This article discusses the cause, effect and treatment involved in slab edge dampness, salt damp or what is commonly known in the industry as ‘edge wetting’.
Visual Landscape Gardening are considered experts in the field of salt damp treatment in Adelaide and can assist in the prevention and treatment required to eliminate edge wetting.
If you’ve ever noticed or been concerned by the build up of salts; called ‘efflorescence’ leaching from your house or carport foundation, you are experiencing slab edge dampness, salt damp or edge wetting.
There is good reason to be concerned. If left untreated, salt damp can cause fretting of the foundation to the point that the structural integrity of the foundation becomes compromised.
The accumulation of salt can cause lifting of tiles and other internal flooring such as parquetry and timber floating floors, and cause mould to flourish under carpets.
If you are experiencing a musky smell in your house chances are you have problems with edge wetting.
What is Edge Wetting?
Edge wetting is the transfer of moisture from the soil; drawn up by capillary action, into the concrete foundation. This happens when the concrete is in direct contact with the soil. Slab edge dampness and salt damp problems are more likely with reactive soils that have a high clay content; common throughout Adelaide, as opposed to soils containing free draining sand. This is not to say that the problem is not evident on sandy sites. Consider your foundation as a sponge and this will help to understand the process of slab edge dampness.
Contributing Causes of Edge Wetting?
Poor drainage can be a contributing factor causing edge wetting. Leaking or broken storm water drains and down pipes are also a contributor. Poorly prepared bases for paving and concrete can also contribute.
Licensed paving contractors or landscapers will ensure levels for concrete or paving around walls falls away from the foundation. In the event sub surface water reaches clay, it is directed away from the foundation edge with the same fall the concrete or paving has on it. The possibility of water entering between the foundation and the vapour barrier or forticon that the foundation is encased in is also eliminated.
Salt Damp Treatment – How To Avoid Edge Wetting
When preparing to pave around a foundation, it is essential to fit a 450mm damp proof membrane to the vertical edge of the foundation.
The ground must be excavated to find the orange vapour barrier or forticon that extrudes from the foundation. Vapour barriers should be maintained and not cut under any circumstance.
Soil should then be excavated in a way that the clay or soil has a positive fall away from the foundation. When dealing with high clay content soils, a minimum of 30mm for the first metre should be set. It is essential that the clay be carefully removed from the vapour barrier that laps out, usually 200-300mm from the foundation trench.
When the top of the vapour barrier has been carefully removed of clay and other debris, a 450mm damp proof membrane is lapped over the top of the vapour barrier and continued up the vertical edge of the foundation.
Quartzite quarry rubble; having a low salt content, as opposed to dolomite that has a high salt content is then spread on top of the damp proof membrane before compacted with a plate compactor. This process keeps soil and especially clay from direct contact with the vertical edge of the foundation. You will now be protected from edge wetting from underground soils.
Where edge wetting is already prevalent, this salt damp treatment procedure will remedy the problem over 1 to 2 years as the concrete dries.
Landscaping Tips To Prevent Slab Edge Dampness
Landscaping to your garden after construction, or alterations to your storm water can inadvertently change site drainage conditions allowing water to pond against a concrete slab. If you are paving a perimeter path around your house, ensure you have a positive fall away from your house of at least 50mm for the first metre.
In reactive soils; with a high clay content (prevalent throughout Adelaide suburbs) storm water pipes should have flexible connections to avoid breakage due to ground movement, allowing water to seep through the ground.
Garden beds that are created against walls should not have earth above the original ground level without extending the vapour or damp proof membrane up past the finished surface fall. Agricultural pipes or other suitable drainage solutions should be employed in all raised garden beds, directing water away from walls.
When landscaping Adelaide gardens, licensed landscapers should always be used to ensure the landscape design you desire takes water flow direction into account.
If you require more information or assistance with salt damp treatment or edge wetting, contact Visual Landscape Gardening for a free appraisal.