coolthaihouse.com -> info -> foundation columns

June 21, 2004 - editor. Pattaya, Thailand house building and construction.  Construction of foundation columns, house support pillars, housing posts, concrete pillars, wall and roof supports.  Concrete strip footings for the house supports.  Use of rebar in the foundation column.  Post holes.  An example of how it should and should not be done.

This is one of the most important aspects of a new house.  The house is anchored with foundation columns which are set in concrete footings in deep square post holes.  The process is as follows:  1.)  Post holes are dug and a square rebar frame which stands about 3 meters tall is concreted in place.  2.)  A rebar frame is put in place for a base 'footing' which attaches the foundation pillar frames.  3.)  Concrete is poured over the footing.  4.)  Lastly, the concrete is poured within wood frames around the post frame to create the foundation pillar.

In case you're thinking that the contractor should know how to do this and they always do it correctly -- just today I saw a house where the columns were being set in an very poor manner, the same way as you would set up perimeter wall posts.  The motivation in this case was an owner who had contracted for a fixed price, including all materials, for a house to be built while he is out of the country.  It is a sad situation because the savings for doing the foundation column in a very very inadequate manner will save about 1000 Baht, where the house price is closer to 2 million Baht.

Here is the story of the poorly done foundation columns:. 

Here is what what should happen.  First a square hole is dug which is 1 meter square.  Then a base of concrete is poured to keep the rebar pillar frame in place.  Then form wood is used to make a large square for a foundation pour up to the ground level.  The sizing of this form box will be about 60 centimeters wide.  This is an important step as shortcuts will lead to foundation pillars shifting and walls cracking, among other things.

In this case the foundation hole was just 60 centimeters wide.  Then a can was used to do the pour.  The can was inserted and then dirt was placed around the can.  The pour was done and then 5 minutes later the can was lifted out of the ground.  This method is commonly used to create the post for a perimeter wall, but if used for a house proper will lead to an substandard structure.  (This is what the picture to the left is showing, ie. the can pulled out 5 minutes after the cement pour).

Doing the foundation column like this can cause a lot of settling cracks, and other problems which only time will tell.  It just isn't very sturdy.  If you compare the house done for a foreigner and that regular Thai house:  The house built for a foreigner will be a lot prettier and will be 'finished' off to a foreign standard.  It will have things we take for granted -- like a sheetrock ceiling.  The Thai house will be much simpler and cheaper (maybe 200,000 Baht or so total cost).  But important things like the foundation columns will almost always be done to standard.

What follows are some shots of the standard way of doing foundation columns for a single story building......

The metal support structures for the house use metal of guage 4 hun full with the cross supports 3 hun full. They are temporarily held upright by a wood support.  (29-Feb-04)	The base rebar (4 hun full) is placed on top of a gravel sub footing. The stick represents the middle of the foundation post which is to be poured.
The vertical metal supports are created from rebar.  The vertical long strands are 4 hun full.  The horizontal support pieces are typically 3 hun full.  This is the structure you see in the following photo which will later have cement poured around it and form the foundation column.	The vertical supporting rebar structure has be wired on. The height of the structure depends on the roof height of the house.  For an average house the columns are 3 meters tall (above ground) for an overall height of 4 meters.
The foundation post holes should be around 1 meter square and 1 meter deep.	The cement is poured to anchor the base in place. The depth of this pour is around 20 cm.  After this there will be a pour up to ground level which is 60 centimeters wide.  Form wood is used as support for this pour.
There is no picture for this step, which covers creating the 'sub base' portion of the foundation pillar under the ground.  A square section is framed (using wood planks) at about 60 centimeters square.  After this there will be a pour up to ground level.  After this sub base dries, the form wood is removed and fill dirt is inserted to fill the hole.	The size of the footing of the house depends on many factors. Normally a minimum of about 15 centimeters is appropriate. (05-Mar-04)
The metal substructure which uses 4 hun full guage steel with 3 hun full cross supports. There is additionally another strand placed in the middle of the pour (4 hun full) which hasn't been inserted yet in this picture.	The cross supports are held in place by wire strands.
The wire being snipped in place.	Form wood is wedged in place over the square upright rebar frames and then the concrete is poured in.  The foundation columns should have a width of about 20 centimeters square. (24-Apr-04)
This shows an example of foundation columns as well as a partially finished roof truss. (13-Mar-04)

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