Building pathology Flashcards
Tell me about a report you have prepared relating to the causes of failure, likely results of failure and apprpraite remedial measures.
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.
Why would you use non-technical language in a report?
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.
Tell me about BRE guidance you have applied and the reasoned advise you provided as a result?
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.
Magdalen damp report, OxfordWhat advice did you give your client about their legal responsibilities regarding damp
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.
Magdalen damp report, OxfordDid you consider the possibility of wet insulation affeceting the temperature of the wall
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.
Magdalen damp report, OxfordDid you determine what type of insulation was within the wall?
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.
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?
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.
Magdalen damp report, OxfordWhat additional inspections did you recmmond to your client should be undertaken?
I recommended that an intrusive investigation of the external wall should be undertaken to ensure that interstitial condensation had not occurred.
Magdalen damp report, OxfordDid you consider increasing the static ventilation of the property?
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.
Magdalen damp report, OxfordWhat external inspection did you undertake?
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.
Prestwick Road SubsidenceWhat did you consider caused the problem? And what inspections did you complete to come to the conclusion?
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.
Wigston Close, Structural WorksWhat immediate measures did you take for the safety of the occupants and the others?
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.
What is the relevant legislation relating to limitation periods and what does it include?
The limitation act 19806 years limitation period underhand contract12 years if the contract is signed as a deed
How can cavity wall insulation cause for damp in cavity walls?
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.
What are the methods for testing dampness in a material?
The oven method - drying and comparing to wet weightConductivity testingCarbide testing
What are the issues with oven and carbide testing?
They are destructive methods of inspectionRequire samples from materialInpracticial to use on siteA range of samples is required
What are the issues with conductive testing?
Does not register low levels of moistureIs calibrated to moisture content percentage of timberOnly test the surface/just below the surface of material
Magdalen Damp Report, OxfordExplani your pcoess diagnosing the damp at Magdalen.
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
Can you give me a definition of damp within buildings?
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.
How does a protimeter test for moisture?
Probes inserted into wallMeaures electrical current between two probesHigher the moisture, the greater the current
What is condensation within buildings?
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
How does condensation occur within buildings?
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
Magdalen Damp Report, OxfordHow did you determine that the damp was likely to be as a result of condensation?
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.
Magdalen Damp Report, OxfordWhy did you recommend the installation of a new passivents and a new extractor fan?
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.
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
What are 3 timber defects?
Wet rotDry RotInsect decay
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.
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
What BRE Digests are available for dry and wet tor?
Wet : 345Brown : 299
Explain insect decay?
BRE digest 307Uncommon is death watch beetle active March to JuneCommon Furniture beetle - Woodworm
What are 3 concrete defects?
Chloride AttackCarbonationHoney Combing
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
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
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.
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.
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.
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
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.
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.
Can you give me 3 defects of masonry walls?
Inadeqaute wall restraintLack of movement jointsLack of lintols
What moisture content is required for dry rot to occur?
Prolonged and regularly levels of WME 22%.
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
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
What documenation would you look to for identification?
BRE Digest 345 for wet rotBRE Digest 299 for dry
What are the primary measures for controlling outbreak of wet rot?
Locate and eliminate sources of moisturePromote rapid drying of structure
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
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.
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
West Hayes Damp ReportWhat were the observations you made when you inspected the ground floor flat internally?
NAME?
West Hayes Damp ReportWhat were the observations you made when you inspected the ground floor flat externally?
NAME?
West Hayes Damp ReportWhat third party investigations were conducted?
NAME?
West Hayes Damp ReportWhat did the investigations determine about the wall construction?
NAME?
West Hayes Damp ReportWhat trace of nitrate did the plaster analysis test find?
NAME?
West Hayes Damp ReportHow did you conclude that the leaking fittings were causing water to travel up the internal walls?
NAME?
West Hayes Damp ReportWhat additional moisture was causing for condensation to occur on the external walls?
NAME?
What experience do you have in identifying damp issues and diagnosing their defects?
NAME?
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.
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
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.
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.
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.
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.
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’.
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.
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.
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.
