OK, I have a bit of building experience helping out my mates when I was younger. I was always suspicious of DPC. What I’m talking about is the black plastic sheets that are put in between the bricks/blocks/stone a few courses up from the foundations. I understand that it’s to stop the damp from the ground from rising up into the wall, though I’m not sure really how big of a problem this actually is.
- Anyway, I always cringed about the structural integrity. If you’ve ever accidentally bumped the wall when it’s being built a few courses up from the damp proof course, you’ll know what I mean. It shifts very easily – it’s obviously a weak spot in the wall. Maybe when everything is built up and the roof is on, you don’t have to worry about it, but you still have to admit that you are compromising the strength of a wall with a DPC, versus one without. And the risk is that it gets so ingrained in a bricklayers habits that people overuse it. I mean I’ve actually seen garden walls and exterior pillars with a DPC. One pillar had shifted 3-4 inches at the DPC and it was supporting a roof, covering a walkway at a supermarket. That one was obviously a forehead slapper and really dangerous, but does anyone share my general DPC scepticism?
- Ydpsceptical -19th Feb, 2011 Bricklaying
- We do a lot of plastering and rendering and you can definetly tell the difference between a wall that has damp course and a wall that doesnt.
A wall that doesnt have dpc within 12 months will start to turn green with moss and constantly be wet, render doesnt stand a chance on a wall with no protection from damp, within 12 months or so it will start to bubble and fall off the wall.
If there is no damp proof on a wall for example a garden wall and it needs sand and cement rendering for example, it would need to be suitably prepared with either a felt backing, damp proof membrane and then meshing fixed with mechanical fixings to create a key or application of a sand and cement tanking system to stop damp penetration into the sand and cement.
If it is not being rendered you will still have problems in years to come with the mortar breaking down and just starting to crumble and worse still the face of the bricks blowing.
If a wall is being painted again this will start to bubble and peel off.
A lot of builders overlook dpc on garden walls etc but for how much it costs and the time it takes to apply it saves a lot of expense in years to come.