Different block types for different leaves?

[elephant_94105]

Hi Everyone,

Lay (French) man in England here.

Im working on a house extension that I would like to be as energy efficient as possible/something as close to a passive house as possible.
2 leaves with 150 cavity, solid concrete slab floor, warm roof.

Now, when it comes to blocks, here's the deal; I used Celcon Aerated 7.3N blocks for the inner leaf, and high density 7.3N strength also but grey blocks for the outer leaf up to the DPC.
I plan to keep on building up with the same block/leafs. I plan to have the inside of the inner leaf barged to seal the envelope of the building and then plasterboarded. My understanding of the thermal mass offered by the aerated block won't be altered by the plasterboard, and therefore help regulate temperature alright.

After perusing this forum however, I have a doubt about these aerated blocks used for the inner leaf. It sounds like they are prone to cracking, don't seem to like humidity too much (hence the use of dense blocks on the outer leaf).
Now given that the aerated blocks are used for the inner leaf, with a 50mm cavity and 100mm solid insulation, I would expect them to be quite dry at all times.

Given that I would have plasterboard used over the barging, I would also not expect to see lots of cracking coming through the plasterboard even if somehow a block shows one (assuming nothing really structural is happening). Has anyone any experience in relation to such design? Does anyone see a problem with the use of aerated blocks on the inside and dense block on the outside?

Thanks a ton

 

[noseall]

After perusing this forum however, I have a doubt about these aerated blocks used for the inner leaf. It sounds like they are prone to cracking,

Prone? That's an understatement. We just removed a ground floor wall, beneath a pair of beams (knock-through). I asked the lads to take the wall down carefully and salvage as many whole blocks as they could. I estimated there were about 80 blocks (140mm Celcon solar or similar) in the wall. Not a single block was salvaged. All were either cracked or shattered.

We also had the daunting task of having to tooth-in and join some 7n blocks into the Celcons. It was a miserable endeavour.

 

[elephant_94105]

That's an understatement.

Hmm, thanks @noseall They seem brittle yes. Now, given I used them for the inner leaf up to DPC (no blocks for floor here) would this create an issue if I were to trade them for a similar strength lightweight block type to build the inner leaf up?

 

[noseall]

. Now, given I used them for the inner leaf up to DPC

We're they specified for sub-DPC use?

 

[elephant_94105]

Engineer only cared about the compressive strength from what I gathered