On 7/13/2024 at 9:46 PM, Dr B said:

All good. Are you familiar with "capillary action". This is based on surface tension, which is what makes your wine climb up the inside of the glass. If you have a small glass tube, called a capillary tube, the suface tension will pull water up the inside above the level of the water surface. Now if you have sand in the ground, you may have a "water table" say 2 m down. That is the level at which the water sits, but above this is a capillary zone, where some of the water gets drawn up by surface tension becasue of the very small gaps between the sand grains. Now if you cast a slab on ground, that will stop the soil from being exposed to the air and the water from evaporating. As a result you will get a dome of damp ground under the house, which will probably reach the underside of the slab. If you don't have a proper vapour proof barrier, then the damp will migrate through the concrete, up the walls a certain distance, and then evaporate. That will leave behind the minerals in the water (efflorescence), and nasty white staining which makes the paint peel off. All of the row of 26 houses opposite ours have that problem, as well as most other houses with ground bearing slabs. Thais see concrete used as walls, with the rain running down the outside, so think that concrete is waterproof. Not true. It is low permeability but not water proof, and it needs to be vapour proof. It is very hard to get a good vapour proof barrier here as there are no fittings for the necessary penetrations. In the end I used a surface waterproof membrane applied in two coats over the top of the slab for the enclosed ground flor rooms.

Compacting the soil with a tamper is a good idea. We compacted the crusher run under our slab. Having done that and made it good and dense, you want to get the concrete slab supported by that compacted soil, but I very often see Thais putting down a layer of loose sand in between. I even see this on highway slabs. I have no idea why. It makes no sense to place a layer of loose sand between compacted soil and good concrete. Be careful with the water cement ratio of the concrete. More water means weaker concrete, but they love to add more water because it makes it flow more easily. That is where the vibrator comes in. Once they get the hang of it they will love it!

Good luck

We call it wicking  .you coated the entire slab before they ran the block ? What product did you use?  Crusher run in the US above the Mason Dixon line we call modified.   thanks

1 hour ago, CLW said:

Thanks, yes. DPC is what I was looking for. So something like this in below pictures, right? Is it available in Thailand?

 

Never seen it used in Thailand mate but is built into every single new building in the UK.I'm sure you could find it somewhere here,good luck.

1 hour ago, CLW said:

@Kinok Farang Since I did not find DPC as a roll, can these products below used equally? One is bitumen paint, the other waterproof cement slurry. Thank you!

I am a bricklayer by trade.Banned from working in LOS of course but i still take an interest in construction.(Sad i know)

Never seen any of those products above used but anything is better than nothing i suppose.

I really admire your thoroughness as all the new work i have ever seen in Thailand never incorporates a dpc and near enough could guarantee that Thai builders have never even heard of it although they will tell you otherwise.

The only thing i could guarantee is that dealing with Thai builders on a daily basis will turn you prematurely grey.Good luck.

54 minutes ago, charleskerins said:

Actually have never seen that on a job before is that because all the jobs i have been on had a vapor barrier below the slab???   Can you lay this on before the first course of block?  https://gbr.sika.com/en/construction/waterproofing/mortars-and-coatingstypea/sika-damp-proofingslurry.html

Because construction here is all about being cheap. That's why they not use it. 

 

From what I understand about this topic, you can either used bitumen-based paint or waterproof cement slurry as vapor barrier between foundation and walls. See my post above with example pictures. 

 

To your link, Sika has a localized Thai website with a similar product (two-component based). 

They also seem to have liners and bitumen products, however I guess they are only for professional applications. I couldn't find them at the usual stores such as Thaiwatsadu etc.

 

https://tha.sika.com/en/construction/waterproofing-systems.html  and go to waterproofing mortar

5 minutes ago, Kinok Farang said:

I am a bricklayer by trade.Banned from working in LOS of course but i still take an interest in construction.(Sad i know)

Never seen any of those products above used but anything is better than nothing i suppose.

I really admire your thoroughness as all the new work i have ever seen in Thailand never incorporates a dpc and near enough could guarantee that Thai builders have never even heard of it although they will tell you otherwise.

The only thing i could guarantee is that dealing with Thai builders on a daily basis will turn you prematurely grey.Good luck.

That's why I want to buy most of the material for building a house by myself and also always observe the work they are doing. I mean it can't be so hard to give the concrete a painting with bitumen or lay a thin waterproof cement layer, right?

26 minutes ago, CLW said:

Because construction here is all about being cheap. That's why they not use it. 

 

From what I understand about this topic, you can either used bitumen-based paint or waterproof cement slurry as vapor barrier between foundation and walls. See my post above with example pictures. 

 

To your link, Sika has a localized Thai website with a similar product (two-component based). 

They also seem to have liners and bitumen products, however I guess they are only for professional applications. I couldn't find them at the usual stores such as Thaiwatsadu etc.

 

https://tha.sika.com/en/construction/waterproofing-systems.html  and go to waterproofing mortar

here is an old video Thais using damp coat