Rising damp is the term given for high water content in a buildings walls which rise from ground level.
Signs of rising damp
When paintwork becomes damp and expands and blisters on the lower part of walls.
Damp walls often smell musty.
Reasons for Rising Damp
The damp proof course (known as d.p.c.) is a layer of plastic built into the original brickwork at ground level to prevent ground damp from rising up walls. This layer is often incorrectly laid or not laid at all by builders and thus water can find its way up walls.
Poor paint work on the exterior side allows water to penetrate into the wall.
The ground level may be higher on the exterior side and above the d.p.c. allowing water to penetrate.
Buildings with wooden floors often have an under floor breathing system. When these are replaced with concrete floors it often results in the floor no longer being able to ventilate and water rises into the walls.
Leaking water pipes above the d.p.c. can cause rising damp symptoms.
Once you have identified the reason for rising damp you will be able to use the following procedures to fix the problem.
Remove damp plaster and drill 70 mm holes into the wall at an 80 mm depth and an interval space of 10 mm between holes. Follow this sequence from floor level to 500 mm above floor level on the interior side of the wall.
Dry walls out with an industrial gas dryer and leave running for 24-48 hours.
Inject Silicone into holes as mentioned below.
You will need to drill a string of holes as close as 20mm apart. Drill the holes along the length of the mortar joint. You can find the joint by noticing the difference in color of the drill dust. The mortar joint is often softer than the bricks and you will be able to drill into it more easily. Using a caulking gun inject liquid silicone into the holes. The silicone penetrates into the bricks and mortar and creates a damp proof course in the brickwork.
Chip the old plaster from the wall and re-plaster using a waterproof plaster mixture. To waterproof plaster add waterproofing additive to the wet plaster and mix thoroughly before applying the plaster to walls.
Wall Cracks And Joints
Check the exterior side of the walls for cracks and fill with waterproof plaster.
Inspect the joints between the wall and door frames and door sills. Remove any damaged sealant. Reseal with builders waterproof joint sealant.