Building pathology Flashcards
1
Q
Tell me about a report you have prepared relating to the causes of failure, likely results of failure and apprpraite remedial measures.
A
I carried out an inspection and developed a report on damp issues within a flat in Oxford. From my inspection, completing both visual internal and external inspections, protimeter and relative humidty checks I determined that the damp was likely a result of condensation. I advised that there was not appropraite ventilation in the property, with the windows being rarely openeing, extract fan not working and 1 bedroom flat having 1 resident and two dogs occupying. I recommended that heat retaining vents be installed into the external walls and a new extract fan installed in the bathrooom with an exract capacity of 16l/s.
2
Q
Why would you use non-technical language in a report?
A
As an expert reporting on the field, I should assume that the reader will not have the level of tehcnical knowledge I do. Non technical language ensures that the reader will understand the information within the report and communictes its contents first time.
3
Q
Tell me about BRE guidance you have applied and the reasoned advise you provided as a result?
A
When compelting my inspection of Esmond Road and developing the report I used the BRE crack classification system. The cracks that I inspected were between 5 and 15mm and classified as BRE 3. I was able to advised that internal remedials could completed with some minor opening up and patching by a mason. The classification also gave me confidence in that the cracks were not structural but could affect the weatehr tighness of the property.
4
Q
Magdalen damp report, OxfordWhat advice did you give your client about their legal responsibilities regarding damp
A
I advised the client that under section 11 of the Landlord and Tennant Act that they are legally responsible for maintaining the water tighntess of the structure. If the damp was a result of penetrating or rising damp it would be their responsibilty to rectify the issue. Also if unaddressed, this could result in a disrepair claim from the resident.
5
Q
Magdalen damp report, OxfordDid you consider the possibility of wet insulation affeceting the temperature of the wall
A
The wall that was showing signs of damp had creduly installed vents at low level. I was able to carefully remove a vent and assess the condition of the cavity wall insulation. Polystyrene bead insulation was present, from touch it was not wet.
6
Q
Magdalen damp report, OxfordDid you determine what type of insulation was within the wall?
A
The wall that was showing signs of damp had creduly installed vents at low level. I was able to carefully remove a vent and see that polystyrene cavity wall insulation had been installed. This eluded to the fact the freeholder had tried to improve the thermal capacity of the property, anc combined with the vents pointed toward condensation.
7
Q
Magdalen damp report, OxfordAs the nomral protimeter pins only penetrate the plaster how could you assess whether the inner skin of the wall was dry or damp?
A
From my desk top study of the instruction before my inspection I understood there would be value in bringing a protimeter with deep probes to allow me to check the dampness of the skin inner skin of the brickwork.
8
Q
Magdalen damp report, OxfordWhat additional inspections did you recmmond to your client should be undertaken?
A
I recommended that an intrusive investigation of the external wall should be undertaken to ensure that interstitial condensation had not occurred.
9
Q
Magdalen damp report, OxfordDid you consider increasing the static ventilation of the property?
A
My recommendations included installing passivents into the external walls. The sytem I recommended removes hot humid air from the property to the outside using pressue, a permeable membrna allows for the moisture to be removed without allowing a draught inside.
10
Q
Magdalen damp report, OxfordWhat external inspection did you undertake?
A
I followed a six step inspection process. 1) Understand the construction and occupancy of the property. 2) Pinpoint the area of damp and key features of its presence. 3) Inspect externally for defects. 4) Test the moisture content of walls. 5) Surface temperature check 6) Check the ventilation of the property.
11
Q
Prestwick Road SubsidenceWhat did you consider caused the problem? And what inspections did you complete to come to the conclusion?
A
Before we carried out t he inspection I compelted a review of the historical documentation, this included a report from a loss adjuster, arboricultural report and trial pit. On site I completed an inspection of all damage internally. The repaired cracks had previously opened up, with the resident advising it had occured over the previous summer. Cracks were wider at the top, trial pit information included evidence of roots adjacent from the foundations, damge was seasonal which all pointed to soil shrinkage.
12
Q
Wigston Close, Structural WorksWhat immediate measures did you take for the safety of the occupants and the others?
A
Due to the wall being deemed as a dangerous structure, immediate works involved decanting residents, proping the walls with accrow props and steel beams and hording the external wall to secure the property.
13
Q
What is the relevant legislation relating to limitation periods and what does it include?
A
The limitation act 19806 years limitation period underhand contract12 years if the contract is signed as a deed
14
Q
How can cavity wall insulation cause for damp in cavity walls?
A
In proper installation can cause for the cavity to be bridgedWater repellent systems must be installed to manufacturers guidanceIf mortar gathers on the insulation it can allow for water to travel insideBatt at gable ends should be taken up to verge, or a cavity tray should be installed to prevent water travelling across the top of themRetrospective cavity fill can prevent evaporation in external skins, make the wall more vulnerable to frost attack and if mortar falls onto the fill can cause for cold bridging.
15
Q
What are the methods for testing dampness in a material?
A
The oven method - drying and comparing to wet weightConductivity testingCarbide testing
16
Q
What are the issues with oven and carbide testing?
A
They are destructive methods of inspectionRequire samples from materialInpracticial to use on siteA range of samples is required
17
Q
What are the issues with conductive testing?
A
Does not register low levels of moistureIs calibrated to moisture content percentage of timberOnly test the surface/just below the surface of material
18
Q
Magdalen Damp Report, OxfordExplani your pcoess diagnosing the damp at Magdalen.
A
1- Understand the construction and occupancy of the property2- Pinpoint areas of damp and mould/identify key features3- Inspected externally for any obvious defects4- Test moisture percentage of walls using protimeter5- Complete temperrature check of wall surface
19
Q
Can you give me a definition of damp within buildings?
A
The presence of unwatned moisture within the structure or elements of a buldinsg, either as a result of intrusion from outside or condensation from within the structure.
20
Q
How does a protimeter test for moisture?
A
Probes inserted into wallMeaures electrical current between two probesHigher the moisture, the greater the current
21
Q
What is condensation within buildings?
A
Moisture that gathers on surfacesWarmer air can hold more moisture than coolIf air contacts a surface that is cold enough it will increase its relative humidity to 100% and water will condense. This is the due point. Mould and staining can then develop from the moisture on the walls
22
Q
How does condensation occur within buildings?
A
Moisture is produced by people living in properties and the activities they carry outAreas such as bathrooms and kitchens produce more moisture into the airCondesnation will then occur on cold parts of walls i.e. where there is a cold bridgeIt will also occur in areas where there is little ventilation
23
Q
Magdalen Damp Report, OxfordHow did you determine that the damp was likely to be as a result of condensation?
A
The areas where damp was forming were to low level and areas of low ventilation, i.e. behind furniture and curtains. I tested the walls with the protimeter and they did not give a reading of excess moisture, there was also no sign of relevant defects externally. The property also had crudely installed vents that did not retain any heat. The resident also lived in the property with three dogs indicating high levels of moisture int he air.
24
Q
Magdalen Damp Report, OxfordWhy did you recommend the installation of a new passivents and a new extractor fan?
A
Crude ventliation had been installed into the external walls that did not have any heat retention function. This would have decsreased the internal temperature of the property and therefore lower levels of moisture it could hold. The extractor fan in the bathroom was faulty, and was not discharging enough air. This meant mositure developed in the bathroom was moving into the flat. A new extractor fan would remove more moisture from the property.
25
What is the relevant building regulation with regard to the ventilation and how was this relevant?
Building regulations part F - VentilationMinimum extract fan ventilation for bathrooms 12l/sA minimum extract rate for the whole building of 19l/s i.e 1 bedroom flat
26
What are 3 timber defects?
Wet rotDry RotInsect decay
27
What are the characteristics of wet rot?
High Humidity 50-60%Musty Smell - cracking lengthways - bleaching - Mycelium (yellow brown) Eliminate source of water, heating and ventilation OR remove timber 500mm beyond affected areas, treat remaining timber and replace with pre-treated timber.
28
What are the characterstics of dry rot?
Smell musky mushroom smellCuboidal cracking to timbersHollow sound when materials is tappedMcelliym (cotton wool strands) beneath surface seeking foodFruiting bodies are creamy pancakes with dark edges20 degrees optimal temperature20-30% optimal moisture content
29
What BRE Digests are available for dry and wet tor?
Wet : 345Brown : 299
30
Explain insect decay?
BRE digest 307Uncommon is death watch beetle active March to JuneCommon Furniture beetle - Woodworm
31
What are 3 concrete defects?
Chloride AttackCarbonationHoney Combing
32
What is chloride attack?
Calcium chloride added to spped up curing timeIt breaks down the alkaline content within the concrete which allows for steels in concrete to become oxidisedOxidisation causes for concrete to bulge and crackLoclaised buldging and cracking
33
What is carbonation?
Calcium hydroxide reacts with the carbon dioxide in airCreates calcium carbonate whichProtection for concrete is no longer thereCorrosion of the steel occurs
34
What is honey combing?
BRE digest - small voids in concrete structureCaused by poor compaction, poor formwork and has the affect of no protection to the steel reinforcement and reduced fire resistance. Treatment is for targetted repairs or wholesale replacement.
35
What is High alymia cement?
BRE digest 392An additive to speed up the curing process. Caused for increased pourosity of the concrete and in turn loss of strength and a reduction to chemical attack.
36
How do you test for High Alumina Cement?
Visual defelction and brown tingesCore sample and lab testing requiredTreatment is Removal of HAC elements, secondary support and carbon plate bonding.
37
Explain the testing proceedure when testing for concrete carbonation?
Use and ACTUAL INDICATOR called a….Phenophthalein Indicator (FENO-FAL-INE)Turn pink if no acidic contentRemain colourless if carbonation is present
38
What are the remedial works for concrete suffering with Carbonation?
1- Remove the water source (carbonation can only occur in a solution)2- Wire brush the corroded areas and apply corrosion inhibilitor.3- Repair the broken concrete. 4- Coat the finished concrete to prevent further carbonation.
39
When investigating structural cracking to brickwork caused by adjacent trees, what recognised standards would you refer to assist in assessing the risks posed by the trees present?
BRE Digest 298- Influence of trees on clay soils BS 5837:2012 - Trees in relation to design, demolision and recommendations.
40
Can you give me 3 defects of masonry walls?
Inadeqaute wall restraintLack of movement jointsLack of lintols
41
What moisture content is required for dry rot to occur?
Prolonged and regularly levels of WME 22%.
42
What is the life cycle of rot?
Spores land on suitably wet substrateThe spores Germinate on the sufarce Mycelium develops and begins to feed on the wood and spreadFruiting body develops and releases more spores
43
How would you profile the rot?
Fruiting bodies and spores are unique and best form of identificationAbsence of fruit bodies, colour and appearance of myceliumForm of decay, brown or white rot - all white rots are wet rotOther features of the wood - size of cracks are unreliable
44
What documenation would you look to for identification?
BRE Digest 345 for wet rotBRE Digest 299 for dry
45
What are the primary measures for controlling outbreak of wet rot?
Locate and eliminate sources of moisturePromote rapid drying of structure
46
WHat are the secondary measures for controlling wet rot?
Establish size and signifcance of attachRemove rottded wood and conisder the need to apply localised preservatice treatmenetUse preservative-treated replacemen timbersIntroduce support measures
47
Why is dry rot considered to be more dangerous than wet?
Dry rot mycelium strands have the ability to extend and 'travel' in search of nutrients.They have the ability to to penetrate through some plaster and mortar joints, potentially spreading through building to building.
48
How can you treat dry rot?
Primarily remove sources of water/moistureRapid dryingDetermine level of outbreak, timbers close to outbreak and their mositure content should be closely examinedRemove affected timberPreservatives can be used to prevent further outbreaksInjected preservatives and be used if wood needs to remain in situeUse of chemical teatements to create barrier to rot finding food
49
West Hayes Damp ReportWhat were the observations you made when you inspected the ground floor flat internally?
#NAME?
50
West Hayes Damp ReportWhat were the observations you made when you inspected the ground floor flat externally?
#NAME?
51
West Hayes Damp ReportWhat third party investigations were conducted?
#NAME?
52
West Hayes Damp ReportWhat did the investigations determine about the wall construction?
#NAME?
53
West Hayes Damp ReportWhat trace of nitrate did the plaster analysis test find?
#NAME?
54
West Hayes Damp ReportHow did you conclude that the leaking fittings were causing water to travel up the internal walls?
#NAME?
55
West Hayes Damp ReportWhat additional moisture was causing for condensation to occur on the external walls?
#NAME?
56
What experience do you have in identifying damp issues and diagnosing their defects?
#NAME?
57
How have you used survey and other information to diagnose the cause and mechanisms of failure?
I have attended expert witness surveys with senior colleauges to understand if properties are in disrepair. We have used survey information gathered such as speaking to residents, understanding construction, air temperature, relative humidity, surface temperatures and moisture readings to determine if damp and mould are occurences of disrepair or whether they have been caused by resident life style i.e. condesnation.
58
What have you done to develop your knowledge of building pathology?
I have used reading sources, attended CPD events and shadowed senior colleauges on surveys. Recently I attended a CPD workshop on condesnation within my organisation that explained the following sections:- Why it is a hot topic- Science and physics behind condensation- The inspection process- Appropirate tools and equipment
59
Desribe a recent project you have worked on where you have applied your knowledge of building pathology?
Outside of the projects that I have included within my summary of experience, th condition survey for Grove View apartments required me to apply my building pathology knowledge.During the inspection I identified a boundary wall that had developed cracking.Using BRE 251 crack classification, i classified the crack as category 3. I used my knowledge and experience of cracks to identify that the crack was wider at the top than the bottom and was likley due to the ground movement. There was a tree in close proximity to the area of damage. I advised the client that the wall should be re-built due to the damage and that it was likely due to the proximity of the tree.I advised that if they wanted to build a potential claim against the tree owner they should complete a trial pit investigation to understand the depth of foundations and determine if there were any tree roots in close proximity to the walls footings.
60
What methods have you used to ensure accuracy and reliability when diagnosing mechanisms of failure?
I have used resources and information gained from sources such as BRE 251 to help me profile and classify cracks to accurately diagnose the mechanism of the failure. When inspecting for damp, I use observations and tools to rule out all other possibilities. By understanding building construction, occupation, profile of damp, moisture content of materials, salt tests, air temptraute etc.
61
Prestwick Road Subsidence ReportWhat were the main findings form the arboricultural and geotechnical reports?
The geotechnical reports showed that the front corner of the building had been previously underpinned at an earlier date, and that building was sat on a clay subsoil.The arboricultrual report found that there were ash tree roots below the levels of the properties original foundations.
62
Prestwick Road Subsidence ReportWhat initial understanding did you gain from reviewing the third party information from the client?
I understood that from the findings in that the previous damage was likely caused by subsidence from trees in close proximity dessecating the soil beneath the buildings footings. As there were no drainage leaks, roots were in close proximity a tree had been removed but further damage had occured.
63
Prestwick Road Subsidence ReportWhat advice did you give to the client regarding the likley cause of the structural damage?
The advised that the damage had occured in areas that had already been repaired, and were still indicative of subsidence. The monitoring and talking from the resident indicated that the movment was seasonal, indicating that the subsoil was still being dessicated by a tree.The partial underpinning of the building was causing damage to be excacerbated, as one section was remaining still and the other moving, causing the building to 'tear'.
64
Prestwick Road Subsidence ReportWhat range of options did you provide to help prevent further structural damage?
I gave the client a range of options to solving the building movement. As an interim and low cost solution I advised that a root barrier could be installed to prevent further dessiciation of the soil in close proximity.I then advised that underpinning the entire flank of the property shoul dbe completed to prevent 'tearing' continuing. To ensure no building movement, the other large trees in close proximity should be removed.
65
Prestwick Road Subsidence ReportHow did you advise the client on the required internal repair works?
I advised that the cracks internally were of BRE category 3 (several of 5mm) and would require some minor raking out and rebuilding.I advised though the cracks were not structural, the resident should be decnated until repairs were complete as they would be allowing draught and vermin entry.
66
Prestwick Road Subsidence ReportWhat process did you suggest for presenting the repair works to the insurance providers loss adjusters.
I recommended that a schedule of work was developed, which could then be priced by contractors as the insurance policy required. I also recommended that in order to build a claim against the neighbours insurance they should carry out further investigations to the soil in close proximity to find evidence of more tree roots.
67
Prestwick Road Subsidence ReportWhat challenges did you face during this project and how did you overcome them?
#NAME?
68
Magdalen Damp ReportWhat was the purpose of your inspection of the flat?
My appointment was to inspect the flat and determine, if the reports of damp were true, if so what the cause of the damp was any remedials to remedy the damp.
69
Magdalen Damp ReportWhat specific complaints had the resident made about damp?
The resident had made claims that damp and mould had been occuring in her property for a number of years and that efforts from the landlord had not been sufficient enough to make the problem go away.
70
Magdalen Damp ReportWhat type of damp did you identify on the external walls of the lounge?
When investigated there was evidence of block spot mould to low levels of the external walls, particularly behind furniture and around vents installed by the landlord. There was also black spot mould around the window reveals.
71
Magdalen Damp ReportWhat tools did you use to test for damp and what readings to you get?
I use a protimeter with deep probes to test both surface moisture levels and the moisture levels of the substrate beneath. The moisture levels of plaster and plasterboard were above 30% in the areas of mould, but the substrate below did not give any reading.
72
Magdalen Damp ReportHow did you present your findings to the client?
I presented all of my findings in a report to the client, the sections were broken down into:- Intro- Construction- Occupation- Damp profile- Test results- Conclusion &Recommendations
73
Magdalen Damp ReportWhat recommendations did you make to the client?
I recommended that the vents that had been installed were replaced with passivents with a humidistat funciton and draught prevention.The extract fan should be replaced in the bathroom.Advice should be given to the resident to open their windows and trickle vents.
74
Magdalen Damp ReportWhat was the defect with the bathroom extractor fan?
The fan was not working and their was no window within the bathroom. When the resident would shower, water vapour would not be able to leave the property and when the door was opened it owuld spread into other areas of the property.
75
Magdalen Damp ReportHow would installing passivents in the external walls improve the ventilation of the property?
Passivents would help to take excess moisture of the property. By installing a vent with humidstat function and draft prevention it would also help to maintain the temperature of the property, further preventing condensation.
76
Magdalen Damp ReportWhat other measures could have been taken to address the damp issue?
We could have improved the heating system or further improved the insulation.
77
What is settlement ?
Settlement is the downward movement of the ground caused by a load consolidating the soil below it or causing displacement of the soil. Settlement often refers to the downward movement of the ground around an excavated space, such as that for tunnels, shafts, or basements.
78
What is sulfate attack (concrete)?
A reaction between the concrete and the ground bearing slab where the presence of sulphates are within the hardcore/soil or introduced via water. typically in properties between 1945 and 1970.This creates a new compound that expands within the concrete to cause cracking.Testing can be carried out via samples of the concrete and sub fill material.Can take several years to come to fruition and is linked to coal mining areas.Measures intorudced include the selection of suitable materials, inclusion of a dpm.
79
What is Concrete Carbonation ?
Carbonic Acid affecting the ph of the concrete
80
What is the Latin for dry rot ?
Serpula lacrymans
81
What is the Latin for wet rot ?
Coniophora puteana
82
What is the measurement of the protimeter ?
Prongs = WME - Wood moisture equivalent| Surface reading = Measured to a depth of about 19mm and a measure from 60-999
83
What may give you false readings from a protimeter ?
Foil backed plasterboard| Black ash mortar - contains carbon and is highly conductive
84
Can you give me some examples of causes of movement in buildings?
E.g. Subsidence, Heave, Thermal/shrinkage, structural failure
85
What are the ideal conditions for dry rot to spread ?
Serpula lacrymans requires wood (hardwood or softwood) or other cellulosic materials as a food source. The fungus grows most rapidly on wood that has a moisture content above 30% though not saturated.
86
For dry rot how far past the affected timber would you remove ?
BRE digest 299 suggests 300-450 mm past the affected area. Treat surrounding timber with bioside. If affected structural timber seek guidance from a structural engineer.
87
Can you expand on BRE 251 ? What are the crack categories ? What are common causes of cracking ?
I have read bre digest 251 assessment of damage in low rise buildings. This defines cracks and assessment of cracking from level 0 a hairline cracking less than 0.1mm up to structural damage cracks greater than 25mm.``` Level 0-5 from bRE digest 251. 0 - Hairline crack less than 0.1mm 1 - fine crack - up to 1mm 2 - up to 5mm 3 - 5-15mm 4 - extensive damage - 15-25mm 5 - 25mm+ structural damage```
88
What is subsidence ?
Subsidence occurs when the soil beneath a building is unstable and sinks downward. This is not the same as ‘settlement’, which is caused by the weight of the building, but it can still have a negative impact in terms of the overall structural stability. The opposite effect of subsidence is ‘heave’, where the site upon which the building is situated moves upwards and/or sideways.
89
Can you expand on what your local building stock is ?
Predominantly Victorian residential buildings
90
What is wall tie failure and how would you identify it ?
* IDENTIFICATION — Horizontal cracking in every 5 or so brick course or in render. It's the corrosion of old steel ties such as large fishtail. The corrosion increases the steel up to 4 times leading to the cracking.* REMEDY — use borescope to determine the defect is wall tie failure. Locate wall ties and isolate or removed to ensure no further damage. Install replacement stainless steel mechanical fixed ties secured with an epoxy resin if required
91
What is rot and how would you identify it ?
* Dry Rot – Wood shrinks and splits into cuboidal cracks. Wood is light in weight and crumbles under fingers. Usually mycelium on the surface which is grey when wet and yellow/purple when dry. Fruiting body usually brown/red in colour. Indoors only.* Wet Rot – Wood shrinks and splits. Wood darkens. Mycelium grows on surface which can be white, brown, green or amber in colour. Fruiting bodies can be different colours and occurs internally or externally.
92
What are the stages of dry rot ?
* Spore* Hyphae* Mycelium* Fruiting Body
93
What are the different types of common damp in buildings ?
* Condensation* Rising damp* Penetrating damp
94
How would you identity between dry and wet rot. ?
Dry rot is the most serious form of fungus decay in a building, spreads onto and destroys much of the timber. On the other hand, the wet rot fungus occurs more frequently but is less serious, the decay is usually detained to where the timber becomes and stays wet.The Wet rot fungus tends to grow on porous surfaces, for example, timber with a high moisture content of around 50% while for dry rot to grow moisture of around 20% needs to be present. If left untreated wet rot can cause major structural problems as it can lead to weakened timbers.For moisture content to be suitable for wet rot growth there has to be a source of constant moisture – this could be as a result of defective plumbing or damaged guttering. Wet rot cannot spread through masonry and will cease to grow when the source of moisture is taken away. Due to the parts of the building that tend to have the correct moisture levels, for example, underfloor areas, dry rot can often cause significant damage before the homeowner is aware that there is even a problem with dry rot in the property.
95
What are wood boring insects ?
A wood boring insect is a common term that covers many species of beetles that as larvae eat and destroy timbers.Wood boring insects are usually found in areas within a property that are poorly ventilated with a high humidity such as for example a sub floor crawl space. This is usually because these conditions become perfect for the larvae to hibernate and transform into a woodworm beetle.
96
How do you use a protimeter and what are the limitations ?
Calibrated for timber, used to verify visual inspection cannot be relied upon.
97
What is a borescope and how do you use it ?
Camera to inspect, normally required to make hole to view into a cavity as an example
98
What is limecrete ?
Limecrete is a mix of natural hydraulic lime (NHL5) and sharp sand. Sometimes glass fibres are mixed in to give a more durable surface.
99
What is concrete carbonation ?
Concrete carbonation is the result of an electrochemical reaction between carbon dioxide, moisture and calcium hydroxide that is present in cement, producing calcium carbonate. Calcium carbonate lowers the alkalinity of concrete from pH12 – 13 to around pH9. This hardens the concrete and increases its compressive strength, but at this reduced pH level the protective passivation layer surrounding the reinforcing steel begins breaks down, leaving the steel vulnerable to corrosion.Rust (Iron oxide) has up to 6 times larger volume than the original steel, so as the steel reinforcements rust, the expansion causes the concrete to crack and spall.
100
Can you give me four examples of wood boring insects ?
COMMON FURNITURE BEETLE (WOODWORM) 3-5m long, dull brown Lines of pits on wings Found on or around damaged timber LATE MARCH – EARLY AUGUST (particularly warm weather. Softwood, European hardwoods 1-2mm dia. Circular flight holes Flight holes random orientation, mainly in direction of grain. Bore dust, cream coloured, lemon shaped pellets. Life cycle 2-5 years LONG HORN BEETLE Adult 10-12mm, black or dull brown. Sapwood or softwoods particularly roof timbers. South-west of London mainly surrey. Flight holes, few large oval, 6-10mm largest dimension. JULY to OCTOBER Cream coloured, sausage shaped.``` DEATHWATCH 6-9mm long, chocolate brown MARCH to JUNE Bore dust, disc shaped cream pellets Flight holes circular 3mm diameter Mostly oak and elm (hardwoods) ``` WEEVIL 3-5mm long, brownish black. Distinctive long snout. All year around. Flight holes, small ragged, 1mm diameter. Decayed softwood and hardwoods in damp conditions. Mostly found in below ground conditions.
101
Can you give me a examples of deleterious materials ?
* Asbestos* Calcium chlorides* Calcium silicate bricks* CFC’s* Formaldehyde * Hair plaster* HAC (High Alumina Cement)* Hollow clay pot floors* Lead* Nickel sulphides
102
What is a deleterious material ?
The term 'deleterious materials' is a broad one, encompassing not only materials that are dangerous to health or which are the causes of failures in buildings, but increasingly, materials which are environmentally damaging.
103
Difference between wet and dry rot ?
Dry rot can penetrate masonry, different humidity, One of the main differences between wet rot and dry rot is that wet rot needs a higher moisture content to grow. Wet rot fungus likes to grow on timber with a high moisture content of around 50% and above while for dry rot to grow it will germinate at a lower timber moisture content of around 20% to 30%.
104
How would you advise the client on a like for like replacement of a timber floor structure affected by dry rot, talk me through the steps.
* Consider the affected area* Remove affected timbers* introduction additional ventilation* rapidly dry out the area* trat area with a pesticide - probor10* replaced timber if splicing go 500mm past affected areas* protect joist ends form moisture ingress
105
Why is dry rot commonly referred to being more problematic than wet rot ?
As it can pass through masonry.
106
What typical building defects might you expect to see on a 1960s residential property?
* Wood wall slabs* snapped headers* Stone defects* sulphate attack in concrete or chimney stack* damp penetration* timber attacks* lead paint* asbestos* shallow foundations to bays - differential movement
107
Explain the different types of cracking you might expect to see on a 2-storey residential property.
Regular Horizontal cracking at regular intervals - wall tie failure Stepped or diagonal cracking - Movement, location dependant Horizontal cracking - Differential movement Cracking larger at top than bottom - Subsidence 0 - Hairline cracks: Less than 0.1 mm in width. No repair action required. 1 - Fine cracks: Up to 1 mm in width. Generally restricted to internal wall finishes. Easily treated using normal decoration. 2 - Cracks easily filled: Up to 5 mm in width. Not necessarily visible externally, but doors and windows may require adjusting to prevent sticking. Can be masked by suitable linings. 3 - Cracks that require opening up: Widths of 5-15 mm. Weather-tightness and service pipes may be affected. External brickwork may need repointing or, in some cases, to be replaced. 4 - Extensive damage: Widths of 15-25 mm. Windows and door frames become distorted, walls lean or bulge noticeably. Requires breaking-out and replacement of wall sections. 5 – Structural damage: Widths greater than 25 mm. Beams lose their bearing, walls require shoring, and the structure is generally unstable. May require major repair works.
108
Where a property is suffering from subsidence, what type of cracking might you expect to see ?
Vertical, larger at the top than the bottom
109
When investigating structural cracking to brickwork in residential/low rise property what recognised standards would you refer to assist in classifying the cracking ?
BRE Digest 251 - Assessment of damage in low-rise budlings - This defines the inspection and cracking sizes to reference
110
When investigating structural cracking to brickwork caused by adjacent trees what recognised standards would you refer to assist in assessing the risk posed by the trees present?
BRE Digest 298 - Low-rise building foundations - the influence of trees in clay soil
111
Give some examples of high-water demand trees.
```Elm Oak Willow Poplar Hawthorn - NHBC```
112
What methods of remedial work are available to deal with cavity wall tie failure?
* Replacement and or removal.* Replacement via remedial replacement resin set wall ties installed into the brick centre* Can also sleeve existing wall tie to limit further expansion* Treat existing wall ties with anti corrosion paint
113
If a property was suffering from dry rot, what might you expect to see?
* Dependant on the outbreak, a lack of ventilation. You would see damage or cuboidal cracking to the affected timber if visible then * Spores the dust presence of the rot* Hyphae 0 fine what strands* Mycelium - a collection of mass of hyphae* fruiting body - mushroom like appearance 0 dark red - releases the spores and the cycle starts again
114
Are there any limitations with the use of a damp meter?
Design and calibrated for timber, foil backed plaster board, black ash mortar will give inaccurate readings, it should be used to back up visual identification
115
How would you identify condensation in a property?
Consider the location and presence of damp, normally is low air flow/changes area, behind furniture, corners of room, near or adjacent to bathrooms and kitchens. Normally black spots.
116
Give some examples of the likely causes of penetrating damp.
• Slipped slates• blocked gutters• failed tanking systemsq
117
What is nail fatigue ?
That as a roof ages the fixings which are often nails start to fail resulting in tile or slate slippage especially in windy weather conditions.
118
What is concrete carbonation ?
Carbonation occurs when the alkaline elements of the concrete react with carbon dioxide creating calcium carbonate which lowers the PH level of the concrete which reduces the passivity. If there is inadequate coverage, the carbon dioxide can react with the protective coating on the steel and corrode it. Levels of carbonation impacted by compaction, temperature, humidity, carbon dioxide levels.Identify by carrying out an onsite test that will change colour when it comes into contact with high alkaline concrete.It is remedied by removing the delaminated concrete, cleaning the re-bar and patching the concrete.
119
Explain the cause of concrete carbonation.
The carbon dioxide being absorbed into the concrete to cause calcium carbonate which lowers the concrete ph., which can affect the protective coating on the steel reinforcement.
120
Explain the testing procedure when testing for concrete carbonation.
* The extent and depth can be confirmed using a phenolphthalein solution. Phenolphthalein solution reacts with the concrete – changes to pink if uncarbonated concrete and remains colourless on carbonated concrete * Carbonation depth is assessed using a solution of phenolphthalein indicator that appears pink in contact with alkaline concrete with pH values in excess of 9 and colourless at lower levels of pH* The test is most commonly carried out by spraying the indicator on freshly exposed surfaces of concrete broken from the structure or on split cores* Alternatively, the powder from drill holes can be sprayed or allowed to fall on indicator-impregnated paper or a core sample and the solution sprayed on* Cover meter can detect reinforcement positions, cover depth and bar diameters * Structural assessment may be required
121
What are the symptoms you might expect to find if a concrete floor was suffering from sulphate attack?
* Cracking* Bulging* Movement on the walls above or below DPC* Unevenness to the floor
122
Explain why sulphates in hardcore can result in sulphate attack.
As they are not protected with a DPM when they comes into contact with a water source they expand and can transfer this up into the slab above
123
Outline some of the key differences between the characteristics of brown rots and white rots.
Dry rot is the most serious form of fungus decay in a building, spreads onto and destroys much of the timber. On the other hand, the wet rot fungus occurs more frequently but is less serious, the decay is usually detained to where the timber becomes and stays wet.The Wet rot fungus tends to grow on porous surfaces, for example, timber with a high moisture content of around 50% while for dry rot to grow moisture of around 20% needs to be present. If left untreated wet rot can cause major structural problems as it can lead to weakened timbers.
124
What are the stages of woodworm ?
* Adult* Eggs* Lava* PupaAdult• The cycle begins with the mating of two beetles. Woodworm beetles only have a short lifespan as a mature adult between 10-14 days.Eggs• The female beetle will then lay her eggs into the cracks of the timber so that the eggs are protected and don’t become dislodged.Larva• After a few days, the eggs then begin to hatch and the new born larva burrow downwards into the timber producing frass – bore dust as they tunnel into the timber. This is the worm stage of an infestation.• This is the lengthy part of the cycle, as larvae can live from anywhere between two to five years.• During this time, the larvae will feed its way up and down through the timber (which can lead to structural damage).• This is also the part of the cycle when woodworm can be detected through the frass being produced. The frass can help us identify the species of woodworm and confirm the woodworm infestation is active.Pupa• The woodworm’s lifecycle is almost at an end now. The larvae form a pupal chamber where it ‘pupates’ and changes from the larva into an adult beetle just below the surface of the wood.• Adult Beetle emerges• These now adult beetles will eat their way through the timber to create exit holes which can be seen on the surface of the timber. From here the beetles will ‘flee the nest’ and start the whole process again.• Visit our woodworm page to find out more about these tiny creatures and how we can treat the damage they cause to your home if left untreated.
125
What is Regents street disease ?
Occurs in steel framed buildings with covering masonry or stone. Often found in early 20th century buildings. The porous cladding allows moisture to come into contact with the steel which then corrodes, expands and causing cracking to the facing around the steel frame.Repairs can include removal of the facework, clean the steel work, apply protective paint. OR Cathodic protection whereby a current is passed through. It does not make good existing corrosion but prevents continuation of process
126
What is High Alumina Cement ?
Defect around 1954-1974. HAC gives high early strength and was originally used in maritime construction. Found in Pre stressed concrete beams. The mineralogical changes increases porosity and reduces resistance to chemical attack. Identified by friable concrete that can turn brown.No real repair solution. Defects include chemical attack causing cracking and blowing of concrete. If you suspect HAC, arrange for lab testing of samples
127
What is Alkali Silica Reaction ?
* Most common alkali-aggregate reaction. Concrete is highly alkaline. Water within the pores will also be alkaline. The water can react with silica in the aggregate which produces a gel which expands and causes the concrete to crack.* Identified by cracking that is bordered by a colourless gel which leads to spalling. Further testing can be carried out in labs to confirm.* For it to occur, it needs silica in the aggregate, moisture and high alkalinity. Remedies include removing the cause of moisture, remove damaged concrete. Introduce secondary reinforcement if needed.
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What is Sulphate Attack ?
* Chemical reaction affecting concrete causing it to expand and crack. This is due to penetration of sulphates into the concrete from external sources such as rainwater or the materials mixed in.* Can lead to large cracks and potential heave.* Remedy is to break out and replace the concrete.* Generally occurs in houses built between 45-70’s in areas with mining or close to the sea. Occurs as soon as concrete comes into contact with moisture with sulphate but the cracks vary in the time they show up, depends on factors such as slab thickness, moisture content etc.
129
What concrete tests can be carried out ?
* BRE444* Hammer testing* Visual inspection* Magnet cover testing* Phenolphthalein test
130
What are common defects associated with flat roofs and what are the remedies ?
* Crazing - Surface crazing caused by lack of protection from UV exposure. No treatment is required if in small localised patches but should be monitored.* Ponding - If the gradient is not sufficient and there are dips in the roof finish, it can lead to pools of water. It can lead to water ingress if there is a gap in the roof finish.* Thermal Movement* Cracks and splits can occur when there is thermal movement between the substrate and membrane. Usually requires localised repair to the area around the crack.* Blistering - Caused when water vapour beneath the roof finish increases. The source of moisture should be traced and the blister opened and allowed to dry before patch repairing.* Flashing and Falls around openings- Defective lead from deterioration or poor workmanship around openings causing water ingress. Depending on the issue with the lead, there are different repairs.* People - Punctures caused by people from impact damage.* Cracks and tears along the line of joists - Caused by thermal movement or saturation of insulation or sagging decking. Repaired by cutting felt back and allowing it to dry before patching over."
131
What methods are you familiar with to assess flat roof defects ?
Firstly, visually inspect the roof for any defects and then use a thermographic camera to identify colder areas that may identify areas of leaks.
132
What should you consider when deciding whether to repair or replace a flat roof ?
The extent of the defect, when the existing roof was recovered, the approximate life span, the cost, timing, clients intentions for the building
133
What are the possible causes of sagging roof ridges and possible secondary problems ?
Decay to the timber forming the structure, inadequate supports or alterations carried out to the structure. Change of roof coverings. Secondary problems may be slipped tiles or opening joints at the ridge allowing water ingress.
134
Wood wool slabs are deleterious materials. Explain why and where their use would be acceptable.
When used as permanent shuttering for concrete, it may lead to grout loss, honeycombing or voids which can reduce fire resistance, corrosion protection and loss of strength. It is adequate for use in flat roof decking.
135
How can you test for damp ?
Speedy carbide meter or protimeter.
136
What is a speedy carbide meter ?
Measures moisture in masonry through adding masonry dust into a container with calcium carbide which releases a gas in proportion to the moisture present.
137
What are three remedies for rising damp ?
It is caused by a lack/failure of DPC or bridging. The remedies can be injecting DPC, removing the cause of bridging which may involve reducing the ground level.
138
How would you identify penetrating damp? What are the causes? How would you remedy it ?
Identify what the building is exposed to. Is there a leak, overflowing gutter etc. Identified by discolouration or damp patches which can darken and grow if left for long time. Remedies can be unblocking a gutter, fixing roof tiles, flashing, faulty pointing, lack of dpc below the parapet.
139
What is cold bridging ?
A cold bridge is created when poor thermal insulators come into contact allowing heat to flow through the path. E.g. at the junction of a concrete slab and external walls.
140
How would you identify condensation? What are the remedial measures ?
Generally occurs in top corners of rooms where warm air rises and collects and due to the change in temperature, the warm air releases vapour onto the colder surface. It is an issue in poorly vented and cold buildings where there is high moisture volume. It can be remedied by venting the property better and maintaining regular internal temperature.
141
How long would you leave brick/plaster to dry out before commencing work ?
Generally should be left for 3-4 months but this is not practical.
142
When was DPC made compulsory ?
1875
143
What other sorts of cracks would you expect to see on a brick building and what might have caused them?
* Subsidence – shrinkage of clay* Heave – saturated clay* Settlement – Movement from increased load.* Differential settlement – when parts of a building are constructed off different foundations or the ground has different soils, they move at different speeds.* Lintel failure – Usually leads to triangular cracking to the brickwork above the window to drop.* Internal alterations – drying of timbers or installation of steel beams without consideration of impact.
144
What size cracks are of concern ?
* BRE Digest 251* Up to 2mm – very slight/aesthetic* 2-5mm – slight / aesthetic* 5-15mm – moderate/ serviceable* 15-20mm – severe/ serviceable* Over 25mm – very severe / stability issues"
145
Cracks between the bay window and main wall. What are the causes and remedies ?
General rule of thumb is that it is caused by differential settlement due to different foundation types. It could also be because windows were swapped and the new window is not strengthened and causes the bay to drop.
146
What is the moisture content needed for Dry and Wet Rot ?
* 50-60% for Wet Rot. Will not survive below 44%.| * 25% for dry rot
147
Ends of the joists in a timber floor built in an external wall have been seriously affected by dry rot. How will you recognise this type of rot and what action would you take to resolve the problem ?
* Features include shrunken wood with cuboidal shapes. Cotton wool type mycelium on the surface. Timber crumbles under finger. Fruiting bodies are red/brown in colour and pancake shaped.* Identify the rot and where it is at its worst. Remove the cause and strengthen the joists as required or fully replace. If the dry rot has passed through the masonry, this will need sterilisation too.
148
Deflected timber floor in early 19th Century building. What methods are available to deal with this if the client requires a level floor ?
Confirm why the floor is deflecting. Notching to joists, not adequate for spans? Inadequate support? Can the issue be remedied without destroying the floor? Supplement the joists, overboard or remove it and replace.
149
A newly cast reinforced concrete slab is exhibiting crazing and cracking on its surface. What are the causes ?
Poor or inadequate curing – environmental conditions being conducive to evaporation and lack of protection. If the mixture is too wet or excessive floating which causes aggregate to sink, the cement paste on top will start to crack.
150
Name the three types of asbestos and examples of where they are found.
* Chrysolite – most common asbestos in buildings. Corrugated asbestos cement sheets.* Amosite – found in fire retardant materials* Crocidolite – pipe insulation, plastics, cement products.
151
What is Japanese knotweed ?
Herbaceous perennial plant.
152
What does Japanese knotweed look like ?
Hallow stems with raised nodes. Similar appearance to bamboo. Can reach 3-4m per year. Broad leaves with small white flowers
153
Why is Japanese Knotweed and issue ?
Invasive species which forms thick colonies that crowd and kill over species. Extend 7m horizontally and 3m deep making excavations difficult. Plant is resilient to normal weed killers and cutting. Needs herbicide application to kill it over a period of months.
154
What legal restrictions are there in dealing with knotweed ?
Offence to plant or grow it. Illegal to cause spread. Classed as controlled waste and requires a licence to dispose at licensed sites.
155
How should it be dealt with ?
Injected with herbicide or excavated with the roots and disposed.
156
What are common causes of stone deterioration and what remedial measures would you suggest ?
* Inherent characteristics – some stones have layers with different erosion rates. Small cracks in the stone can cause problems.* Salt crystallisation – salts in solutions pass into the stonework. As the stone dries, the salt crystallises which expands and blows the stone. Damage usually shows ass a powder on surface but can split the stone.* Frost Attack – General freeze thaw particularly if the stone has large pores.* Incorrect bedding – Stones should be laid in natural bedding position as it is stronger like this. If laid vertically, the layers are vertical making them more vulnerable to damage.* Incorrect pointing – inappropriate mortar mixes can cause issues with the mortar and stone. If it is too strong, the mortar will crack with movement or shrinkage which may allow water penetration. Strong mortar may also prevent moisture evaporating out and will instead go through the stone and potentially cause salt crystallisation.* Expansion of Metal – Iron and steel cramps have been used as fixings for stone. When they rust, they expand and can fracture the stone
157
What typical defects are associated with Victorian terraced houses ?
* Failed on lack of DPC* Insufficient foundations* Poor ventilation to floor voids* Damp penetration* Lead pipework.
158
What are the causes of staining to chimney breasts and the remedial work required ?
* Sulphate attack* Defective flashing* Removal of stack below
159
What are the likely causes of a leaning chimney breasts and what are the remedial works ?
Erosion, acid attack, salt crystallisation could all cause the stack to lean. BRE Guide states any lean of the stack of more than 1 in 100mm is unsafe. Consider lining the flue with a liner and replace broken bricks and pots. Relaunch the top if needed. Worst case scenario rebuild the stack.
160
Name some typical defects of a Georgian building (1700's) ?
* Water paths through parapets, hidden valleys and gutters* Springy floors resulting from decaying timber floor joists. mainly caused by poor cross-ventilation. heel drop test to test the springy floor. * Rotten or stuck sash windows* Blocked internal gutters. * Damp penetration in solid walls* Corroded cast iron railings bursting stonework* Bowed brick walls, caused by the practice of lightly bonding high-quality facing bricks in with poorer quality bricks of the main wall, unbonded party walls and front walls and decaying coursed timbers buried in walls* Failure in roof trusses caused when roof ties rot and begin to spread. Dislodged joists and ridges caused by bomb blast damage. * Leaning chimneys/over-tall stacks/damp penetration via stacks* Perforated lead work or splitting caused by over-beating or poor maintenance * Missing or badly altered load-bearing timber partitions* Damp basements* Failure of timber lintels* Poorly applied or painted stucco limiting water evaporation from walls* Downpipes decanting on to lower roofs from roofs above, causing temporary flooding in heavy rainfall
161
Name some typical defects of a Victorian 1800’s (1837 – 1901) ?
* Blocked air vents to ground floors, causing dry rot* Failed or lack of damp proof course – rising dampness, penetrating damp, efflorescence on plaster, decay to skirtings * Delamination of brick skins – bulging of brickwork * Over notching of floor joists for retrofit of services – deflection of floors, reduction in load bearing capacity* Poorly fitting sash windows, risk of decay within window reveals, water penetration beneath sub-sills, draughty or dangerous operation, decay in concealed areas, lack of security* Roof covered with concrete interlocking tiles – overloading of roof structure, bowing of rafters and purlins, roof spread* Settlement of bay windows – internal cosmetic damage, distortion in load-bearing elements * Wall tie failure (particularly in black ash mortar)* Heave or subsidence of shallow foundations* Nail sickness – ferrous nails corroded
162
What is HAC High alumina cement ?
High Alumina Cement was used in the production of pre-cast concrete sections. This has very high strength at an early stage, however, loses strength as it ages and is susceptible to chemical attack in damp conditions. Introduced in 1925, cement producer Lafarge commenced the UK manufacture of High Alumina Cement to provide concrete that would resist chemical attack, particularly for marine applications.Used in the UK from 1950-1976 in the manufacture of pre-stressed concrete beams
163
When was HAC banned ?
HAC concrete was banned in 1976 for structural use although new uses are now becoming established under the name Calcium Aluminate Cement (CAC).
164
What are the problems with HAC ?
HAC concrete undergoes a mineralogical change known as conversion. During this process the concrete increases in porosity which in turn results in a loss of strength and reduction in resistance to chemical attack. The higher the temperature during the casting of the concrete the more quickly conversion takes place.
165
Remedial measures for HAC ?
* An investigation should be undertaken consisting:* Sample testing* Collect details of construction materials used – the local authorities hold records of HAC buildings* If the strength has been reduced – reduce the live loads or strengthen* In the case of reinforcement corrosion – localised repairs can slow further deterioration
