Chap is cracking

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Chap is cracking

Postby Auggie » Tue May 13, 2008 3:37 pm

The interior rendering that my contractor did with chap is cracking, nothing major, but still, cracks none the less. My friend who does lots of renos said that if done properly, it should not show cracks. Any idea what the problem might be? Are they using too much water in the mix, or not wetting it enough before applying? Any solution to "fix" the cracks? If a wet slurry of cement and sand was made up, would that work?
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Postby dozer » Tue May 13, 2008 5:54 pm

Interestingly enough it is normally to do with the skill set of the person applying the render, not the materials. After the first coat is applied, the worker must wait between 5 to 10 minutes to have it set up a bit. He will know by feel. Then he applies another coat on top. If the process is rushed you get a lot of small cracks.

Thai workers take great pride in the ability to apply render well, all workers and foreman will immediately recognize and not argue that render with a bunch of cracks is 'not well done'.

Small cracks are covered up with regular paint, if they are a bit more pronounced an elastomeric paint should be used such as TOA 7 in 1.
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Postby jazzman » Sat May 31, 2008 4:24 pm

It would also be interesting to ask the workers if they use proper Boon Chap, or if they were using standard cement whether they added the plasticizer to it - they DO forget sometimes.
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Re: Chap is cracking

Postby Auggie » Wed Sep 17, 2008 10:37 pm

Well, returned after a few months to find ALOT of cracks in all of the chap. Looks terrible. I wanted to get a textured wall, and leave it as it is, except for a sealer,but as it is now I need to think of something else. Would a slurry of cement, sand, latex and water help? If I made it quite wet and just slurred over the entire wall, or would the slurry crack as well? What if I added some plasticizers to the mix?

Or how about lime? Is it available here in Thailand? Can I use lime for interiors? If so, I would just get some grey pigments to wash over it.

Any thoughts?

Thanks
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Re: Chap is cracking

Postby jazzman » Wed Sep 17, 2008 10:53 pm

One of the reasons the chap gets cracks here in the tropics is because the chap is thin and the water can dry our or evaporate where it should become part of the curing process. The plasticiser prevents this. However, these problems usually manifest themselves within days of applying the chap. More serious cracks could be a sign of the wall moving behind the chap. It might be an idea to troubleshoot this before applying anything new in case the cracks are going to continue to appear or widen.
How to build a $20,000 / £14,000 house and a $???? MOTEL Updated 21 March 09 - with BOQ and costs
Don't let this happen in YOUR house.
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Re: Chap is cracking

Postby Auggie » Thu Sep 18, 2008 9:55 am

Thanks for the reply. It is a condo unit, so the walls are stable (I hope). I think it was down to poor skill and possibly the wrong type of cement used. Do you think my idea of a slurry would work to cover the cracks, or would the slurry then crack as well?
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Re: Chap is cracking

Postby jazzman » Thu Sep 18, 2008 12:19 pm

If it was a new condo maybe you can get it fixed under a guarantee. if the building is mmoving or settling down, the cracks will continue to appear. I don't know much about your idea of slurry. See Dozer's reply on plastometric paint. - it might be the solution as it should stretch with the cracks.
How to build a $20,000 / £14,000 house and a $???? MOTEL Updated 21 March 09 - with BOQ and costs
Don't let this happen in YOUR house.
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