wall construction for outbuilding

[wheelerssjkel]

Hi looking for some advice on what materials to use for the walls on a proposed detached outbuilding I want to build at the bottom of my garden.

I have been told by Building Control that the walls on my building need to achieve a 'u' value of 0.35. I didn't realise that the many different combinations of block types effect the brand and thickness of insulation and cavity.

I want blocks for the outside skin to be rendered at the front of the building and just painted at the sides & back as it is close to fences, and blocks plastered on the inside.

Can anyone recommend an industry standard brand of block, insulation and cavity thickness that will achieve this 'u' rating, also could I plaster straight onto the blocks inside or would I have to dot & dab plasterboard and then plaster.

Sorry for the long winded question, any advice would be much appreciated.

 

[^woody^]

So this must be a habitable room you are creating?

The easy way for most is; 100mm lightweight concrete block external, then 100mm Dritherm insulation in a 100mm cavity, and then 100mm Thermalite/Celcon and then plaster

If you don't want walls 340mm thick, then there are other ways

And you are presumably aware of the need to insulate the floor and roof, and thermal requirements for doors and windows?