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Rising Damp

Rising Damp in York Harrogate and Leeds

The Cause / The Effect / The Repair


The Cause

The majority of building materials used to construct your home are porous, which means they can absorb moisture. When a modern home or building is constructed, a barrier is installed into the base of the walls and floors to prevent moisture from the ground being absorbed into the building materials. This is known as a damp proof course or membrane. Its purpose is to either repel or physically prevent the movement of moisture upwards through the building.

Rising damp occurs when moisture from the ground is absorbed up into the fabric of the building by porous building materials - a process known as capillary action. This unwanted moisture can then deteriorate the masonry, plaster, timber floors, internal decorations and joinery.

Not all buildings have a damp proof course. Many old properties constructed in the early 1900's did not have damp proof courses installed into the walls and floors during construction, leaving them vulnerable to rising damp.

Some properties constructed after this time with early damp proof course designs such as; slate or bitumen felt also suffer, as these designs can fail due to poor practice, design or material composition.

Now modern building regulations and advanced understanding of materials and practices should result in the problem of rising damp in newly constructed properties becoming a problem of the past. However, for many older property owners rising damp can be a formidable problem.


The Effect

Rising damp can be recognised in a number of ways; decayed skirting boards or floor timbers in contact with walls, deteriorating and salty plaster or discoloured and peeling internal decorations, often with a dark wavy tide mark appearance, can all suggest a rising damp problem.

If you recognise any of these symptoms it is essential that you contact a professional company to undertake a survey, correctly diagnose and propose a strategy for repair.

When rising damp occurs, salts within ground water migrate in solution into the walls and plaster. These salts aggressively attack the plaster and may appear on the face of the wall or plaster as a white powdery crystal. These salts can be hygroscopic which means they have the ability to absorb airborne moisture.

Where salts are present, it is essential that replastering is carried out to remove the salt contaminated plaster. If contaminated plaster is left, these salts may prevent the wall from drying due to their hygroscopic effect, continuing to give the appearance of an ongoing damp problem..

Be wary of any damp repair or contractors who states that replastering is not essential, without justification.

Our surveyors have specialist salt analysis equipment which can be used to detect the presence and quantity of problematic hygroscopic salts. Where necessary we can also remove samples of plaster and masonry for specialist in house laboratory analysis if required. This may reduce the overall extent of replastering needed, in some cases.


The Repair

Fortunately, it is possible to rectify the problem of rising damp without dismantling and rebuilding your home. Modern chemical, electrical and physical barrier systems exist which can be installed into an existing structure without too much disturbance.

By far the most common system is a chemical water repellent liquid or gel. Typically, these involve drilling a series of installation holes around the base of the walls to allow for the installation which is normally accompanied by re-plastering the walls internally with a salt retardant plaster.

Not all remedial DPC systems are suitable for all types of construction, therefore it is essential that the correct system is chosen for the method of construction to ensure successful treatment.

At Dryfix we also design chemical free systems for listed and period properties.


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