Post formula, Typical Thai construction.

[dddave]

For a typical, single level, brick and mortar Thai house...say a footprint of 10mX12m (120 sq.m), what is the usual formula for post placement assuming a tile roof?

Would a 2 story house have the same placement?

[eyecatcher]

As a rule the columns are set out in a maximum 3m x3m grid, but 2.5x2.5 is typical.

But obviously each house design is unique so sometimes extra column are included and some can be omitted thus increasing the loadings on those left.

Columns at ground floor level 200mm square and upstairs can be the same but normally 150 square.

I would suggest however if you have no construction background to obtain the services of a structural designer or architect as guessing is unwise.

I am not giving advice just general info.

[dddave]

Thanks; just what I was looking for. A friend is in the initial stages of conceptualizing a house she wants to build so just helping her to develop a very basic floor plan.

She has the land and inherited enough to build a decent house. When she does decide to build she will hopefully get a decent contractor who will turn her ideas into something build-able.

[IMHO]

Actually, it's a 4M x 4M grid max, if using 20cm posts.

For single storey the rebar is normally 4x12mm with 6mm ties at 15-20cm spacing. For two storey, the ground floor posts will normally have 6-8x12mm rebar (same ties), while the upstairs posts will remain 20cm, but reduce to 4x12mm rebar.

The posts are pretty easy - it's the beams that are much harder. Always use a structural engineer.

[bankruatsteve]

My experience is 3.5m. With 3-4m being the range. My issue with this is that it doesn't HAVE to be on a grid like that - but Thai builders don't seem to understand how to do otherwise.

[IMHO]

My experience is 3.5m. With 3-4m being the range. My issue with this is that it doesn't HAVE to be on a grid like that - but Thai builders don't seem to understand how to do otherwise.

It's the architects & engineers of Thailand that created the 4M max grid.

I can see several reasons why they created the grid system though...

Rebar must be in the range of 15-35mm from the outside edge of a post or beam - less than 15mm and the rebar won't have the fire resistance it should have, and is also susceptible to corrosion from water entering through small fissures. More than 35mm and the concrete outside doesn't have the support it needs and is susceptible to cracking. It's much easier to get/guess this spec right in a 20cm post than it is in a 30 or 40cm post.

Then there is the strength of the finished concrete, which is effected by both mixing quality and curing process - 20cm posts can handle around 20 tons of load each - but if poorly mixed or cured, that could drop to 12-15 tons each. By placing them at <= 4M intervals, even if they are not very well mixed or cured, there's still plenty of safety margin.

Then, there's the cost.. A 20cm post needs only 4-8x 12mm rebar at around 190 Baht per length. A 40cm post needs 8-16 x 20mm rebar at 500 Baht per length, and the beams connecting to it also need proportionally more steel and concrete as well - it's substantially cheaper to make 3x 20cm posts with an 8M long 40x20cm beam, than it is to make 2x 40cm posts, with a 40x80cm beam.

Lastly, there's the difficulty of getting heights correct when you've got a mixture of large beams with smaller ones (not every room needs to be > 4M wide). For example, think about how 1st floor ceiling height, 2nd floor height, and the staircase design would be impacted if you had 40x80cm beams instead of 20x40cm..

The bottom line is, larger spans are very much doable - practically every public place you've been in shows this - but your builders will need to have a proper understanding of steel fixing, concrete mixing and curing, and you'd need to be prepared to spend well over double, maybe even triple, on construction materials (which are usually around 75% of the total building cost).

Edited September 15, 2014 by IMHO

[wayned]

I used 4 meter spacing with 20cm posts when I built mine, single story 320 square meters Trying to maneuver around a house with 2.5m spacing would be claustrophobic for me, more like a maze! Internal corner posts, non load bearing, were poured in situ. There are a lot as I have walk-in closets in all of the bedrooms and a pantry, Budda room and workshop as part of the house.

[Crossy]

It's worth looking at these government plans a couple of which have much larger spans, if you find one that's near what you like you can adapt, so long as you don't change any structural elements no need for an architect or engineer.

http://www.crossy.co.uk/Thai_House_Plans/index.html

Our adapted No30 has a 7m unsupported span, bloody big beam mind.

[splitlid]

7m, bah, this 800 beam is going to span 11m hopefully.

[dddave]

It's worth looking at these government plans a couple of which have much larger spans, if you find one that's near what you like you can adapt, so long as you don't change any structural elements no need for an architect or engineer.

http://www.crossy.co.uk/Thai_House_Plans/index.html

Our adapted No30 has a 7m unsupported span, bloody big beam mind.

Wow! What a great page for someone thinking about a house. I immediately forwarded it to the person I mentioned in my OP...really helpful.

These days, is B10,000 sq/m all in (not including land) a fair guideline for cost for a good quality, standard home; such as #8, for instance?

[Crossy]

These days, is B10,000 sq/m all in (not including land) a fair guideline for cost for a good quality, standard home; such as #8, for instance?

A lot depends upon your location, but 10k/m² is towards the low end. Think more like 15k/m² if you are expecting more 'Western' quality, we paid about 22k/m², but our home is a bit special and Wifey does not do cheap

Have a look here to see what can be done with a little imagination and the free plans http://www.thaivisa.com/forum/topic/481794-housebuilding-thread/ or here if on a budget http://www.thaivisa.com/forum/topic/494413-bojangles-budget-bungalow-in-the-boonies/

[bankruatsteve]

FYI: 10 years ago, I did a very high quality house by architect for close to 20K/m2. 4 years ago did another good quality but not fancy with lots of work ourselves for about 13K/m2.

Edit: Just to say, the one 10 years ago was before construction materials like concrete and steel prices went much higher.

Edited September 16, 2014 by bankruatsteve

[kannot]

7m, bah, this 800 beam is going to span 11m hopefully.

Wowser what are you building splitty?

[splitlid]

its a private residence, the 3 x 800 beams are for a triple carport and triple workshop.

[IMHO]

its a private residence, the 3 x 800 beams are for a triple carport and triple workshop.

We have 9M open span on our carport (with Monier roof tiles) - our engineer designed up a ladder beam for that, which I imagine cost a whole lot less than those I beams - several years on, it's still standing, and no sagging

[splitlid]

that's nice

[IMHO]

that's nice

Yeah, it wouldn't support a 10 ton beam crane like yours would though