Deal with Rising Damp

Creating a chemical damp proof course

Damp patches

When a damp patch appears, most people do one of two things. They either ignore it or panic. Neither approach is the right one. Damp should not be ignored, but it is not usually the disaster that it may first appear to be.

Rising Damp

Rising damp occurs because the ground is naturally damp and the wicking properties of bricks and mortar naturally draw moisture up. Normally a damp proof course is found after the 1st or second layer of bricks and that stops the damp from rising. However, if the course is breached, damp will rise.

The solution is often quite simple. Silene based water repellants can be injected into bricks and mortar where they spread out and create a new waterproof course.

Creating a new chemical damp proof course.

These days this is a very simple process and quite within some people’s DIY skillset. The photo below shows an external cavity wall which was showing rising damp.

chemical dpc


We hacked off the plaster to a height of a metre and drilled a series of holes from the inside (see the white dots at the bottom of the wall)

drill cavity


The holes were drilled into the mortar between the bricks and extended from the inner leaf, through the cavity and halfway through the outer leaf, so you will need a long drill bit. Alternatively you could drill inside and outside separately.

Now it is just a matter of pumping the silene gel into the holes.

damp proof course


There are various little tools similar to garden sprays for this. You don’t need a motorised one. A cheap (£20) hand pump is fine and some manufacturers even supply the gel in tubes for use with standard skeleton mastic guns. Look out for the brand names Ultra Cure or Dry tech, although there are plenty of others on the market.

Replastering is the next job after inserting your chemical damp proof course and here many people prefer to call in an expert. We got Ian Gray, a berkshire plasterer based in Windsor round to do ours and he did a great job. Ian explained that if you are doing it yourself, you should leave a gap between the floor and the bottom of the plaster. This will be hidden by the skirting board, but is a good extra safety feature to prevent recurring damp problems.


Print Friendly, PDF & Email

About the author

Loves to learn new things and make stuff...properly. Born and living in the Thames Valley west of London, England. I have an office job during the day, but evenings and weekends are all about making.

Leave a Reply

Your email address will not be published.