Control joints in walls

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Control joints in walls

Postby Chris@huahin » Thu Apr 20, 2017 6:52 am

I'm planning to build a house and I would like to know if anyone has had any experience in using control joints in the walls of the house to reduce cracks that may appear In it. I will have a long straight wall on one side of the house and I would like to put a couple of control joints into it. I have never seen it done in any Thai house and I wonder if it would help to reduce cracking. I understand that good foundations and building on firm ground will help, but is there any reason why Thai houses don't use control joints?
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Re: Control joints in walls

Postby Sometimewoodworker » Thu Apr 20, 2017 8:47 am

Chris@huahin wrote:I'm planning to build a house and I would like to know if anyone has had any experience in using control joints in the walls of the house to reduce cracks that may appear In it. I will have a long straight wall on one side of the house and I would like to put a couple of control joints into it. I have never seen it done in any Thai house and I wonder if it would help to reduce cracking. I understand that good foundations and building on firm ground will help, but is there any reason why Thai houses don't use control joints?

As most current house are built with concrete posts infilled with concrete blocks (either AAC or concrete wetabix blocks) which is rendered with a cement based mixture the render expands and contracts at the same rate as the base structure there is no need for control joints.

All you need is to reinforce the junction between the posts and infill walls with stainless steel mesh to resist cracking at that point (due to wall movement not differential expansion) then you have crack free walls.

However if you want to add control joints, though unnecessarily, go ahead and enjoy the fun of trying to explain to your workers what you want and exactly how to make it :lol: you will have to be on site all the time they are being installed as no Thai worker will understand how to make them and why you want them.

Take a look at any builds here and you will never see control joints and, after the render has dried, crack free walls. FWIW one of mine is 18 metres long.
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Re: Control joints in walls

Postby Chris@huahin » Fri Apr 21, 2017 6:39 am

Hi sometimewoodworker,
Thanks for the explanation, that explains why it's done that way.
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Re: Control joints in walls

Postby canopy » Fri Apr 21, 2017 7:10 am

While that response has a number of useful facts, it is not completely accurate. For instance, if you read the instructions written on the bag of the popular render from SCG (makers of q-con) it describes when to use control joints to prevent cracking. In the case of a large continuous wall you seem to be describing, that is an absolute ringer for exceeding what the render is capable of doing without cracking. The blocks may also specify additional areas for control joints, but that only comes into play if doing something unusual for Thailand.

Chicken wire is an additional guard to prevent cracking, but note it is not limited to just block to post joints. It is also required in other areas such as window openings and over chases. I am not sure what kind of blocks you are using, but where and how to do this is outlined in the q-con manual which has an English version. I have read a lot of the building documents in Thailand and have experience with control joints and would be happy to provide any additional information about them.
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