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Dean W.

04-30-2012 11:15 PM

Arbor/ Trellis design questions

I'm building an arbor/ trellis and am wondering if anyone can give me suggestions how to build this thing. I have attached a basic sketch of the dimension of what I'm going for. On the right hand side I drove some t-poles into the ground. So far I tied some 2x4s with wire to two of them. My question is should I plant the 2x4s in the ground instead? These are pressure treated 2x4s. If so how deep would it be necessary to prevent the collapse of this thing? I was estimating 12" deep though I could go as deep as 18" and still have enough board left over to equal 6.5' on top. Only problem is digging that deep turns into more and more rocks. So if anyone is pretty handy please advise.

Thanks for looking!

sunfish

05-01-2012 07:35 AM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by Dean W. (Post 192737)

Dean I don't think 2x4s will be rigid enough. 4x4s or even metal pipe would be better for the uprights.

Dean W.

05-01-2012 07:44 AM

Re: Arbor/ Trellis design questions

Okay, do you think they might last a few years? I don't really need this to last a long time. I just wanted to build it cheaply.

sunfish

05-01-2012 07:54 AM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by Dean W. (Post 192759)

Okay, do you think they might last a few years? I don't really need this to last a long time. I just wanted to build it cheaply.

Treated wood should last at least a few years. I think only the four corner post need to be a little beefier. Even maybe just double up the 2x4s n the 4 corners.

Dean W.

05-01-2012 07:57 AM

Re: Arbor/ Trellis design questions

Cool, I guess I'll dig the corner poles then. It will have cross members going across and all the way across on one side. So this should stabilize it somewhat.

Dean W.

05-01-2012 05:22 PM

Re: Arbor/ Trellis design questions

This is what I built. Nothing to fancy. Decided to stay w/ the 2x4s they were cheaper. I hope the 1x2 atop the structure can support some weight. I'll add a few more.

GreenFin

05-01-2012 11:51 PM

Re: Arbor/ Trellis design questions

Congrats! Looks like you're making good progress.

Did you dig holes and set the 2x4's into the ground a ways? Did it end up stable enough for you? Hopefully it did, but if not it would add a lot of rigidity to add "X" bracing on the sides. You can use small stuff like 1x2's for it if you wanted.

What I mean by X bracing is this: the long sides of your trellis have 4 vertical posts; if we number them in order 1 through 4 from one end to the other, then what I'm suggesting is nailing one end of a 1x2 to the top of post #1 and to the bottom of post #2, then adding another 1x2 nailed to the top of post #2 and the bottom of post #1, then repeating that process to put X bracing all around it. I think you'd end up with 6 X's: 2 on each long side, 1 on each short side. Or 8 if you put a couple over the roof as well.

That could well be overkill, I don't know, but you'll make it work. I'm looking forward to the pics of it once it's covered in flora :)

Dean W.

05-02-2012 12:23 AM

Re: Arbor/ Trellis design questions

Hey GreenFin,

Yes, I put 6 of them in the ground about 13" deep. I think it's pretty stable and can handle the wind and what not. I just don't know about the weight from the vine and fruits that will be on top. Time will tell I guess. I didn't think of X bracing it. That's something for me to consider though it doesn't seem wobbly.

Thanks for the advice!:bananas_b

Scuba_Dave

05-02-2012 07:30 AM

Re: Arbor/ Trellis design questions

What is going to be growing on the trellis ?
How long do you expect/want to use it ?
More important then the weight is the effect of wind on the structure once the vine etc grows out
Once the structure has vines on it then the wind force increases & in many cases will blow it over
If you only want to use it for 1 growing season then what you built may work
But a 40-50 mph wind may blow it over

If the 1x2's are reg wood then they will not last long, the grade of wood used to make them is not that great
Also a single nail in each end of the 1x2 shown in the pic will not prevent the structure from moving/swaying
The "X" bracing will greatly increase the strength of the structure
"Fresh" built most things seem stable, its once wind/water & sun start taking their toll that the wood/structure will start to move as time goes on

I use PT 4x4's for (almost) all uprights when I build something, or larger - for my deck
One exception being my greenhouse -but its attached to the house & bolted to a cement foundation

Dean W.

05-02-2012 08:47 AM

Re: Arbor/ Trellis design questions

Hi Scuba_Dave,

I only expect it to last a few years. I plan on planting gourds on there. The 1x2s are treated wood. You and Tony are right about using 4x4s. I think I'll check the price on them and maybe reconsider. At least maybe 4 of them.

Thanks!

GreenFin

05-02-2012 11:19 AM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by Dean W. (Post 192866)

Hey GreenFin,

Yes, I put 6 of them in the ground about 13" deep.

Probably wise.

Quote:

Originally Posted by Dean W. (Post 192894)

When I made the vertical supports for my greenhouse, I did like Tony suggested above and used pairs of 2x4's screwed together to form my own 4x4's because it was cheaper than buying 4x4's. So rather than buying four 4x4's you could just get four more 2x4's and augment your existing corners if you wanted.

Your trellis looks like it'll be pretty sheltered from the wind. Is that the case, or is it somewhat exposed?

Gourds will look nice on it.

Dean W.

05-02-2012 12:54 PM

Re: Arbor/ Trellis design questions

Hey GreenFin,

Yes, I planted those bushes there years ago that act as a wind screen from the North and also provide some privacy.

I went ahead and bought 6-4x4s as per the suggestions I got here. I'll use the 2x4s as cross supports. Already got two holes dug 18-20" deep so I just need to dig 4 more. Then I'll need to line them up and level them a bit. It's a little difficult because it's on a slight hill. So I may use a string with a level.

Thanks for everyone's suggestions. I should have listened the first time, but sometimes we don't want to hear the truth I guess.

GreenFin

05-02-2012 01:55 PM

Re: Arbor/ Trellis design questions

That thing might be hurricane-proof by the time you're done with it :)

Scuba_Dave

05-02-2012 05:49 PM

Re: Arbor/ Trellis design questions

I actually have over a dozen "spare" PT 4x4's & a few 4x6's
I've taken down 2 pool decks that people were getting rid of & reclaimed the wood

On my greenhouse instead of attaching the 2x4's width to width to make a 4x4 I made an L shape at the corners with the 2x's

Dean W.

05-02-2012 05:53 PM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by GreenFin (Post 192940)

That thing might be hurricane-proof by the time you're done with it :)

It should be now and it's a lot of work I hope they're worth it. :ha:

Quote:

Originally Posted by Scuba_Dave (Post 192963)

That's good that you got to reuse some wood. I put an add on freecycle didn't turn up anything, but some 1x4s which I might use across the top.

Dean W.

05-03-2012 02:27 PM

Re: Arbor/ Trellis design questions

Finally got the 4x4s in the ground. It may get a little shade in the late afternoon, but I think I should be able to grow them here. Need to nail the 2x4s atop this thing and prepare the soil.

sunfish

05-03-2012 03:22 PM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by Dean W. (Post 193053)

Finally got the 4x4s in the ground. It may get a little shade in the late afternoon, but I think I should be able to grow them here. Need to nail the 2x4s atop this thing and prepare the soil.

Looks good.

Olafhenny

05-05-2012 11:42 PM

Re: Arbor/ Trellis design questions

Sorry, Dean, I am a bit late, but it looks, like you need a bit of engineering advise. As your structure
stands now, I disagree with Scuba Dave that it will blow over at 40 to 50 mph winds. If you put
anything on it, which will catch the wind, such as vines, it will blow over at less than 20 mph. Your
joints at the corners will act like hinges and make the structure fold like a card house, digging the
posts deep will help a little, but not enough.

The very least you will need is diagonal cross strapping. No need to do it across the whole span of
the beams. 3 feet x 3feet from the cross beams to each post will give it plenty of stability.

But if you want that structure to stand up for 10 years or longer, I am afraid you will have to start from
scratch: Dig the post holes about 1 foot deep and at a diameter of about 8 to ten inches. Important
is, that the walls of the holes are undisturbed soil (no lose dirt). Fill the holes with ready mix
concrete. You will need a bag for each 2 to 3 holes. Into that concrete you plant a post bracket
for each post as you see in the top left corner of this site:

post base brackets - Google Search

Make sure these brackets are lined up, sighting from post to post. Having them all the same
elevation will help too. You can ensure that, by using a carpenter’s level and the straightest one
of your 2x4s for the top frame to get them all to the same height.

The idea of the brackets is, that you do not want to have direct contact between concrete and
wood, no matter how well the wood is treated, incised or otherwise. Concrete will make and
wood rot prematurely.

Another bit of advise: Don’t torture yourself by using nails. Beg, steal, borrow or rent a
cordless drill and use 3” special screws for treated lumber. The job will go twice as fast and will
require a lot less foul language to get it done. :)

Good luck,
Olaf

PS: I am adding a couple of pictures from my own gazebo construction eight years ago.

You can see, I kept the diagonal strapping a bit shy, but I could afford that, because of the diagonal grid of all the
minor straps.

This is an attempt to blow up part of the previous picture to show the post sitting in the bracket,
which in turn sits in the concrete. It is important, that the concrete is right against the base of the
bracket, for stability, but does not touch the wood.

sunfish

05-06-2012 12:05 AM

Re: Arbor/ Trellis design questions

Use galvanized steel post 2' in ground and carriage bolts it will last 100 years

Olafhenny

05-06-2012 12:39 AM

Re: Arbor/ Trellis design questions

Quote:

Originally Posted by sunfish (Post 193379)

Use galvanized steel post 2' in ground and carriage bolts it will last 100 years

No it won't. Thin posts like that won't give enough purchase. They will 'cut' the dirt unless set in
concrete to provide a larger surface to withstand lateral force.

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