Do Your Boundary Walls Look Like This?
This photo I took during a client’s comprehensive buyers inspection had rising damp, falling damp and penetrating damp in the boundary and garden walls. In addition, the white marks on the wall were caused by efflorescence.
These walls are very important in that they protect our privacy and security and are our first line of defence against intruders. Unfortunately, we sometimes do not make enough effort to protect them!
The greatest enemy of these walls is damp which penetrates into the wall from below, above and from the sides of the walls.
Rising damp occurs as a result of capillary action at and below ground level into porous building materials. These materials are mainly concrete, bricks and mortar. The moisture rises up the wall in this way. It usually occurs where there is no damp proof course (DPC). Freestanding walls such as boundary and garden walls do not normally have DPC built into the walls because it would make the wall unstable. A layer of DPC would break the bond between the wall and its foundation.
The height to which the moisture will rise is determined by the evaporation rate and the nature of the wall. However, the normal limit for rising damp is generally about one metre above ground level.
Rising damp may show as a stain on the plastered and painted wall, the blistering of paint and loss of plaster. A damp area may be evident at the base of walls and in extreme situations, may cause the structure of the wall to wear away and crumble.
Falling damp is caused by downward water penetration from the top of porous masonry walls. This is as a result of the top of a boundary wall not being adequately waterproofed, if at all.
Walls should be:
- properly sealed at vertical expansion joints;
- repaired at copings that have cracked or deteriorating mortar joints;
- cleaned to prevent the build-up of dirt and moss on upper surfaces of stone or brickwork.
- Leaves, bird manure, moss and dirt on top of the walls contain weak acids and salts which can promote decay of the masonry and paint if absorbed.
Penetrating damp is a common form of damp. It occurs as a result of the horizontal ingress of water through gaps, cracks and joints in the wall’s structure. Penetrating or horizontal damp can be due to your or your neighbour’s irrigation system spraying against the boundary wall. Moreover, foliage growing against the wall (bushes and trees)can also be the cause. Other causes are deteriorating paint finishes and inadequately ruled joints which allows moisture intrusion into faced brick or stone walls.
Penetrating damp tends to produce localised patches of dampness and decay, whereas rising damp may affect the base of the wall.
Efflorescence occurs when an appreciable quantity of soluble salts and moisture is present in the masonry. It routinely occurs in masonry construction, particularly in brick and concrete. It typically occurs during the initial curing of the cementitious product. Moisture carries these salts to the face of the masonry or concrete where the moisture evaporates.
As the water evaporates, it leaves the salts behind as a white fluffy deposit. Therefore, to remove it, brush the deposit off when the wall is dry. It usually disappears with time after rains or washing with water.
Efflorescence is generally an aesthetic concern and not a structural one. However, where there is excessive efflorescence, the crystallizing salts within the pores of the masonry can disrupt even the strongest material. As a result, this can lead to the breaking up and crumbling of the structure.
How to prevent damp damage in your freestanding walls
Rising damp is not easy to resolve in any freestanding, boundary or garden walls because of the lack of DPC. However, you can do the following:
- Make sure that there is no pooling of water against the wall. Good drainage away from the walls is essential. If you have a low point in your garden against your boundary walls you will need to create a hole in the wall at the lowest point for the stormwater to drain away. Your neighbours have to accept a certain amount of your stormwater by law.
- Try not to overwater your gardens against boundary and garden walls. overwatering will result in sodden earth around the walls and, as a result, rising damp in the wall.
- Keep leaves and other debris on the ground which may retain water away from the walls.
- You should waterproof the tops of all freestanding walls with a layer of an acrylic waterproofing system or any other system to prevent moisture intrusion into the top of your boundary and yard walls.
- If there is a concrete or brick coping on top of the wall you must ensure that the joints form a water-resistant seal. You should seal all deteriorated joints or porous joints between the bricks and copings.
- Seal the top of expansion joints to prevent water from entering the joint with a silicone sealer.
- If your freestanding walls are plastered, check the paint finish regularly. It may be time to repaint if the finish is chalky.
- If you have a sprinkler system make sure that you are not watering your boundary walls. Sprinklers heads are normally adjustable. If yours are not, change them.
- Trim bushes and shrubs so that there is a gap between the foliage, branches and the walls.
- If it appears that the moisture is from your neighbours’ sides, you will need to talk to them about the problem.
- Clean out and seal vertical expansion joints with a good silicone sealer. Any cracks should be sealed as well. Furthermore, if your plastered walls are covered in crazing cracking wash the wall down. Thereafter, when the wall is dry, seal the wall with a sealer and repaint the wall.
Efflorescence is a sign of damp
Efflorescence is caused by moisture absorbed in the wall evaporating and leaving behind salts as a white powder. Therefore, if you repair and maintain your walls as suggested above, very little efflorescence should appear on your walls.
I am not specifically promoting Prominent Paints as all the well-known paint manufacturers produce the same required paints and sealers. You can use most of them to repair and maintain your freestanding walls.
However, Prominent’s video provides very good advice on how to repair moisture damage to boundary and garden walls!
Inspected Once, Inspected Right!®