Received Today The Report Of The Site Soil Test To Determine The Thai House Foundation Design

Today (September 23, 2010) I have received from Thailand the report from the survey company, commissioned by the Kensington Company (our architect in Bangkok), who undertook the site soil tests that will be used to determine the design of the foundations for our retirement house in Pakchong, Thailand.

Photographs Showing The Soil Tests Being Undertaken On Our Land

These two photographs were taken on September 8th, 2010, at the land we intend to build our house to retire to at Pakchong, Thailand, and show the soil testing team at work on site. The rig you can see is the rig for the Standard Peneration Test (SPT) used to test the soil from which the safe ground bearing pressure is determined.

Site Soil Test Thailand Borehole No. 1

Testing The Soil On Our Land in Pakchong - Borehole No. 2

Site Soil Test Thailand Borehole 2

Testing The Soil On Our Land in Pakchong - Borehole No. 2

What This Report Tells Me About The Design Of The Foundation Design For The Retirement House We Will Build In Thailand

First and foremost, although the report of the soil tests is interesting information for me, it’s prime purpose is to give to the structural engineer the information he neeeds to design the concrete house foundations.

The report is highly technical and I had to engage the help of a civil engineer friend of mine to confirm my interpretation of the 32 page document, entitled “Survey Report, Subsoil Investigation, Private residence Project, Ampoe Pakchong Changwat Nakhon Ratchasima”.

(By the way “Ampoe Pakchong” means “District of Pakchong” and “Changwat Nakhon Ratchasima” means “Province of Nakhon Ratchasima”. Ampoe is often written as Ampur)

There are three key pieces of information in the soil investigation report.

Soil Type

The type of soil changes at 1.5 to 2 m depth below ground level. The top layer, down to 1.5 to 2 m, is what is called “very stiff clayey silt”. This has a good bearing pressure when dry, but when wet rapidly becomes saturated and turns into a slurry which cannot support much weight. Foundations should not be places in this layer of soil.

Below that there is a layer of “very stiff to hard silty clay, some sand and gravel”. This has a good allowable bearing pressure and is where the foundations must be formed.

Depth Of Concrete Footings

The report shows that the foundations (footings) should be located at 2 m below the ground floor level. That means that the builder must excavate 2 m deep to place ths foundation pads.

Safe Ground Bearing Pressure

The safe ground bearing pressure (allowable soil bearing capacity) is given as 26 to 35 t/m2 (ton per square metre or 260 to 350 kN/m2) at a depth on 2m.

The safe bearing pressure is the safe pressure that the soil can be loaded to. If the safe bearing pressure is divided by the total weight of the house the result is the area of foundations required.

The above is a very brief summary of a 31 page report. For more detailed information on foundations design and the importance of undertaking a site soil test go to the “Site Testing Of The Soil For House Foundation Design” web page.

Concrete Pad Foundation Design

The information in the site soil test will now be used by the structural engineer employed by the Kensington Company (our architect in Bangkok) to calculate and design the concrete foundations for our retirement house.

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5 Responses to “Received Site Soil Test Report For Foundation Design”

  • ian noble:

    Dear Alan,
    Many thanks for your very informative site.
    We plan to move to Thailand in the near future when we have sold our house in Hong Kong.
    We are looking in areas around Pataya as the country side and coast are wonderful and also very convenient for Bangkok.
    Interestingly, we have been in contact with Kensington as potential architects.
    How are you finding them?

    Wishing you well with your build.
    All the best Ian.
    Ian Noble


    admin Reply:


    Many thanks for your post on the website. These posts by visitors do provide additional information for other people and keep the website alive.

    Regarding Kensington I highly recommend them. I have only just this morning received a complete set of construction drawings for our retirement house in Pakchong. There are 46 sheets and the detail is amazing. I will be uploading them to the website soon.

    I must add that I have never seen such a high quality and large set of drawings for such a small building, and I have been practicing as a professional Chartered Building Services Engineer (B.Sc, C.Eng, MIMechE, MCIBSE) in the industry for over 30 years. The drawings were received just before the promised date.

    You can read why I recommend the Kensington Company and maybe even receive special attention from the Managing Director, Chris, on this web page. Also the Kensington Company can send you a free cost estimate when you contact them using the online Form here.

    I wish you luck with your hunt for the perfect retirement house in Thailand.


  • ???????:

    Although soil testing is valid as astm standard, soil conditions maybe change when the time passing.


    admin Reply:

    Hi and thank you for your post.

    I am sure readers would be interested to know how and over what period of time soil conditions can change. The site soil investigation that I have had carried out by a professionally qualified company is the same type of investigation that is used all round the world to establish the correct basis for the foundation design. That is why there are various Standards such as the ASTM Standard.

    If you can give a bit more information on how the soil conditions may change and how that might affect foundation design it would be of value to readers. Without a bit more explanation your comment could mislead readers into thinking that the results of the site soil investigation are invalid and that surely is not the case.

    Many thanks for your comment.


  • You are correct to have this study done – too many people build without checking the conditions first – and suffer cracks or structural damage later!
    We used for our foundation soil earth works and found them very efficient, and they recommended we leave the filled land to go past a rainy season before building, or to dig piles that went beyond the filled depth of land otherwise. We have decided to do both!


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