Carpentry & Joinery Question

Rafter size/grade

what grade or size timber would be best used for rafters, lean to roof with 30 deg pitch and roughly 1.8 span as well as ceiling joist size ( single story extestion no 1st floor) Would there be any need for perlins, struts etc for extra strength... large concrete tiles being used.
Anymore info please ask!

7 Answers

Best Answer

hi as this is such a small span or roof i would recomend graded 5x2 timbers which can also be used for the ceiling ,at 16 in centres this is more than adecuete and will keep with building regs ,but it wont hert to contact any building control if you are using one ,you wont need to use purlins ,you will have to use joist hangers on wall side ansd best to birds mouth the fascia end

Answered 25th Feb 2011

Finebuild Builders

Member since 26 Feb 2009

150mm by 50mm stress graded timber would be sufficient for this span and 125mm by 50mm for the ceiling would be fine. Purlins are only used for big spans where the rafter is likely to sag e.g house roof or large extensions.

Answered 22nd Feb 2011

D&N Carpentry and Property Services

Member since 25 Jan 2009

I would agree with D&N on the size of timbers to be used, use c24 grade timber.
I would also add, just make sure you bolt the ridge plate (top of Rafters)to the wall well using thunder bolts etc. Also the plate at the ends of the ceiling joists.
ps why not ask your building inspector?!

Answered 23rd Feb 2011

J Chappell Joinery

Member since 30 Jul 2008

6x2 at 400 centres purlins not required c16 or c24 grade timber

Answered 8th Mar 2011

page timber roofing and carpentry

Member since 1 Jan 2011

No feedback

6"X2"graded timber

Answered 23rd Feb 2011


Member since 18 May 2010

Hi there 5x2 graded timber for rafters and ceiling joist as 6x2 is only used in loadbearing situations and would be cheaper than 6x2. No need for purlins it would be a steel beam you would need to use but that is not necessery as it is only a lean to roof.

Answered 23rd Feb 2011

DB Joinery, Fencing & Decking

Member since 15 Feb 2011


150mm x 50mm C16 graded timber - any roof work.

100mm x 50mm graded or ungraded timber - ceiling joists.

Hope this helps.

Matt Norman.

Answered 24th Feb 2011

M R Norman

Member since 15 Aug 2009

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