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Pergola - best fixing location (#1, #2 or #3?)

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Molynoox

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I would try a re-design - which could eliminate a lot of (expensive) ironmongery:

One option would be to arrage for the back beam to be a few inches higher than the front one, with through mortices (roughly square I guess) cut into it. You then cut tenons in the ends of each of the 2m 'rafter' pieces. If you wanted to get fancy-pantsy/oriental-stylee you could make wedged tenons.

The advantages, besides eliminating ironmongery, would be no holes in the top surface of your timbers to collect rainwater.

Don't forget that the bases of your posts supporting the 'back row' will be trying to rise up and will need to be very securely attached to your base plates.

e.g. a bit like this:
View attachment 118691
that's a really nice idea! similar to what I modelled in post #18 based on a suggestion on here - I wasn't too keen on that design in the end because the height differential between the front and rear support beams didn't quite look right to me. I might have a go at modelling your idea up, I quite like the fancy wedged tenon version too (y)

the only issue is the spars sitting above the posts - I would need to use screws for those :D
 

Molynoox

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Having just read all of this thread, and to go off at a slight tangent, a lot of very informative comment has been made. Most of that information will realistically give you at least 30 years of beauty. I suspect the primary failure will eventually be the base of the posts. My pergola lasted 30+ years with common sense fixings, but the eventual failure was the ground fixing. I soaked the base end of the posts for 2 days in creasote, treated the above ground stuff a couple of times, but when I decided to replace it last year, I was amazed how little strength was left in the support. How are you planning to fix / maintain your base support?
There is a picture in my first post in this thread showing the groundscrews which I have already installed, there are 9 in total and they are 800mm long, sunk to about 95% depth
The Cedar posts will sit inside the 'U' brackets, and the posts will be raised off the bottom of the U bracket so the post isn't ever sitting in water. I didn't want to put these posts into the ground or have them sitting in water and that was the best solution I could come up with, Quite expensive, but then so was the wood and I figured keeping them away from moisture could add 10 or 20 years to their life - so it could actually be a cost save.

by the way, 30 years is a good innings - well done!

Martin
 

Molynoox

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I would like to extend a warm welcome to the humble nail which has just entered the discussion :D
 

Zedgeezer

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There is a picture in my first post in this thread showing the groundscrews which I have already installed, there are 9 in total and they are 800mm long, sunk to about 95% depth
The Cedar posts will sit inside the 'U' brackets, and the posts will be raised off the bottom of the U bracket so the post isn't ever sitting in water. I didn't want to put these posts into the ground or have them sitting in water and that was the best solution I could come up with, Quite expensive, but then so was the wood and I figured keeping them away from moisture could add 10 or 20 years to their life - so it could actually be a cost save.

by the way, 30 years is a good innings - well done!

Martin
It looks like you've got the base sorted, sorry I missed the U bracket implication.
 
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