Subsidence, fungal decay, woodworm, termites and damp can all affect a building's structure. All these problems will be highlighted by us, which any mortgage lender will request you provide when buying a property. But, should you notice anything yourself, you might also need to provide a survey when making a claim. So what should you look out for?
All about subsidence
Subsidence is caused by a downward shift of a building's foundations, usually because of changes in the moisture content of the soil. By contrast, ‘heave' is an upward ground movement, which occurs when dry soil swells due to increased moisture or the removal of mature trees.
What causes it?
Soil: Clay soil is particularly susceptible to subsidence.
Vegetation: Trees and shrubs can extract moisture and cause shrinkage, especially during long periods of dry weather.
Drainage: Damaged drains can also contribute towards subsidence.
Do cracked walls indicate subsidence?
Not necessarily. Although they are obvious signs, all houses suffer from cracking and many cracks are due simply to settlement. Buildings also shrink and swell naturally due to changes in temperature and humidity, which can lead to minor cracks, and routine maintenance such as grouting or sealing is usually all that's needed.
How can I tell if I have it then?
Subsidence cracks are normally around 1mm or more wide and are, quite often, wider at the top than at the bottom. If a series of small, often diagonal cracks suddenly appear in plaster work or at weak points around doors and windows or between different parts of the property, especially after long periods of dry weather, then it's time to take action.
Checking for damp
There are three main types of damp: rising damp, penetrating damp and condensation.
- Rising damp is the most common form and is caused by moisture from the ground rising up through the walls. The moisture often carries salts, which are deposited on the face of the wall when it evaporates. Internal decorations are stained and damaged, while plaster can de-bond and become loose. Rising damp only extends up to one metre above ground level but ground floor slabs are also likely to be affected, unless your house is modern.
- Penetrating damp is caused by moisture penetrating through the roof or walls. Roof problems are usually evident and damp penetrating through walls, which include flashings at roof and chimney abutments, is also easy to spot. It can also sometimes be caused by gutter or roof problems where rainwater has spilled onto and saturated areas of wall.
- Condensation is a damp problem usually caused by the occupants, as opposed to a problem with the property. A lack of ventilation and a tendency to dry clothes on radiators are both common causes.
Shouldn’t I already be protected against damp?
Normally walls are protected against rising damp by a damp proof course built into the wall. Really old properties did not have damp proof courses however, while fairly old buildings may have courses that have become invalid. Also, only modern properties have damp proofing under the floor slabs, as older properties relied on tile finishes to control it.
How do I cure it?
By injecting a chemical damp proof course and re-plastering the internal walls with a waterproof layer up to 1.2 metres high. If the problem lies in the ground floor, you can either use an impermeable covering, such as a vinyl sheet flooring or replace the slab with one that has a damp-proof membrane. Penetrating damp is a little more difficult to pinpoint and cure.
How do I know if I have it?
A Building Building Report will identify the areas where damp is present and will either identify its cause and give recommendations for any repairs or recommend that experts be brought in to ascertain the type and extent of the damp.
If you are buying a house and the survey highlights damp, you can usually negotiate a reduction in the price of the house, which takes into account the cost of the work that has to be done.
Structural problems that can affect the wood and timber in your home include fungal decay and termites.
What exactly is fungal decay?
This is more commonly known as dry rot and wet rot and, like many other structural problems, they are caused by dampness.
- Dry rot needs a moisture content of over 20 per cent for the fungal spores to develop. When this happens, fine grey strands of fungus spread over and through the wood, as well as other materials. As it grows, it gives off spores, which spread the fungus even further. In extreme cases the timber grows so dry, weak and brittle it can be broken up by hand.
- Wet rot, meanwhile, needs a higher moisture content (between 40 and 50 percent) and will become dormant if it falls any lower. Wet rot doesn't usually spread to other materials, but stains wood a dark brown colour and causes splits and cracks.
To treat fungal decay, you must first remove the sources of damp that are feeding the outbreak and to then carry out exposure works to ascertain the full extent of the problem. Repairs and replacement of badly affected timber may be necessary and all timber needs to be treated with an approved fungicide in order to prevent future attacks.
I think I have termites
It's not uncommon for old wood to display evidence of previous termite attacks in roof spaces or other structural timber. Treatments for active attacks consist of brushing or spraying insecticides onto the wood.
Do I have to replace my timber?
It would require a very severe attack to weaken the structural timbers to the point where they would need replacement or repair, so it's not unusual for wood that has been attacked to be considered structurally sound after treatment. However, repair and replacement may be required in extreme cases and your surveyor's report will show this.