Mixing Concrete Blocks and Celcons?

Hi all,

Conservatory going very well almost at DPC and sorted out all the issues with blocks & bricks (frost etc..). Everything spot on a square and level. Very pleased.

Are there likely to be any cracks/settlement issues if I were to do the entire outside skin in concrete blocks and then 1 wall (roughly 2m) (from DPC up) with Celcons on the outside?

My main reason for this is mainly safety perspective and lifting them that high. Since laying concrete blocks, I actually prefer them to laying Celcon's but without a decent plank etc would not be good. And also my first time building something like this I was thinking of doing the lot on concrete blocks but using Celcon's on the outside of just 1 wall but they will be laid on some concrete blocks.

I was concerned as I read somewhere on the H+H website that block types shouldn't be mixed but I can only assume due to the different strengths could perhaps cause cracking?

Also, it means the nightmare Celcon's to render would all be done on the side we won't see Incase cracks do appear.

Cheers

The thermal performance values of aerated blocks v's dense concrete are such that you risk condensation issues.
It's ok to use say dense conc's on the outside and a lightweight fella internally.

As a single panel these would be OK to use, but consider using some expanded metal reinforcement in the bed joints where the two different blocks are bonded. This will control the different thermal movement at the point where the two different blocks meet.

Thanks Woody, its interesting to see noseall's response re condensation using these on both skins as I have not seen that mentioned anywhere before.

Regarding the metal reinforcement... Horizontally, is it enough to expect the DPC to cope with that seeing as it would be separating the two courses? Vertically there will only be about two blocks meeting, I can use something for those joints.

Cheers

Put a couple of tie wires across the bed joints for those two courses

noseall said:

The thermal performance values of aerated blocks v's dense concrete are such that you risk condensation issues.
It's ok to use say dense conc's on the outside and a lightweight fella internally.

Click to expand...

Hi noseall,

I am assuming you mean condensation inside the cavity? If so and the risk is quite high then I will probably avoid them.

Cheers

Just avoid using dense fellas on the inner skin.

Theory suggests that mixing thermal values on the inside skin can promote condensation patches etc.

noseall said:

Just avoid using dense fellas on the inner skin.

Theory suggests that mixing thermal values on the inside skin can promote condensation patches etc.

Click to expand...

Hi noseall,

My thread was about using thermalites (Celcon's) on the inside and outside skin on one wall?

I will always be using Celcon's on the inner skin - not dense.

Do you see condensation issues with that?

Cheers

No, none.