Damp Proof Course For New House

[simon43]

The architect plans for one of the buildings we are building shows a plastic sheet which is to be wrapped around the outside of the concrete footings and concrete postings in these footings, and then continues under the concrete floor, (perhaps lying on or almost touching the bare ground)

This doesn't seem right to me! On a traditional brick-built house in the UK, the DPC is laid over the first course of bricks that are above ground level. In the Thai plan, I would have thought the best place for this DPC would be on top of the concrete floor, stretching right into the corners - and then the tiling is laid over this DPC. So the DPC has little chance of being punctured/damaged, which most certainly could/would occur if it was wrapped around the buried concrete footings!

In any case, our builder says that the concrete has a water repellant in it, so do we even need a plastic DPC?

Advice much appreciated!

Simon

[Dragonman]

The architect plans for one of the buildings we are building shows a plastic sheet which is to be wrapped around the outside of the concrete footings and concrete postings in these footings, and then continues under the concrete floor, (perhaps lying on or almost touching the bare ground)

This doesn't seem right to me! On a traditional brick-built house in the UK, the DPC is laid over the first course of bricks that are above ground level. In the Thai plan, I would have thought the best place for this DPC would be on top of the concrete floor, stretching right into the corners - and then the tiling is laid over this DPC. So the DPC has little chance of being punctured/damaged, which most certainly could/would occur if it was wrapped around the buried concrete footings!

In any case, our builder says that the concrete has a water repellant in it, so do we even need a plastic DPC?

Advice much appreciated!

Simon

Of course there are many corners to be cut with regard to damp proofing! You can install Damp Proof Membrane attachment to specialised underlay nowadays for tile or wood floor installation. If I was constructing however it would always be from soil up as follows:-

hard core-sand-damp proof membrane ( to be attached to damp proof course 6 inches above ground level)-insulation-concrete-floor screed.

[briley]

In the UK you put down the damp proof membrane (plastic sheet) and build on top of that.

There is an additional dampproof membrane in the wall a couple of courses up from ground level.

[BKK90210]

In the US (per US building code), if you have a slab on grade....then you MUST put down the "vapor barrier first" and build on the top of it....thus preventing the concrete slab from absorbing any moisture from the bare ground, so you won't have molds underneath your flooring or musty smell inside your home.

And make sure all seams are overlapped by at least 6 inches, if you couldn't get it in one piece.

[simon43]

OK, thanks for the replies, useful info. But my Thai builder ays he has never used a DPC before. He says that the water inhibitor within the concrete itself is enough to stop any damp ingress.

I must say that in all the Thai houses that I have visited where there is no DPC, I have never seen a problem with damp ingress anyway...

Simon

[Dragonman]

OK, thanks for the replies, useful info. But my Thai builder ays he has never used a DPC before. He says that the water inhibitor within the concrete itself is enough to stop any damp ingress.

I must say that in all the Thai houses that I have visited where there is no DPC, I have never seen a problem with damp ingress anyway...

Simon

I have seen numerous cases of rising damp in thai homes, including my wife's parents. Perhaps because being a former Building Surveyor I look by instinct. Waterproof concrete may delay problems, but I doubt whether many thai builders use this, and certainly not vaporproof. Cost! Your builder is likely saying this because he is clueless on DPM's & DPC's, and I'm not really surprised.

[Rinrada]

Agree DPM should be installed but the Thais tend to make all thir plastic into little bags to hold the som tam and rice portions (getting their priorities right )

Recon they consider that with the generally hot weather concrete never has time to absorbe rising damp...name of Rigby rings a bell ...and no need...

Where we are we have also "installed" a termite barrier-chemical mixture which will probably be eaten by the little bast**ds as soon as they get a whiff of it.

Only alternative is to build them their own tree house

[The Skipper]

Put the vapor barrior down first.

That contractor will be long gone when your are dealing with moisture problems.

[lingling]

Here's how we did it:

ground > sand > barrier > gravel > barrier in the thin areas of the slab (not under the beams) > concrete

http://www.thaivisa.com/forum/index.php?ac...pe=post&id=7330

http://www.thaivisa.com/forum/index.php?ac...pe=post&id=7333

We had trouble finding proper barrier sheets so we used ordinary tarp. No idea how long it will last, but better than nothing. I also put tarp over the gravel outside the slab on three sides and will cover that with soil. (no pic yet)

Oh, and no footings - instead a properly reinforced slab. ~140 tonnes concrete, gravel and sand - if it hasn't moved after the rainy season then we can throw up the house on top of it.