Strategy: Renovation

Article 2 – March 2010

Dr. Dennis Coote Dennis has renovated over four hundred properties mainly Victorian over the last thirty years. Read more about Dennis….. To contact Dennis email dennis.coote@justdoproperty.com Resources Property Development for Profit Ebook View All Dennis’s Articles

Dampness in Buildings

Dampness in Buildings is one of the main factors in causing dilapidation in properties, apart from the obvious risks to the human inhabitants. Living in a damp house is likely to cause all sorts of problems connected with the mould, which will or has occurred and other related effects such as rheumatism.

Causes of Dampness

Dampness in a property is one of the main causes of rapid deterioration and all efforts must be made to find the cause or causes of the dampness and eliminating it. For the residents of a damp house, all kinds of health problems will arise, as well as the massive expense if left for too long.

One broken roof tile costing a pound or two, if left unattended over several seasons will cause hundred of pounds worth of damage to walls and ceilings.

There are five main ways in which a property may become damp. The following are the main causes.

• Leaking roof or gutters
• Rising Dampness from the ground
• Porous Brickwork or Stonework
• Internal leaks in the plumbing system
• Local flooding

Leaking Roof or Gutters

Tell tale signs within the building will be damp patches or areas of mould on upstairs ceilings or walls. If a gutter is blocked with leaves or moss, for example, the water will overflow down the external walls. If the walls are porous, the water will penetrate the wall.

An external visual inspection will show if any slates or roof tiles are broken or missing. In some cases the ridge tiles may have broken or blown off in a gale leaving it wide open for rain to enter.

An internal inspection of the roof is necessary, if it can be arranged. There is usually a trap door leading to the roof space, and a detailed inspection should be carried out. Check if there are any places where the daylight is showing through. If daylight can get through, so can rain. A careful diagram should be made so the holes can be related to the exterior and to identify broken slates or tiles.

Flashing (the sealing around a chimney stack or roof light) can be defective. Originally it would have been lead sheet, or for cheaper constructions, possibly zinc sheets.

Often a fillet of cement is used to make the joint between the roof slates or tiles and the chimney brickwork. This cracks within a short time and allows damp penetration.

If there are any doubts about the soundness of the gutters and down pipes, I strongly suggest that they are all replaced. The cost is inexpensive and trying to repair old gutters and down pipes is a pointless and futile exercise.

Rising Dampness

There are several causes of dampness rising from the ground.

One of the commonest is where the property has a wooden floor suspended on joists. There should be good air circulation under the floor by means of airbricks or gratings. These allow a flow of air through the under floor space. Upon inspection, one finds that the airbricks have become blocked with dirt. Even worse in some cases, garden soil is heaped up against them.

Without this air circulation, condensation and moisture from the ground will quickly affect the property. In older properties particularly, there may be no over-site concrete, i.e. concrete covering the bare earth under the floors.

This rising damp causes patches of discolouration to appear at low level on the ground floor walls and if untreated will cause the plaster to decay, and the ends of the floor joists to rot. The skirting boards will show signs of wet rot and start to decay if the dampness is not controlled.

In addition, the damp proof course (usually shortened to DPC) may be ineffective. In older buildings those of cheaper construction often relied on the density of the bricks at ground level to act as a moisture resistant barrier or damp proof course. In better building construction a slate course was built in at ground floor joist level.

Technical stuff: According to Building Regulations, the DPC should be installed at 150mm (6 inches) above the outside ground level. If the floor is a suspended wooden floor, the bottom of the joists should be laid on this. The DPC must cover the full width of the masonry leaf and project 5 mm beyond any external face.

More recently, bituminous felt was used as a damp proof course. The bituminous felt often deteriorated and allowed moisture to pass upwards into the upper wall.

This is known as ‘bridging’ of the damp course.

The remedy here is to install a new damp course along the area that is affected by rising damp and is fully discussed in detail later in the course.

The present method is to use heavy quality polythene strip.

Porous Brickwork or Stonework

Brick or stone walls can deteriorate over the years and brick particularly can become porous. Added to this, the cement between the bricks, the pointing, can decay and even fall out, allowing dampness from driving rain to enter the building. Creepers such as ivy may be present and the roots may open the brickwork sufficiently to allow water ingress.

An inspection should be made of the condition of the brickwork and of the pointing, particularly if there are otherwise unexplained wet patches on the walls. Defective chimneystacks are notorious for allowing damp to enter the building. Damp patches can appear on the wall above the fireplace. Because of the difficulty of accessing chimneystacks, the pointing is often neglected until the problem has become serious.

Leaks in the plumbing system

Upstairs bathrooms can become defective and a minor leak in a waste pipe for instance can, over time, develop a substantial amount of dampness. This is often not noticed until it becomes serious.

Careful investigation is the only answer for tracing these causes of dampness.

Local Flooding

The cause of the flooding is usually generally easy to discover, but it is important to make sure that everything has been dried out thoroughly after a flood. Both wet and dry rot can be started by saturation of a floor or wall.

An idyllic spot near to a brook, but this brook can become a raging torrent at certain times of the year and the cottages on the right are flooded.

Therefore dampness should be tackled as soon as it appears, the longer it is left the more expensive will be the remedies.

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