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Friday, 31 March 2017

9 signs your home has penetrating damp


With the average value of a home in Britain rising £18,000 in 2015, according to official government data, owners who fail to carry out regular maintenance on their properties could be paying a very high price.

One of the most common faults in older properties is penetrating damp, according to independent estate agent Best Gapp.

A spokesman for the central London firm, which is based in upmarket Belgravia, says penetrating damp is the result of water leaking into a property.


The problem is often caused by structural problems, such as faulty roofing or guttering. This type of damp can move around a building, although this generally happens through horizontal movement rather than climbing up walls like rising damp.

You’re more at risk of penetrating damp if you live in an older building with solid walls, as modern cavity walls provide some protection – if water crosses the cavity it’s usually because mortar has spread onto a wall tie.

The tell-tale signs that your property may have penetrating damp include damp patches on walls, ceilings or floors that become darker when it rains. 

Here are 9 signs your home could be suffering from penetrating damp, along with the possible cause and a solution. 

1. Damp patches appear on the ceiling around the chimney breast
Possible cause: The flashing sealing the joint between the chimney stack and roof might have become dislodged or cracked, allowing water through the joint.Solution: If possible, refit the loose flashing. Otherwise, replace it with the same type of flashing or a self-adhesive flashing strip. 

2. Widespread damp on the inside of an external wall that spreads in wet weather
Possible cause: Old bricks can become porous over time, advises Fulham estate agent Lawsons & Daughters. This type of damage can allow water to penetrate through the wall.

Solution: Replace or repoint the bricks before treating the entire area with exterior water-repellent fluid.

3. A damp patch appears on the inner side of a cavity wall after heavy rain
Possible cause: If your brickwork isn't causing the problem, it could be mortar on a wall tie in the cavity that’s allowing water to cross to the inner wall, says London Bridge estate agent Williams Lynch.

Solution: Remove some bricks in the offending area to inspect the cavity. Chip off or rake out any mortar on the wall ties.

4. Damp patches or mould appear at the top of an upstairs wall
Possible cause: Blocked or broken guttering can send water gushing down your walls causing saturation that seeps through to the inside.

Solution: Regularly clear your gutters, and repair or replace any that are damaged.

5. Rot at the base of an external door or damp patches on the floor just inside the door
Possible cause: A door in an exposed position has a damaged weatherboard, or hasn’t been fitted with one.

Solution: Repair the damaged weatherboard replacing any rotten pieces of wood. Alternatively, fit a new weatherboard to ensure the door is weatherproof.

6. Damp patches appear around windows
Possible cause: Mortar may have become dislodged from the gap between your wall and window frame, according to Central London estate agent  LDG.

Solution: Seal any gaps with a flexible frame sealant.

7. A damp patch appears on an upstairs ceiling after heavy rain
Possible cause: A roof tile or slate has slipped, broken or fallen off, letting water through your roof.

Solution: Replace the tile or slate.

8. An isolated damp patch appears on an inner wall
Possible cause: You may have cracks in your brickwork or damaged pointing in the joints, allowing water to seep through your wall.

Solution: Replace the damaged bricks and ensure any gaps in the mortar are filled.

9. A damp patch becomes visible along the underside of a window frame
Possible cause: Exterior windowsills have a drip groove underneath to prevent rainwater running under and onto the wall. If this groove is filled with debris, such as layers of paint, water can run onto the wall.

Solution: Clear the groove. If the window sill doesn’t have a groove, glue and nail a 6mm square hardwood strip to the underside of the sill about 35mm from the front edge, and paint to match your window sill.


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