Do DIY Damp Proofing Kits Work?

You can buy DPC injection cream, damp-proof paint, mould sprays, sealers and waterproof coatings from any DIY shop. Some of them are the same products professionals use. The product is rarely the issue. The diagnosis is.

Where DIY can help

• Condensation. Most of the fixes are things you can do yourself: ventilation, heating, extractor fans, trickle vents and changing habits.
• Mould cleaning. A proper fungicidal wash, used safely, deals with surface mould while you fix the cause.
• External maintenance. Clearing gutters, fixing downpipes, lowering soil levels and clearing air bricks will sort out a lot of damp.
• DPC creams, in the right hands. If rising damp has genuinely been confirmed, a competent DIYer can inject a DPC cream. It needs drilling at the right height and spacing to the manufacturer’s instructions, and all the affected walls need treating, including internal walls where needed.

Where DIY tends to go wrong

• Injecting a DPC for a problem that isn’t rising damp. If it’s a bridge, a leak, penetrating damp or condensation, you’ve wasted your money and the damp carries on.
• Not replastering. Injecting a DPC and then patching or painting over the old salty plaster nearly always looks like a failure.
• Damp-proof paints and sealers on internal walls. They can hold moisture back at the surface for a while, but the water’s still in the wall and often moves sideways or upwards to escape.
• Waterproof coatings in cellars. Painting slurry onto unprepared brickwork rarely works for long.
• Mould sprays as the only fix. They treat the symptom.

The real cost

A DIY kit is cheap, but if it’s the wrong treatment you’ll pay for the redecorating, then pay again to have the job done properly. You’ll also have no guarantee, which matters when you come to sell.

I’m all for people doing what they can themselves, and I share plenty on the channel to help with that. Just get the cause right first. If you’re not sure, a survey costs a lot less than doing the wrong job twice.