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Lean to timber frame roof for conservatory

I have a lean-to conservatory, 4m length x 3m width. It currently has polycarbonate sheet roof and I want to replace it with a new lightweight tiled roof and possible 600mm Velux window in the centre.

Just wondering what size rafters I would need and the spacing between them (I've read 600mm seems to be normal). I plan on insulating with Celotex boards, plasterboarding and plastering.

Will also fit noggins for strength and to hinder any twisting.

3 Answers from MyBuilder Roofers

Best Answer

7x2 @ 400 ctrs , doubling up both joists and trimmers around the velux . The easiest way is to design from the inside so your living area is how you want it . Much nicer than lightweight tiles is a flat roof with a lantern . Efficient pretty and easier . Take a look at our pictures for inspiration and good luck with your project . Regards Rob


Answered 8th Mar 2017

If anyone can ever get onto it, I'd advise 400mm centres with noggings.

Normally I use something about 6" x 2". It might be worth asking your local council building regs folks for absolute rules, but I would quote the job on this basis. But I like to over engineer, stops any problems in the future.


Answered 8th Mar 2017

Hi Scott you would need to use 600mm timbers putting noggins in is definitely a good idea as will strenghten the structure of the roof and stop timbers twisting like you quoted in you question. How to install the 600mm rafters is fix a rafte each end of the building and then measure from each rafter to the center of the building to get center of your roof fix a rafter in the center. Measure 300mm centers both sides of center rafter fix 2 rafters centers and measure inside to inside to make sure that it is 600mm wide for your new window. The rest of it should then be put in at 16inch centers and no more then that. Once you have fitted remaining rafters go back to center of roof measure the height of you new window put in supports top and bottom and cut out center rafte should leave you the with the opening to fit your new window
Hope this helps


Answered 10th Mar 2017

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