Size permitted on garage area.

[collectors]

Hi, the permitted area for a garage / workshop is 30 SQ'm without planning or building regs, if built from none combustible materials & allowing for the 50% of property area.
Can anyone say if the 30 sq'm is total area or internal floor space area.
Also! It will be built in block, but will the wooden roof have to be fire checked with plaster board or something similar?.

Thanks

Chris.

[welsh brickie]

i think its 30msq total area. and the roof does not need any fireproof plasterboard if its detached away from the house