Last week Barbra (a reader) wrote in to ask me this: “I need to know how to get rid of the mould in my old terrace house.” Here’s what I can suggest:
In the section of my book called Building and Battling, in the chapter called Look out for trouble, I said that mould (and other symptoms like stained or swollen skirtings and fungus growth) can indicate that there’s been what’s called water ingress. I’m not sure where in Barbra’s terrace the mould actually is but if it’s in a bathroom then it could well be because of a waterproofing failure behind the scenes. If it’s on walls that aren’t in wet areas then it could be because there’s rising damp.
Rising damp is the action of moisture travelling vertically through porous building materials like bricks for example, that are in contact with the ground. The natural drying action of the upper wall draws moisture upwards to a level of about 1 - 1.5 metres above the floor level. If this is happening, it probably means that either the damp proof course has failed or a bridge has been created from outside gardens for example, which has allowed the moisture to travel over the damp proof course.
Sometimes people try and fix this by repainting or replastering. This is really a bandaid approach though and can make the problem worse by forcing the dampness to a higher level. Longer term fixes often involve using an injection of chemicals - damp course fluid - into the affected wall to provide a new damp proof course.
You can get specialist companies to come in and fix this for you, but there are also DIY solutions. One of these is Techdry. This Australian company says that they researched and developed their damp coursing fluid in partnership with Victoria University of Technology. There are detailed instructions available from them, but essentially, what you’ll do is drill a horizontal series of holes along the brickwork, at or below floor level, insert tubes in each hole and then fill them with the fluid. You then let the fluid soak in and permeate the bricks and surrounding mortar, over a 3 to 15 hour period. Later you take out the tubes, and then leave the walls to fully dry out before painting or plastering over them.
Another solution is Lectros Technology. Proponents say that this system uses electrical osmosis to permanently eliminate dampness.
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