Pitched Rood - Final Rafter Position

[Rob_Quads]

Hi,
I am looking at converting my conservatory to an extension. Got my head round most of the various aspects that I have to make sure to keep the BCO happy but one area I am not 100% sure about is where the final rafter should sit on either side.

Below is a birds eye picture showing the general layout of the roof. Does the final rafter go up against the inside wall? I presume it must so you have something to secure the plasterboard etc again. I presume this would mean the wall plate would be butted up against the side of the inside blockwork.

Thoughts?

Thanks

 

[noseall]

The 'final' rafter, as you say, can either be positioned 50mm in from the wall, thus allowing the floor joist to run flush with the wall or position them the other way around. If it were me, i would have the rafter close to the wall and the ceiling joist 50mm away from the wall, as this allows easier ceiling board fixing.

All of the above is based upon a conventional roof and not vaulted, obviously.

However it ain't necessarily the final rafter if your roof design involves barge boards and soffit. In this instance you would need to fix ladder noggins to the 'final' rafter, in order to cradle the gable rafter.

Don't forget that you may need to fix restraint straps to the gable should the span require it.

 

[Rob_Quads]

Thanks for the information.

Can you explain how the roof rafter positions affects the floor joist positions?

I was not planning to have barge boards, The outer wall was going to be the final support with a fibreboard to give me a 40mm overhang

Luckily I only have a 1.7m span so I don't need any restraint straps

 

[noseall]

Can you explain how the roof rafter positions affects the floor joist positions?

The ceiling joists sit along side the rafters (and are spiked together) so that the centres of the joists are 50mm from the centres of the rafters.*

* based on 50mm thick timbers.

 

[Rob_Quads]

AH sorry - You said "Floor" joist not ceiling.

I'm going with a vaulted ceiling so the rafters will be acting as the ceiling joists. I understand what you mean with the ceiling joists.

 

[noseall]

AH sorry - You said "Floor" joist not ceiling.
I'm going with a vaulted ceiling so the rafters will be acting as the ceiling joists. I understand what you mean with the ceiling joists.

Sorry for the confusion.

Vaulted - cold or warm deck?

 

[Rob_Quads]

Unventilated Roof (Breathable Membrane) with Insulation Between Rafters - 110mm Kooltherm K7 between and 25mm Kooltherm K18 under to get U-value 0.20 W/m2K