playpen
12th January 2007, 07:39 PM
Hi Folks,
Long time lurker, first time poster..
I am helping a friend of mine complete a pergola he started a few weeks ago.
It is attached to the house via a ledger board, and is roughly 3180 X 3000. 2 posts 90 x 90 support a parallel beam of 175 x 50 (in excess of A Staines tables).
I got involved after he had already concreted the posts in place, and discovered that they were slightly out of square at the base.
When we put in the outside rafters, we braced the posts to measure an equivalent distance to the joist hanger positions on the ledger (about 20mm). We also put in the first outside rafter at a measurement of 2955 from the ledger. When we measured up for the opposite outside rafter, the 'natural' measurement was 15mm shorter.
My advice at the time was to cut and install at an equal length - pushing the post out to the point where the pergola would be square at the roofline.
However, since we installed the outside rafters (that's as far as we have gotten), his SWMBO has discovered 'cracks' (I haven't seen them yet) in the posts and is worried that the structure has no strength...
I'd really appreciate your thoughts on whether or not pressuring a 90*90 post (F7) 20 & 15mm from base to top over a height of 2400 would weaken it to the point of fracturing?
Thanks a bunch
Long time lurker, first time poster..
I am helping a friend of mine complete a pergola he started a few weeks ago.
It is attached to the house via a ledger board, and is roughly 3180 X 3000. 2 posts 90 x 90 support a parallel beam of 175 x 50 (in excess of A Staines tables).
I got involved after he had already concreted the posts in place, and discovered that they were slightly out of square at the base.
When we put in the outside rafters, we braced the posts to measure an equivalent distance to the joist hanger positions on the ledger (about 20mm). We also put in the first outside rafter at a measurement of 2955 from the ledger. When we measured up for the opposite outside rafter, the 'natural' measurement was 15mm shorter.
My advice at the time was to cut and install at an equal length - pushing the post out to the point where the pergola would be square at the roofline.
However, since we installed the outside rafters (that's as far as we have gotten), his SWMBO has discovered 'cracks' (I haven't seen them yet) in the posts and is worried that the structure has no strength...
I'd really appreciate your thoughts on whether or not pressuring a 90*90 post (F7) 20 & 15mm from base to top over a height of 2400 would weaken it to the point of fracturing?
Thanks a bunch