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Discussion Starter · #1 ·
I'm putting up a 56' by 6' grape arbor. I had shown her some plans and we had come to a decision, but she's changing it at the last minute. What she wants is a freestanding pitched arbor.

The back side where the grapes will start trellising up she wants at a height of 5'. The front side she wants at 8'. This is all pitched over a span of 6'.

I had originally thought to set 6x6s every 12' on the front and back and span them with doubled up 2x10 purlins with 2x6s spanning the 6' width. She was not happy with the price this runs up however.

My question is this: Can I get away with 4x4 posts every 8' front and back and a 2x10 purlin (not doubled up) and span the 6' width with 2x4s? I would do some knee bracing as well as perpendicular bracing with a 2x8 at each post.
 

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Discussion Starter · #3 ·
Of course ... where are my manners!

I'm live at a retreat center in Central Wisconsin as a maintenance man for the facility. I know this is explicitly a contractor forum here but I've found that the DIY forums tend to provide only a fraction of the information I've found on this and other contractor sites.

We are constantly working on our facilities and have a two story addition planned in the near future so I figured I'd start an account here for future knowledge.

The grape arbor project is one of several summer/fall projects we are tackling at the moment and any advice on this matter would be greatly appreciated.

Thanks,
Alex
 

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Discussion Starter · #8 ·
The reason I was thinking to go heavier is because there will be seating underneath and it would be nicer to have the 12' spans as opposed to posts every 8'. I wasn't sure what would be structurally acceptable to get those 12' spans.
 

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I would think if you are actually going to have grapes growing there it would make it much easier to pick them if not ducking on the lower side. A neighbor had one where I grew up, granted I have to wipe away the cobwebs to think back that far, but pretty sure it was level & tall enough to walk under without ducking.
 

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I have to agree with Mark, CA. I build a lot of arbors/pergolas and I agree that 2x4's are not going to span that distance without sagging, even without any weight on them.

You said the posts will be 8 feet from front to back and the front will be 8 feet high while the back is 5 feet high, that is if I read you correctly.

What type of materials are you going to be working with? some species are stronger that others and can span a greater distance. For instance redwood is stronger that rough cedar but because of cost we tend to use more cedar.

You did not mention and your drawing did not show it are you planning on any joist overhang from the beams. Also if the posts are set 8 ft. apart front to back and the front is 8 ft. high and the back is 5 feet the joist span would then be 8 ft.6-1/2 inches not including any overhang. You also did not mention how far apart you were planning to space your joist.

I for one don't really like the look of 4x4 posts but that may be a personal preference.

Why not just make a lever arbor? What are the heights of the people who will be walking underneath and could there be a liability issue there? I for one am 6 ft. 7 in. or I used to before old age set in.
 

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Discussion Starter · #12 ·
Thank you all for the input. I'm sorry I was not more clear in my descriptions. The posts are spaced 8' on center and the span between the 5' posts and the 8' posts is 6'. After reading some of the responses I'm thinking to switch from 2x4s to 2x6s for the joists. My original question was regarding the spacing of the posts and the support beams for the joists.

I was hoping to find a way to space the posts every 12' as opposed to 8' and wasn't sure if I could accomplish that with 4x4 posts and a 2x10 support beam or if I needed to go larger on the posts and double up the 2x10.

One facility at our retreat center is a renovated 100+ year old farm/homestead and there is an existing 4' tall grape trellis that is 56' in length. The owner of our retreat center decided to make the arbor "lean-to" style with the shorter side just in front of the existing trellis to aid the old grapes in climbing a new direction. She also seems to like the appearance of a lean-to and hopes to have seating underneath. I'm just trying to execute is all!
 

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Discussion Starter · #13 · (Edited)
"What type of materials are you going to be working with? some species are stronger that others and can span a greater distance.

You also did not mention how far apart you were planning to space your joist."

The lumber is AC2 pressure treated pine from the local yard. I prefer to use cedar but we run a fairly thin budget and the treated wood is relatively cheap. The joists are every 12".
 

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4x4 posts will probably carry the load, but like Bob, I prefer bigger. Double 2x10's will span 12'. Definately go with the larger 2x6 rafters.

Limit you cantilevers with PT lumber, as it will twist. Bolt everything you can. Are you planning on splitting up the 2x10's or tieing them together?

These 2 pics were from the same job, you need to combine them.
 

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Grapes don't put much vertical load on, but they can pull like crazy sideways, side to side, basically any direction they're growing. With a double 2X10 on a 12' span, I'd run each side of the 4X4 and block every 3-4 ft to help keep it from being bent sideways from the vine climbing over it, at least on the short side.
 

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Discussion Starter · #16 ·
I'll be splitting the 2x10s. I'm not sure if we can afford to put stainless bolts on everything. I was planning on using these FastenMaster TimberLok timber screws. The price difference is pretty significant but if there's a potential problem please let me know so I can take that into account.

Thanks for the tip about the blocking as well ... hadn't even considered it.
 

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Discussion Starter · #18 ·
Sorry to bump this back up but I'm curious as to your thoughts on a finish for a grape arbor. I've never built an arbor that would actually carry perennial plants of any kind and am a little perplexed about how to do maintenance on the finish. Even with pruning, the arbor will be a little difficult to re-coat in certain areas.

Does anyone have any experience with this issue?
 

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Sorry to bump this back up but I'm curious as to your thoughts on a finish for a grape arbor. I've never built an arbor that would actually carry perennial plants of any kind and am a little perplexed about how to do maintenance on the finish. Even with pruning, the arbor will be a little difficult to re-coat in certain areas.

Does anyone have any experience with this issue?
Easy. Dont finish it and let it weather on its own.
 
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