Which one of the following damp proof membranes should I use under a concrete slab for a workshop/garden room?
- 1000g (250MU) BBA POLYTHENE 4mX25m
- 1200g (300MU) BBA POLYTHENE 4mx25m
- 2000g (500MU) BBA POLYTHENE 4mx12.5m
Thank you
Which damp proof membrane should I use under a concrete slab for a workshop/garden room?
Jul 18, 2026
Last reply: 1 day ago
4 Replies
1200 guage is generally enough, but check with your Building Control, as they may have different ideas.
Unless your outbuilding exceeds 30sqmts as far as I know building control does not apply. Any electrical installation however will require Part P compliance. So what you do for your base is entirely up to you and I agree that 1200G is probably OK.
Richard
If 12.5m is enough, and you have no need for an extra 12.5m, use the thickest.
Yes, so long as it is more than 1 metre from the existing property, but if you build to Building Regs requirements, it will be known to be a sound build. Skimping on DPM is a false economy, theres a reason why the thicker stuff is used, and the price is not excessive.
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