Building Pathology Flashcards
1
Q
How do you apply your understanding of building pathology in your day-to-day duties?
A
As a Building Surveyor, my understanding of building Pathology is crucial in identifying and recording defects whilst analysing the causes and recommending appropriate remedial actions.
2
Q
Could you elaborate on how the CPD events have been beneficial to your understanding of building defects?
A
The CPD events have been beneficial in keeping me updated on current standards and guidelines, learning about new technologies and their applications, and networking with fellow professionals.
3
Q
Can you explain the limitations when using laser measure devices during building inspections?
A
Limitations of laser measuring devices include:
- Inaccurate readings due to obstructions
- Difficulty in sighting in bright light
- Short battery life.
Accuracy can be improved by taking multiple measurements and using visual markers where necessary.
4
Q
What other forms of equipment have you used aside from a moisture meter, borescope and laser measure devices?
A
Infrared thermography for assessing heat loss and dampness.
5
Q
What is Japanese knotweed?
A
Japanese knotweed is an invasive plant that can cause damage to foundations and structures.
6
Q
What does Japanese Knotweed look like?
A
- Hollow bamboo like stems that can reach a maximum height of 3-4 m
- The leaves are are a shield like or shovel-shaped.
- The flowers are generally small, cream or white.
7
Q
Why Japanese Knotweed an issue?
A
Knotweed can extend 7 metres horizontally making removal by excavation extremely difficult.
The invasive root is strong and can cause damage to foundations and structures.
The most effective method of control is by injecting with herbicide close to the flowering stage in late summer or autumn.
8
Q
Why is Japanese Knotweed an issue for buildings and construction sites?
A
- There are legal restrictions on its removal and disposal.
- It is listed by the World Conservation Union as one of the world’s 100 worst invasive species.
- Cutting it down will just cause it to spread around the site therefore to irradicate it from a site it may take several attempts with herbicide injections which is time consuming.
- It can also be disposed in licensed landfill sites however this is a costly process.
9
Q
What legal restrictions are there in dealing with Japanese Knotweed?
A
Classed as “controlled waste” in Britain under part 2 of the Environmental Protection Act 1990 which requires disposal at licensed landfill sites.
In the UK, it is an offence under section 14(2) of the Wildlife and Countryside act 1981 to “plant or otherwise cause to it grow in the wild”.
It was made illegal to spread Japanese knotweed in the UK by the Wildlife and Countryside Act 1981.
10
Q
How does timber decay?
A
Decay of timber occurs when wood is allowed to remain damp over long periods.
11
Q
Name me some timber defects?
A
- Dry Rot
- Wet Rot
- Insect Attack
12
Q
How would you recognise dry rot?
A
- Wood shrinks and splits into large cuboidal cracking.
- The wood is light in weight, crumbles under touch and has a dull brown colour with a cotton wool type texture.
- Mycelium is often visible and greyish in colour when wet and yellow or purple when dry.
13
Q
What’s the cause of dry rot?
A
- Airborne spores come into contact with damp timber which has a moisture content of more than 20%.
- This may be cased from leaking plumbing, poor ventilation leading to condensation or water ingress from a faulty roof or window.
- Causing shrinkage and warping of timber.
- Moisture content less than 20-35% which most would consider “damp not wet”.
14
Q
How do you remedy Dry Rot?
A
- Removing the source of moisture.
- Remove all rotted wood by cutting away timber 300–450 mm beyond the last evidence of fungus or rot.
- In some circumstances, full replacement may be necessary depending on the extent of decay and site conditions.
- Applying a fungicide treatment to the remaining nearby timbers.
- Ventilation must also be ensured to prevent further occurrences.
Note: If structural timbers are affected, I would arrange a structural survey to determine whether structural repairs are necessary and, if they are, take appropriate steps to ensure structural integrity.
15
Q
How would you recognise wet rot?
A
- Surface cracking where cracks follow the timber grain.
- Hyphae strands which are light brown & yellow (a key difference from dry rot).
- Infected timber turns dark brown in colour.
- Wood shrinks and splits on a smaller scale with the wood becoming darkened. Mycelium can be white, brown, amber, green or black with strands that are flexible when dry. The fruiting bodies can be a number of different colours and can occur both inside and outside.
16
Q
What’s the cause of wet rot?
A
- Excessive moisture present over a long period of time.
- High moisture content 50-60%
- Leaking services
- Building material failure
17
Q
How would you remedy wet rot?
A
- Removing the source of moisture.
- Wet rot is limited to areas in which wood has become wet: therefore, size of outbreak is closely linked to extent of wetting.
- Remove all rotted timber and replace – the wood that remains structurally intact and in a safe condition should be treated with a fungicidal spray to protect them whilst they dry.
18
Q
How do you identify the presence of woodworm?
A
- Holes in the wood members in question are present typically 1 – 1.5mm in diameter.
- Live infestations showing powder known as frass which is faeces around the holes.
- Adult beetles will emerge from the wood and may be found in the summer months.
19
Q
How do woodworms affect timber in buildings?
A
- The beetle’s lays eggs on, or just under the surface of the wood.
- The resulting grubs then feed on the timbers causing both structural and cosmetic damage.
- They then hatch as beetles which then breed, lay eggs, and repeat the process causing further damage.
20
Q
How is a woodworm infestation treated?
A
- Woodworm infestation is generally controlled with chemical insecticides.
- However, I would ensure to solve the damp issues as damp timber may be re-infected at a later date.
21
Q
What skills or knowledge did you gain from the timber defects CPD?
A
During the CPD event, I gained detailed knowledge about the causes of timber decay and defects, their effects, how to diagnose them and appropriate treatments.
22
Q
Are you aware of any industry standard and guidelines related to timber defects?
A
BRE Publication on recognising wood rot and insect damage in buildings.
- BRE Digest 299: Dry rot: its recognition and control
- BRE Digest 345: Wet rot: its recognition and control
23
Q
What is damp?
A
Where moisture becomes visible through discoloration and staining of finishes.
Or, causes mould growth, sulphate attack, frost damage or even drips and puddles.
24
Q
How can you test for damp?
A
Moisture meters – Timber.
Speedy Carbide Meter – Masonry
Thermal imaging - used to record the temperature of building fabric and isolate areas that are either close to, or below dew point. These areas will suffer interstitial condensation and damp.
25
What is a protimeter / moisture meter?
- A protimeter works by measuring the electrical resistance between two applied electrodes.
- Protimeters are generally used to monitor the moisture content in wood, when used on other materials, the actual readings may be misleading however this approach does give a sense of moisture content.
26
What is a Speedy Carbide Meter?
- A speedy carbide meter is a device to measure moisture in masonry.
- Drilled samples are taken to determine the moisture content of walls, and the level of damp.
- Masonry dust generated into a sealed container with a known measurement of calcium carbide allows the moisture content to be determined.
- This works as the dust and calcium carbide releases a gas in proportion to the amount of moisture present.
The primary advantage of this procedure is the ability to assess the moisture content profile through the wall.
It allows us to establish whether the moisture content is higher towards the external face, suggesting wetting by rain penetration, or higher towards the inner face, suggesting condensation.
27
What are the main forms of Dampness?
- Penetrating Damp
- Rising Damp
- Condensation
28
How would you identify penetrating damp?
- Appearance of damp patches on walls, ceilings or floors.
- These patches tend to grow or darken after periods of heavy or prolonged rain.
29
What’s the cause of penetrating damp?
- Rain driving through exposed masonry walls.
- Defective roof covering.
- Cracked or detached rendering.
- Defects to window cills.
- Blocked cavity ties.
30
How do you remedy penetrating damp?
Remedies for penetrating damp include:
- Repointing of defective mortar joints
- Inspection of cavity ties to address any blockages.
- Inspection of areas of roofs such as chimneys, parapets and thresholds to address any defects in these elements.
31
How would you identify rising damp?
- Visible staining in the form of a tide mark at the point where the ground water has reached.
- Does not usually rise above 1.5m from internal ground floor level.
32
What’s the cause of rising damp?
Moisture rising from the ground via capillary action.
This can be caused either:
- Lack of a damp-proof course
- Defective damp proof course
- Where the damp proof course has been bridged by external features such as paving or blocked cavities.
33
How do you remedy rising damp?
- Removing the external feature causing bridging.
- The injection of water repellent chemicals into the brick work.
- Installing a new physical damp proof membrane.
34
How would you identify condensation?
Staining and mildew /mould growth.
Typically found in poorly ventilated areas with high humidity, kitchens, bathrooms, bedrooms and rooms used for drying clothes.
35
What’s the cause of condensation?
Causes of condensation include a lack of insulation, lack of ventilation and unheated areas of the building.
Where warm moisture in the air hits a cold surface it loses some moisture as condensation.
This water vapour comes from breathing, domestic activities such as cooking and bathing.
It can lead to staining at cold bridges, peeling wallpaper and mould growth.
36
How do you remedy condensation?
- Reduction in moisture generation
- Providing adequate ventilation
- Provide adequate heating
- Improving the building insulation.
37
Can you describe the process of elimination you use to differentiate dampness in a building?
Differentiating types of dampness involves a systematic approach:
- Visual inspection (internally & externally)
- Identifying symptoms like mould, peeling paint, efflorescence.
- Moisture meter to measure presence and degree of moisture in timber.
- Tactile inspection for temperature and moisture.
- In some complex situations, laboratory analysis of collected samples.
- Eliminating the source of moisture is key.
38
Are you aware of the Joint Position Statement, is so what is it?
The RICS collaborate with Property Care Association and Historic England to produce a joint position statement ‘investigation of moisture and the effects on traditional buildings’.
39
Could you explain further on the use of a moisture meter in identifying dampness in buildings?
A moisture meter is used to identify dampness on timber by passing a small, harmless electric current through the material and measuring its resistance.
If moisture is present, this will lower the resistance and hence indicate higher moisture content.
40
How do you ensure accuracy while identifying the cause of dampness using various surveying equipment?
Ensuring accuracy in dampness detection involves using calibrated and properly functioning equipment, interpreting readings in context of visual and tactile inspection findings, and corroborating findings with other lines of evidence.
41
What types of building movement defects have you learned about and how can they be identified?
I have learned about various building movement defects such as:
- Subsidence
- Settlement
- Heave
- Thermal movement.
These can be identified through signs like cracking patterns, distortion of building elements and monitoring over time.
42
What is subsidence and how would you identify this?
- A downward movement /shrinkage of ground beneath the foundations.
- In clay soil, the growth of large trees which remove water from the ground can cause this.
- Typically diagonal cracking at the corner of the property.
- The cracks will be larger at the top and thinner at the bottom.
43
What is settlement and how would you identify this?
- A downward movement due to an increased load.
- Buildings will settle when first constructed or if there is a change in the load as the new load settles to the bearing capacity of the soil.
- Hairline cracks may appear internally – doors and windows may become jammed.
44
What is differential settlement and how would you identify this?
If two sections of a building are constructed off different foundations or the ground is made up of different soil types, then one may settle more than another causing cracking between the two sections of the building.
This issue is most common with extensions.
45
What is heave and how would you identify this?
- An upward movement in the ground level.
- In clay soil the removal of a tree will lead to an increase in the moisture content of the soil which will cause the soil to swell.
- Vertical cracking if in the centre of the building or diagonal cracking if at the corner of the property.
- The cracks will be larger at the bottom and thinner at the top.
46
What is lintel failure and how would you identify this?
Lintel failure allows a triangular section of brickwork above the window to drop down creating a triangular crack from the corner of the window toward the centre.
47
How would you identify a corroded steel lintel?
Where a steel lintel has been used above an opening and the edge is exposed or close to the surface this can corrode over time and expand causing cracking.
Horizontal cracking.
48
What size cracks are of concern?
Cracks over 4mm that widen at any point or pass the through the DPC.
49
What is the BRE Digest 251?
BRE Digest 251 ‘Assessment of damage in low-rise buildings’.
This identified six categories of cracks together with the typical damage caused and the remedy required.
50
What are the categories of BRE 251?
Category 0: Hairline cracks. Less than 0.1 mm in width. No repair action required.
Category 1: Fine cracks: Up to 1 mm in width. Generally restricted to internal wall finishes. Easily treated using normal decoration.
Category 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.
Category 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.
Category 4: Extensive damage: Width of 25mm. Windows and door frames become distorted, walls lean or bulge noticeably. Requires breaking-out and replacement of wall sections.
Category 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.
51
If there was stepped cracking on the corner of a building, what might have caused it?
- Settlement.
- Subsidence.
- Heave.
52
When and why would you use a borescope?
To inspect a cavity wall to identify wall tie failure or breach of cavity.
53
What are the limitations of using a borescope in building surveying and how do we address them?
- Difficult access in restricted spaces.
- Low visibility due to cavity filled insulation restricting view of wall ties.
54
What are the common causes of concrete failure?
– Inadequate protection of reinforcement.
– Carbonation.
– Freeze-thaw action.
– Chemical attack.
– Crazing.
55
What is Carbonation?
– Carbon dioxide in the air affect the concrete.
– Carbonation changes the alkali nature of the concrete to acid.
- This causes cracking of the concrete cover exposing the rebar which is the suseptible to corrosion which will expand and spall the concrete.
– The risk can be reduced by providing as much cover as possible.
– To test for carbonation a small piece of concrete is broken off (not cut with a saw). The concrete sample is then sprayed with a solution (phenolphthalein) to measure the PH level.
– Alternatively, a more accurate test would be to send a sample to the lab for further investigation under a microscope to view the change in aggregate.
56
How do you treat carbonation?
Anti-carbonation coatings can be applied to the concrete with a life-expectancy of 10-years.
57
What is freeze-thaw effect in concrete?
- Concrete is a porous material subject to forces that absorb and release water.
- Absorbed water can freeze within the concrete and cause spalling and cracking.
58
What is Efflorescence of concrete?
– Efflorescence is more likely to be found on concrete that has been in place for a while.
– Concrete contains water-soluble salts.
– As water from the interior of the concrete migrates to the surface and evaporates, salts are deposited on the surface, usually as a white stain.
– Efflorescence can occur with concrete, brick, or concrete block construction. It can be removed with acid etching.
– The best way to prevent its recurrence is with adequate waterproofing.
59
What are Deleterious Materials?
Hazardous to health or
Affect the buildings performance or structure.
60
Can you name some Deleterious Materials?
- Asbestos
- Lead (when used in water pipes or paint)
- High Alumina Cement Concrete
- RAAC
61
Can you explain in more detail the different types of asbestos?
White: Chrysotile (Banned in 1999)
- Least dangerous (curly fibres)
- Cement sheeting
Brown: Amosite (Banned in 1985)
- Needle like fibres.
- Used for fire resistance (AIB board)
Blue: Crocidolite (Banned in 1985)
- Needle like fibres.
- Sprayed coatings (insulation).
62
What is the issue with lead based paints /lead water pipes?
- Due to the toxic nature of lead its use in plumbing was banned in the UK since the 1970s.
- Risk of contamination of drinking water.
- Risk of inhalation of lead dust during maintenance (paint).
63
What is High Alumina Cement Concrete?
- HAC found in structural concrete such as pre-cast concrete beams.
- First produced in 1925.
- Widely used in the UK from the 1950’s – early 1970.
- HAC concrete banned 1976 for structural use following a number of publicised collapses.
- HAC develops full strength very quickly; it equally loses its strength when it comes in contact with water.
- This process known as ‘conversion’ which is a mineral change.
- Once conversion occurs the HAC will reduce in strength and become vulnerability to chemical attack (poor roof detailing)
- Issues mainly stem back to manufacturing faults (high water content and high temperatures when casting).
- Testing should be carried out by chemical or laboratory testing of samples.
- If confirmed to be HAC the strength and durability should be assessed.
- Building Regulations Advisory Committee (BRAC) published guidance for design checks.
64
What type of property were you surveying when you identified damp staining at Grasmere Road?
I was surveying a residential house when I identified the damp staining.
The property was a 1900's terraced building in Blackpool.
65
What level of survey did you undertake at Grasmere Road?
RICS Level 3 survey.
The property was in a poor condition and had been extended /altered extensively for a previouse use as a care home.
66
What RICS document outlines the levels of survey available?
– RICS Home Survey Standard 1st Edition (professional statement).
– This document sets out mandatory requirements for RICS members and firms who undertake residential surveys.
– You MUST ensure your services are benchmarked against one of the defined levels (1, 2 and 3).
67
Can you explain to me the different types of survey levels noted in the RICS Home Survey Standard?
Level 1: Least extensive survey, general condition of the building elements and grounds. No advice given on repairs or ongoing maintenance. Usually more suited to modern dwellings in satisfactory condition.
Level 2: General condition of the buildings elements with a more extensive visual inspection to include opening up roof spaces or basements where safe to do so. This report advises on repair and maintenance of building elements. Not suitable where the client intends to carry out extensive repair and refurbishment works or the property has been extensively altered in the past.
Level 3: Detailed visual inspection to include opening up concealed areas and although not tested they are observed in normal operation (such as drainage, flushing toilets and running taps etc.) Level 3 surveys should provide the client with all information they require without further investigation to make a decision if possible.
68
Grasmere Road; How far up from the internal floor level was the damp staining located?
The damp staining was located 2 metres up from the internal floor level.
I therefore ruled out the probability of rising damp which typically does not exceed 1.5m from the internal floor level.
69
Grasmere; Where on the property was the damp staining located?
The damp staining was located on the ground level of the property on the internal face of external solid wall.
The damp patch was localised and adjacent to the blocked rainwater goods externally.
70
Grassmere; What did you find when you inspected the area externals?
I discovered a significant build up of vegetation within the rainwater hopper.
This was causing rainwater to spillover and wash against the wall, which contributed to the damp stain.
71
What was the impact of the rainwater over spilling the hopper?
Large quantities of water penetrating the wall in one area, resulting in high moisture contents and localised damage. The moisture was then able to ingress internally leading to damp staining.
72
How did you record the location of damp?
I recorded the location of the damp using a detailed sketch of the property layout, specifically highlighting the affected area.
73
Grassmere; What did you advise your client on remedial works required?
- Remove vegetation from external hopper.
- Re point external masonry to the affected area.
- Hack off and remove contaminated plaster internally.
- Allow sufficient time for drying out the wall.
- Apply a lime plaster to the walls and decorate.
74
Grassemere; How long was required to dry out the wall and why did you advise this?
The wall needed drying out to prevent any trapped moisture damaging the new plaster.
I advised that the time required for drying would be dependant upon the extent of damage known once the internal plaster had been removed.
I recommended the use of dehumidifiers and improved ventilation were used to encourage the drying out phase.
As a rule of thumb, brickwork can take 1 month per inch of wall thickness for drying. (9inch wall could take up 9 months depending on conditions)
75
Grassmere; Did you photograph the affected area and if so, how was this information used?
Yes, I photographed the affected area.
These photographs were used in the report as visual proof of the situation and highlighted the need for immediate remedial action.
76
Grassmere; What was the construction type of the building?
The property was constructed early 1900's with solid masonry wall (lime mortar).
77
Grassmere; How did you identify the construction type?
– The property was of solid wall construction.
– I identified this through the presence of header coursed brickwork.
– I also measured the window and door reveals with a tape measure to confirm.
78
What common issues can you find with sold wall construction?
Heat loss: No insulation as with cavity walls making the properties less efficient.
Dampness: Single skin can allow moisture seep in.
Inadequate repair works: cementitious pointing to solid wall causing moisture to become trapped.
79
How does lime mortar work, what happens to the moisture?
- Lime mortar is applied to solid wall construction to allow the moisture to evaporate and move out freely.
- When moisture levels are high the lime mortar can absorb water vapour preventing potential damage from moisture penetration.
- When conditions are dryer, lime mortar releases the trapped moisture back to the environment.
80
Grasmere; What were the probable causes you ruled out before identifying the actual problem?
I ruled out rising dampness due to the location of staining and the presence of a DPC that had not been breached externally.
I ruled out the presence of any embedded pipework - walls were solid wall with plaster. The wall plaster where deteriorated had no evidence of pipe work behind.
The staining was a localised patch adjacent the build up of vegetation externally - i determine the cause to be penetrating dampness.
81
Ashfield Rise; What was the purpose of the survey?
I was carrying out a residential building survey for my client who was looking to purchase the property.
82
Ashfield Rise; what type of property was this?
Fairly modern detached residential building constructed circa 1990 of cavity wall construction.
83
Ashfield Rise; Where were these vertical cracks located on the property?
The vertical cracks were located on the rear-south facing wall corners.
Thermal movement forces has pushed the corners outward, and causing vertical cracking at the corners.
83
Ashfield RIse; What did you consider as the cause of the cracking in your report?
The cause of the cracking was due to thermal expansion and contraction of the building materials due to weather changes.
Horizontal expansion had pushed the corners out causing the cracking.
84
Ashfield; How did you infer that the cracks were due to thermal expansion and weather changes?
- I determined the cracks to be due to thermal expansion and weather changes from the location and direction of the cracking.
- The cracks did not pass the DPC and was not wider than 4mm. Therefore, I advised the cracking was not of structural significance.
85
What else could cause vertical cracking?
- Settlement
- Heave
- Thermal Movement
86
Ashfield; What things did you consider and how did you determine this was thermal movement?
– I inspected the affected area internally with no identifiable cracking noted.
– I put a spirit level on the walls which were all vertical in alignment.
– The cracking did not taper or widen at the top nor did it pass the DPC level.
– The subject wall was facing south vulnerable to significant temperature variations.
– This brought me to my diagnosis of thermal movement.
87
Ashifeld; How did you document the affected areas?
I documented the affected areas by taking photographs, noting down the specific locations, and measuring the cracks. I used this data to create a report.
88
Ashfield Rise; What was the measurement of the width of the cracks?
The wideness of the crack was of a consistent width approximately 1.5mm.
(Any less then 2mm this is not of concern)
89
Ashfield; What classification did you give to the cracks as per BRE Digest 251?
I assigned a category 2 to the cracks as they did not exceed 5mm in width.
90
Ashfield; What advise did you provide in your report regarding the cracks?
I advised the client that the cracks were due to thermal expansion and contraction caused by seasonal weather changes.
I recommended the cracks are considered to be a more aesthetical issue at present; however, I analysed some repair options to prevent dirt or moisture getting into the cracks which could cause further issues. These were:
- Installation of movement joint to the brickwork.
- In-filling the cracks with a mastic compound.
I advised that although the issue was not of structural significance and could be left to expand and return to the original position naturally – this would require monitoring to ensure brickwork was returning to the existing position.
For this reason, I recommended the cracks were infilled with a mastic compound to prevent the ingress of moister and dirt whilst allowing for natural movement.
91
Ashifeld; Why did you not recommend movement joints?
The cracks were relatively minor (circa 1.5mm) and therefore filling with a suitable mastic compound would suffice in this instance.
Should the cracks have exceeded 4mm I would have recommended movement joints were installed.
92
What kind of property did you survey at Wenning House, Lancaster?
The property I surveyed in Lancaster was a large commercial retail unit.
93
Wenning House; What did you identify in the commercial unit?
I identified cut edge corrosion on the metal roof sheets.
93
How does cut edge corrosion happen?
Where the sheet is cut during the manufacturing process exposing an unprotected edge which is exposed to the elements and vulnerable to corrosion.
Typically to sheet laps and sheet ends.
The sheet will continue to corrode via capillary action up the sheets unless treated.
94
What are the effects of cut edge corrosion?
If left untreated the protective coating will continue to peel away exposing more of the substrate which will then corrode.
Rust can eat away at the roof sheet causing leaks and weakening of the sheets leading to sheet replacement.
95
Do all metal sheets corrode?
No, if the sheets are aluminium they won’t corrode.
Aluminium forms a protective layer when exposed to moisture that prevents further oxidation.
However, it can be more expensive than steel.
96
Wenning House; What type of documentation did you prepare to pinpoint the defective areas?
I prepared a comprehensive building survey report that included photographs and descriptions to pinpoint the defective areas.
97
Wenning House; Could you elaborate on the effects of cut edge corrosion that you explained to your client?
Cut edge corrosion, if unchecked, leads to deterioration of the roof and could result in leaks which could cause internal damage to the property.
It could also shorten the lifespan of the roof besides increasing maintenance costs.
98
Wenning House; You recommended the corrosion had not advanced far up the sheet – why was this relevant?
- If corrosion surpasses the fixing bolts the structural integrity of the sheet may have been compromised and replacement would be required.
- Cut edge treatment generally has a band width of 150mm.
99
Wenning House; What did your recommendation include in order to enhance the lifespan of the roof?
I recommended the application of a corrosion treatment to the affected areas of the roof, followed by a protective coating to prevent further damage.
100
Wenning House; What preventative measures did you advise to avert future sheet replacement?
For preventive measures, I advised regular inspections to detect early signs of cut edge corrosion and timely maintenance works to avert future sheet replacement.
101
Wenning House; Who did you suggest should carry out the works?
I suggested that an approved installer should carry out the recommended work. This is to ensure that they follow prescribed procedures, which is essential for guarantee purposes.
102
Wenning House; What importance do an approved installer bring to this job?
An approved installer brings expertise and quality assurance to the job.
Also, using an approved installer is often a requirement in order for the material's warranty to remain valid.
103
Wenning House; What significance does the manufacturers warranties hold in this situation?
Manufacturers' warranties offer assurance on the longevity and performance of the materials used.
In case of a failure, they provide coverage for replacement or repair.
Often 15-year product performance guarantee.
104
Whats the difference between rust and corrosion?
While rust is a form of corrosion, it only occurs in iron and iron alloys.
Corrosion can happen to other types of metals. For example, copper doesn't rust, but it does corrode over time.
105
Westcliffe Drive, Layton - What type of property was this?
Residential property built circa 1930 with cavity wall construction and more modern additions to the rear.
106
Westcliffe Drive; What had happened to the lead abutment flashing on the mono-pitched roof?
The lead abutment flashing on the mono-pitched roof had split centrally and was detaching from the brickwork.
This was due to thermal expansion and contraction of the lead
Installed incorrectly (continuous across the rear) I measured internally to identify the width.
107
Westcliffe Drive; What process did you follow after identifying and photographing the affected areas?
After identifying and photographing the affected areas, I documented the findings and reviewed the Lead Sheet Association manual to identify the root cause of the problem.
108
Westcliffe; What resource did you consult for further investigation of the problem?
The resource consulted for the further investigation of the problem was the Lead Sheet Association guidelines.
109
Westcliffe; What was concluded as the likely cause of the lead flashing failure?
Thermal movement due to the flashing being oversized - approximately 3m continuous length.
LSA recommends 1.5m in length to prevent the effects of thermal movement.
110
Westcliffe; What course of action did you advise the client to undertake?
Replace the defective lead flashing
Apply silicone sealant to the lead /brickwork abutment.
Open up the brickwork during the works to confirm the presence of a cavity tray.
Make good the plaster work internally.
111
Westcliffe; What requirements did you find in the Lead Sheet Association for replacing the lead flashing ?
I identified the correct length of lead flashing - 1.5m
The code of Lead - Code 4 lead (minimum thickness for all flashings)
Laps between the flashing should not be less than 100mm.
Flashing to extend over the roof covering no less than 150mm.
Fixing should hold the flashing in place without restricting thermal movement.
112
Westcliffe; Why did you recommend silicone sealant and not mortar pointing for the lead flashing?
Mortar is not considered a long-term solution for pointing lead flashings.
Mortar is unable to adhere to both the lead and brickwork - when changes of temperature occur it cracks and allows for rainwater to penetrate.
The Lead Sheet Association recommends silicone sealant for pointing.
113
Westcliffe; From reviewing the flashing detail in the LSA what did you advise your client?
Flashing should be Code 4 lead (minimum thickness for all flashings)
Not exceeding 1.5m in length.
Laps between the pieces should not be less than 100mm.
Flashing to extend over the roof covering no less than 150mm.
Fixing should hold the flashing in place without restricting thermal movement.
114
How would you identify sulphate attack brickwork?
- Horizontal cracking within mortar joints
- Expansion of mortar causing disruption or even bowing of brickwork
- Crumbling of mortar
115
How would you identify sulphate attack in concrete?
- Salts buildup on concrete surfaces
- Surface scaling
- Spalling with traces of salts
- Change of texture of concrete becoming like tooth paste.
116
What is sulphate attack?
This is a chemical reaction where water soluble sulphates react with components in the concrete /mortar.
The chemical reaction causes expansion of the tri-calcium aluminate found in portland cement.
This leads to the breakdown and failure of the concrete due to softening and a loss of cohesion.
Sulphates are salts found in rain water, absorbed ground water and sea water.
117
How would you prevent sulphate attack in a concrete floor?
An intervening waterproofing membrane between the concrete floor and sulphate baring hardcore.
118
How would you prevent sulphate attack in masonry?
The quality of mortar /workmanship to minimise the movement of water.
119
What needs to be present for sulphate attack to happen?
- Continuos ingress of water
- A source of sulphate
- Tri Calcium Aluminate in the cement
Without all three present, sulphate attack will not happen.
NOTE: Tri Calcium Aluminate is a component of Portland cement for the hydration /workability of the concrete
120
Wenning House; What cut edge system was proposed?
Giromax Edgecoat protection - 15 year guarantee.
- Moisture tolerant using a laminar flake coating.
- Cures to an elastic coating to withstand minor surface movement.
- BBA certified product (British Board of Agreement) approved inspection testing certificate.
121
Westcliffe Drive; what probable causes did you eliminate and why?
- Weep holes had been installed above the flashing indicating the presence of a cavity tray.
- There was no visible sign of defect to the roof covering.
- I ruled out the presence of leaking services within the roof void.
- Insufficient overlap of the lead flashing (100mm) due to dislodgement from the wind.
- Flashing installed at a continuose 3m lenght - thermal movement causing the flashing to crack and allow water to penetrate the junction between the wall and extension.
122
What is a laminar flake coating (cut edge treatment)?
The flakes are produced using materials such as aluminium, zinc and stainless steel.
The flakes are platelet-shaped overlapping parallel to the substrate.
They seal and block the path for attacking the substrate.
123
In terms of insurance which would be covered Subsidence or Settlement?
- Subsidence is generally covered by insurance.
- Not covered by insurance for settlement.
124
What is settlement?
- Downward movement of the structure due to an increase in load.
- Settlement is the weight of the building compressing the ground below.
- Usually within 10 years of construction
125
Are you aware of different types of settlement?
- Uniform (typically no cracking)
- Tipping (typically no cracking)
- Differential settlement (cracking can be vertical or diagonal – depending on where settlement has occurred).
126
How did you measure the width of the cracking at Ashfield Rise?
Avongard cack width gauge /ruler.
This is a basic measuring tool for gauging the extent of a crack on a flat surface.
127
What causes settlement?
- Additional loadings (extensions)
- Unequal loadings
- Variations in soil types
128
How would you identify Settlement?
- Windows /doors jambing.
- Unevenness of the structure.
- Cracking of brickwork /internal finishes.
- Lime mortar rarely shows cracking.
129
How would you identify if diagonal cracking was settlement or subsidence?
I would investigate external influences such as surrounding trees and drainage.
I would consider the date of the build and ask questions of when the cracking occurred.
130
How would you remedy settlement?
- Check if progressive through monitoring.
- Internal alterations (floors, doors, windows) to accept the settlement.
131
What is Relative Humidity?
The percentage of moisture in the air.
For example, Relative Humidity of 80% means the air is holding 80% of the maximum water vapour it could for that temperature.
Ideal is between 30-50% - it should not exceed 60%
132
What is dew point?
The temperature to which the air needs to cool to become saturated.
133
How would you measure dew point?
Calculating the:
- Air temperature and
- Relative humidity
134
What types of insect infestation in timber are you aware of?
* Various types of beetles (deathwatch, common furniture, house long horn)
* Wood wasps
* Carpenter Ants.
* Carpenter Bees
135
What plaster did you recommend using at Grasmere Road following remedial works?
* Lime plaster with a salt retardant additive.
This maintained the breathability of the solid wall whilst holding back any residual salts.
NOTE: Gypsum plaster would not be suitable on a solid wall as they absorb /trap moisture. Gypsum plaster cannot stop the passage of salts present in the wall when damp.
136
How do you calibrate a damp meter?
Every time you use it - In accordance with manufacturer instructions.
The one that I use; I insert the measuring pins into the calibration holes on the device's lid readings between 16-20%.
137
How do you determine damp using a moisture meter?
I use the readings to obtain a moisture profile by taking measurements at regular intervals and comparing them.
This gives an indication to determine that damp is present.
138
Why are moisture meters not suitable for masonry?
Due to the variations in conductivity in the masonry.
Moisture meters measure the resistance between the pins.
139
How would you measure the Relative Humidity?
With a hygrometer to measure the % of moisture in the air
140
Grasmere Road; why did you recommend hacking off the plaster – could this not have been stain blocked /painted?
Due to the plaster being contaminated with salts.
The only way to fully remove the salts was to hack off and remove the plaster.
Once the plaster is contaminated the salts will always remain.
Applying a stain block would not have been a long term solution.
141
How do injected DPC’s work?
Injected holes in the external wall inserting a water repellent solution (damp proofing cream).
This lines the brickwork with active ingredients forming a barrier to protect from moisture rising from cappiliary action.
142
What would you consider the cause of staining on a chimney breast to be?
Hygroscopic salts in the brickwork presenting as damp.
- Burning fuels such as coal or wood can allow the salts to accumulate over time.
- When the air is warm and humid, the salts in the wall soak up water and the wall will appear damp with staining present.
Condensation if the flue isn’t lined.
If the chimney was redundant I would consider if any ventilation is provided to the base of the stack and if it had been capped off externally.
143
What is capillary action?
This is where water can travel horizontally or vertically against the force of gravity due to surface tension.
144
Ashfield Rise, Preston; how would you rectify thermal movement?
The cracking at Ashfield Rise was only 1.5mm wide causing more of an aesthetical issue.
The cracking in this instance was ok to be left or filled with a flexible sealent.
I am aware of the installation of vertical movement joints to allow for the natural expansion /contraction of the brickwork.
- Clay Brickwork: 10-12m apart.
- Calcium Silicate Brickwork: 7-9m
- Blockwork: 6-9m apart
145
What would cause horizontal cracking of brickwork?
Cavity wall tie failure – corrsion of the wall tie expands causing horizontal cracking.
Corrosion of large steel fishtail ties will lead to cracking every 4 or 5 courses as the steel expands.
Keep prodding for any thing else… If the brickwork is cracking horizontally; this could be a sign of the foundations moving upwards causing the wall to bow inwards. Or, lack of lateral restraint.
I would in the first instance inspect the cavity with a borescope and consult with a structural engineer if the ties were intact.
146
Example of different brick bonds?
- English Garden Wall bond: Stetchers in one course headers in the next (solid)
- Flemish Bond: Stretchers and headers alternate in each course of brick (solid)
- Stretcher Bond (cavity)
147
What is the typical mortar mix of a brick wall?
This would depend on the brick type:
Typically a ratio of 4:1 (4 parts sand to 1 part cement)
Note: 5:1 for softer brick.
148
What would affect the readings of a protimeter?
- Hygroscopic salts
- Lead based paints
- Foil back plasterboard
Readings are based on measuring an electric current between two prongs – the current can be compromised by these issues.
149
What are hygroscopic salts?
Hygroscopic salts are moisture absorbant salts usually caused by rising damp where the moisture carries the salts from the ground.
When the water evaporates from the wall salts are left behind on the surface that will continue to absorb moisture until completely removed.
150
What affect would Hygroscopic salts have on an internal wall?
The effects of condensation can worsen as high humidy levels give the salts plenty of moisture encouraging severe damp patches.
151
Wenning House; what other defects would you associate with a metal profile roof?
- UV Degradation: Causing fading of the covering
- Chalking: Powder residue caused by a separation of pigments in the coating caused by sunlight or salt spray.
- Damage by people walking on the roof incorrectly during maintenance.
152
What are the risks of RAAC?
Unexpected collapse
Corrosion of reinforcement from water ingress - this is often concealed not leading to spalling due to the aerated nature of the concrete.
Alterations to the building /service penetrations could cause a loss of strength.
DFE are working on removing all RAAC from school /college buildings across England.
153
Can you name me some deleterious materials?
- Asbestos
- RAAC
- Lead pipework
- High-Alumina Cement
154
What is a dead load?
Permanant load on the structure such as:
- Walls (non-moveable)
- Roof
- Floors
155
What is a live /imposed load?
They are either moving loads such as people or movable loads such as furniture and movable partitions.
156
What are environmental loads?
Loads caused by wind and other external forces.
157
Grasmere Road; Is there any documents you referred to for investigating moisture ingress in the building?
Joint Position Statement: Investigation of moisture and its effects on traditional buildings.
This document provides best practice for inspection of traditional buildings.
This considers a ‘whole building approach’ when identifying the cause of moisture ingress.
158
What is a traditional building?
Solid wall construction built from permeable materials such as brick, stone and timber.
In traditional buildings, water enters and exits the building fabric as conditions become wetter and dryer.
Modern materials have impermeable barriers to prevent moisture entering all together.
159
At what distance would you expect to see movement joints in a wall?
Clay Brickwork: 10-12m apart.
Blockwork: 6-9m apart
Calcium Silicate Brickwork: 7-9m
160
What is Efflorescence and what affects can this have on building materials?
Efflorescence is a deposit of salts found on the surface.
The Salts appear as white flour-like dusting or crystallisation deposits on the wall surface.
Efflorescence are salt commonly found in building materials such as brickwork and concrete.
When the water evaporates from the wall salts are left behind on the surface.
This can cause a break-down and spalling of the existing plaster/decorative finishes.
161
Can you explain your understanding of Level 1 Surveys under the Home Survey Standards?
- General condition of the property – usually displayed by a condition rating
- Least extensive inspection
- Suited to; modern dwellings in satisfactory condition.
- Roof spaces inspected via head & shoulder inspection if access panels have previously been removes /opened.
- No advice on repairs /ongoing maintenance issues (should be in enough detail for the client to understand repair works required /prioritised).
- Further investigations are often recommended (due to the extent of inspection).
162
Can you explain your understanding of Level 2 Surveys under the Home Survey Standards?
- Extensive visual inspection (without tests) – usually displayed by a condition rating.
- Concealled areas such as roof spaces are inspected if safe to do so.
- Includes advise on repairs /ongoing maintenance issues
- Level 2 services does not suite: Complex Buildings (extensively extended /altered) & Properties in neglected condition.
- May contain advise to obtain further investigations before entering legal commitments.
163
Can you explain your understanding of Level 3 Surveys under the Home Survey Standards?
- Construction form and materials described in detail /performance characteristics.
- Concealled areas such as roof spaces are inspected if safe to do so.
- Services observed (not tested) in normal operation: switched on and off /flushing of toilets /running of taps.
- Includes advise on repairs /ongoing maintenance issues with timescales.
- Further investigation should be an exception rather than a rule
- Level 3 will suite any domestic residential property.
164
What level of survey was undertaken at Grasmere Road /Westcliffe Drive?
- Level 3 Survey as per the Home Survey Standard.
- The property had been extended and was in a poor condition.
- The levels of survey was explained to the client and they agreed to proceed with Level 3.
165
Should a client rely on cost advice given in a Building Survey report?
The costing figures are for guidance only which is outlined in the terms of appointment.
The methodology of cost calculation is listed and the client is advised to obtain formal written quotations prior to legal commitment.
166
When should further investigations be recommended in a Building Survey report?
Concealed building elements.
Building elements
167
If a roof coverings cannot be viewed in full – would you recommend further investigation?
If there was no evidence of defect in the roof internally I would advise the client of restricted visibility during the inspection but not recommend further investigations.
168
What are the requirements for residential surveys under the Home Survey Standard?
- Service must be benchmarked against one of the defined levels.
- RICS members must be qualified and experienced to deliver the service.
- Knowledge of the locality and nature of the property
- Clear terms of engagement must be set /agreed upon before commencement.
169
What environmental issues do you consider before a survey?
- Flooding Risk (surface, river and sea)
- Radon
- Former Mining activites
- Listed Building Designations /Conservation Areas
170
Why did you review the Rolled Lead Sheet Manual?
The Rolled Lead Sheet Manual contains technical standards for specifying rolled lead sheet under BS6915 Code of Practice.
The Lead Sheet Manual provides:
- Technical information
- Detailed drawings and photographs
- Sizing charts and illustrations
171
Wenning House: What was the build-up of the roof?
Plastisol coated profiled steel sheets.
172
What was your advise at Wenning House?
The plastisol coatings were peeling back by approximately 5-10mm.
I advised cut edge corrosion works to be carried out in the short to prevent excessive peel back of the coatings and subsequent corrosion of the steelwork beneath.
173
How long does cut edge corrosion take to begin?
Once the metal cladding has been cut in the factory and installed to the roof.
The cut edge is then exposed to the oxygen in the air and water which will begin to peel back the coating and expose the metal substrate.
Timing would depend on the environment /weather conditions /exposure.
174
Wenning House: was the roof covering fragile, how did you determine this?
I always assume the roof is not safe to walk on until confirmed otherwise.
I reviewed the planning portal which identified the building was constructed in 2015 so the roof was relatively new.
A general access scaffold was provided for safe access to the roof level works with a working platform around the edge.
Guard rails were installed round the roof lights as these can be fragile.
175
Are you aware of any guidance for safe roof works?
HSE Publication: Health and Safety in Roof Work.
Work at Height Regulations 2005.
176
How does cut edge corrosion happen?
During the manufacture of the metal cladding, a plastic coating (Plastisol) is applied to protect the metal beneath.
When cladding is cut in factories, its cut edge is left with no coating leaving the metal exposed.
The steel edges of the sheet are exposed to the air /oxygen making them vulnerable to corrosion which is often made worse by water.
Eventually, the protective coating peels back leaving uncovered edges and exposed metal.
177
Westcliffe Drive; what code of lead was used and how do you identify this?
Lead flashings should be at least code 4 which is detemrined by the thickness.
Lead rolls are colour coded; Code 4 is blue
178
Westcliffe Drive; what was your advise for the new lead flashing from the Lead Sheet Manual?
Code 4 Lead flashings to be installed to:
- Not exceed 1.5m in length
- Laps not less than 100mm
- Flashing to extend down the roof covering by at least 150mm
- Flashing to be lead wedged into the the mortar joint 25mm
deep and at least 75mm above the tiling level.
- The joint should then be sealed using a suitable exterior grade sealant.
179
Westcliffe Drive; Any other guidance for lead flashings?
- Lead Sheet Association: Rolled Lead Sheet Manual
- NHBC Standards
- BS6915
180
What is RAAC?
Reinforced Aoutoclaved Aerated Concrete
- Pre-cast concrete panels (commonly roof panels /wall panels)
- Concrete is aerated so has no course aggregate like traditional concrete.
- Predominatnely used between 1950 – 1990
- Aerated nature makes the concrete highly permable leaving the reinforcement vulnerable for corrosion.
181
What would you consider if you was to inspect RAAC?
- Presence of Asbestos
- Review of Building Information (date of construction /alterations)
- Deflections
- Cracking
- Signs the panels have been cut post-manufacture
- Reinforcement corrosion (electrochemical testing)
- Panel bearing position (as little as 45mm in design at the time)
182
What are the risks relating to RAAC?
Unexpected /sudden structural failure.
183
Where could you go to research information on RAAC?
RICS Articles /Frequently Asked Questions
BRE Research papers
184
What is meant by the term Technical Due Diligence?
Systematic Review, Analysis and Data Gathering about the physical characteristics of a property.
This could be; building surveys, condition inspections, or pre-acquisition surveys.
185
Ashfield Rise; what advise would you give for remedial works for thermal movement?
This could be left to open and close naturally with the provision of a flexible mastic sealant to prevent the ingress of dirt or moisture.
Movement joints could also be provided as close to corners as possible (but not less than 665mm from a corner) to allow for natural expansion and contraction.
186
Ashifeld Rise: what was the location of the cracking?
To the rear elevation corners.
The corners had pushed outwards causing vertical cracking of masonry at the corner.
187
What are movement joints and how do these work?
Movement joints are gaps which allows for natural expansion and contraction.
The gap is filled with a compressible filler and a weatherproof sealant is layered on top.
188
How would a mastic sealant be installed?
A small flexible nozzle is used to inject the ‘polysuphide’ sealant into the cracked brickwork.
This provides a waterproof seal to protect against moisture and dirt ingress.
189
Ashfield Rise: what sealent did you recommend and why?
Polysulphide sealant.
This is a flexible and waterproof material with little shrinkage or UV degradation.
General life expectancy of 10 to 20 years depending on manufacturer.
190
How do you install movement joint? How is it tied?
- Cut a vertical line in the masonary ensuring all dirt and debris are removed.
- The gap is filled with a compressible filler and a weatherproof sealant is layered on top.
- To maintain stability of the wall ‘slip ties’ are installed across the movement joint spaced at maximum 300mm centres vertically.
191
Where should movement joints be installed?
- 12m centres for clay brick
- 6m centres for blockwork
Vertical movement joints should be located in sections of full height masonry.
Not where window /door openings are present due to the difficulty of continuing the joint between the frame and masonry.
192
How does a movement joint differ from mastic sealant?
Movement joints is a compound material inserted to the brickwork to allow for the free movement of brickwork.
Mastic sealant provides a watertight seal as a precautionary measure against moisture /dirt ingress.
193
Grasmere; what was your advise in relation to the cast iron down pipe?
The cast iron rainwater good where viewed appeared in relatively good condition for their age.
The hopper couldn’t be viewed in full due to the build up of vegetation.
I am aware of common problems such as fractures or corrosion which can cause failure if not maintained.
The block of terraces all retained the original cast iron features and I considered this to be important to retain the original materials where possible.
194
If you were looking at a 1960’s property and you found horizontal cracking what steps would you take and what would your advise be?
- Cavity tie failure (borescope /metal detector)
- Expansion of steel lintels.
195
If a client calls you and asks for a level 3 survey, how do you advise them?
I would first make sure they understand what the Level 3 survey entails.
The Level 3 Survey is the most detailed survey available, designed for:
- Complex builds that have been extensively extended or altered.
- Properties in a neglected condition.
In these instances a client may be disappointed with a L1 /L2 survey that contains numerous referrals for further investigations.
L3 surveys provide a comprehensive analysis of both the construction and condition of the property.
It's also crucial they understand that a Level 3 survey is more expensive than Level 1 or Level 2 surveys due to the thoroughness of the inspection and the complexity and length of the report.
Costs can range greatly depending on the size, type, and location of the property.
196
Would your advice in relation to a Level of Home Buyers Survey change if you found out the client had passed on incorrect information about the age of the building?
A Level 2 survey may be appropriate for some older buildings /historic buildings depending on the age /construction.
For example, a level two report on buildings built much before 1850 is likely to be inconclusive and be of little use to the client. (for instance if they have a traditional timber frame).
If the instruction was not suitable, I would explain the reasons why to the client and advise on the appropriate level of service.
197
What would you do if you noticed ‘Wood Wool Slabs’ on site /what considerations would you have?
Wood wool slabs were often used as permanent formwork and left as a ceiling soffit.
This may result in:
- Reduced fire resistance
- Reinforcement corrosion
- Loss of structural strength
Structural strength is impacted due to inadequate compaction of the concrete due to the compressible nature of the board.
This lack of compaction resulted in voids and honeycombing on the soffit of the slab sometimes leaving no cover to the reinforcing steel.
198
Why was High alumina cement used?
High Alumina Cement was used as an accelerator for quick setting of concrete.
It was considered to be resistant to chemical attack.
However, HAC was prone to a process known as ‘conversion’, which results in reduced strength and vulnerability to chemical attack when exposed to water for long periods.
199
What are the different stages of the dry rot cycle?
Dry rot begins with airbourne spores which will germinate on damp timber with a moisture content over 20%.
The spores fine white strands known as hyphae.
As the hyphae grow they will eventually form a large mass known as mycelium.
200
At Grasmere Road in Blackpool, what was the reason for the hopper being there?
Victorian way of managing the flow of water.
Means of draining 2-3 pipes into one outlet.
201
I see you undertook some CPD damp by Peter Cox. Where might you find further guidance to deal with damp issues?
BRE Digest 245: Rising Damp
JPS: The effects of moisture in traditional buildings.
202
Can you tell me what are the common defects on industrial buildings with profiled metal sheet roofs other than cut edge corrosion?
impact damaged coverings
Corrosion of fixings
Aged /brittle roof lights
Roof penetration flashings
Gutter defects
Aged/out of service mansafe systems
Wildlife/seagulls.
203
Could you tell me what Regents Street disease is?
The corrosion of the steel frames within masonry clad buildings.
When structural iron or steel corrodes, it expands (up to eight times its original size) causing cracks, spalls, or wholesale failure
These steel frames were at their most popular from the early 1900s to 1950
204
What health and safety considerations would you make when dealing with remedial works on profiled metal sheet roofs?
- Falls from height /fragile surfaces.
- Preventive measure sin place such as:
- Edge protection scaffolding with guardrails.
- Restraint system such as harness and short lanyard (ManSafe System)
- Internal nettings if not mansafe
- Edge protection surrounding roof lights which can often be fragile.
