Building Pathology Flashcards
What types of structural movement are there?
a. Subsidence
b. Ground Heave
c. Land Slip
d. Settlement
What is Subsidence?
a. Caused by downward movement in the ground level. In clay soil, the removal of moisture within the soil causes it to shrink. This can be caused by large trees drawing moisture out of the soil. This can cause vertical / diagonal cracking which is wider at the top and thinner at the bottom.
b. If the subsidence is serious the property may need to be underpinned.
What is Ground Heave?
a. Caused by an upward movement in the ground level. In clay soil, an increase in moisture within the soil causes it to expand. This can be caused by the removal of large trees. This can cause vertical and diagonal cracking which is thinner at the top and wider at the bottom.
What is Land Slip?
a. Cause by downwards movement of loose / gravely soils on a sloping surface. Usually occurs by the erosion of soils due to abnormally wet weather and fast flowing water.
What is Settlement?
a. Caused by a downward movement in the ground level due to an increased load / compression. Buildings will settle when first constructed or if there is a significant change in the load i.e an extension.
- What type of soil is susceptible to heave and what are the possible causes?
a. Cohesive soils such as clay and silt are susceptible to heave as they are sensitive to changes in moisture.
b. Possible causes include the removal of large trees, changes in the water table, leaking drains and inadequate foundations built within movement zones.
What is Damp?
The presence of moisture within a building substrate which can cause discoloration and staining of finishes, mould growth, sulphate attack, frost damage or even drips and puddles.
Which areas would you typically test for dampness?
a. Ground / Basement walls below a height of 1.5m
b. Chimney breasts
c. Window surrounds and behind shutters
d. Roof voids
e. Adjacent walls to bathrooms/WCs
What are the 4 main types of dampness?
a. Rising damp
b. Penetrating damp
c. Condensation
d. Leaks from plumbing
What are the 6 common groups of rot to affect timber in the UK?
a. Brown Rot
b. White Rot
c. Soft Rot
d. Stains
e. Moulds
f. Plaster Fungi
What is Rising Damp, how does it occur, how do you identify it and how is it treated?
a. Caused by water penetration and spreading through capillary action
b. No damp proof course, DPC bridged by pointing, render, soil, paving, mortar droppings etc. It affects both solid and suspended floors
c. Identified by high tide markings up to 1.5m in height, blistering and peeling of wall finishes, musty smell, rotten timber, visible salt staining. Rising damp only occurs in basement and ground floor levels.
d. Repair / Replace DPC or install a chemical injected DPC which can be done to solid stone and cavity walls.
What is Wet Rot, how does it occur, how do you identify it and how is it treated?
a. Wood destroying fungus Coniophora Puteana
b. Occurs when excess moisture is present in timber over long periods of time
c. Two main types; White and Brown rot. White rot feeds on the lignin of timber and Brown rot feeds on the sugars and cellulose. Indications include darkening or lightening and a soft, spongey texture of the timber. There may also be localised fungus growth and a damp, musty smell.
d. Repair the source of dampness, allow the timbers to completely dry and treat the affected areas with fungicide.
What is Dry Rot, how does it occur, how do you identify it and how is it treated?
a. Wood destroying fungus Serpula Lacrymans
b. Occurs when excess moisture is present in timber over long periods of time. It can travel through building materials other than timber making it a high risk.
c. Indications include shrinkage, darkening and cuboidal cracking of timber and development of orange-ochre coloured fleshy mushroom bodies in humid conditions. Red coloured spore dust can be found around the fruity bodies.
d. Repair the source of dampness and removal / replacement of affected timbers and those within a 1m radius of pre-treated timber. Any other areas at risk should be treated with a fungicide.
What is Penetrating Damp, how does it occur, how do you identify it and how is it treated?
a. Can be found anywhere and is caused by water soaking through to the internal building fabric.
b. Caused by leaking downpipes, gutters, roofs and faulty bath/shower/window seals
c. Indications usually include staining, bowing plaster, warped wallpaper/paint etc
d. Repair the source of water ingress and either allow the area to dry out or replace the affected area.
How can you test for damp within a property?
a. The use of a Protimeter (Damp Meter)
What moisture content percentage can lead to rot?
a. 20-22% for dry rot, anything above can lead to wet rot.
What is woodworm, how is it identified and how is it treated?
a. It is a wood-eating larva of many species of beetle which burrow through wood causing it’s structural integrity to be jeopardised
b. Indications include bore holes (1mm – 1.5mm in diameter), frass (timber dust) and the beetle themselves.
c. Usually treated with insecticides
What are the 4 main types of wood-boring beetles found in the UK?
a. Common furniture beetle
b. Deathwatch beetle
c. House Longhorn Beetle
d. Powderpost Beetle
What is nail sickness?
a. The corrosion of the nails attaching the external roof covering to the roof timbers caused by moisture penetration between the sarking and roof covering.
