Pergola - keeping the rafters straight when the span is 5m

I am constructing a pergola 5m x 4.8m(span), but am having problems getting/keeping the rafters straight as i screw on the battens. I can get 1 couple right then the warp begins as i screw in the remainder.

Can anyone suggest a tip trick or method that can help.

PS:The rafters 190mm x 45m and are 4.8 long, and are attached to the house.

cheers

Neville

:confused:

buy straight wood helps. I have used a large set of stilsons to twist the timbers straight then nail them.

Nev,

Fix the first batten at mid span on the top, get the spacing even as you go, then fix a temporary batten at mid span on the underside of the rafters, pulling out any twist as you go.

Then fix the remaining battens on the top, working outwards from the centre batten. Last remove the temporary batten and hope for the best. Sometimes the wood will stay basically straight.

Nev,
what Ian said, plus attach a temporary diagonal brace to the underside until you get the roof sheets on. The roof sheets will brace it al when you're finished. If there is no sheeting you may need to fix some permanent bracing.

Mick

Thanks guys

Got the beast under control now.

Its not perfect but is within tolerance levels of the average man.

thanks again