Reducing size of a block building with wood

[jacko555]

I'm not a builder. I have built a deck and some stud walls and false ceilings before. Enthusiastic DIY'er.

Have a old outbuilding, 5x5m. Corrugated metal gable roof, very slight angle. Really poorly built roof and roof structure/ beams are end of life. The building height is 2m at the lowest ends and 2.5m at the top of the roof.

Structure is made of breezeblocks and rendered. Built into chalk hill, floor is lino covered chalk.

I'd like to reduce it from 5x5m to 2.5x5m.

Could I convert it into a pent roof structure by removing a "side" wall (5m long) and half of each gable end (remove 2.5m from each) and rebuild a new side wall as a wood frame and clad the lot? So a shed / outbuilding hybrid, with 3 existing block walls and 1 new wood one.

Idea being concrete a new "foundation" in the chalk, lay a sole plate, attach the outermost side studs to the existing gable ends? I can then replace the beams holding up the half roof that's left and reattach the corrugated sheets.

Structurally, is this a good idea? Confident I can build the structure and securely attach it.

Unsure about movement/wood swelling/ shrinking. The new side wall frame will be 5m long and 2m high.

Crack on or bad idea? Advice?

 

[Deleted member 323070]

You need to isolate the potentially damp walls (including the new dwarf wall) from the timber.
Strips of DPC will do the job.
Any joint between the timber and the brick will move, opening and closing with the weather, etc.
You can trap 'backer rod' between the two surfaces, as well as the dpc:

Foam Sealant Joint Backer Rod 10m Lengths - Sealant Supplies Ltd

Foam Sealant Joint Backer Rod 13mm, non-absorbent compressible grey closed cell polyethene foam backup material. For instance, you can use it to insert into a joint to control sealant depth and create a backstop to allow proper sealant tooling. Joint Backer Rod is a non-absorbent compressible...

www.sealantsupplies.co.uk

It's designed to provide a depth control for sealant squeezed into the joint. But it also creates its own filler in the joint.