Small DPM question

[ladwey]

Hi -- small question about a DPM for an extension. I installed the DPM on hardcore and sand blinding, then 150mm insulation boards over that, then a further DPM over that, then poured the slab this morning. It's awkwardly placed so there was a lot of raking the concrete along to get it from the spout to the far end. At one point the rake got caught under the pouring concrete and pushed down, and, though I'm not sure, I think I felt it puncture the DPM. Couldn't do anything about it at that point as there was the whole of the rest of the pour to see to. It would be a small hole, if there is one. Is this going to be a problem?

 

[yorksbuilder]

You don't need to worry about one small hole in the secondary DPM, your slab will be fine

 

[ladwey]

Can't tell you what a load off my mind that is mate, thank you.

 

[yorksbuilder]

No worries, good luck with the rest of the project

 

[^woody^]

The secondary DPM is not a DPM. It's optional, and is really [theoretically] just to stop and water or concrete or air getting below the insulation and lifting it when pouring the slab. Normally it can be any thin-gauge polythene for this.

 

[noseall]

and is really [theoretically] just to stop and water or concrete or air getting below the insulation and lifting it when pouring the slab. Normally it can be any thin-gauge polythene for this.

That's the third reason I've heard for the secondary layer.

First it was touted to us that concrete can slip between the gaps and cause a slight cold bridge - so we started taping the joints.

Then they began telling us that the concrete reacts with the foil. WTF!

 

[ladwey]

Haha I just do what I'm told ... building control said to put a 'small section' of A124 mesh around the pipes where they come through the insulation before I pour the slab -- mentioned this to a builder and he just laughed ---