2 skin blocks or single wide celcon block

[macadonald]

Hi guys,

Planning to build a single story rear extension and was chatting to a builder the other day who suggested using the wider (I think they're 300 mm) blocks with insulated plaster board on the inside and render on the outside. I know that old school builders would say that a double skin with insulation in the cavity is better, but will the wider blocks do the job? Once rendered, does it really make a diference?

I have driven past a number of jobs where the wider blocks are being used.

Also, to make the most of space, surely, a double skin of 9 inch blocks and then plaster board on the inside is goign to be thicker than the wider block option.

Any ideas or advise would be helpful.

Thanks

 

[RedHerring2]

(I think they're 30 inches)

Thanks

That's about 750mm wide. Surely you mean 300mm wide??

 

[stuart45]

Solid block external walls are normally 300mm wide using the thin joint system. It's the same width as as 100mm block/100mmcavity/100mm wall.

 

[macadonald]

Thanks for the advice and sorry about the confusion, was not thinking straight. Have ammended the dimensions.

So is it okay to use the 300mm blocks or are 2 skins always better. I understand 300mm celcon blocks meets all the structural and thermal regs..

 

[stuart45]

I think the solid still works out a bit dearer. I've only used the thin joint system once. The most important thing is to get the first course spot on, as you can't adjust the beds as with normal mortar.

 

[noseall]

I think the solid still works out a bit dearer. I've only used the thin joint system once. The most important thing is to get the first course spot on, as you can't adjust the beds as with normal mortar.

What are you on about Stu?

Thin joint what...?

 

[noseall]

Thanks for the advice and sorry about the confusion, was not thinking straight. Have ammended the dimensions.

So is it okay to use the 300mm blocks or are 2 skins always better. I understand 300mm celcon blocks meets all the structural and thermal regs..

Go for an air gap i.e. two skins + full fill dritherm.

 

[stuart45]

I think the solid still works out a bit dearer. I've only used the thin joint system once. The most important thing is to get the first course spot on, as you can't adjust the beds as with normal mortar.

What are you on about Stu?

Thin joint what...?

It's a system that uses a white glue instead of normal mortar. Said to lose less heat through the joints. Google thin joint blockwork. It's used now for solid 300mm block walls. It's been used on the continent for a long time.
You use a scoop with teeth instead of a trowel.