Damp in a property survey: how surveyors detect it and what it means

Damp is one of the most common problems uncovered during a property survey, particularly in older homes. The signs range from a patch of black mould in a bathroom to a tide mark running around a ground-floor wall, and the implications range from a simple ventilation fix to a structural issue that affects your mortgage. For an overview of all issues a survey can flag, see our common survey problems guide.

Here, Surveyor Local explains the main types of damp, how a RICS-qualified surveyor checks for them, what treatment typically costs and what damp could mean for your mortgage application.

• There are three main types of damp: rising damp, penetrating damp and condensation
• Both a Level 2 and Level 3 survey will look for evidence of damp and assess its likely cause
• A specialist damp report is often recommended where the problem is significant
• Rising damp treatment typically costs £800-£2,000 for a semi-detached home; penetrating damp repairs range from £500 to £2,500 depending on the source
• Serious damp can cause lenders to withhold funds or reduce valuations until repairs are completed

Rising damp

Rising damp occurs when moisture travels upward from the ground through brickwork and masonry by capillary action, the same process by which a sponge absorbs water placed beneath it. Because of this, it is confined to ground-floor walls.

The signs are fairly distinctive: a tide mark running around the lower section of a wall, stained or flaking paintwork, crumbling plaster and lifting wallpaper. Rising damp is almost always linked to a failed or missing damp-proof course (DPC), which should sit just above ground level to act as a moisture barrier.

Penetrating damp

Penetrating damp happens when the outer fabric of the property allows water to get in. Common causes include cracked or missing roof tiles, blocked or leaking gutters and downpipes, defective flashings, cracked brickwork and leaking internal plumbing.

It shows up as brown staining on interior walls and ceilings, and is typically more noticeable after heavy rainfall. If left untreated, black mould will often take hold.

Condensation

Condensation is the most widespread form of damp. It forms when warm, moist air comes into contact with cold surfaces, most commonly in kitchens, bathrooms and rooms with poor ventilation. Activities like cooking, showering and drying clothes indoors all contribute.

The tell-tale sign is black mould, usually appearing in corners, on window reveals and behind furniture. It is generally a ventilation and heating problem rather than a structural one.

Flooding or burst pipes

Water ingress from one-off events such as burst pipes, overflowing appliances or external flooding can also leave lasting damp damage if not addressed promptly. This is distinct from the structural damp types above and is typically identified through the property's history rather than the fabric of the building.

Yes. Checking for damp is a standard part of both a RICS Level 2 Survey and a RICS Level 3 Survey.

The surveyor will identify visible signs of damp, assess their likely cause and flag the severity in the report. Where damp is extensive or the cause is unclear, the report will typically recommend a specialist damp investigation, a separate report carried out by a qualified damp surveyor, often accredited by the Property Care Association (PCA).

A Level 3 survey is generally the better choice for older properties or those where extensive damp is already visible, as it includes a more detailed inspection of construction and building fabric.

Compare RICS Level 2 and Level 3 surveys →

Many signs of damp are visible to the naked eye: mould growth, stained or peeling paintwork, damp-stained plasterwork, damaged skirting boards and a musty smell. These are often what prompt buyers to raise concerns at the viewing stage.

In every room, and especially in kitchens, bathrooms, utility rooms and ground-floor spaces, the surveyor will use an electronic moisture meter to take readings from walls, floors and other surfaces. High moisture readings in areas that appear dry on the surface can indicate a hidden problem.

Where damp is suspected beneath carpets, behind heavy furniture or in a location that is not easily accessible, the surveyor will only investigate with the homeowner's permission and will not lift flooring or move fixtures unless this can be done safely. Any inaccessible areas will be noted in the report, along with a recommendation to investigate further.

The surveyor will also look for two secondary problems that damp can cause in timber:

• Wet rot: a fungal growth that feeds on damp timber. It can often be treated with a fungicide, though badly affected timber may need to be replaced.
• Dry rot: a more serious fungal decay that can spread beyond the original damp area. Early treatment is important to prevent structural damage.

The table below gives indicative ranges to help you frame a conversation with the seller or assess the scale of the problem. A specialist damp survey (£150-£350) is the right way to get an accurate figure for any specific property, as costs vary considerably depending on the extent of the problem, the property size and the treatment method required.

Note that replastering and redecoration after treatment are usually priced separately and can add several hundred pounds per room.

It can, depending on the type and severity.

Mortgage lenders generally treat rising damp and penetrating damp as structural concerns. If a significant problem is identified in a Level 2 or Level 3 survey, the lender may put the mortgage on hold until a specialist damp survey has been carried out. Their decision will then depend on the findings of that report.

In some cases the lender may retain a portion of the funds, or reduce their valuation of the property, until the problem has been remedied by a reputable contractor with a written guarantee.

Where rising damp or wet and dry rot have caused serious structural damage, the lender may decline the mortgage entirely until satisfactory evidence of completed repairs is provided.

Condensation alone is unlikely to affect mortgage lending, unless it has caused significant mould damage or secondary timber decay.

A RICS Level 2 or Level 3 survey is the right first step for any property purchase. Get a free quote or call our friendly team on .