Lean-to roof

[davedevon]

Hi,
I've got an old stone house with a 60's single storey lean-to kitchen extension, block cavity construction with asbestos roof.
I'm planning to remove the asbestos sheets & purlins fit a wall plate, pitching plate & rafters and as the roof is only 10° treat it as a warm flat roof with EPDM membrane finish. I can't increase the pitch as there is a landing window in the back wall of the house just above existing kitchen roof flashing.
My question is regarding the join between the rafter end and the pitching plate. Three of the rafters will be fitted with glazing bars with fixed rooflights the full 3m depth of the roof (ridge to eaves) thus it would look much better from inside if the rafters were cut plumb and fixed to the face of the pitching plate and not sat on top of a bearer plate.
I'm worried about the loadbearing on such a shallow angle (10°) between the rafter end & the pitching plate which I assume is normally screwed as its almost in the realms of a flat roof but I don't want to start fitting joist hangers, brackets etc as these will be on show. I've had an idea of leaving the M16 chemical anchors fixing the pitching plate a couple of inches longer and jig boring the end of the rafter to give added strength and it will also hide the fixings in the area of the windows.
Has anyone used this method or have any suggestions of an alternative fixing.
Thanks in advance.

Dave.

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[noseall]

Even at 10 degrees, the rafter can not go downwards unless the wall pushes in or the plate pushes out.

Regular sleeve bolts will do so long as the masonry is sound.

Be sure to fix plenty of restraint straps to the wall plate.

Be sure to cut your joints tight and true.

Otherwise you could notch into the bearer.

Have you calculated the heat loss through the roof or are you doing this on a whim, i.e. no building control?

 

[catlad]

You can get get some builders band and fix it behind your bearer, and fun it on top of your rafters if you are worried about them coming apart.

 

[davedevon]

Thanks for the reply Noseall.

As you said, I will fix plenty of straps to the wall plate and take plenty of time on the joints.
I decided on chemical fixings as the main wall is stone & lime mortar and although it looks fairly sound I thought it would be less stress than expanding bolts.
When you say notch into the bearer do you mean similar in principle to a halfing joint?
The work is being done on a building notice which also covered some other building work. The heat loss through the roof window was a problem with BC but the guy seems very helpful, I've had to stick a very thick slab of kingspan on the roof, getting cavity wall insulation and the rooflights are triple glazed Low E argon filled.

Dave.