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Dealing With Damp

By: Alan Cole - Updated: 27 Dec 2015 | comments*Discuss
Damp Proofing Damp Course Rising Damp

Damp problems are very common in older houses especially in the UK which has a wet climate. Read on to find out how to identify the signs of damp and to find out what you can do to cure and prevent damp from damaging your home.

Problems with Damp

Any home which is not properly looked after has the potential for a damp problem. If the problem is not tackled the consequences can include damaged furnishings, expensive structural repairs as well as ill health.

Causes of Damp

In older houses the walls are usually solid which encourages damp but in many cases damp is encouraged due to poor maintenance. The roof, walls, floors, windows and doors and pipe work in and outside the house, are all potential causes of damp. Usually a damp patch inside the home is easily identified as being linked to a problem outside the house. A damp patch at the top of a chimney breast will indicate the probable cause is a leak through the chimney stack. A wet patch at the top of a wall might be due to a leaking gutter outside. Damp near windows and doors also offer vital clues. Sometimes though, a damp patch is not near the source of the leak on the outside. Instead the damp is coming from a distance away. The water could be finding its way along a joist, for example.

Signs and Remedies for Damp

There are many signs to look for and a variety of remedies:

  • Loose flashing – Replace broken bits with adhesive flashing patch.
  • Cracked chimney stack or crumbling mortar – Repair with mortar or sealant.
  • Damp chimney stack – May need slating and ceiling at the top or adding ventilation bricks to increase ventilation.
  • Gutters and down pipe blockages and leaks – Clear gutter and pipe and repair broken joints and cracks as necessary.
  • Cracked walls – These can let in rainwater so repair with suitable filler.
  • Blocked airbricks – Clear these to encourage ventilation.
  • Cracked or missing tiles on the roof – Repair immediately.
  • Plumbing leaks in the system, bursting tanks – Repair as necessary. Insulate pipes and tanks to prevent freezing in winter.
  • Gaps between doors and frame – Fit insulation rubber or weather bar.
  • Gaps between windows and frame – Clean or refit sills. Add weather bar.
  • Damp patch on wall – A damp proof paint is often enough to prevent damp from spreading.

Installing a Damp Proof Course

Modern homes built in the last 60 years normally have cavity walls – two layers of bricks with a space between - which helps prevent damp. At the base of the wall a damp proof course is usually installed. This is normally a waterproof covering such as slate or a bituminous material, etc. Many older houses will have had a damp proof course injected at a later date. Damp proof courses are controversial because they are often expensive when using a contractor and if not properly implemented or maintained they are not brilliantly effective, leaving you out of pocket. Rising damp due to a faulty or deteriorated damp proof course can cause considerable damage to your joists and walls. And while a faulty damp proof course cannot be repaired the good news is that it can be replaced fairly easily. It is really worth considering doing this yourself as it will save you money and it is not that difficult to do.

Probably the easiest method is to use a chemical/silicon injection:

  • You can hire all the equipment you need for pumping in the liquid.
  • You simply drill 10mm holes, downward sloping, about 150mm below floor level.
  • The holes should be angled so they slope to the centre of the wall.
  • You may need to drill holes from both sides if the wall is thick
  • The brickwork around the holes sweats when there is enough chemical injected into it.
  • Then you seal the holes with mortar or plastic plugs. If you don't, the damp course will be become ineffective.

Prevention and Monitoring

Often the best cure for damp is plenty of ventilation. A few preventative measures or early intervention can also work wonders in keeping your home dry.

  • Get up in the loft and check under your roof for leaks.
  • Check your chimney stacks and around them.
  • Check insulation on doors and windows.
  • Open windows and allow ventilation around your home when weather conditions allow.
  • Keep airbricks clear to ensure good ventilation.
  • Maintain and clear gutters.
  • Check outside walls at ground level and check damp proof courses are operating successfully.
  • Maintain external and internal paintwork – use plenty of coats and special damp proof paint if necessary.

Don’t Panic

Remember, the very best cure for damp is often simple - ventilation. A well ventilated property will do a lot of work towards preventing damp. Also, remember that damp may occur after very heavy rain when older brick work becomes sodden. It may then rectify itself when normal weather returns. So don’t rush into expensive repairs unless you are sure they are absolutely necessary. Often the remedy is quite simple. If in doubt consult a trusted professional.

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My son's bedroom is at the front of the house and is the old garage that has been converted.It has a slopping roof.we starred noticing a horrible smell from his bedroom but could never find it then noticed patches on the ceiling by the Windows which we concluded was Damon& what had been causing the smell.The guttering in the roof was blocked with leaves, debris etc so cleared that but the smell is still there and it's awful & the patches are still on the ceiling.What can we do to get rid of the smell etc?
Tasmin3 - 27-Dec-15 @ 7:16 PM
I had a leak that was fixed around 8 years ago but recently a brown mark is showing where old leak was, we didn't treat the damp after the roof problem was fixed is this causing an old stain to show through? Don't think it's leaking again as it's not wet just a brown patch showing through white paint. What should we put on old damp patch before painting to stop it coming through? or should we get a roofer in again although I am worried roofer might say it needs done when it doesn't. Any ideas welcome
TEA - 3-Aug-15 @ 8:23 PM
We have an old cottage that has some damp patches on the internal walls. No one seems to know where the damp maybe coming from as the patches are in the middle of the walls so it is not rising damp, any ideas that may help?
bongo - 4-Sep-12 @ 4:39 PM
Ventilation is vitally important in houses, doesn't matter whether they're old or new (if anything, more important in new houses where the standard of building and materials isn't as high). Use it as a preventative measure to avoid problems with damp. Similarly, clear the gutters every autumn after leaves have fallen, and check the flashing to make sure it's tight, with no water getting through. Simple measures can save a fortune.
Carl - 25-Jun-12 @ 10:47 AM
if air bricks are blocked will this cause the house to become damp
tootsie - 28-Nov-11 @ 11:37 PM
Brown damp patches appeared on our dining room walls recently exactly where air bricks were located on the exterior wall. I have now cleared the air bricks having discovered they were blocked, however, the wet patches still haven't dried out properly after several weeks. Is this normal or will it dry out eventually or should I get it looked at by an expert ?
JOHN - 22-Nov-11 @ 4:06 PM
Hi there I like your advice maybe you could answer a question for me, I have a concrete built house it now has a damp patch which is travelling to interior wall from outside wall there is a crack from window sill height,could this be the problem as it only seems to be in the outside render I have drilled a hole to hang air vent as it did not have one.Did I do the right thing or should I have got in the profesionals to deal with this?
monkey - 5-Apr-11 @ 7:53 PM
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