Water damage survey: signs, causes and what a surveyor checks in a house

Most water damage starts small. A blocked gutter, a cracked tile or a failing seal around a shower can let water in for months before any sign appears inside. By the time a stain or damp patch shows up, the problem has often been at work for some time. That is why finding the source matters more than treating the mark on the plaster.

The most common sources of water damage in a home are:

Blocked or damaged gutters: water pours down the front of the building instead of into the downpipes. It saturates the brickwork and eventually penetrates through to the inside.

Poor drainage around the property: where the ground slopes towards the building, water can pool at the base of the wall. This lets moisture get inside and, at worst, affect the foundations.

Broken or missing tiles: high winds and falling debris can crack roof tiles or cause them to slip out of position. Water can then seep into the roof space and the structure below.

Failed flashings: where the roof meets another part of the building, such as a chimney or a parapet wall, the joint is protected by flashing, often made of lead. When flashings perish or crack, water gets in at the joint.

Failed or missing damp-proof course: the damp-proof course is a barrier built into the walls at least 150mm above ground level. It stops ground moisture rising into the structure. If it is breached, bridged or absent, water will eventually make its way into the home.

Plumbing leaks: a slow leak from a pipe under the floor, a worn tap connection or failed sealant around a bath or shower can soak floors and ceilings unnoticed. A hidden leak like this often shows first as a damp patch in the room below. Pipes in unheated lofts and garages can also freeze and burst in cold weather, releasing a large amount of water in a short time.

Condensation: moisture from cooking, washing and drying clothes indoors settles on cold surfaces. In poorly ventilated rooms this leads to mould, peeling paint and rotting window frames.

Flooding: surface water or river flooding can cause extensive flood damage in a short time, particularly to floors, plaster, electrics and kitchen units. Even after the water has gone, building materials such as plaster and timber can take months to dry out fully.

Water damage is not always obvious. Common signs include:

• brown or yellow stains on ceilings and walls
• bubbling, peeling or flaking paint and wallpaper
• a musty smell, particularly in cupboards and under stairs
• black mould around windows, in corners or behind furniture
• swollen skirting boards, warped floors or loose tiles
• soft or crumbling plaster
• cold or damp areas on floors and ceilings
• tide marks on the lower part of internal walls
• an unexplained rise in your water bill

Any of these can point to damp, and the pattern of the damage usually helps identify the cause. A stain spreading from a ceiling suggests a leak from above. A tide mark near the floor points to moisture coming up from the ground or through the base of the wall.

Besides being unsightly, water getting into a home creates the right conditions for mould, which can affect health. Left untreated, persistent dampness can lead to wet rot in timber floors, joists and window frames. In the worst cases it can lead to dry rot, which can spread through the structure.

Once you notice the evidence, it is worth getting it resolved as soon as possible. That might be water cascading from a gutter, damp patches indoors or staining on a ceiling. Delaying only makes the repairs more expensive, because you end up fixing both the original fault and the damage it has caused. After a significant leak, the affected areas also need proper drying before they are redecorated, otherwise mould can return.

The key ongoing tasks are:

Check and clear gutters and downpipes, especially in autumn and winter when leaves and other debris build up.

Clear standing water that collects near the house and plan how to make sure water drains away from the property.

Check the roof and flashings for cracks and missing tiles. Do this from the ground if it is not safe to get closer, or ask a roofer to take a look.

Check external seals around doors and windows for wear and replace them if necessary.

Inspect timber window and door frames for flaking paint, then strip and repaint where needed.

Look for moss on brickwork and roofs. Moss holds a lot of water and its presence suggests a constant source of moisture, so it should be removed.

Check sealant around baths and showers and look under sinks for drips or damp cupboard bases. A small leak here can go unnoticed for months.

Improve ventilation by using extractor fans in kitchens and bathrooms and opening windows when drying clothes indoors.

Once the cause has been fixed and the surface has had time to dry, cover water stains with a stain block paint and then paint over them with standard emulsion. Covering a stain before fixing the cause will not work, as it will reappear.

When you are buying a home, water damage is one of the main things that can turn an attractive property into a money pit. It can also be easy to hide with a fresh coat of paint before a viewing.

A RICS Level 2 survey includes checks for damp and water ingress. The surveyor uses a moisture meter on accessible walls and floors and looks for the signs listed above. A RICS Level 3 building survey goes further. It explains the likely cause of any damage, the repairs needed and what could happen if the problem is left. It is usually the better choice for older properties or homes that show signs of previous repair work.

Neither survey involves lifting fitted floor coverings, opening up the structure or testing drains. Where the surveyor suspects a hidden leak, they may recommend that a plumber, drainage specialist or damp specialist investigates further before exchange. Specialist leak detection can use thermal imaging and other non-invasive methods to trace hidden moisture without opening up the property. If the survey report does uncover water damage, you can use it to renegotiate the price or ask the seller to carry out repairs first.

It is also worth checking whether the property is likely to flood. You can check the long term flood risk for an address in England on GOV.UK and in Wales through Natural Resources Wales. Your conveyancer's environmental search will also flag flood risk. Ask the seller whether the property has flooded before, whether any flood damage led to an insurance claim and whether it has been hard to get buildings insurance. A history of flood or escape of water claims can make cover more expensive or harder to find, so it is worth getting an insurance quote before you exchange.

Surveyor Local works only with RICS-accredited chartered surveyors across England and Wales. Your surveyor will look for water damage, damp and the defects behind them, and the report will set out what needs attention. That way you know what you are taking on before you commit to a purchase.

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