Slab edge dampness will occur when moisture from various sources is absorbed into the concrete. At first, the dampness affects only the surface layer. However, with repeated and prolonged exposure, the moisture begins to seep in and slab edge dampness occurs. The effects of the slab edge dampness are exacerbated if the concrete used in the structure is also of poor quality.

Most houses will not suffer from the slab edge dampness since they are well constructed and are protected by well-detailed slabs and footings. When you experience problems of slab edge dampness on your property, there is usually a myriad of possible causes that can be addressed with a little intervention.

Homeowners must carry out comprehensive investigation into the state of their properties and take corrective actions where they notice dampness problems. Most of the dampness on the slab edges is normally caused by various factors such as garden watering, rain water and even contact between the slab edge and the ground. In more serious cases, the dampness may permeate the concrete and get into the inside of the building thereby damaging the internal finishes and walls.

When it comes to slab edge dampness problems, the preventive measures are generally more effective. They shield homeowners from having to embark on costly repairs and maintenance work once the dampness has caused more serious damages on concrete structures and interior finishes such as the floor coverings.

What Causes Slab Edge Dampness?

Slab edge dampness occurs when moisture is absorbed into the concrete material through capillary action. This occurs when moisture is sucked into the concrete via air voids or tiny pores in the concrete. If the concrete surface is only exposed to intermittent dampness, only the surface layer of the concrete may be affected by the dampness. However, if there is prolonged exposure to the wetting or to a source of moisture and the concrete is of poor quality, it will absorb the moisture leading to slab edge dampness and in some cases moisture ingress.

The slab edge dampness issues may not be apparent during construction. Most of it will manifest itself post-construction, during landscaping or when making alterations in the building. These alterations may inadvertently affect the site drainage conditions thereby leading to slab edge dampness.

Some of the main causes include the following:-

  • Inadequate detailing or inadequate installation of moisture barriers around the external walls and the slab edge.
  • Poor stormwater discharge or poor site drainage: water ponds will end up forming adjacent to the footing or slabs.
  • Poor construction of the concrete footing or slab which leads to increased permeability.
  • There is direct contact between the soil and the concrete footing or slab.


How does Slab Edge Dampness Manifest Itself?

The first sign of slab edge dampness is generally the persistent dampness that will be discernible in the exposed parts of the slab or the footing. Other signs include:

  • Mould growth
  • Watermark stains occurring on your wall linings or joinery.
  • Bad odours on your floor coverings such as carpets
  • Blistering or peeling off of the external paint.
  • Surface corrosion or rusting of metallic structures that are adjacent to the footing or the slab edge.
  • There is the delaminating of the render.


Managing Slab Edge Dampness

Preventative measures are always the most effective when it comes to managing moisture ingress and slab edge dampness. The first step is hiring a professional and licensed builder who understands this problem. If it can be arrested during construction, the better. It is also important to ensure that your house has adequate drainage that prevents the overflow of stormwater. If slabs are too close to the walls, they may need to be removed to control the dampness.