damp coarse

[ozz1]

I have built  a lot houses in Australia  but i notice that the thais don't seem to use damp coarse or plastic sheets under their foundations as i am biulding my house in isaan now i was wondering if you can buy damp coarse here  and where is the best place to buy aac block adhesive thanks for any information

[Crossy]

You can certainly get the damp-proof membrane to go under your slab (we have it) but since the walls tend not to be built on footings as we would know them (they sit on the slab) there's not much point in having a DPC.

 

I'm not aware of anyone with rising-damp issues here.

[eyecatcher]

Most builders yards will sell the aac adhesive. The q con brand will be circa 180bt a bag and Thai brands around 160bt.

It goes a long way also. Hence my firm belief that building with aac is cheaper than crappy blocks and mortar.

I used just two bags on my house and bought another for a boundary wall of which i still have half left.

[canopy]

I have heard about a number of houses where rising damp is a problem here causing paint to blister off. Watsadu for one has rolls of membrane up to 150 micron. Note that if you follow the q-con instructions, they want a DPC between the slab and the first course of the exterior wall. As far as building materials go, SCG is of better quality than others for everything I have seen so far. Price is also higher. I can't say which block adhesive is best, but when in doubt I always go with SCG.

 

[Crossy]

Yeah canopy, I'd forgotten that instruction although I thought it only applied to wet rooms, AAC block sucks up water like a sponge.

[superal]

Does anyone know where I can get a plaster/ cement sealer . In the UK there is Unibond which used undiluted is a glue / bonding agent or if diluted can be used as a sealer on plasterboard .  Thanks in advance 

[eyecatcher]

On 3/3/2017 at 7:35 AM, Crossy said:

Yeah canopy, I'd forgotten that instruction although I thought it only applied to wet rooms, AAC block sucks up water like a sponge.

Yes, its always a good idea to wall in a course of bricks first onto the connie slab; then start your aac work.

 

Even internally, the first 2 inch is always covered by mortar and floor tiles so why waste a third of block that isn't being used to its real benefit.

 

What I would say is, yes there isnt really any rising damp its all penetrating damp and a lot that I have inspected has been the result of topsoil being filled too high up the wall or paving slabs not throwing rain water away from the house.

 

The worst cases are splashbacks from pavings or the turf onto the wall. This will often only cause external staining, its when water is collecting/ponding adjacent to an external wall that becomes and internal disaster.

[canopy]

On 3/4/2017 at 8:20 PM, eyecatcher said:

What I would say is, yes there isnt really any rising damp

 

For slabs less than 70cm above grade, q-con wants a DPC installed under the blocks. If that's not a strong case for rising damp in Thailand, I don't know what is. I recall one gentleman who said his greatest regret building his house was not putting waterproofing under the walls due to the paint and mold problems that came about from rising damp.

 

[eyecatcher]

Yes I agree and for those very rare cases where someone here actually constructs a ground bearing slab its the obvious thing to do.

However its rare indeed and most floor levels are already 100mm above the ground beam which itself is 2/3/4/500 above the external level.

But dont pick on aac blocks all walling materials are prone to rising damp in the correct circumstances.

[canopy]

According to q-con, a DPC  is needed even if putting the blocks on beams like normally done in Thailand. You can watch the q-con demo below where they explain it (in thai).

 

 

[eyecatcher]

I watched that video, didnt understand a word but in my opinion what they are doing is a complete waste of effort.

Firstly thats not a dpc, its looks like cling film?

Secondly if they dont take a dpc vertically at the columns then you get bridging

Thirdly even if they used a 2000g dpc traditionally it would become pointless when they render over the blocks and the ground beam...bridging again.

 

A dpc is supposed to be a vapour barrier, i dont think what they are doing is anything like that; if anything its created a slip membrane as the blocks are so light they can easily move.

 

[canopy]

Agree with your observations. Your conclusion is logical about it being a slip sheet, but the video explains the reason for the sheet is to guard against rising damp even though as you mention damp could seemingly find ways around it. Maybe just a case of Thailand being low-spec. Like in Thailand using 7.5cm thick q-con blocks for external walls would astonish people in other countries with concerns for suitability for that purpose. So perhaps things like thin blocks and low quality vapor barriers are just enough to work in most cases even though not totally bullet proof designs.

 

[Goodison]

Here is my 2 penny worth on the subject. Unlike what I have seen for modern American House Build Water Proofing Philosophy the one used in Thailand is completely different. American style I seen is Plastic Membrane to keep all water out with Plastic Membrane on the roof, in the walls & under the slab basically the whole house wrapped in Plastic. They also have DPC layed on the top of the concrete slab where the walls go and lay the bottom of the house wood frame on that. Thailand Philosophy is water will get in but let it get just as easy coursing no damage. So roof tiles are over lapped so water can enter the small gaps between them & rise up but not so far as to spill into the roof space & when the rain & wind stops the water drains out easy the same way it got in. Even full length steel roofs have this principal at the roof ridge. Walls are rendered with a lime cement & sand mix mortar. Cement pros are it is strong & hard but it's cons are is not very porous so when it gets wet by rain water can enter but not easily leave & stagnant water in the shade with oxygen available is ideal for mold (which is a Fungi) to grow. Lime pros are it is porous & water can enter & leave easy with no damage, it is a fungicide & will kill any mold culture, in addition it makes the motor more plastic & so less susceptible to settling cracks & it increases the workable time of the mortar. Houses are reinforced concrete framed & concrete is a dense material (or should be if it was poured right) but it does have porosity & moisture will travel through it but moisture only gets so far through the surface (hence the required concrete cover thicknesses to protect the rebar from moisture & corrosion). This is proved by foundation columns rising out of the ground & the above ground painted sections having no paint bubbling or blistering as the amount of moisture rising is small enough that it can exit through the porosity of the paint to the atmosphere unlike render were the water rate is so great the paint porosity can cope & the moisture courses the paint to bubble & blister. As for rising damp I have only seen this when water from the ground or pools at the bottom of the external wall enters the render & travels up through the render passing over the concrete then into the porous block work & into the inner walls render. If you was to to put a DPC in how would do it. If you laid it on top of the slab beam you still got the columns make of exactly the same reinforced concrete. In my 20 odd years experience here you get no rising damp through the concrete because of it's dense structure & any moisture traveling up is near the surface & escape to the atmosphere through the porosity of the paint. That leave only the underside of the Slab. there are 3 ways I know of that lay slabs. 1st Slab, with 2" of blotting sand under that than a plastic membrane. The idea was that the plastic membrane would stop moisture rising up under the slab & the blotting sand would allow the slab to dry out from both the top & bottom side. This now seems to be frowned upon (but still promoted by some) as it was found that the moisture absorbed the blotting sand took a long time to rise up and dry out & that the flooring had already been put down & this rising moisture got under it. 2nd with the plastic membrane placed directly under the slab on the top layer of gravel (which should smooth rounded type like PEA gravel & not sharp edged crushed gravel that could easily tear the membrane. As the slab could now only dry from the top surface no blotting sand was needed but the drying takes about twice as long. 3rd is the same as 1st but with no membrane. So what was the problems incurred by moisture rising up through the slab. It depended on the type of floor covering. If it was carpet the carpet would get mold & rot. If it was wood, laminated or vinyl all these are stuck down with moisture hating adhesives & the moisture coursed the break down of this adhesives & the flooring to break free of the slab. However all of these are common in the likes of America but not Thailand were the most popular is ceramic tile. So if moisture rises up through the slab it will then pass through the ceramic cement & hit the under side of the tile which it can't pass through so it travels to the edge of the tile & passes through the grout & evaporates in the air in the room above. I have had this system in my house for over 20 years with no problems & never heard of any body having a floor tile come lose from moisture rising through the slab but I heard plenty have had wood block floors come lose. So for me the best system is no plastic membrane under the slab (If you put & it gets a tear all the rising moisture will go there giving you concentrate wet spot) with 2" of blotting sand for a better slab dry out & a ceramic tile floor. Last but not least the Thailand system sometimes gets a knocking but for me Engineering water enters water leaves easy in the design is a whole lot better than wrapping the whole house in plastic sheets which if ever gets a tear in it will damage or destroy what ever is behind it.

[Goodison]

I forgot to put the Lime in the Mortar cons which are it is weak & soft but the cement in the mix adds the strength & hardness.

 

[Goodison]

Found this which pretty more explains Vapour Barriers  R all about stopping problems with floor coverings but she doe's say the 6mm Poly from the DIY is not Man enough for the job of a Vapour Barrier & that Ceramic Tiles R an option @ 48.28 mins in & Millions of homes in Thailand with no VB & no Popping Ceramic Floor Tiles can't be wrong. Who would have thought Chelsea Clinton was so knowledgeable  on this Topic.