Rendering AAC blocks, the best way...

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Rendering AAC blocks, the best way...

Postby Khunchai » Wed Nov 05, 2014 12:43 pm

What is the best way to render AAC block walls in Thailand?

In Australia they sell special "polymer enhanced render" under Hebel® HighBuild™ name.

What's so special about this render?

What is the equivalent of this kind of render available in Thailand?

Why can't we just use standard sand cement renders for AAC blocks?
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Re: Rendering AAC blocks, the best way...

Postby cooked » Wed Nov 05, 2014 2:54 pm

I built two houses with AAc blocks, one using the expensive rendering recommended by the manufacturers, one a traditional plaster. Both houses, standing together, look ok after 40 years (switzerland).
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Re: Rendering AAC blocks, the best way...

Postby MGV12 » Thu Nov 06, 2014 9:09 am

cooked wrote:I built two houses with AAc blocks, one using the expensive rendering recommended by the manufacturers, one a traditional plaster. Both houses, standing together, look ok after 40 years (switzerland).


Interested to know the composition of the "traditional plaster". For sure different things work ... and work differently in different climatic conditions possibly.

The rendering that is produced for AAC blocks does genuinely have additives that assist in performing well and resisting cracking. Not rendering but the same principal: I have recently been laying some AAC blocks and just had a few left to go when the bag of AAC mortar ran out ... didn't want to open another one so I just mixed up Portland cement and fine sand [which is the basis of AAC mortar] plus added a 'plasticising' additive. Didn't work half as well.

Sure the genuine AAC render is more expensive but there are many manufacturers these days, and I have not noticed any significant difference between the performance of the high-profile expensive brands and the others. Chances are many come from the same cement works! Worth that little bit extra [insignificant in a house build budget] I suggest to use the product designed for the task.

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Re: Rendering AAC blocks, the best way...

Postby canopy » Thu Nov 06, 2014 10:23 am

Don't you think it will sound a bit ludicrous to others down the road when they see your expensive problems and you explain you decided to throw out the manufacturers instructions and do something you made up with no practical knowledge of the subject? AAC blocks have different characteristics than other blocks. That's why AAC render is used. As mentioned AAC render takes into account the considerable expansion and contraction these blocks have without cracking. The render also prevents moisture entrapment normal render will cause to prevent the blocks from decaying. And so on and so forth. Using the right render and applying it properly will have good results. That's the important part. Unapproved methods are asking for problems and throw out the considerable knowledge experts have built up over time that was made for people like you.
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Re: Rendering AAC blocks, the best way...

Postby Khunchai » Sat Nov 08, 2014 10:59 am

Is it really necessary to make two stage plastering for AAC block walls?

The first stage of plastering: base coat

The second stage of plastering: finish plastering

In the Q-CON brochure "Q-Con Fast Track" they don't say anything about 2 stage plastering... :?:
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Re: Rendering AAC blocks, the best way...

Postby MGV12 » Mon Nov 10, 2014 4:29 pm

Khunchai wrote:Is it really necessary to make two stage plastering for AAC block walls?

The first stage of plastering: base coat

The second stage of plastering: finish plastering

In the Q-CON brochure "Q-Con Fast Track" they don't say anything about 2 stage plastering... :?:


Not sure why you didn't get any responses to this question .....................

When rendering traditional Thai walls ... skinny concrete blocks/red bricks ... they always do two coats. One to correct the 'imperfections' [Lao Khoa induced or otherwise] and the second as a finish coat. Similar in the UK [not so much for the imperfections!] with something like a Browning plaster thick coat and then a plaster skim. If they are building with the 40 x 20 'concrete' blocks then letting the first coat set a while will reduce the block pattern showing through; even sometimes after painting!

With AAC it is not necessary to do two coats but try telling them that! If there are 'imperfections' [as there usually are] best let them do it their way.

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Re: Rendering AAC blocks, the best way...

Postby Mike Judd » Mon Nov 10, 2014 6:55 pm

I can't understand why anyone would question the Thai way of plastering , if it's one thing they are pretty good at ,it's plastering . My guy who had never ever built Q-Con walls before mine, still put a thin scratch coat on, let it go off for a while and then finished it off with a top coat. I was only interested in the final result, straight as a board, perfect. :D :D
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