Checklist: Is your home at risk of damp problems?

Retro fit cavity wall insulation causing damp is becoming more and more common – you can use the checklist below to assess whether your home could be at risk.

Damp could occur in properties as a result of retro fit cavity wall insulation if there is a combination of these factors:

  • your home is exposed to severe levels of wind-driven rain (zones three or four in our map)
  • your home is located in an unsheltered position, eg not protected by trees or other buildings
  • the external walls are poorly built or maintained with, for example, cracks in the brickwork or rendering.


Published guidance by the Building Research Establishment says that in these cases there is ‘an increased risk of rain penetration if a cavity is fully filled with insulation’. Rain could penetrate the outer wall, bridge the cavity via the insulation material and transfer moisture to internal walls, causing damp.

What kind of damp can affect homes?

There are three main types of damp in the home: condensation, rising damp and penetrating damp

Condensation in the home

Condensation is the most common kind of damp. It is caused by moist air condensing on walls/ceilings and is a problem that mainly occurs during the winter, as at this time of year the external walls are much colder, with the temperature also dropping within the loft area or space – Condensation occurs when large quantities of water vapour from general everyday living becomes trapped within a property. When the warm moist damp air comes into contact with cooler air, or a surface which is at a lower temperature, the result is condensation.


Condensation can be exacerbated by poor ventilation and heating that comes on and off, as this allows warm, damp air to condense. The removal of existing chimneys and fitting air-tight double glazing can reduce ventilation. Make sure trickle vents are in the open position.

trickle vent

Symptoms of condensation include the following:

You may notice water droplets on windows or walls, see dark mould appearing and/or notice an unpleasant smell. If left untreated, condensation can damage paint and plaster and cause window frames to decay.


How to get rid of condensation

On the whole you can improve condensation problems with better ventilation. This can be something as simple as opening windows – in our experience, more than half of those with condensation problems can get this solved by a simple change like this.

Condensation damp is reasonably easy to sort and can often be dealt with by simply opening windows more often, stopping drying clothes indoors, turning your heating on more, fitting new vents or installing new bathroom and kitchen extractor fans.

drying pic

If you don’t have a fan in your bathroom or kitchen, you should consider installing one – these two rooms are responsible for most moisture in the home.

Dehumidifiers can also help, but they are expensive to run, so it is worth getting to the source of the problem before investing.

Rising damp in the home

Rising damp is caused by ground water moving up through a wall via capillary action. Most walls allow some water in, but it’s usually stopped from causing damage by a barrier called a damp-proof course. This is usually a horizontal plastic or slate strip in the wall.

If this is missing or ineffectual, your wall may suffer from rising damp. This type of damp can also happen when the level of the ground outside your home is higher than your damp-proof course, allowing water to get above it.


Symptoms of rising damp

If you have rising damp, you may notice damaged skirting boards and floorboards, crumbling or salt-stained plaster and peeling paint and wallpaper. There may also be a tide mark along the wall.


If your damp-proof course isn’t working effectively, you may need a new one. The most common remedy is for a damp specialist from Extract4homes to drill series holes and inject damp-proof cream, but there may be alternative solutions.

Dig away soil below the level of damp-proof course

If you have a perfectly good damp-proof course (you will need an survey to confirm this), you can solve the problem by digging away the soil on the exterior side of the damp wall to below the level of the damp-proof course. 150mm- 300mm. Back filling with pea shingle for extra drainage.


Penetrating damp in the home

Penetrating damp is caused by water leaking through walls. This type of damp may move around within a building, but this is through horizontal movement rather than by travelling up walls. Penetrating damp is usually caused by structural problems in a building, such as faulty guttering or roofing, cavity bridging or defective insulation.

Symptoms of penetrating damp

Penetrating damp often shows up through damp patches on walls, ceilings or floors, which may darken when it rains. You’re more likely to get penetrating damp if you live in an older building with solid walls, or cavity walls which have retro fit insulation.

Don’t assume your damp problem will always be expensive to solve.  With penetrating damp, something simple such as clearing your gutters can also help.