Building a Modern Home in Bangkok

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Re: Building a Modern Home in Bangkok

Postby newhomepages » Sat Jan 26, 2013 9:31 pm

Cat had babies. House construction continues. Please see our Facebook page for updates.
http://facebook.com/thewavehome

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Re: Building a Modern Home in Bangkok

Postby newhomepages » Thu Feb 21, 2013 9:36 pm

Just when I thought we were going to be the only people in Thailand to finish building a home with no major disasters, now we have one:

Our house has a concrete roof that was poured along with the beams, it is slightly sloped for drainage. Our contractor cut-out and re-poured areas of the cement layer on the roof that is poured over the roof slab because there were cracks and separation from the main concrete underneath. Then cracks and hollow areas developed on the 2nd floor cement floor layer and he cut our and re-poured those. Then he poured the first floor. At this point all three levels of cement floors over concrete have cracks and hollow areas - most for the 2nd time. Now he is cutting up the roof again and I don't want to go any further till I am satisfied that it can be done right, or at least that it will keep out leaks for a few years. I don't mind a few cracks, almost every cement floor has them, but I don't want to be walking on chunks of loose cement in a few years.

I am going to start to add photos and more details about this in hopes that someone more familiar with concrete can offer suggestions. I think this is normally referred to as a "screed". Please correct me if I am wrong.
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Re: Building a Modern Home in Bangkok

Postby newhomepages » Thu Feb 21, 2013 11:09 pm

Here is a picture of the material they removed from the roof. I believe it is mainly portland cement and sand. Painted on the top is acrylic water shielding paint.

At one end of the roof it is a lot thicker than this, I guess for the drainage slope.

To me it looks too light in color, but I've never examined the interior of concrete before. It doesn't feel very strong - I can chip away a little with car keys.

Any comments are appreciated.

cement-layer.jpg
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Re: Building a Modern Home in Bangkok

Postby Mike Judd » Fri Feb 22, 2013 4:53 am

That stuff looks like the common way of finishing off concrete roofs to get the right amount of falls to all the drains. It is then covered with a couple of layers of waterproof sheeting put down with a heat torch. This has a light traffic surface but depending on the amount of traffic either loose river stones are spread all over or concrete tiles resting on plastic legs placed down. You have to remember that concrete on it's own as a roof is not waterproof , it needs some sort of protection especially from puddling in areas that have turned out lower than intended when the slab was poured as is usually the case unless great attention is used with the falls, even then you could have little areas that settled lower on the surface, always it seems at the opposite end of the drain. Too wet a mix with concrete (Common Thai problem) will result in surface cracks especially if the concrete is not kept damp for a few days after pouring.
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Re: Building a Modern Home in Bangkok

Postby gliffaes » Fri Feb 22, 2013 5:08 pm

newhomepages wrote:Here is a picture of the material they removed from the roof. I believe it is mainly portland cement and sand. Painted on the top is acrylic water shielding paint.

At one end of the roof it is a lot thicker than this, I guess for the drainage slope.

To me it looks too light in color, but I've never examined the interior of concrete before. It doesn't feel very strong - I can chip away a little with car keys.

Any comments are appreciated.

cement-layer.jpg

Too light as in not enough cement? so its all crumbly?
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Re: Building a Modern Home in Bangkok

Postby gliffaes » Fri Feb 22, 2013 5:11 pm

newhomepages wrote:Just when I thought we were going to be the only people in Thailand to finish building a home with no major disasters, now we have one:

Our house has a concrete roof that was poured along with the beams, it is slightly sloped for drainage. Our contractor cut-out and re-poured areas of the cement layer on the roof that is poured over the roof slab because there were cracks and separation from the main concrete underneath. Then cracks and hollow areas developed on the 2nd floor cement floor layer and he cut our and re-poured those. Then he poured the first floor. At this point all three levels of cement floors over concrete have cracks and hollow areas - most for the 2nd time. Now he is cutting up the roof again and I don't want to go any further till I am satisfied that it can be done right, or at least that it will keep out leaks for a few years. I don't mind a few cracks, almost every cement floor has them, but I don't want to be walking on chunks of loose cement in a few years.

I am going to start to add photos and more details about this in hopes that someone more familiar with concrete can offer suggestions. I think this is normally referred to as a "screed". Please correct me if I am wrong.

One of the problems here is they simply dont prepare the next layer properly, its the same with tiling, they just chuck down some cement onto an already dusty floor and then hey presto 12-18 months later the tiles sound hollow and finally lift.
SO did he prepare the surface first, he should have jet washed it down and then covered it with some pva solution to get the two layers to bond together
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Re: Building a Modern Home in Bangkok

Postby newhomepages » Fri Feb 22, 2013 5:42 pm

gliffaes, I was just thinking that it would be a good idea to prepare the surface by jet washing. I am sure they didn't do anything like that. I have a pressure sprayer that I've seen break up concrete sufaces. I just hope it won't wash the entire roof away. I also read about using PVA. Where can I get some in Bangkok? I am kicking myself that I didn't learn more about this and pay more attention before. Thanks for the suggestions.
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Re: Building a Modern Home in Bangkok

Postby newhomepages » Fri Feb 22, 2013 5:52 pm

gliffaes wrote:Too light as in not enough cement? so its all crumbly?


I know almost nothing about cement and concrete except for what I have read about in the last few days. It's not crumbly, but it doesn't feel as hard/dense as some of the other patches of concrete I've examined which are darker in color. Maybe they did not use enough actual cement in the mix. The contractor speculated that there may have been something wrong with the cement because he has done it this way before without problems.

Tomorrow we are having an engineer come and inspect/consult.
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Re: Building a Modern Home in Bangkok

Postby Sometimewoodworker » Fri Feb 22, 2013 10:55 pm

newhomepages wrote:gliffaes, I was just thinking that it would be a good idea to prepare the surface by jet washing. I am sure they didn't do anything like that. I have a pressure sprayer that I've seen break up concrete sufaces. I just hope it won't wash the entire roof away. I also read about using PVA. Where can I get some in Bangkok? I am kicking myself that I didn't learn more about this and pay more attention before. Thanks for the suggestions.

You can get PVA in any hardware shop as its a standard wood glue. However if you look around in places like HomePro you can get big tubs of powdered PVA that you can mix yourself
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Re: Building a Modern Home in Bangkok

Postby gliffaes » Sat Feb 23, 2013 7:58 am

Lanko is one brand mame
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Re: Building a Modern Home in Bangkok

Postby gliffaes » Sat Feb 23, 2013 7:59 am

Did they use readymix concrete or mix it themselves?
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Re: Building a Modern Home in Bangkok

Postby MyobJefke » Sun Feb 24, 2013 12:38 am

I am following this with great interrest as i am looking to use a concrete roof, without additional cover/layers.
As i heard from your problem, i asked my friend concrete contractor in Belgium about this.
Minimum 20 cm of concrete, with the right amount of waterproofing additifs, guaranty a watertight roof, when correctly mixed and poured.
The second layer is only needed for evacuate the water more quickly in the preferred direction, and can hardly got named "concrete".
Cracks in the concrete-layer, if they appear after curing, have to be filled with compound (in our countries to exclude freezing up in winterdays ).
The second slopelayer, normally poured from a semi-dry mixture, need as already mentioned by gliffaes, placed with enough attention to attach to the concrete underlayer and been very hard compacted when level the surface. Extra attention for the drying in the sun and the minimum thickness of the layerMinimum :)
Hollow areas can be avoided only this way. They can NOT be prepared and always lead to cracks and damaged areas in the layer.
Minor cracks, without hollow spots, do not have big negative influence on the waterproofing.
My advise... remove the player complete or at least make sure NO hollow spots remain.
and stay away with high pressure cleaners from the toplayer.
Wish you goodluck to solve this issue.
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Re: Building a Modern Home in Bangkok

Postby Mike Judd » Sun Feb 24, 2013 7:49 am

I have posted other articles on concrete which over a number of years absorbs moisture slowly depending on it's initial strength but at an average rate of 1m.m. per year ,when it then hits the steel and in one year starts to expand that steel. Something to do with a chemical reaction according to studies over many years by a very large institution in the U.S.A. A study done because of the high amount of so called Concrete Cancer in modern building facades. This you can believe or not, but in my personal opinion the easiest way to protect concrete is to paint it with a good Acrylic paint, and with roof concrete use a good quality paving type paint, which there are several on the market which allow traffic afterwards. Attention to the correct slope helps but obviously after the event you need to concentrate on the protective cover. In the planing stage, waterproof additive in your concrete should help as well. Most members who are familiar with High Rise building will have noticed that the trend has gone away from concrete panel facades of the past and it's nearly all Glass and aluminium now.
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Re: Building a Modern Home in Bangkok

Postby Maseratimartin » Sun Feb 24, 2013 8:55 am

Agree totally to the comments of Mike.
The issue with concrete is that when you see the issues mostly after years, then it is unfortunately also too late as the rebar is already affected...

Best way is a good seal applied and it should be flexible enough to cover slight cracks.

A thinn top layer of concrete will always get cracks.
The slight difference in mixure...cement amount....size and kind of gravel...will lead to diffrences in termal expansion and finally causes cracks!
In the case of roof application imagine the differnces in temp between afternnoon in direct sun and night...

During my time back in Germany with my civil construction business I tried to avoid thinn toplayers (in my case it was mostly related to floors).
Slightly slope the main conrete and look for a smooth surface...then apply a good seal and voila.

Only way to avoid cracks in thinn (4-5cm) layers is: Make it floating and with mesh or fibers!
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Re: Building a Modern Home in Bangkok

Postby newhomepages » Sun Feb 24, 2013 10:51 am

Thanks for your suggestions about getting the PVA. I would like to do some tests with it. Previously I think they worked cement into the surface as a bonding agent before pouring the top layer. I think that did more harm than good, maybe because it dried out before they they laid the cement so it had the opposite effect.

gliffaes wrote:Did they use readymix concrete or mix it themselves?

For the floor layer I think it was all mixed on site. As for quality, I feel it can be controlled better on-site. Is there any advantage to readymix other than being able to get larger quantities?

I asked the structural engineer about making the top layer thicker, 10cm, so that it might hold together on its own without needing to bond to the base concrete(floating?). He said that would be too much weight for the structure.

Looking at the acrylic paint we used, I don't think it would do a very good job keeping water out over long term. It split along with the cracks. I really want to put on something more like multi layered, flexible plastic that might hold together despite what the cement under it is doing.

Now that I have done my research, I think our contractor did a very bad job with much of the concrete in the house. In his defense, he is clearly embarrassed by the problems and is taking responsibility and trying hard to fix it. Please, people, study everything you can about concrete and brick building construction before you start building a typical house like this in Thailand and be sure you have lots of time to spend at the construction site and are able to climb scaffolding.

The engineer, brought yesterday be the contractor, said that the structure is sound, but agreed the surface of the base concrete on the roof was week, probably due to poor curing. From what I can tell it will never bond to a layer placed on top of it. But still we have to try so we will develop a plan to do it as carefully as possible and I will watch and approve each step. Then, after its had time to crack and bubble up some, we will apply a thick, flexible topping of some kind. Actually, I've always thought that we would eventually cover the roof deck with a canopy so that might happen sooner than later.

-EE
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