Ask the Agent: What is Damp and What Can I Do About It?

If a survey has revealed that the property you are about to buy has damp, what does that mean and what do you do about it?

What is damp?

Damp is generally defined as unwanted water or at least, moisture, in quantities that are unsightly or could cause deterioration to the building or furnishings. There are several types of damp:  penetrating damp, rising damp, damp caused by plumbing defects and damp caused by condensation. 

Penetrating Damp

Penetrating damp occurs as a result of problems with the fabric of the building that can allow water to leak into the walls or floors. 

Penetrating damp can also make your house smell musty, and can also cause health problems, especially among asthmatics or people with other respiratory ailments.  Damp can also contribute to a feeling of cold in the home and therefore could cause you to crank up the heat, making your utility bills more expensive.

What causes penetrating damp?

The damp could stem from problems on the interior or the exterior of the property or both.

• cracks and unsealed joints
• cracked and damaged rendering
• brickwork in need of pointing
• missing or damaged roof tiles or slates
• missing flashings and badly fitted windows - Flashing is the lead strip that is meant to provide protection when a structure abuts to or joins directly onto an existing structure. Snow and melted water can get behind lead 'flashings' and create a temporary leak when the flashing has become worn or damaged, or if it was not installed correctly.  A good example of this would be a lean-to conservatory or on an extension. 
• Faulty rainwater gutters or missing down pipes - Rainwater that is meant to flow out of the pipes and into the drains or a water butt, instead collects at a certain place on an external wall causing damp, usually indicated by a "tide mark" or stain, or the formation of green mould.  The water could also leak into windows, doors and cracks in the walls.  When water runs down walls, it could freeze within the walls, expand and cause cracks, leading to a vicious circle of allowing more damp into your home.
• Continuously running overflow from tanks and toilet cisterns - When this problem is not fixed, this can result in the overflowing water soaking your external house walls and causing water penetration, and ultimately dampness. 
• Un-swept and blocked chimneys with inadequate or broken chimney pots and cowls  - Chimneys could allow rain water to enter and eventually seep through the chimney breast internally and produce damp.  
• Cavity wall tie failure - this allows water penetration through both inadequate mortar joints (pointing) and also allows water to travel across the corroded wall tie through the internal skin of the brickwork.

To stop penetrating damp, the source of the moisture needs to be tackled and this usually involves repair work to your house of some kind.

Rising Damp

Rising damp is water from the ground that enters a structure by capillary action. Water that enters or affects a building through any other route can move about in various ways but is not rising damp. Rising damp can be cured by the installation of a chemical damp proof course.

What can I do about rising damp in my house?

Rising damp comes from water slowly rising UPWARDS into the building fabric from the ground or from any other source such as walkways and deck access and paths that run around your house, but are directly next to the walls

This is important to note the difference. Also one strange fact is that in most houses, damp will rise in what's called "capillary action" and will usually rise about 4 or 5 feet and then stop. So if you have damp in UPSTAIRS rooms its probably penetrating damp and NOT rising damp.

The main cause of rising damp in houses is the lack of an adequate damp proof course.  The damp proof course may be missing altogether or may have failed or have been bridged or bypassed in some way. The damp does not rise quickly and does not normally reach higher than 1 metre up the wall. It leaves characteristic tide marks and sometimes salt deposits on this edge. The marks will look the same for long periods and are not normally affected by changes in climatic conditions.

This damp is usually seen on external and party walls above the skirting boards.

Plumbing defects

This type of damp can be caused by:

• serious leaks or small leaks over a period of time from pipes or pipe joints.
• burst or fractured pipes following a freeze and thaw.
• unsealed gaps between wash hand basins, sinks and baths and showers and walls.
• corroded and faulty tanks and cylinders, including worn out valve washers producing continuous overflow.
• automatic washer connections and faulty drain and waste pipes under sinks.
• leaking radiator valves and central heating pipe work.
• broken and cracked toilets and soil pipe connections behind a WC

Plumbing defects are typically solved by:

• investigating and repairing leaking pipe work.
• sealing joints correctly between baths, sinks and walls.
• replacing valve washers to tanks and cylinders.

Condensation Dampness

Condensation is caused when moisture produced by everyday activities such as cooking and bathing meets a cold surface and condenses forming water droplets. Mould growth will quickly appear and spread all over the cold surface such as a wall or window frame. The amount of moisture deposited is dependant on how warm the air is, how much moisture the air is carrying and how cold the surface is.

The signs of common condensation are:

• misting of window panes.
• water droplets on window panes.
• pools of water on window sills
• damp patches on walls around windows.
• black or green mould growth in corners of rooms that are crescent shaped.
• mould growth around windows and isolated areas on walls (cold spots/cold bridging).
• mould inside cupboards and behind furniture.

Condensation control is a complex issue and is a balance between:

• adequate affordable heating
• improved insulation
• the reduction of moisture production
• controlled ventilation

If a survey has suggested that the property you have made an offer on has a damp problem, then it is best to seek the advice of a professional to assess the job and advise on the costs involved in solving the issue.  At this point you could choose to pull out of the sale or alternatively, you could ask that the sale price be re-negotiated to reflect the cost of repairs.  If you decide to undertake repairing the damp it is best to employ a professional builder or specialist.

If you need the advice of a damp specialist, Northfields can refer you to our preferred contractor so that you don't have to take a risk with the phone directory.  Call 0208 840 6666 and we would be happy to provide you with the contact details of our damp specialist.

Comments

[Peter Jackson]

Hi,
Excellent post. I think this all about the damp and rising damp. Rising damp is a very common problem by which a house can get affected as there are water sources in very house. The sources of the incoming water can be mainly the rainfall, humidity and ground water. Climatic conditions also play a major role, particularly in the levels of exposure of buildings and their location near the sea or in marine environment. Rain water is more likely to pass through a wall constructed in a material with a low porosity than it will do through a wall constructed in highly porous brick or stone that has the ability to absorb and hold water. It is very necessary to treat this problem so that we can save our property from this hazardous problem.

Thanks a lot for such useful post.