Flat roof conversion to sloping roof

[Sadjers]

I have a small extension measuring 2.3m by 1.35m which runs along the rear wall of my bungalow. It has a flat, felted roof which is in a poor state of repair.
The bungalow roof slopes down toward this extension and guttering runs along, above the flat roof, to capture rain water from the bungalow roof. The bungalow roof slope is around 90% which is covered in clay tiles.
I would like to replace the flat roof with a 22.5% pitch roof using reclaimed clay tiles. I would like to feather this into the original bungalow roof.
I believe I should raise the wall plate of the extension to the same height as the bungalow roof wall plate and run a ledger along the bungalow roof rafters. The new extension roof rafters would the sit on the installed ledger and extension wall plate.

• Is this the correct method?
• Please advise what size timbers (ledger, rafter, wall plate)
• Please advise what are the correct jointing techniques I should use along the ledger.

Another issue is the wall along the edge of the roof. I can build up along the extension side wall but the sloping roof will now need to be built up inside the original roof, between the new ledger and the bungalow roof wall plate. The external walls are all rough rendered so could I use a wood sheet to construct the wall where it raises above the original bungalow roof tiles?

Thank you
Chris

 

[noseall]

• Is this the correct method?

There is no right or wrong. What is more important is that the design looks like it belongs there.

• Please advise what size timbers (ledger, rafter, wall plate)

Probably 100mm x 50mm will do for the rafters. 100mm x 75mm for the wall plate and a pole plate can be any section depending upon how it is anchored. Or if the plumb cut of the rafter abuts the plate (as opposed to resting on it) then it needs to be deep enough to collect the whole of the plumb cut.

• Please advise what are the correct jointing techniques I should use along the ledger.

No Idea what this means. We use screws, nails and galvanised metal clips, brackets or straps to connect one timber to another. Use lead where tiles wont bend. Timbers (rafters etc) are bids-mouthed onto a recipient timber to ensure a good seat.