Can I build Two skins in Blocks
- Thread starter Brianno6
- Start date
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yes
Affirmative.
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Use aerated blocks or light weight aggregate blocks.
I'm not sure whether two skins of concrete blocks and a 100mm cavity of full fill quilt will meet b/regs on their own. I'll check later
Otherwise, the inner leaf may need to be an aerated block possibly "standard" or "solar" or even a 115mm block. Or dry line with an insulated plasterboard
Personally, I don't like to use aerated blocks externally as there is a much greater risk of shinkage cracking, and the render is difficult to stick on - and you can get pattern staining showing through
Otherwise, the inner leaf may need to be an aerated block possibly "standard" or "solar" or even a 115mm block. Or dry line with an insulated plasterboard
Personally, I don't like to use aerated blocks externally as there is a much greater risk of shinkage cracking, and the render is difficult to stick on - and you can get pattern staining showing through
I would advise you to stay away form any sort of aerated blocks, use concrete blocks for a much more solid job and have a wider cavity if necessary.
No body can answer your question with out the following information.
What will the finish be to the external blockwork? Paint finish, render, tile hung or boarding?
Do you want full cavity fill or partial cavity fill?
Light weight plaster, dense plaster or dot and dab?
What U value do you wish to achieve? 0.28 W/m2K or lower?
Answer questions and will give you route to take.
Regards oldun
Just to add to my previous coments,
I'm my experience aerated blocks (Thermalites) are very prone to cracking and they don't seem to stick together very well when using standard mortar, I know this as the inner leaf of my extension has been built with them, given my time over again there is no way I would have used them and would have went with concrete blocks for a much sounder job.
You could use concrete blocks on the outer leaf and if you must aerated blocks on the inner. The one thing I would say however is that if you intend for the inner blocks to be rendered and plaster skimmed any cracks in them may extend through the plaster. I've read that plasters put expanded metal laths over the aerated blocks so the cracks don't come through.
Regarding U values, I don't know a lot about this subject, I have a 75mm full fill cavity, this is with a brick outer leaf and a Thermalite inner, the walls are going to be boarded, I'm not sure if using concrete blocks for the inner leaf would have made much if any difference to the cavity required.
My honest advice to anyone considering using aerated blocks would be to try their best not to as I can only describe them as rubbish, yes on paper they may give a better U value than concrete blocks but I wonder if that still stands when they have cracks in them! I can fully understand why some builders refuse to use them and will only use concrete blocks, if I were in business I would do exactly the same.
Cheers.
I'm my experience aerated blocks (Thermalites) are very prone to cracking and they don't seem to stick together very well when using standard mortar, I know this as the inner leaf of my extension has been built with them, given my time over again there is no way I would have used them and would have went with concrete blocks for a much sounder job.
You could use concrete blocks on the outer leaf and if you must aerated blocks on the inner. The one thing I would say however is that if you intend for the inner blocks to be rendered and plaster skimmed any cracks in them may extend through the plaster. I've read that plasters put expanded metal laths over the aerated blocks so the cracks don't come through.
Regarding U values, I don't know a lot about this subject, I have a 75mm full fill cavity, this is with a brick outer leaf and a Thermalite inner, the walls are going to be boarded, I'm not sure if using concrete blocks for the inner leaf would have made much if any difference to the cavity required.
My honest advice to anyone considering using aerated blocks would be to try their best not to as I can only describe them as rubbish, yes on paper they may give a better U value than concrete blocks but I wonder if that still stands when they have cracks in them! I can fully understand why some builders refuse to use them and will only use concrete blocks, if I were in business I would do exactly the same.
Cheers.
To comply with current BR L1B 2010 small domestic works, you need to achieve a U value of 0.28w/m2k
Will give you two routes to take, the first the most narrow width of wall you can achieve 0.28 and second the way we would go.
Rendered 100mm block with a K value of 0.11w/mk, e.g. Thermalite Turbo or Durox Superblock.
65mm cavity fully filled with Dritherm 32.
100mm block inner skin all as external skin
Internal finish either, 13mm lightweight plaster or dot and dab
Total width of wall 293mm.
Our way.
Rendered Plasmor Aglite block, strength 7.3N with a k value of 0.32w/mk.
100mm cavity fully filled with Dritherm 34.
100mm block inner skin all as external skin
Internal finish either, 13mm lightweight plaster or dot and dab.
Total width of wall 328mm
Reasons for our way.
Aglite is an easy block to lay. It does not suck the muck in the moment it lands on the runway. They cut well, they are a one handed lift and most importantly they are open textured and accept render and plaster more easy than an aerated block, altough we often wonder why people make such a song and dance over plastering areated blocks.
What part of Beds do you live in son?
Regards oldun
Will give you two routes to take, the first the most narrow width of wall you can achieve 0.28 and second the way we would go.
Rendered 100mm block with a K value of 0.11w/mk, e.g. Thermalite Turbo or Durox Superblock.
65mm cavity fully filled with Dritherm 32.
100mm block inner skin all as external skin
Internal finish either, 13mm lightweight plaster or dot and dab
Total width of wall 293mm.
Our way.
Rendered Plasmor Aglite block, strength 7.3N with a k value of 0.32w/mk.
100mm cavity fully filled with Dritherm 34.
100mm block inner skin all as external skin
Internal finish either, 13mm lightweight plaster or dot and dab.
Total width of wall 328mm
Reasons for our way.
Aglite is an easy block to lay. It does not suck the muck in the moment it lands on the runway. They cut well, they are a one handed lift and most importantly they are open textured and accept render and plaster more easy than an aerated block, altough we often wonder why people make such a song and dance over plastering areated blocks.
What part of Beds do you live in son?
Regards oldun
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