What kinds of mortar will you recommend to cover light weight concrete blocks (q-con and pcc) Adhesive mortar or normal Mortar? And what brand name?

When I ask where they use light weight concrete blocks some says;

1. Adhesive mortar is difficult to work with so there for they use normal mortar.

2. You have to add sand in the Adhesive mortar to work more easily.

3. Only use Adhesive mortar.

Will normal mortar over time work ok or will it fall of easily?

What will you recommend and why?

I ask because we have to cover over 3000 square meter of light weight concrete blocks, and there are none I asked there really have any long term experience with those blocks or have any good professional knowledge.

Years back when we built our house the local builder used adhesive type cement ( assume it was special but maybe a marketing ploy)for building the white lightweight brick walls ( white.. in smaller bags 25kg?)..When we could not find any more in local supplier we told 'em to use regular cement. The plaster was ordinary (green bag) cement with fine sand added...has not fallen off yet 5 years later and walls still standing...

2 points here

If built with care + blocks glued and cut perfect then covering with mortar is not needed as can paint the block walls directly..

If you want to cover the blocks with mortar then use the correct stuff, sure it is more expensive but if mixed correct it is like plaster or tile glue and goes a very long way as you are just skimming over the blocks...

It is easy to work with, there again are you doing it yourself?

If the wall was not built perfectly then 1st fill any holes.. mix the mortar to a smooth paste then hose down the wall and apply the mortar to the wet wall, do not try doing it if the sun is shining on the wall as it will all dry out fast and will never get a smooth finish, ADD washing up liquid to the mortar when you mix it, makes it slide much easier., have a bucket of water handy and a big soft brush to keep wall wet if it starts drying out.

Remember the wall built with these blocks are skimmed, same way as the ceiling boards on your ceiling are skimmed

Years back when we built our house the local builder used adhesive type cement ( assume it was special but maybe a marketing ploy)for building the white lightweight brick walls ( white.. in smaller bags 25kg?)..When we could not find any more in local supplier we told 'em to use regular cement. The plaster was ordinary (green bag) cement with fine sand added...has not fallen off yet 5 years later and walls still standing...

2 points here

If built with care + blocks glued and cut perfect then covering with mortar is not needed as can paint the block walls directly..

If you want to cover the blocks with mortar then use the correct stuff, sure it is more expensive but if mixed correct it is like plaster or tile glue and goes a very long way as you are just skimming over the blocks...

It is easy to work with, there again are you doing it yourself?

If the wall was not built perfectly then 1st fill any holes.. mix the mortar to a smooth paste then hose down the wall and apply the mortar to the wet wall, do not try doing it if the sun is shining on the wall as it will all dry out fast and will never get a smooth finish, ADD washing up liquid to the mortar when you mix it, makes it slide much easier., have a bucket of water handy and a big soft brush to keep wall wet if it starts drying out.

Remember the wall built with these blocks are skimmed, same way as the ceiling boards on your ceiling are skimmed

So here David006 sais I can use both and ignis sais use adhesive mortar.

Any other opinions or experience?

I did a build in England with lightweight blocks and used regular mortar.

I would reiterate previous advice about making sure the blocks are wet, have a tub to dip them in as you lay them, and when rendering water liberally.

So regular mortar will be ok. Thanks for all your advice.Any other recommendations are welcome.

We used CPAC brand lightweight blocks for our home, similar to QCON or SUPERBLOCK brand. There is an instruction manual for the blocks at any building materials supplier. Seems to me it would not matter which brand of that TYPE of rendering material you used. In the instructions they are clear about the need to wet down the blocks the night before and the day of the rendering. CPAC actually has a video presentation on how to build with those blocks for instruction of construction crews. See if your building block supplier will give you the dvd or link to the video. It was all in Thai, but it was of great use when shown to our building crew in 2008. You still may end up with random cracks on the surface of the rendering no matter how hard to try to be professional and buy the right materials, hire a decent contractor, and have actual CPAC technical staff come to train the crew. All part of the joy of building in Thailand. The CPAC instruction brochure is ten pages in one fold out design, folded it is 5 inches by 8 1/4 inches with the Cementthai call center phone number 1-800-300-900 or 02-2586-2222 The brochure has instructional photos and quite a bit of information in Thai.

We use the Mortar that in Thai are call sitong, but there comes many tiny cracks.

It is very marshy and wet mixture and the wall are very wet also.

How to avoid the tiny cracks?

We used CPAC brand lightweight blocks for our home, similar to QCON or SUPERBLOCK brand. There is an instruction manual for the blocks at any building materials supplier. Seems to me it would not matter which brand of that TYPE of rendering material you used. In the instructions they are clear about the need to wet down the blocks the night before and the day of the rendering. CPAC actually has a video presentation on how to build with those blocks for instruction of construction crews. See if your building block supplier will give you the dvd or link to the video. It was all in Thai, but it was of great use when shown to our building crew in 2008. You still may end up with random cracks on the surface of the rendering no matter how hard to try to be professional and buy the right materials, hire a decent contractor, and have actual CPAC technical staff come to train the crew. All part of the joy of building in Thailand. The CPAC instruction brochure is ten pages in one fold out design, folded it is 5 inches by 8 1/4 inches with the Cementthai call center phone number 1-800-300-900 or 02-2586-2222 The brochure has instructional photos and quite a bit of information in Thai.

CPAC is almost on par with SUPERBLOCKS, but Q-Con is of much lower quality

I have build in all 3 products. Ordinary mortar for rendering/plastering works fine, cracks due to sunshine while rendering occurs both at these walls and at red brick walls.

Important to use sand not containing salt, which is hard to find here in Phuket, so ready mixed mortar is preferred

If your crew does not have experience with special glue-mortar, avoid it

Interior walls do not need plastering, can be painted as is if you like this look

Exterior walls, finsih with a high quality nano tech paint, as these walls do not like humidity/water

CPAC is almost on par with SUPERBLOCKS, but Q-Con is of much lower quality

I have build in all 3 products. Ordinary mortar for rendering/plastering works fine, cracks due to sunshine while rendering occurs both at these walls and at red brick walls.

Important to use sand not containing salt, which is hard to find here in Phuket, so ready mixed mortar is preferred

If your crew does not have experience with special glue-mortar, avoid it

Interior walls do not need plastering, can be painted as is if you like this look

Exterior walls, finsih with a high quality nano tech paint, as these walls do not like humidity/water

I dont think there are any salt in the sand here in Chiang Mai

so are there no tricks to avoid all the tainy cracks?

When I built we used the same cement that was used for the foundations, posts and beams. Of course we did not add heavy aggregate and sifted the sand thoroughly. Ten years now and the surface of brick and block is still going strong.