Damp Problems Information Guide
- regular maintenance and intelligent building practice will prevent most causes of dampness in buildings
- moisture ingress is the main cause of building defects
- moisture meters can not diagnose damp, they will only highlight the pattern of dampness (moisture profiling)
- gravimetric testing (oven drying mortar samples) is the most accurate way of establishing the moisture content of a material
- defective gutters and blocked fall-pipes are a common cause of dampness
- high external ground levels are responsible for many damp problems
- timbers encased in damp masonry are at risk from wood rotting organisms
The effects of dampness in buildings is a subject that is often misunderstood, exaggerated, misdiagnosed and has given rise to an industry which sells many different products that are marketed to remedy damp problems. Unfortunately, many property owners have unwittingly spent good money on unnecessary and damaging works.
The key to successfully resolving any building defect is to correctly diagnose the problem before consideration is given to how best repair the defect.
There are many ways by which moisture can travel into a building and some of the more common sources of moisture are briefly described below.
Rising damp
This source of moisture is caused by moisture traveling vertically and to a lesser extent laterally, through pores in building materials (capillary action).
Penetrating dampness
This is classified as a source of moisture ingress from outside the building. These sources include seasonal wetting from rainwater, snow, sleet and ingress from overflowing or blocked rainwater goods (gutters, fall pipes etc). Flood or standing water pooling up against a building will also encourage water to penetrate into the building.
Condensation
The lifestyle of the buildings occupants, seasonal weather conditions and the design and construction of a building will determine the likelihood and extent of condensation within a property.
Below ground sources of moisture
Moisture can enter the building as a result of a leaking domestic mains water supply, defective drains or high water tables.
Internal plumbing leaks
Burst or leaking pipes, cisterns overflowing and leaking shower and bath seals can all attribute to dampness within buildings.
Site specific moisture
Some buildings are constructed on sites with high water tables, surrounded by trees and in sheltered valleys, which will create its own micro-climate, attributing to dampness in a building.
Maintenance and repair
Poor maintenance of rainwater goods, roof coverings, pointing of brick and stonework will all lead to potentially damaging amounts of moisture entering the building. Repairs and alterations to the building using inappropriate techniques and materials will also lead to excessive amounts of moisture passing through the fabric of the building.
Our experience
I am often asked for my opinion on the subject of rising damp and the following explanation is based on my experience in the field and is supported by scientific studies.
Rising damp does exist, moisture will rise through many building materials, however, the term ‘rising damp’ is very ambiguous and is more often used to describe rising damp caused by penetrating dampness.
To simplify, if outside ground levels are higher than the internal floor level, moisture can penetrate laterally, before rising. Is this rising damp or laterally penetrating dampness? It is both, rising damp caused by laterally penetrating moisture.
Buildings are designed to manage moisture, with modern buildings reliant on physical barriers and older buildings reliant on the breathability of materials to control moisture.
Problems arise when these control mechanisms are ill designed, deteriorate or modified.
The causes of damp problems can sometimes be easily explained, sudden wet marks on a bedroom ceiling may suggest a roof tile has slipped. However, other symptoms may require the help of a suitably qualified and experienced person.
Before you call for professional assistance, you may want to undertake the following diagnostic test for yourself, it could help to resolve the problem.
Draw a pencil line around the edge of the damp patch, write the date along a section of the line and monitor the defect. If you unblock a gully or gutter and the dampness recedes, then you have probably solved the problem.
If the problem persists after you have exhaustively investigated the most likely causes, call a consultant for some further advice. You can help the investigator by taking photographs of the defects and noting any changes in the severity and appearance of the defects.
Professional assistance
- Independent consultants
The independent consultant will investigate the defects and hopefully correctly diagnose the cause of the problem. They should be able to provide you with recommendations that resolve the problems and may also be able to provide specifications for any corrective repairs that may be necessary. They may also direct you towards trade associations for the recruitment of any specialist services that are deemed necessary.
2. Remedial treatment companies
Often referred to as damp and timber treatment companies, they will usually undertake free assessments of damp and timber defects or charge a nominal fee. Some of these companies will give you the option of a separate report for damp or timber defects and may be members of a recognised trade association. If they find problems they will often recommend chemical treatments that will try to manage the defects.
Corrective repairs
We promote and describe corrective repairs as those that address the causes not the effects of the building defect.
Prevention is always better and cheaper than cure so try to plan a maintenance programme for the building.
Get into the habit of looking at your property from a maintenance point of view, look up and check the roof covering and chimneys, clean out gutters and drainage gullies.
Today, many property owners undertake maintenance repairs themselves, however, should you prefer, a general builder will often be capable of repairing the problems that have caused damp defects without the need to employ a ‘damp specialist’ to undertake repairs.
During our investigations we find that the most common sources of moisture ingress are caused by poor maintenance, ill advised alterations or the design limitations of the original building.
We do not recommend a reliance on chemical treatments, cementitious resin or plastic membranes as a means of managing the effects of dampness but promote targeted, corrective repairs and good building practice as the long term solution to building defects.
It is not only as a result of our work in the conservation of historic buildings or because we care about the environment that we are against chemical treatment companies, targeted chemical treatments have their place, it’s their misguided and unnecessary use that doesn’t.
To speak to a surveyor,
for a free no obligation quote, call 0871 2185767