Double Walls

[bledu]

Hi,

in our plans, we have double walls on the different buildings (3 buildings connected).

They will be build with aerated concrete blocks for the outside and red bricks for the inner side.

But I 'am not sure if it is correct ? Is it the best ? Or should we have the bricks outside side and aerated concrete for the inside wall ?

Thanks for your answers and ideas.

[Svenn]

seems like it'd be a lot easier for the aerated blocks to dissipate the heat if they were on the outside and the bricks only got heated up from the interior, rather than if the blocks were on the interior trying to insulate against red-hot bricks getting baked on the outside. not sure though?

[PattayaParent]

In the UK where you would be using expensive facing bricks and cheap concrete blocks it's bricks outside and blocks inside.

Here where the bricks are cr@p and the outer walls are plastered over it doesn't make a bit of difference.

[longball53098]

I would suggest the AAC blocks on the outside as they are the heat dissipation layer if the sun is hitting the wall. The air cavity will dissipate any heat that may get thru to the red brick inner wall. The red brick inner wall is much stronger than the AAC block for the use as a support of cabinets and all other items that need to be hung/supported from the wall.

[teacup]

In your case, seems like the plan is using....

The cmu (aerated concrete blocks) as the structural wall, and red bricks as part of the insulation system.

Therefore the aerated blocks should be on the outside and red bricks on the inside.

However there should be a small air gap between the blocks and red bricks for the reduction in heat transfer, unless you are substituting - insulation Styrofoam sheeting - instead of red bricks, then you can slap the sheeting flat against the aerated blocks.

[kamalabob2]

IN our home we used the CPAC brand aerated 12.5 thick blocks for all exterior walls of the home, pool house and garage. We used 7.5 thick CPAC brand aerated blocks for ALL interior walls. It is now COLD season, but frankly it is not cold inside the home and during HOT season it was relatively cool inside all rooms of the home. We have had ZERO problems mounting kitchen cabinets, an office book shelf, and LCD TV shelves to the 7.5 thick aerated blocks. ALL of our air conditioning piping, electrical conduit and water pipes had zero problems being installed into the two different thicknesses of aerated blocks. So perhaps you can save the time and expense of a red brick "double interior wall" if you look at various thicknesses of the aerated blocks. I suggest you compare the delivered prices of the five major brands of aerated blocks for different thickness. And which supplier will give you the lowest price on the proper rendering material for aerated blocks.

It was our experience that even different Home Marts had different prices for the exact same blocks, but I can see no real difference between the brands of these aerated blocks. Make sure your builder has good saws and plenty of blades for cutting the blocks along with RUBBER mallets for installing the blocks. I strongly suggest you request and not back down on having a MANUFACTURER representative come to your building site for a FREE instructional demonstration on how to PROPERLY install and render these blocks. They also have written instructions in Thai for the workers, but the LIVE on site demonstration will put your building crew on the right path. Even the men who supposedly had worked with these aerated blocks previously were unaware of the "correct' methods until they participated in the presentation form a sharp company representative.

One real item to stress is that the rendering material on aerated blocks should NOT be smooth where you plan to install TILE on the walls. What TWO times to wet the blocks prior to rendering was stressed at this seminar.

The thickness and tint of your window glass and window coverings (reflective on the exterior side of the curtain?) in my opinion will also greatly impact your interior comfort level.

[Rimmer]

The Q-Con style block goes on the outside.

But why for the small cost saving use red brick at all? The labor cost and time saved with exact size Q Con makes using red bricks a nonesense. Better still look at the large size Q Con blocks, one block is the width of the sow poons so you don't get those funky corners. Better still Q Con is load bearing so you can throw away the sow poons altogether and build UK style with proper footings and O Con lapped corners.

[JimmyGreaves]

Q Con is load bearing so you can throw away the sow poons altogether and build UK style with proper footings and O Con lapped corners.

Never seen this done, is that for real?

[Rimmer]

Q Con is load bearing so you can throw away the sow poons altogether and build UK style with proper footings and O Con lapped corners.

Never seen this done, is that for real?

Yep it's real, read the Q Con literature.

Makes for a very firm structure in a short space of time. Friend of mine built this way up to and including the roof in seven weeks.

[khundon]

If you go for blocks outside and bricks inside make sure that correct type of wall ties are used to tie block wall to brick wall. Galvanised or stainless steel ties should be used.

Approw 1 tie every metre lengthways and every 2 courses of blockwork high. Stagger the ties so all sections of walls are connected.

The Thai way of fixing the concrete pillars to the wall using mild steel bar protruding from the cast concrete colums is not very effective, mainly as they do not fit enough of them.

I would prefer to use a system where a stainless steel channel is fixed to upright columns and the walls are built up, as they rise up the column, special ties are slid down the channel onto the courses of bricks/blocks and cemented into place. This will give the walls a secure fixing to the columns and will when used in conjuction with correct wall ties as mentioned will give you a solid wall structure.

Make sure that they use correct sand /cement mix, I recommend minimum 1 part cement to 3 parts salt free sand and that bricks and blocks are wet when used to stop moisture from mix being dried out to quickly by dry blocks/bricks.

Thais tend to use very coarse sand for brickwork mortar. I would get them to pass sand through a 5mm sieve before use this will give you a better smoother mix. You can also add a plasticiser to the mix if you cannot get any a little squirt of washing up liquid added to the mix will do the trick.

When walls are built a scratch coat of render should be applied and left rough (scratched) then allowed to dry to give a good key for second finishing coat.

I would use a cement stabiliser liquid after walls were rendered before I applied any exterior wall paint. This will stop cement mix from "dusting etc and make you paint last a lot longer.

[bledu]

Firts of all, thank you very much for all theses precious informations.

Some very detailled.

So we will stick with the two walls, the exterior one in QCon and the interior one in what our builder called "Lampang red bricks" (we are on Chiang Mai site). KhunDon, I will check for the "ties" that attach the two walls together. I never thought really about that…

Edited December 15, 2008 by bledu