How to build a house that won't develop cracks in the walls

[pferdy62]

Hi,

 

How would I go about building a house using the normal Thai method of concrete posts and beams so that the walls will not develop cracks?  This will be a single story house using AAC bricks for the walls, a steel frame roof and colourbond type roofing steel.

 

I have considered:

• using larger footer pads to lower the load per m2 on them, possibly up to 4m2 on each corner and 2m2 for the rest
• making the beams taller, possibly as much as 60cm high
• adding additional re-bar to the lower part of each beam which could mean 7 lengths of re-bar versus the standard 4

 

 

[JAS21]

Foundation requirement vary with where you are building. Where we live piling to a depth of 20M is required ... I think the cost now is 18K/pile.

[Artisi]

You need to differentiate between structural cracks and cracks in the plaster/cement render.

Two different problems / approaches. 

[lovelomsak]

Many time here in Thailand the reason the walls crack is they haul in dirt to raise the level of the land and do not wit for the ground to settle.

  What was done at our place was extreme but it works. 

  After all the beams were in place  a 18 inch base of cement was poured as a subfloor. This made the whole thing strong. The dirt could wash away under the house and the structure would still stand straight just like a huge deck.

[pferdy62]

I am building on high ground that has no landfill, so that is not a concern.  

 

A floor that is 18 inches thick (about 45cm) must have cost quite a bit to pour.  I'm not sure if we would be able to do this.

[BEVUP]

20 minutes ago, pferdy62 said:

I am building on high ground that has no landfill, so that is not a concern.  

 

A floor that is 18 inches thick (about 45cm) must have cost quite a bit to pour.  I'm not sure if we would be able to do this.

Compaction is the key

I would say the 18" is between the columns

The cracks you are talking about may be just in the mortar 

It may depend on the mix they use but also the weather/ curing 

I think most houses will get some form of minor render cracking 

 

PS : There is no need for your wide foundations as there is no real weight in your building

[CanuckThai]

Sounds like you will be building on "undisturbed ground".  If proper footings are poured for your posts, on a gravel base of 30-45cm, re-bar for horizontal pours, and structural fibers added, it limits (or can eliminate) cracking.  One of the biggest factors in cracking here, is speed of the curing, in the high temperatures we have.  A retardant can be requested, and water sprayed on a dry, hardened, but curing pour and helps minimize visual (aesthetic) cracking.   Sometimes ordering your "mix" for a slightly higher MPa,  a slight increase in percentage of aggregate (gravel) and an equivalent drop in sand % helps....

[Pogust]

I have many times wondered about those footings. My take is it's a leftover from the times when Thai houses were built above ground on poles to allow for a cool area under the house to spend time during the hot days. This of course before the days of A/C.

 

Then a footing deeper than what water would get during rain period would be essential. Now when most houses has a whole foundation I see no reason to continue old traditions that no longer is meaningful. Why all this extra work when using the same amount of steel and concrete in a foundation at ground level in most cases would be stronger? And a lot faster and cheaper to do. I have built two houses recently this way as we are doing it in the west.

 

Anyone that has a logic explanation to this? I'm well aware thinking and logics are not things Thai workers are especially interested in...

[mogandave]

I think the focus for Thai builders is that the foundation for the structure be sound. They dig deep, pour large footings, and pour the columns in place. This makes for a solid structure. Unfortunately, the ground floor and the stoop are technically not part of the structure. When these sink-out, often you get big cracks in the walls.

Another type of construction common is when they use a “pile-driver” to punch holes in the ground, and columns are either poured or driven in. I think the poured footing configuration is better.

I think the big issue here is with the site-work. The sandy ground just does not seem to compact well.

There is generally a reason a particular construction method is used in a particular area, and to be fair, while there are a lot of non-structural cracks, there does not seem to be a lot of buildings falling down.