Opinions Pls

[mnorman007]

Hey all,
Just lookin at a potential pergola plan for the back and wanted opinions.
Building it out of treated pine is this plan with colourbond/laserlite sheeting as roof.
Ive got Alan Staines book and been through it for referencing. Love you opinions on the plan, not sure of some of the spans/measurements.

cheers,
m.

[pawnhead]

I would assume that your house has an eaves overhang. You can't just attach a pitching plate to a fascia board on the end of an overhanging eaves, and expect it to carry a 4.1 metre wide roof.
Your new roof would have to be supported by the wall of the house which would require some fairly substantial beams and engineering.
Additionally, on that drawing there's nothing to stop the rafters from spreading at the bottom. A collar tie, half way up as you've shown, won't do the job with rafters that are only 90X45. They will end up bending in time.
With a gable arrangement, you're also creating a box gutter against the house which isn't a great idea.

[mnorman007]

Hey John,
Thanks for the response.
The plan is definately to support it off the walls but to be honest, I hadnt really thought of the gutter situation.
I had planned the end and middle rafters to look as attached. Would that be suitable?
Im all about gabled pergola's, partly because im 6ft 6" so flat pergolas always feel so low, but really open to suggestions and improvements.
Keep giving suggestions and thoughts
Cheers,
m.

[Spoon Man]

Can you post a photo of the propsed area for the pergola? I would love to assist you in designing something but would be good to see the existing conditions. Also, the plan shows a hip at one end, is that intended or is it going to be gable all the way through?

[mnorman007]

Thanks spoonman,
to be honest I was being a little lazy and was kind of hoping someone had an idea that I could borrow without doing the research.
I have done the research now but SWMBO has told me I have other jobs to do first so the plan is back on hold for now.
Will definately start up the conversation again (including photos) when I'm allowed.
m.

[echnidna]

A collar tie, half way up as you've shown, won't do the job with rafters that are only 90X45. They will end up bending in time.

Hi Pawnhead
That's a traditional coupled rafter roof frame.
Are you saying that a traditional roof frame is inadequate or that 90x45 is too small?

[pawnhead]

If you have a look at his drawing (if I've interpreted it right ), there's no coupling at plate level (i.e. no ceiling joists). 90x45 would bend and spread with that configuration. The collar ties would hold, but with time, I reckon you'd end up with a Chinese roof unless you increased the rafter size.

[echnidna]

There doesn't need to be a coupling at plate level,
but I do agree about the 90x45 in that scenario