Foundations

[keithkarmann]

Hopefully I will start building a house in the Sukothai area later this year. Not wanting to spend millions of baht I am looking at ways of keeping the cost down. I have been planning to make the foundations with concrete pillars as far as necessary below ground and about 1 meter above ground with a concrete ring beam about 16 meters x 7 meters on top of these pillars. I know the reason to have the house above ground in case of flooding but according to my girlfriend (who owns the land) it never floods where I will build the house. As an alternative I am considering building the house on footings similar to the way houses are built in the UK. I will use plenty of concrete and rebar in the footings to make sure they are strong enough then use 14 cm concrete blocks (which are not porous) to build up approx. 1 meter above ground level and then install the concrete floor (pre-made concrete slabs) which can be supported by a second layer of blocks for each room. Then the outer blocks can be built up to the correct height for installing the roof. The blocks I will be using are 40cm wide x 20cm high and 14cm deep they also have two large holes running vertically though them which can be ideal to run cables and pipes through and also fill with concrete and re-bar in the corners of the house. With the floor level at 1 meter above ground level I can build a 45 degree roof without it looking top heavy (hope I am making sense). Then later I can add a room in the roof. Building this way it will not be too complicated and I can be more hands on. With the concrete pillar foundations I calculated that I would need at least 27 concrete pillars and what would they look like? and all of this concrete shuttering would have to done by a contractor (greatly increasing the cost). One or two questions I have are: 1. Do I need to have concrete pillars at the corners and a few more to support the roof? 2. Is there anything wrong with this type of foundation? 3. How deep and wide do the foundations need to be? bearing in mind the blocks alone would weigh 30-40000 kgs.

Apart from the outer walls there would be at least 3 dividing walls supported on additional foundations running across the house.

Thanks in advance for your answers.

[IMHO]

I'm not 100% sure I'm following you right here - are you suggesting constructing a house without posts or beams at all - i.e. the whole thing is just supported by cinder blocks?

If yes, I do not see any Thai engineer signing off on that, even if normal 'post' locations were filled with rebar and concrete. The 'posts' would still be undersized compared to a normal (20x20cm) and I can't imagine how this style of construction could possibly be a substitute for beams to support the walls.

Assuming a rectangular design, 16M x 7M would only need 12 posts & footings - I'm not sure where you plan to put the other 15?

As an alternative option, consider using pre-cast posts so the only formwork needed is the beams. If you and the builder are prepared to take it slowly, you could just form a couple of beams at a time to save on wood costs. Leave the wood forms on for 2-3 days, then wrap the beams in plastic (so they continue to cure properly) and move onto the next beams... Wood planks can usually be re-used up to 10 times, and plywood 3-4 times before they become firewood, so another way to save will be to look around for some used planks..

[wayned]

In the US they also build houses that way where the ouside wall and usually an interior wall are load bearing walls and carry the enrire load of the roof structur, no ploesor beams. I've never seen houses built like this here, only outbuildings and sheds. Thre's no reason that it could be done that way as long as you use the correct blocks and rebar construction.

[IMHO]

In the US they also build houses that way where the ouside wall and usually an interior wall are load bearing walls and carry the enrire load of the roof structur, no ploesor beams. I've never seen houses built like this here, only outbuildings and sheds. Thre's no reason that it could be done that way as long as you use the correct blocks and rebar construction.

What supports the interior walls on his 1M high suspended slab?

[trogers]

Have to consider whether this area needs a design against potential earthquakes.

[Crossy]

There are plenty of threads on ThaiVisa and other Thai building related fora showing that attempting anything outside the 'normal' Thai post and beam construction will result in a negative cost saving.

Download one of the free government plans http://www.crossy.co.uk/Thai_House_Plans/ adjust it to suit your needs (don't mess with the structural elements), submit to your local planning department for a building permit, find a contractor who is known locally and reasonably priced, build.

You will have enough headaches going the standard route.

[wayned]

In the US they also build houses that way where the ouside wall and usually an interior wall are load bearing walls and carry the enrire load of the roof structur, no ploesor beams. I've never seen houses built like this here, only outbuildings and sheds. Thre's no reason that it could be done that way as long as you use the correct blocks and rebar construction.

What supports the interior walls on his 1M high suspended slab?

There are footings or concrete beams wherever there is an innterior wall. The prefab concrete subfloor slabs come in different lengths -2m, 2.3m, 3m, 4m, etc. They are placed on the footings as a subflooor and then covered with wire mesh and a final floor is poored on top. The walls are then bullt on the final floor. I used this method when I built my houses, suspended about 1.5 meters above the ground, and most multistory buildings are built this way.

[lanng khao]

Lay your block flat so it's 9" wide for ykur foundation, 7 courses high, on a 140 concrete block, sit your conrete planks on the inside 4" skin, set a 4" block upright and then screed your floor to your height, then build the house in a 140 concrete block using good precast or insitu Intel's over all your openings and block tie all your dividing walks into the outside skin to roof height then sit your roof on the blockwork.by the time you have rendered both sides you will be looking at a 7.5 to 8 inch wall , save all those conc sows (pillars)

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[IMHO]

In the US they also build houses that way where the ouside wall and usually an interior wall are load bearing walls and carry the enrire load of the roof structur, no ploesor beams. I've never seen houses built like this here, only outbuildings and sheds. Thre's no reason that it could be done that way as long as you use the correct blocks and rebar construction.

What supports the interior walls on his 1M high suspended slab?

There are footings or concrete beams wherever there is an innterior wall.

So not what the OP is talking about - they way I understand it, he wants to build a house that has no beams or posts, but yet still has a 1M high suspended slab.

[keithkarmann]

There are plenty of threads on ThaiVisa and other Thai building related fora showing that attempting anything outside the 'normal' Thai post and beam construction will result in a negative cost saving.

Download one of the free government plans http://www.crossy.co.uk/Thai_House_Plans/ adjust it to suit your needs (don't mess with the structural elements), submit to your local planning department for a building permit, find a contractor who is known locally and reasonably priced, build.

You will have enough headaches going the standard route.

Thank Crossy I am thinking a bit more clearly now, as I can't be sure how strong the blocks are when they are under compression from about 40,000 kgs of blocks I guess it would seem to be obvious that the concrete pillars are needed all the way up from the foundations to support the weight of the roof and the blocks can crack or fall out but the roof would still be supported. Secondly I have been on the crossy.co.uk site (any relation?) and have decided to go for plan 8 with some minor modifications to room sizes - have to find out what the walls are built of as my concrete blocks could be heavier and I may need to build stronger footings. I agree with IMHO with the idea to build one or two pillars at a time but with the modifications of using either round blue plastic pipe (with the equivalent cross section of 20 x20 cm) which can be cut in two halves and clamped together for the concrete pouring or round concrete pipe that can left in place once the pillars have set.;b++){var>

I like Lanng Khao with his idea of laying the blocks on the side but this would have to be built up on a wide concrete (below ground footing/ring beam) as opposed to the concrete pad idea. Personally I think the concrete footing all the way round the perimeter of the house would be more stable than pad which could sink individually. A lot depends on weather or not I build 1 meter off the ground in an area which is not know to flood or I keep the house closer to the ground.

The plan 8 house has about 21 pillars and is roughly the same floor size as my original plan.

Please keep posting ideas and thoughts.

Edited July 22, 2014 by Crossy
Removed some superfluous scripting data

[Crossy]

That is actually my site Keith, the plans came from the site linked at the top of the page.

Most of the plans have a ground ring beam, nothing to stop you jacking the whole structure up by 1m or so if you're afraid of flooding etc.

The walls on the government plans show those small red bricks, if you replace with aerated concrete (superblock) they will be a lot lighter.

The drawings also show two foundation types, driven piles and pads, your contractor will be able to tell you which is the correct foundation for your area (on Bangkok clay we have 16m driven piles).

[IMHO]

I agree with IMHO with the idea to build one or two pillars at a time but with the modifications of using either round blue plastic pipe (with the equivalent cross section of 20 x20 cm) which can be cut in two halves and clamped together for the concrete pouring or round concrete pipe that can left in place once the pillars have set.;b++){var>

What's your reasoning behind wanting round posts?

This is probably best done using 10" sections of concrete drain pipe so there's no need for removal and the overall surface area gets close to the standard 400 sqm cm square post, but when rendering you really can't go more than about 35mm thick, otherwise you will get cracks - so you're either going to have round corners everywhere, or unstable render...

if you're looking at this method to save costs on form wood, bear in mind that post forms only need to be on for 2 days (at which point the concrete achieves ~40% strength) - after 2 days you can remove the wood forms and wrap the posts in cheap plastic for the remaining 26 days of curing needed to achieve full strength.

[casualbiker]

Or just hire the correct forms and don't bother with the wood forms.

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[keithkarmann]

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I agree with IMHO with the idea to build one or two pillars at a time but with the modifications of using either round blue plastic pipe (with the equivalent cross section of 20 x20 cm) which can be cut in two halves and clamped together for the concrete pouring or round concrete pipe that can left in place once the pillars have set.;b++){var>

What's your reasoning behind wanting round posts?

This is probably best done using 10" sections of concrete drain pipe so there's no need for removal and the overall surface area gets close to the standard 400 sqm cm square post, but when rendering you really can't go more than about 35mm thick, otherwise you will get cracks - so you're either going to have round corners everywhere, or unstable render...

if you're looking at this method to save costs on form wood, bear in mind that post forms only need to be on for 2 days (at which point the concrete achieves ~40% strength) - after 2 days you can remove the wood forms and wrap the posts in cheap plastic for the remaining 26 days of curing needed to achieve full strength.

Thanks for that IMHO, any round pipe above 9 inches I.D. would be more than 20 x 20 cm post forms. Weather or not to use round pillars depends on weather or not the pillars extend above ground or not. If wooden post forms are used and they extend above ground then they would need rendering, adding this work with the cost of all the labour involved with assembling and dis-assembling the post forms, then it could be cheaper to use one of my alternatives yes Thais do not worry about the cost labour as it is cheap. I will not be based near the project all the time while it is been built but with the concrete pipe idea all the pillars could be poured in one day while I am there. I guess I will have to do a costing with all the different ways of doing the pillars. I am not in a hurry to complete the house so if I oversee the pad construction and pillar construction then I can go back there a month later to oversee the construction of the ring beam then I can forget about it for several months before the next stage which will be the post formed pillars which I guess will have to be constructed 20 x 20 cm square.

I have got a figure in mind for the foundations including the ring beam and if the contractor who I have got in mind can get within that figure then they can do the work, they have given me a quote for the concrete floor and I thought that was reasonable.

[keithkarmann]

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That is actually my site Keith, the plans came from the site linked at the top of the page.

Most of the plans have a ground ring beam, nothing to stop you jacking the whole structure up by 1m or so if you're afraid of flooding etc.

The walls on the government plans show those small red bricks, if you replace with aerated concrete (superblock) they will be a lot lighter.

The drawings also show two foundation types, driven piles and pads, your contractor will be able to tell you which is the correct foundation for your area (on Bangkok clay we have 16m driven piles).

Thanks Crossy, you say the house plan I am adapting is made of small red bricks, have you any idea how much they weigh when compared with the 40cm x 20cm x 14cm blocks I want to use that weigh 15kg each. I do plan to build the ring beam 25cm wide (to accommodate the 14cm blocks) and 50cm deep which I believe is bigger than the plans so hopefully this will be strong enough to handle any increased weight.

I have never seen them use piles here, only for taller buildings. On the savings side I am adapting the plan no.8 which has two sceptic tanks one for each bathroom, so have moved both bathrooms to one side (no large pipes running under the house) so I only need one sceptic tank

[IMHO]

I will not be based near the project all the time while it is been built but with the concrete pipe idea all the pillars could be poured in one day while I am there. I guess I will have to do a costing with all the different ways of doing the pillars. I am not in a hurry to complete the house so if I oversee the pad construction and pillar construction then I can go back there a month later to oversee the construction of the ring beam then I can forget about it for several months before the next stage which will be the post formed pillars which I guess will have to be constructed 20 x 20 cm square.

I'm having troubles visualizing your build.. normally it's footings first (which include a short section of 'post'), then the ground beams (however high they are), then the main posts.

If you mean to use the round pipes for the footing 'posts' that's fine - we also do that as it allows the holes to be back-filled a day or two after the pour, so the rebar for the posts, and beam rebar + formwork can then begin without too many delays (because the formwork never comes off the footings).

However, if you want to have 20x20cm square main posts, you'll need to use pipe at least 28cm diameter at the footing stage, otherwise the square posts will not sit 100% on the round footings:

Bearing in mind the the rebar for the posts must be in the range of 15mm-35mm (nominal 25mm) from the outside surface of a 20cm x 20cm post - otherwise you end up with posts that fracture (>35mm gap), or posts that have rusting rebar and/or have poor fire safety (< 15mm gap).

[keithkarmann]

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I will not be based near the project all the time while it is been built but with the concrete pipe idea all the pillars could be poured in one day while I am there. I guess I will have to do a costing with all the different ways of doing the pillars. I am not in a hurry to complete the house so if I oversee the pad construction and pillar construction then I can go back there a month later to oversee the construction of the ring beam then I can forget about it for several months before the next stage which will be the post formed pillars which I guess will have to be constructed 20 x 20 cm square.

I'm having troubles visualizing your build.. normally it's footings first (which include a short section of 'post'), then the ground beams (however high they are), then the main posts.

If you mean to use the round pipes for the footing 'posts' that's fine - we also do that as it allows the holes to be back-filled a day or two after the pour, so the rebar for the posts, and beam rebar + formwork can then begin without too many delays (because the formwork never comes off the footings).

However, if you want to have 20x20cm square main posts, you'll need to use pipe at least 28cm diameter at the footing stage, otherwise the square posts will not sit 100% on the round footings:

Bearing in mind the the rebar for the posts must be in the range of 15mm-35mm (nominal 25mm) from the outside surface of a 20cm x 20cm post - otherwise you end up with posts that fracture (>35mm gap), or posts that have rusting rebar and/or have poor fire safety (< 15mm gap).

Thanks IMHO, I am having troubles visualising it as well. After a re-think and bearing in mind my girlfriend tells me the land never floods, at the moment my thinking is to pour the footings with a short length of post up to road level (these can be square posts 25cm square as they will not be visible as they will be below ground) and the 25cm wide x 50cm deep ring beam on top of these posts. Two reasons for the 25cm wide ring beam, 1. to accommodate the 14cm deep blocks, leaving enough to mount the floor slabs and 2. Maybe the blocks are heavier than the bricks used in the plans I got from Crossy. I can see there would be problems with round posts, especially if I wanted to brick up between the below ring beam posts (if they go above grond level) at a later date.

You probably realise I have never built a house before and I will probably never build another one so it would be good to get it right first time.

[trogers]

What would the footings be resting on? Be they round or square.

Normal construction would be to rest on a large square pad, or a smaller rectangular pile cap when piles are used. Rebar would be brought up vertically in the same arrangement right to the top of the column of the house.

[keithkarmann]

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What would the footings be resting on? Be they round or square.

Normal construction would be to rest on a large square pad, or a smaller rectangular pile cap when piles are used. Rebar would be brought up vertically in the same arrangement right to the top of the column of the house

Don't quote me but I guess a big hole is dug and hopefully solid ground is not too deep, failing that then piles would have to be used. My plans show square pads about 1.4 meters square and 20cm thick but if piles are used then the pads are reduced to about 90cm square. The pads have a lot of rebar in them before concrete is poured and the vertical rebar is connected to the rebar in the pads.

[cliveshep]

My wife liked the idea of house no 3 on Crossey's web site as she wants to build a couple of blocks like that as rooms to rent.and we downloaded that one. Unfortunately when we opened it up it wasn't rooms as such but a toilet block it seems?

[Crossy]

My wife liked the idea of house no 3 on Crossey's web site as she wants to build a couple of blocks like that as rooms to rent.and we downloaded that one. Unfortunately when we opened it up it wasn't rooms as such but a toilet block it seems?

It's rooms with a separate toilet block out back, look at A-03 for the overall layout.

Nothing to stop you adapting the internal layout to incorporate separate ablutions for each unit, the structure will be the same

[cliveshep]

My wife liked the idea of house no 3 on Crossey's web site as she wants to build a couple of blocks like that as rooms to rent.and we downloaded that one. Unfortunately when we opened it up it wasn't rooms as such but a toilet block it seems?

It's rooms with a separate toilet block out back, look at A-03 for the overall layout.

Nothing to stop you adapting the internal layout to incorporate separate ablutions for each unit, the structure will be the same

Ahhh - sorry, you're right. Many thanks for that - I'd have discarded it otherwise.

[sirineou]

I Have being working with Plan #8 from the government plans for some time now, it is a simple elegant design , but it has the limitation of small bedrooms.But these limitations can be easily rectified with some simple alterations.

First some comments on the OP's idea of load bearing walls.

In the US the cement blocks that he is familiar with are manufactured to strict industry standards, and can be trusted to perform, here in Thailand there are no standards and I would be worried about their load bearing capacity, further more, since you will be constructing columns for the footing foundation, there would be very little additional cost to continue the columns to the roof, and no additional savings to now change to load bearing walls.

This plan is being build right now by ThaiPete in the coolthaihouse .com forum if you are interested.

below is a screen shot of one version of the modifications i made to this plan.In this version the Master bedroom has being made a meter longer. and the hallway in front of bath #1 eliminated since it is no longer needed , portion of the hallway is used to make the bathroom bigger and the other portion used as a closet. I have also changed the roof style to Hip style, just as a matter of personal preference

There is an other version with both the bathrooms moved to one side and the second rear bedroom moved where the second bathroom used to be.

If anyone is interested PM me for additional info.

[media]

[media] Edited September 21, 2014 by sirineou