Can I build internal leaf of cavity entirely of blocks

[Thepenetrator1]

Hi, I'm building an extension and was wondering, can I build the internal leaf entirely of blocks. 7n below ground up to dpc and 3.5n above. Also do I need two course of blues on the inner leaf? I was thinking 9 course of blues outside (ground slopes away a tad and nearly all are visible) and two course of block internal with 3 course of blues if needed? Also are class b second blues ok to use? I'm using a rustic looking brick so chips won't matter as long as their water resistant is up to scratch. Thanks in advance

 

[jeds]

It's normal practice to build the internal leaf from blocks - entirely from blocks! The blocks needn't be 7N for single storey. 3.6N is fine. No brick courses needed on internal leaf unless it is convenient for coursing, and then you'd use concrete bricks not eng bricks. Use as many eng brick courses on external leaf as needed for practicality and aesthetics.

 

[^woody^]

You should not mix materials on internal leafs.

 

[Thepenetrator1]

thanks

 

[garyo]

You should not mix materials on internal leafs.

Why not?

 

[noseall]

You should not mix materials on internal leafs.

Where thermally relevant i.e. above DPC.

 

[John D v2.0]

We are having to put a row of insulated blocks in, I think it's just above or below dpc level. Not sure whether the ones above matter significantly, but I think the insulated ones are more expensive hence the single row!

 

[^woody^]

Why not?

Different thermal properties equals increased risk of localised condensation.

 

[John D v2.0]

Yes I checked and as noseall says above DPC is all the same for ours, lightweight block Cemex 850 on both leaves. Below DPC is Cemex 1400 and marmox thermoblock and also at first floor level, presumably to avoid a thermal bridge where it joins to the existing solid walls.
Hope those product numbers useful to the OP.

 

[tomfe]

You can't build a wall entirely out of blocks it will fall down really easily, you'll need some mortar....