Building Pathology Flashcards
What is Dry Rot
Dry rot (also known as serpula lacrymans). Dry rot requires unprotected timbers to become damp with a moisture content of approximatly 20% to thrive.
What are some symptoms of dry rot
Damp musty smell,
Large concentrations of fine brown dust (spores),
The presence of Hyphae, fine strands of fungal growth that combine together in order to spread,
Mushroom like orange fungus, the fruiting body is often found in warm, damp, dark unventilated places such as under floorboards,
What is Wet Rot
Wet rot (also known as coniophora puteana). Wet rot thrives at a moisture content between 30% - 60%. Wet rot can cause severe structural damage if not treated.
What are some symptoms of wet rot
Damp musty smell,
Affected timber will appear discouloured often darker,
Affected timber will be soft and spoungy,
Fungal growth will appear near the moisture source as the fungus does not spread over masonry,
Mine Fungus
What is mine fungus
Mine Fungus (also known as fibrovaillantii). A form of wet rot often mistaken as dry rot. The fungus grows on coniferous trees such as pine. The fruiting body is an irregular white plate with a thickness of 2-12mm. White cotten like mycelium can grow, in newly formed mycelium fine drops of clear liquid maybe present.
How do you treat rot
Stop the moisture source in order to dry out the affected area.
Remove damaged area in order to prevent any further spread.
Rot treatment of neighbouring material such as fungicidal paste to form a protective chemical barrier.
Damaged timber replacement with preservitive treated timber.
Methods of detecting high moisture content
Electronic damp meter,
Speedy carbide meter,
What is an electronic damp meter
damp meters usually work by measuring the electrical resistance between two pins. Often displaying the moisture content as a pecentage.
What is a carbide speedy meter
carbide speedy meter requires a small drilled sample of material is mixed with a weighed quanityiy of calcium carbide inside a pressure vessel.
What are the limitations of an electronic damp meter
Meters are only calibrated for timber,
Hygroscopic salts can exaggerate reading (it is important to test for salts),
Different species of timber have different resistances,
The following can provide exaggerate readings;
- Copper, Chrome or Arsnic treated timber
- Foil lined wallpaper
- lead paint
What are the limitations of an carbide speedy meter
Destructive technique,
Danger of fire/explosion if the regent is exposd to moisture,
Generally not as quick as other methods,
What are some crack monitering techniques
Crack width gauge, Plastic tell tale, Glass tell tale, Brass screws and callipers, target and total station
What is crack monitering
Observing crack width changes is one technique used to monitor structural damage due to movement.
What is a Crack width gauge used for
Steel ruler is simple instrument used to monitor crack width variation. The crack can be measured to the nearest 0.5mm. Typically used at the start of a crack investigation.
What are Plastic tell tales used for
The plate with scales marked in millimeter units of measurement is fixed on one side of the crack and the other plate marked with cursor is fixed on opposite side of the crack. Pros include; They can measure cracks along two axis, can get corner crack monitors. Cons include; fixings can come loose expecially if stuck on with adhesive or if knowcked. Typically 1.0mm degree of accuracy.
What are Glass tell tales used for
This technique used to measure crack width variation in the past, but it is not popular any more. It basically consists of strip of glass cemented on to the cracked structural element. This method is no longer used because there is no way of measuring the extent of the movement or direction.
What are Brass Screws and Calipers used for
In this technique of monitoring crack width variation, two screws are fixed on each side of the crack at 90 degrees. The screws will guarantee the correct measurement of the crack width and prevent errors. Digital calipers often have a resoloution of 0.01mm. In some cases discs are glued onto the wall.
What are targets and total station used for
Typically used to monitor larger scale movement i.e. bridge subsidance. Recorded from a known datum to ensure co Accuracy up to 1.5 at a distance of up to 1,500 meters. This can also be achived by laser reflective targets fixed to the structure. This is typically more expensive and time consuming.
What are common types of wood boring insects
Longhorn beetle, Deathwatch beetle, Powderpost beatle, Common furniture beetle, Wood boring weevil.
What is the lifecycle of woodboring insect
Egg - Laid in or on the surface of the wood
Lava - 4 weeks to years feeds within the wood
Pupa - 1-4 weeks+ lava is nearlly fully grown and begins to surface
Adult - 1-35 days fully grown mates and lays eggs
What are signs of wood boring insects
Flight holes,
Frass,
Damp timber,
What are flight holes
Flight hole are where the lava emerge from affected timber.
Typically sized 1-3mm, can help identify the type of insect e.g. longhorn beetles have flight hoels between 6-9mm.
Typically round the shape can help identify the type of insect e.g. weevils create jagged holes, Longhorn beetles create oval holes.
What are some factors that impact wood boring insects
Location some insects are exclusive to a reigion or country e.g. termites are not found in Northern Europe, Longhorn beetles are restricted to surry
Types of timber certain types of insect prefer certain types of timber. Some only attack soft wood or hardwood e.g. Powderpost beetle. Some attack only rotten timber e.g. weeviles. Some only attack sapwood.
How do you erradicate woodworm
The application of insecticide is ussually sufficent to erradicate woodworm.
Application of a liquid formulation to the surface of affected timbers by brush or typically low pressure spraying of permethrin, cypermethrin and cyfluthrin.
Bat friendly gels and pastes are avalible.
What is mundic block
Blocks produced from waste rock worked from mining, quarrying and beach gravel. The blocks breakdown overtime. The blocks typically degrade from the inside of the cavity to the surface.
What are the classifications of mundic block
A1 - Sound concrete in satisfactory condition
A2 - Concrete suitible subject to protection and maintenance
A3 - Stage 3 tested containing less than 30% possible problem aggregates
B - Contains more than 30% possible problem aggregates although appears sound
C - Clearly unsound from examination
Options A1-3 are morgagable, B-C are not.
How is mundic block tested.
Routine testing is taken in a 50mile radius of Tavistock.
Preliminary test screening - serveral 50mm core hole samples are taken from various locations.
Stage 2 examination will test the percentage of possible problem aggregates
Stage 3 examination will employ a petrographer to access if the material has no visible deteriation.
What are RAAC planks
Reinforced autoclaved concrete planks. BRE issued an Information paper on planks designed before 1980 following the collapse of a collapse in 2018.
