Ricefield....Can Build Then Raise Dirt?

[cheeryble]

Hi

I have found a great rice field to build on. I understand they usually have a layer of clay to hold the water in.....is that brought in originally?

Anyway the main thing is:

If i need to raise the level say 1metre everyone is saying you have to put the earth in then wait at least a year. I'm wondering....

It seems to me there is going to be some sort of foundation which will support a house properly regardless of (or more strictly, designed specifically for, the ground type).

So can i not just sink my foundations in the field as it is, allowing extra height, then fill afterwards.....thus saving the year's wait?

Alternatively is it possible to use compacting machinery?

As a matter of great interest....if on built directly on to rice field, what sort of foundations would suit? Is rice field good or bad for building? (I'm aware the ground will stay muddy on the surface for much of the year, but is it intrinsically weak for foundations underneath or not at all?)

I'm even considering keeping the rice field for decorative purposes and raising some "islands" of earth for the house/drive/lawn/sala/whatever.

Any experienced input or thoughts appreciated!

[InterestedObserver]

Does your rice field have a proper Land Depertment title deed, not just a local possessory right document? If not, then you cannot legally build there. Thais can get away with it, but a foreigner could not register the house.

Edited February 6, 2011 by InterestedObserver

[slapout]

Most paddy land is lower than surrounding land/roads, etc. Runoff from rains will flow onto your land as well as high water in irrigation camels in the vicinity. Most homes on paddy land will be built on stilts for this reason. I have seen some 8 foot off the ground. Several moo bans have been built on former paddy land in the CM area and first fill is anywhere from 3 to 5 foot just to get above drainage of area. Many of the houses will be 1 meter above this first fill, to have a safety factor against the occasional flood.

You can shoot elevations on your proposed building site, using the mentioned factors, throw in history of flooding in your area also, and you can determine the height of your pilings, floor of house, etc. You can then know how much fill you will be working with.

[PattayaParent]

As slapot says you'll need to raise the level of the land that the house is buit on to prevent flooding, but not necessarily over the whole field if you want to live on an 'island' in the middle of the field.

To do it quickly you can surcharge the fill. That is put in more fill than is needed for the required level and then it will settle to the level you want as the house is built on top of it. It should be well compacted though and a civil engineer will need to do the calculations based on foundation / house designs and soil bearing capacities.

[cheeryble]

Thanks for all your thoughts....

I'm rather surprised at just how expansive it can be to put dirt on a couple of rai. If it was 5 foot and allowing for some topsoil it could run into the best part of a million baht. I presume that means ricefield should have a discount?

I was chatting with a knowledgeable farang last night and he said to do it properly you need pilings OR you can do a "raft" foundation. I believe my parents had this type once for a bungalow in the UK.

I shall look it up but I believe is just that the elements of the footings are designed and bonded together so strongly that if there is any movement the whole thing will move rather than break. On an alluvial plain I presume the worst one could get is a slight sinking.

Any more input appreciated!

[flying]

Seems like you are mixing a bit of terminology & granted it could be different in LOS than elsewhere

But when you say pilings I am assuming you mean a driven post/pile...ie: a column of wood or steel or concrete that is driven into the ground to provide support for a structure

When you say raft foundation...I am guessing you mean a concrete slab type of floor on grade with thicker edges under the bearing walls.

These thicker edges are also called continuous footings in such a situation

Lastly when you say footings they could also be a foot or base from which you will set your posts on. Also called post & pier type foundations.

These footings/piers are placed below or above grade at times.( size determined by load calculations) At no time would I assume all footings would move together if there ever was movement/sink as they are separate entities.

As to the back filling of the lot to achieve desired grade. It is funny that they would suggest waiting a year. But I am not surprised as it is probably the *Thai* way

Do they not have heavy equipment there like a D9 that could provide the compaction?

In any case good luck to you & hope you enjoy your project.

[Khun Jean]

If a house like this can be build that floats on water surely a house can be build on a ricefield.

Just make sure the land you displace with the foundation is enough to let it 'float' like a 'raft' on the land.

Or build it exactly like on the picture and when there is a flood you just float with it. Make sure you have some guides to allow only vertical movement.

Imagine walking on the beach. First with your feet as flat as possible even spreading your toes and see how far you sink. Then walk on your toes and see how far you sink.

That is the difference between a raft and pillar/footing foundations.

Edited February 7, 2011 by Khun Jean

[cheeryble]

Seems like you are mixing a bit of terminology & granted it could be different in LOS than elsewhere

But when you say pilings I am assuming you mean a driven post/pile...ie: a column of wood or steel or concrete that is driven into the ground to provide support for a structure

Yes that's exactly what I mean, but Ive only seen these used for multi storey condominiums.....

When you say raft foundation...I am guessing you mean a concrete slab type of floor on grade with thicker edges under the bearing walls.

These thicker edges are also called continuous footings in such a situation

Lastly when you say footings they could also be a foot or base from which you will set your posts on. Also called post & pier type foundations.

These footings/piers are placed below or above grade at times.( size determined by load calculations) At no time would I assume all footings would move together if there ever was movement/sink as they are separate entities.

But I think the whole idea of a raft foundation is that it is strong enough to move as one entity....

Do they not have heavy equipment there like a D9 that could provide the compaction?

Yes it had occurred to me to get a dozer....until it dawned on me that although it looks like it's weight would compact better I believe that in fact it has a softer footprint than a car or truck (especially a dirt-loaded truck), because of course pressure = force/area and the track area is very large.

In any case good luck to you & hope you enjoy your project.

thankyou kindly....and really I need to learn anything anyone has to teach me about this.

Edited February 7, 2011 by cheeryble

[cheeryble]

If a house like this can be build that floats on water surely a house can be build on a ricefield.

Just make sure the land you displace with the foundation is enough to let it 'float' like a 'raft' on the land.

Or build it exactly like on the picture and when there is a flood you just float with it. Make sure you have some guides to allow only vertical movement.

Imagine walking on the beach. First with your feet as flat as possible even spreading your toes and see how far you sink. Then walk on your toes and see how far you sink.

That is the difference between a raft and pillar/footing foundations.

You obviously did inhale!

Edited February 7, 2011 by cheeryble

[trogers]

If a house like this can be build that floats on water surely a house can be build on a ricefield.

Sorry to differ. Why would a strong swimmer die in quicksand in the same manner as a non-swimmer?

Floating on water and floating on mud are two separate things.

[Khun Jean]

You watch to many movies trogers. :)

It is impossible to die in quicksand unless you go head first, if you do nothing you would sink until about your waist (density of quicksand is about twice that of your body). Pulling you out though can be very dangerous as the forces needed are very high. Diluting it with lots of water while slowly wiggling and pulling yourself up very slowly would be the way to get out.

You would sink a little further and quicker if you move a lot (quicksand reacts the same like when you vibrate concrete).

It all has to do with densities. Concrete is very dense and as such it would sink into the mud. However if you make a hollow structure it will displace more and would only sink a little and the just 'float' on the mud/sand/clay/whatever.

Edited February 7, 2011 by Khun Jean

[trogers]

You watch to many movies trogers. :)

It is impossible to die in quicksand unless you go head first, if you do nothing you would sink until about your waist (density of quicksand is about twice that of your body). Pulling you out though can be very dangerous as the forces needed are very high. Diluting it with lots of water while slowly wiggling and pulling yourself up very slowly would be the way to get out.

You would sink a little further and quicker if you move a lot (quicksand reacts the same like when you vibrate concrete).

It all has to do with densities. Concrete is very dense and as such it would sink into the mud. However if you make a hollow structure it will displace more and would only sink a little and the just 'float' on the mud/sand/clay/whatever.

You are only assuming a static model in your flotation exercise. Mud has much higher viscosity and adhesion than water. A boat that sprung a leak and sink in water can be re-floated, but not in mud. What kind of watertight concrete hollow shell do you think can be achieved in the rural area using site mix when simple basement construction in the city using ready-mixed concrete frequently faces water leakages?

And do you think the density of mud will be the same along the length under a house when the flood comes?

[Khun Jean]

I don't want to take it to far off topic. The picture and suggestion to float your house in a flood was tongue in cheeck, but obviously it would have been better to put some smilies in that post.

It was more intended to explain the difference between a raft and pillar/footing foundation. In not so stable ground conditions a raft foundation is often used. Having a large area spreads the pressure and prevents sinking, real world raft foundations actual use pillars to reduce settlement, because that settlement with a raft only can be uneven.

Thus the best solution is a combination of the two techniques. Using the surface area of a raft foundation to minimize sinking and weight distribution and pillars to reduce settlement. A raft foundation that extends beyond the house and made strong enough will prevent cracks and settlement in the house structure itself.

The standard Thai technique of footings is not really suitable unless they reach down to the bedrock.

Edited February 8, 2011 by Khun Jean

[trogers]

I don't want to take it to far off topic. The picture and suggestion to float your house in a flood was tongue in cheeck, but obviously it would have been better to put some smilies in that post.

It was more intended to explain the difference between a raft and pillar/footing foundation. In not so stable ground conditions a raft foundation is often used. Having a large area spreads the pressure and prevents sinking, real world raft foundations actual use pillars to reduce settlement, because that settlement with a raft only can be uneven.

Thus the best solution is a combination of the two techniques. Using the surface area of a raft foundation to minimize sinking and weight distribution and pillars to reduce settlement. A raft foundation that extends beyond the house and made strong enough will prevent cracks and settlement in the house structure itself.

The standard Thai technique of footings is not really suitable unless they reach down to the bedrock.

The raft/friction piles foundation you proposed is technically feasible, but too costly for a rural house to be built on rice fields. Most cost effective will be a lightweight timber house on reinforced concrete stilts supported by spread footings with friction piles.

This will entail excavating down 5-6 feet to place the piles and build the footings, avoiding the soft topsoil/mud. Do not forget to tie the stilts together with reinforced concrete cross beams just above ground level.

[cheeryble]

Most cost effective will be a lightweight timber house on reinforced concrete stilts supported by spread footings with friction piles.

This will entail excavating down 5-6 feet to place the piles and build the footings, avoiding the soft topsoil/mud. Do not forget to tie the stilts together with reinforced concrete cross beams just above ground level.

"Friction piles"??

What are those TR?

I have a drawing for the groundwork of a friend's stylish masonry bungalow I admire which I think may fit your bill.

I shall try to dig it out...

[trogers]

Most cost effective will be a lightweight timber house on reinforced concrete stilts supported by spread footings with friction piles.

This will entail excavating down 5-6 feet to place the piles and build the footings, avoiding the soft topsoil/mud. Do not forget to tie the stilts together with reinforced concrete cross beams just above ground level.

"Friction piles"??

What are those TR?

I have a drawing for the groundwork of a friend's stylish masonry bungalow I admire which I think may fit your bill.

I shall try to dig it out...

Friction piles are any pile that uses its surface area in contact with soil to support the load bearing on it, usually because firm ground is deeper than the length of the pile.

Common short concrete friction piles are H-shaped or hexagonal with a hole at the centre, from 5-10 feet in length. The shorter ones (5-6 feet) can be driven into the soil by a sledge hammer, while the longer ones pushed in by a backhoe excavator.

Edited February 9, 2011 by trogers

[Khun Jean]

I am still amazed that i not see more steel construction work. It offers most of what you need when soil conditions aren't great and need a light building. The structure will be light weight, strong, no termite problem and easy to construct. I see many industrial buildings using it, why not residential buildings.