punctured Damp Proof Membrane

dont know if it works but i just put another piece of DPM over the puncture when i did my shed. then to prevent further punctures, i put some building sand over the membrane so it wouldn't puncture when hit with concrete or walked over.

See earlier reply, or, frankly, does it matter that much? As the BCO said to me, 'buildings are not designed to be perfect, just good enough'

A small tear will not let enough water through that the whole floor will become damp - all a damp proof layer does is reduce water ingress to a level that the natural (and unnatural!) heating and ventilation can cope with and that doesn't allow moulds to form.

How did they come about? Is it properly blinded with sand underneath?

I'd patch it and treat the patch as a "join".

How did they come about? Is it properly blinded with sand underneath?

I'd patch it and treat the patch as a "join".

Lavenders,

Try putting the 'building sand' on top of the hardcore (not on top of the DPM) and THEN lay the DMP on the sand - *that* will stop it being penetrated by sharp 'bits'.

Brian G

But surely a proper 1000ga membrane if laid correctly will do better than reduce water ingress to a reasonable level... I mean, that thickness of polythene is going to be totally impervious to water, so it all comes down to how well it's laid as to whether it does it's job properly - ie, no gaps, holes etc.

I imagine a small hole in a membrane well below ground level in a very wet enviroment could quite easily let in a lot of water, permeating in under some pressure, between the slab and the membrane, surely?

David

Yes, but as long as the rate of ingress is much less than the rate of evaporation, it causes no damage.

Try finding out how much water the average human being sweats into a room per day...