Hi Neil,
Thank you for the reply. Regarding the FD30 FED's is there any reason a hard wood ply board could not be pre cut into strips and fixed to the brick sub strate, then we pack the frame off this and firestop accordingly? I understand the material should be the same as the sub-frame but our client is making us use hardwood only which cost wise will spiral and I do not believe it is required.
The denisty of the hard wood ply is higher than the frame density and is re sessed in between a plaster finish and external brickwork, so wondered if this could be an option.