Damp

 

Is your house damp? 

There are many different types of dampness that exist, mainly damp walls and salt damp that results in damp rooms. The type of dampness in a building can include the following;

 

Rising damp

This can occur for many reasons, but is usually related to the age of the building where the ground level is close to the damp course which has then deteriorated with age and salt attack. There can be many contributing factors such as lack of stormwater drainage and the roof water discharging to the ground which results in a wet area beside the house. Also, the ground level can be raised to either close to the damp course, or above and that accelerates the deterioration of the damp course.

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There are varying methods of repair for dampness within a building where rising damp is evident. What must be first investigated is whether contributing factors exist and if additional works are required to reduce the dampness to a more acceptable level. This should be inspected and reported on by an experienced building consultant. Where the damp course needs replacement, then chemical injection or a new physical membrane can be installed. The chemical system sets up a horizontal barrier usually at floor level. This involves drilling of the bricks and injecting the chemical into the wall. Where a physical barrier is installed, then a horizontal cut is made into the wall so that the new membrane can be slotted in. This system can work well, but requires adequate sealing at the joins to the damp course material, adequate supporting of the brickwork above to prevent movement and the use of a suitable material that can be pushed across the full width of the brick and not "buckle" if there are any obstructions.

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Where the rising damp has been occurring for a prolonged time, then salt damage and blistering of the wall surface can be evident, mainly within the building. This requires an additional treatment called a desalting treatment. The plaster is removed on internal walls and the bricks are treated to stop the salt from forming on the surface. The wall will require replastering after the treatment. If this desalting is not done, then the salt will continue to bleed through the new paintwork which is applied over the wall.

Lateral or penetration damp

This is mainly in Victorian era buildings (constructed prior to 1900) where the walls are a solid brick construction.

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The walls were constructed that way for strength due to the soft nature of the bricks that were used. The solid wall construction if not adequately constructed and maintained will allow for rainwater to be absorbed into the bricks and through capillary attraction, the moisture would penetrate the bricks and be evident on the internal surface. The paint on the external surface was the waterproofing on this type of building. Where the paint has not been maintained in a reasonable condition, then water can be absorbed into the bricks. 

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With prolonged exposure, the plaster on the internal walls will soften and possibly fall off the brick wall.  Examples of penetration damp and plaster deterioration are shown in these photographs below.

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Penetration damp can also occur on later buildings where the cavity wall is blocked, or partially blocked, with obstructions or cement droppings. In these cases, the blockages must be removed.

Descending damp

This generally occurs where the top of the brick wall extends above the roof line and is exposed to the weather.

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Rainwater is absorbed into the brickwork, such as a parapet wall, and then descends down to the internal wall surface. The rainwater enters the building because the paint to the parapet wall has deteriorated or the flashings within the wall are deteriorated or defective. Descending damp can also occur below brick chimneys as the metal flashing at roof level has rusted out with age and allows the rainwater to descend to the walls below.

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Condensation mould damp

Condensation mould is mainly a winter problem and differs to the above in that it is not a result of actual water entry. It is a lifestyle issue in that the air within the building is moisture laden and over time is allowed to collect on a colder surface, such as a ceiling and form a dark spotty effect. The type of repairs on condensation can be varied and will depend on the actual cause of the moisture laden air.

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Each of the above damp issues require professional expertise by a building consultant to identify the cause and then offer a positive solution. Independent advice should be obtained prior to engaging tradespeople as some of the products offered may not be the most appropriate for the problems that are evident.  Each of the above defects require a different solution to provide an acceptable outcome.  For that reason our experts are able to assist you in assessing the actual defect and the best solution to that defect.  Our office telephone number is 02 94187750.

 

August 2012 ©