutions which reduce the alkalinity of the concrete which is known as carbonation. This offers little protection to the steel reinforcement which causes corrosion. Corroded steel can expand up to 7x its volume causing further cracking to the concrete and may lead to structural problems.

Identification: The first time that carbonation is evident is usually when the concrete around the reinforcement spalls and cracks. Over time this will worsen and expose the corroded reinforcement.

Investigation: Carbonation depth is assessed using a solution of phenolphthalein (FEE-NOL-FEE-LANE) 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.

BRE Digest 444, Part 3 provides guidance on the appropriate repairs:

  1. Undertake hammer test to establish all loose areas of concrete.
  2. Hack off loose concrete from around the exposed steel bars.
  3. Grit blast to remove corrosion and other deposits from the exposed steel reinforcement including hidden faces, to the back of the steel bars, and to intersections of bars.
  4. Treat the steel re-bar and apply a corrosion inhibitor and bar primer to the surface of the reinforcement.
  5. Patch repair areas of concrete using a cementitious material and sand, and a polymer dispersion.
  6. Apply protective anti-carbonation coating.

NOTE: It is possible to undertake Re-Alkalisation to the Concrete by passing an electrical current through the concrete to the reinforcement using an externally applied anode that is attached to the concrete’s surface

19
Q

Tell me about thermal movement?

A

Materials will usually respond to thermal movement by:

  • When heated expansion occurs (increase in size)
  • When cooled contraction occurs (decrease in size)

This is particularly prominent during seasonal change.

When two different materials are bonded together differential thermal movement will occur and the weaker of the two materials will fail.

20
Q

Tell me about moisture movement in building materials?

A

Porosity - The absorption of water into porous materials usually increases the volume of the material with a loss of such water resulting in a decrease.

Materials such as mortar will result in a decrease during the drying out as they require more water in their manufacture.

Materials such as soil will expand with moisture and decrease with a loss.

21
Q

Tell me about efflorescence?

A

Efflorescence occurs where dissolved salts in porous materials evaporate. During the evaporation process the salts will concentrate to the surface where they will crystallise and form deposits known as efflorescence.

This usually occurs in new brickwork, though in older installations this will indicate a presence of consent saturation.

22
Q

Tell me about lichen, mosses and algae?

A

These grow on surface materials which are usually rich in salts.

Play a natural part of the eco system in the decomposition of materials.

The biological growths may cause micro-cracking to some materials such as tiles or stonework and algae can block rainwater goods resulting in other issues.

23
Q

Tell me about Settlement?

A

Settlement usually occurs in the early stages of construction work and is usually associated with compression of the soil due to the increased new loads of the soil due to the installation of a building/structure.

24
Q

Tell me about Subsidence?

A

Subsidence is the downward movement of the buildings foundation caused by a volumetric change of the soil which may be caused by erosion, mining, change in water level, leaking drains, trees taking too much water causing shrinkage, Clay soils becoming shrinkable.

Cracks usually occur in stepped form and larger at the bottom and smaller at the top. sometimes get horizontal cracking too.

Rectified by underpinning, fixing leaking drains, pruning trees or mass filling to the eroded soil. - MUST RESTORE EQUILIBRIUM IN THR SOIL

25
Q

Tell me about Heave?

A

Heave is the volumetric expansion of the soil beneath the building foundation which is usually swelling of the subsoil this can be caused by:

  • Cut down/pruned trees
  • Damaged drains
  • Seasonal action on the ground.

Cracks usually occur in stepped form and smaller at the bottom and larger at the top.

Usually resolved by putting the ground back into equilibrium:

  • Fixing leaking drains
  • Allowing trees to grow by not pruning as frequently, this will result in them using more water.
26
Q

Tell me about landslip?

A

Landslip is the sudden movement of soil.

This could be attained due to a slope or gradual creep or could be the collapse of near mine.

27
Q

Tell me about failed foundations?

A

Movement may also occur through the failure of a foundation i.e. heave or subsidence

28
Q

What are in-direct defects in buildings?

A

Poor design
Poor workmanship

Change of requirements
Inappropriate alterations

29
Q

What is the best practice initial process of detecting/identifying defects?

A
  1. Understand the construction and services of the building
  2. Understand the use of the building
  3. Any changes to the building
  4. The original building use
  5. Identify the current issue.
  6. Process any potential defect.
  7. Determine the likely defect.
  8. Monitoring if required and confirm the defect.
30
Q

How do you differentiate between a cavity and solid wall

A

Look at the brick bond

Measure the thickness at window or door openings

31
Q

Your client wishes to purchase a 1970’s industrial building, what particular defects would you look out for?

A

Thermal Insulation (If any!) – Identify type with LPCB stands for Loss Prevention Certification Board. Flammable core.

Services (electric/gas)

Deleterious materials.

32
Q

What are the key indicators of cavity wall tie failure?

A

Non-intrusive visual inspection:

Cracking in bed joints
Bulging or movement of the walls.

Invasive inspection would be required to determine condition.

33
Q

What do the lead codes refer to?

A

Lead codes refer to the thickness and use of lead to specific activities.
The latest British / European Standards now specify Colour Markings.

Code 3 = Green = Used for soakers
Inbetween 3 & 4 = Yellow = Used for soakers
Code 4 = Blue = Flashings and small sized flat roof coverings
Code 5 = Red = Flashings and medium sized flat roof coverings
Code 6 = Black = Large flat roof coverings
Code 7 = White
Code 8 = Orange

34
Q

Please tell me about High Alumina Cement in Buildings?

A

High Alumina Cement was popular for use in concrete between 1950-1970 due to fast curing period; about eighty percent of its ultimate strength is achieved at the age of 24 hours.

It was banned in 1976 due to various failures. Usually found in pre-cast beams and lintels.

HAC gradually converts and re-arranges its composition properties which results in loss of strength. It also reduces its resistance to chemical attack when saturated which may cause ASR or Sulphate Attack.

The process occurs at room temperature and is accelerated by an increase in temperature. The extent to which this occurs is largely a function of the original water/cement ratio, i.e. the effects are minimised by a low water/cement ratio.

Instruct SE to determine condition, may be fine to leave and control temperature with the elements monitored. Or replace.

35
Q

What are the common causes of subsidence?

A
  • Eroded soils (shrinkable clay or leaking pipes washed away)
  • Tree overgrown taking up too much water from ground causing clays to shrink.
  • Instable/change in ground conditions (failed mines or near excavations)
  • Failed foundations
36
Q

What is Alkali Silica Reaction? and how can it be rectified/avoided?

A

AKA: Concrete Cancer - A reaction between the alkali in the cement which reacts with silica in the aggregates, when in the presence of water/moisture.

Jelly-like/Gel forms around the aggregates, absorbing water and expanding thus causing cracks, exposing any reinforcement to water penetration and oxygen and results in corrosion causing further defects.

Problem can be avoided by USING LOW ALKALI CEMENT or by AVOIDING CHEMICALLY REACTIVE AGGREGATES.

Treatment: Replace the concrete if it has become structurally defective with concrete, steel or timber replacements taking the advice of a SE.

37
Q

What are the common defects you would find with a timber pitched roof?

A
  • Water ingress by Slipped tiles, inadequate overlaps
  • Wet Rot
  • Dry Rot
  • Woodworm attack
  • Defective flashings and/or rain water goods.
  • Inadequate ventilation
  • Overloading structure due to replacement of original roof covering with heavier product i.e. slate to concrete tile.
  • Bowing/Sagging between structural members due to failed lateral restraint.

Are the trusses evenly spaced 600mm centres?
Is wind cross bracing present?
Are the trusses fixed to the wall plates/hangers?

38
Q

Discuss the likely causes of staining to chimney breasts and the remedial work?

A

Is the chimney exposed on an gable wall? Is it protruding or within the wall?
Rain penetration / Dampness at changes of direction

Salts / efflorescence left over on surface, attracts waters, moisture staining.

Staining internally = Lack of ventilation to the stack. Water penetration or condensation.

Deposits from the use of the fire.

Nb. Problems occur when where the flue liner does not terminate with the Chimney pot. Moist air condenses against the flue above the liner and then trickles back into the building

39
Q

What might a sagging roof on a Victorian building indicate?

A

Replacement of the original roof covering with a new heavier roof covering (concrete interlocking tile).

40
Q

What sort of ways might dampness enter a building?

A

Penetrating Damp
Services leak
Rising Damp
Condensation

41
Q

What defects are you likely to find with a flat roof?

A

90% of roof leaks occur due to faulty detailing. BRE

Bituminous Felt systems
Blisters – Bitumen not hot enough when applied (Shiny Film). Over cooked bitumen (Charcoal crusty appearance). Surface of felt was damp. Areas of not bitumen applied.
Poor construction and detailing – Upstands, outlets, service penetrations
Poor material quality – cheaper domestic roofing felt
Damaged lap joints
Premature failure due to lack of solar protective coatings
Excessive deflection, springiness or sponginess. (Saturated insulation)
Blocked rainwater outlets / general ponding
Movement at changes-in-direction / junctions

Mastic Asphalt
Entrapped moisture causing blistering,
Crazing of the surface
Lack of adequate movement joints – Cracks
Upstand sagging or cracking
Flashing details not correct / missing. Not 150mm minimum
Other materials placed on surface. i.e. Tiles – indent themselves, or trapped moisture under.

Service plant fixings, penetrations, point loading.

42
Q

What is blistering (in relation to a flat roof)? What are the likely causes of blistering? And what remedial methods would you advise?

A

Occurs to Bituminous Felt and Mastic Asphalt roof coverings.

The likely cause is entrapped water or condensation trying to evaporate. Alternatively, incomplete bonding of layers.

If blisters are small, inspect regularly. If they grow then further investigation of condensation problem is needed.

These defects do not necessarily give rise to leaks, but they do need careful examination.

43
Q

What are deleterious materials? Please name 3 and give examples of the problems experienced from them.

A

A Deleterious Material is that may or does have a harmful or detrimental effect on people and/or buildings. All materials, if used incorrectly can perform badly.

Asbestos – Health risk through inhalation of its microscopic fibres.
High Alumina Cement – Strength of concrete can decrease significantly and fail catastrophically
Lead pipework. Poisoning in drank.

44
Q

How would you tell the difference between rising damp and condensation with a moisture meter

A

Rising Damp = Tide mark staining which was close to or directly above the floor or skirting level. Accompanied by efflorescence, staining, or wet and damaged decoration.

Condensation = Surfaces with a reasonable moisture content and dry.

45
Q

What is nail fatigue?

A

Also called nail sickness. The nails fixing tiles or slate to a roof structure decay over a period of time as a result of corrosion of the metal aided by condensation forming on the back of the tile or slate surface or by water penetration.

Many repairs which are carried out by inserting replacement tiles/slates in a nailed roof rely on hanging the replacement tile upon the lower tile, placing extra weight on the lower units, thus speeding up further failures.

Slate roof that is over 40 or 50 years old is liable to suffer continual failures until the surface is stripped off and the tiles re-nailed.

46
Q

What defects might you find with profiled steel cladding?

A

Under creep or spot corrosion
Impact damage
Soiling
Redundant holes and fixings.

47
Q

Why is it important to promote rapid drying of walls?

A

Saturated walls are susceptible to frost damage as the internal moisture freezes and expands. Rendered surfaces will retain moisture for longer and are then susceptible to delamination by frost damage.

48
Q

What is the average drying time for a Solid wall?

A

More than a year.

49
Q

How does a protimeter work and What are the limitations of using a protimeter when diagnosing damp?

A

It measures electrical resistance between the two metal probes. Water is a conductor so can measure the moisture content.

Limitations are that moisture pockets etc in materials can give a false readings.

Only calibrated for timber but can give a good indication of other materials.

Cannot differentiate free moisture and hygroscopic salts.

50
Q

Tell me about BRE 251?

A

0 – hairline – no action
1-Fine cracks up to 1mm - decorate
2-5mm cracks – fill cracks
3-5-15 (0r several 3mm) - repoint
4-Extensive damage (15-25mm) – major repairs
5-structural damage (25+mm) – major repairs

51
Q

What is a Latent defect?

A

Defects which existed prior to practical completion of a project but remained undiscovered at that time and the defect became apparent during the policy (i.e. 12 years under deed).

Can get different insurance policies for design, workmanship, materials etc. The Latent Defect insurance policy is called Decennial Insurance which usually covers up to 10 years.

52
Q

What is an inherent defect?

A

An inherent defect is one that comes with the property.

i.e. cut edge corrosion on a metal roof due to not coating the edges.

53
Q

What are some typical defects to a pre-1900 property?

A

Failure/lack of DPC causing rising damp, efflorescence, decay of timber skirting

Poor ventilation of roof void causing decay of timbers

Roof re-covered in concrete/clay tiles could be subject to an overloading roof as originally intended to be slates.

Lack of restraint to walls could cause bowing, displacement or bulging.

Alterations could have led to the removal of structural elements particularly within the roof void.

Lead water mains

54
Q

What are some typical defects of a 1900 - 1939 property?

A
  • Wall tie failure to cavity walls, bulging brickwork or horizontal cracking
  • Nail fatigue
  • Lead water mains
  • Failed DPC
  • Outdated services - potentially dangerous
  • Timber decay
55
Q

What are some typical defects of a 1945 - 1970 property?

A

Poor lateral restraint to trusses - roof spread to walls, bulging walls.

Poor cavity trays - water ingress

Wall tie failure, as before bulging brickwork or horizontal cracking.

Poor mortar jointing - water ingress/decay of cavity.

56
Q

Tell me about Fungai?

A

Fungai lives on dead organic materials and plays a natural role to breakdown the dead organic material which includes timber. Timber is usually too try for this to occur however if the moisture content is increased it is not.

Fruiting bodies are often the first visual instance of the problem.

Wood rotting Fungai is familiarly classified as Dry or Wet Rot.

57
Q

What is the only true dry rot? How many wet rots are there?

A

Serpula Lacrymans. There are many wet rots.

Major wet rot in UK is Coniophora Puteana (Fruiting body similar to dry rot)

58
Q

Tell me briefly about the woodworm infestation process in timber?

A
  1. An adult female beetle lays eggs in cracks or end grains of timbers.
  2. The eggs feed on timber creating tunnels and frass.
  3. Once fully grown the the eggs emerge as adults leaving behind flight holes.

Species:
Common furniture beetle, death-watch, bark, house long horn, powder post.

59
Q

Tell me about Japanese Knotweed?

A

Introduced in UK In 19c,

Highly invasive plant and hard to control due to its root system which allow the plant to survive when all of the sections above ground is removed. Therefore is able to cause damage to floors and foundations.

Identification:
Green leaves and white flowers appearing in late autumn. Long singular stems.

Remediation:
Can be killed by chemical treatment but can take multiple treatments and up to 3 years.

Can be killed by controlled burning.

Can be buried and a geo-textile matting installed at at least 5m but care must be taken.

60
Q

Tell me about Giant Hogweed?

A

Thin stem with white flowers, often 3-5m.

Poisonous if the stem releases sap which burns the skin and reduces your skin to resist UV light.

61
Q

How do you cure Condensation?

A

Reduce moisture generation (i.e. lifestyle, household activities)
Provide ventilation (to replace saturated air with clean air)
Provide adequate heating (to increase RH threshold)

62
Q

Tell me about composite cladding panels?

A

Cladding panels which are sandwiched together off-site. (MMC).

Polystyrene EPS systems are bad as these are thermal insulation systems within the cladding which is highly flammable. Sun Valley Poultry case in 1993 highlighted this to the industry. Insurers may not insure the building.

Aluminium Composite Material (ACM) Cladding.
Banned on residential buildings over 18m high - action came from Grenfell.

63
Q

How can Dry Rot be identified?

A

Deep cuboidal cracking to the timber, darkening of the wood, dry and parched looking.

20-40% moisture content (can survive in as low as 14%)

Dry rot has a damp mushroom smell. It may also smell musty.

The fruiting body is soft, fleshy and looks like a pancake or a bracket – often orangey in colour, rust coloured in the centre, with wide pores, red dust from spreading spores, often found around fruiting bodies. When fruiting body dies it turns brown.

Hyphae (strands) or mycelium (skin) that are a grey colour and looks like cotton wool.

Fruiting bodies from 3mm in diameter a day and are yellow during early stages appose to red/orange

64
Q

How to treat dry rot?

A

BRE Good Repair Guide 12.

Remove the source of moisture should form the core of any dry rot eradication strategy.

Replace any weakened timber with pre-treated timber, steel or concrete.

If the structure has not weakened and the timbers are below 20% moisture content - no treatment required.

If timbers have not been weakened but and can dry out below 20% moisture with 8 weeks no treatment required.

If the timbers cannot dry out within 8 weeks but up to 6 months apply preservative injection or paste.

If the timbers cannot dry out within 6 months - replace with treated timber, steel or concrete.

All effected masonry should be treated with a masonry fungicide fluid. Hack off plaster 1m beyond area. Remove surface mycelium with wire brush

Remember to cut back timber approx 300mm past infected area and remove all fungai from area to prevent regrowth.

Chemical treatments can be used in some cases dependant on the extent of the rot. COSHH assessment must be carried out by specialist. Treatments includes Zinc Acypetacs or Hexylene Glycol)

65
Q

How do you treat a wood worm infestation?

A

Follow BRE Good Repair guide 13 Part 1 and 2.

  1. Identify locations
  2. Identify activeness (monitoring perhaps)
  3. Identify type of infestation
  4. Determine remedial action - Repair or treat. There are various types of options which include Pastes or solutions etc. Each which are suitable dependant on the type of infestation.
66
Q

What is Chloride Attack on Concrete?

A

Form of chemical attack.

Chlorides can be found in soils, concrete mixes, marine environments.

Chlorides enter the pores of concrete and react with the material breaking down the concretes passive layer which results in corrosion and production of Hydrochloric acid. This results in cracking, spalling and eventually failure.

Repair similar to Carbonation and Sulphate attack.

67
Q

What moisture content should timber be?

A

8 - 15%

68
Q

What moisture content should plaster be?

A

12%

69
Q

How can you test for dampness in masonry?

A

Visual inspection

Speedy carbide test

70
Q

What is interstitial condensation?

A

Condensation build up within a void such as a cavity or roof void etc (this is why a vapor control detail/layer is needed)

71
Q

What would you recommend if radon levels are high at a site?

A

Install a radon sump w/ ventilator.

Install further ventilation provisions at site.