resetting a trellis in concrete: any advice?

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Old 09-12-07, 11:36 AM
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Question resetting a trellis in concrete: any advice?

I recently had my house painted, so I dug out our trellis to ensure the painters had sufficient clearance to do a good job. (They did do a good job, by the way. )

I now need to reset this trellis, but I've never worked with concrete before. So, I'd appreciate any advice or tips.

The trellis was previously installed in concrete by landscapers 3 or 4 years ago. It is 10' high and 4' 3" wide. Here's a picture:


Notice that the vertical posts are simply two by fours. The "legs" are 2' long.

I know this isn't rocket science, but here are the areas where I could use some help:
-I've got no clue how deep I should dig with my handy $20 post hole digger. What do you think?
-How much concrete I should buy?
-Would "quick concrete mix" acceptable for this type of application? (I think you just dump this into the hole, add water, then mix it around until it gets to a certain consistency.)
-Unlike the previous landscapers, I'd like to make the extra effort to situate the trellis so that it doesn't tilt or lean over time. So, I'm guessing that my holes will need to be around 2' deep or so? However, considering the legs are only 2' long, is it reasonable to have only 1 feet of the legs immersed in the concrete? (I'd prefer that the base of the trellis be around 6-12" above the ground.)
-To add to the last point, I'm a little concerned that the surrounding dirt is now too loose because of my efforts to dig up the old concrete. Considering this, should I dig my holes even deeper, and drop some rebar in there? Or, is loose dirt not an issue for setting posts in concrete?
-Is it necessary to put gravel at the bottom of the holes? (FYI, I live in San Jose, CA--we never get snow, but we can get some winter days that fall under 35 degrees F.)

Sorry for being so anal, but this trellis is in a highly visible spot, and it starts to look very tacky when it is not perfectly vertical and aligned with the house.

Thanks in advance!
 
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Old 09-12-07, 08:14 PM
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I think that if I were attaching it, I would not put any of the wood into the concrete. Instead, measure the distance between the legs and embed some galvanized angle iron into your concrete so that about 12" of it will be above grade. (make 1 cut on one side of the angle iron and bend the angle iron into the shape of an L so that it won't ever pull straight up out of the cement. Then push the whole works down into your wet cement, measuring to make sure you have them the right distance apart, also checking them with a torpedo level to ensure they are plumb. A piece of 6" PVC pipe would work good as a cement form. And I would imagine that 2' deep would be sufficient. No need for gravel or rebar. Although backfilling the hole (around the PVC form) with pea gravel would be better than backfilling with soil.) Once the concrete has set up, you would then be able to bolt the trellis to the 12" or so of angle iron that is sticking up. And it would then be removable for paint jobs down the road. Depending on how you want to landscape it, the cement could stand proud from the ground, or if you prefer, it could be kept below grade so that it could be covered with your ground cover- rocks, mulch or what have you.
 
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Old 09-12-07, 09:25 PM
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Thanks XSleeper--this sounds like a good opportunity to also work with angle iron (as I've never done that before, either). Plus, it seems relatively risk-free considering if I blow it, I can simply dig up one (or both) of the angle irons and try again. Couple quick question: I'm assuming galvanized angle irons come in various sizes.... What size do you think would work best with the 2x4s? Also, what do I use to cut and bend the angle iron?

Thanks again!
 
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Old 09-12-07, 10:00 PM
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You'd use a hacksaw to cut one edge of the angle iron. If you have a vise, you could clamp it and probably bend it with some elbow grease. Some hardware stores sell angle iron that already has holes in it. (sometimes its in the aisle with nuts, bolts and threaded rods) Useful for hanging garage door openers and such. I think it's galvanized (won't rust for many years, and you should be able to paint it if desired). You'd probably just want something 1 1/2" x 1 1/2" and it could be bolted or lagged to the corners of the trellis. The longer the angle iron is, the more stable the trellis will be.

Not sure if you missed it, but I was suggesting setting these angle irons into concrete so that they'd be super sturdy. Measuring carefully when you stick them into the cement will be critical, so that your trellis will fit exactly. Of course I suppose you could also bolt the angle irons to the trellis and then set the whole thing into your wet cement. But if you do that you'd need to temporarily stake up the trellis so that it stays plumb and level, and it would need to stay immobilized like that until the cement sets up.

I suppose you could try putting the angle iron into the dirt with a sledgehammer too. Not a bad idea if your soil will hold it. Like you said, you could always yank it out if it doesn't work as planned. The cement could always be a backup plan.
 
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Old 09-12-07, 10:07 PM
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must_golf_more,

Judging from your posts and from the picture, your trellis has a wood frame. I agree with XSleeper -- you don't want to bury wood in the dirt. So you need a couple of footings that will support it. For what you are dealing with, the fact that the surrounding soil has been disturbed really isn't going to be much of an issue. San Jose has no frost issues, and really has no wind issues either. So if you dig a couple of holes that are 10" to 12" in diameter and 18" to 24" deep, you're fine. After the holes are dug, pour concrete in the holes, lay the trellis down (so that you have the exact width of the posts), and set a steel plate in each hole to the exact width of the legs of the trellis. Give the concrete a day or two to cure, (take two days off and go golfing!!) then attach the trellis to the steel plates.
 
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Old 09-13-07, 12:13 PM
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Sounds great, gentlemen! XSleeper--Sorry for my misleading earlier response. I'm definitely going to be using concrete with your angle iron suggestion.

Before I head off to the store, were you suggesting that a single 1 1/2" x 1 1/2" angle iron is sufficient for each leg? Also, where do you recommend I situate the angle irons? (I'm guessing I should put them in the inside/rear corners of the legs?)
 
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Old 09-13-07, 05:14 PM
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The 1-1/2" angle iron at each leg as suggested by XSleeper would be plenty. Another option would be to use something along the lines of a Simpson PB44 or even a PBS44 and cut the inside leg off before you install it. That would give you a stell plate to seperate the concrete from the bottom of the wood leg of the trellis. Paint it white to match the trellis after it's installed.
 
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Old 09-13-07, 05:34 PM
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Back/inside would work... plants might eventually hide it if it's oriented that way.
 
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Old 09-13-07, 10:23 PM
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I just got back from Home Depot. I did find 4' long angle irons, but they were merely zinc-plated, not galvanized. Will these work, or should I continue looking for galvanized angle irons? (I didn't buy them, by the way.)

Also, I thought it would be fairly simple to pick out the bolts and lags to use with the angle brackets, but apparently I overestimated my intelligence.

-I couldn't decide on the size to use. Would you think 1/4" lags/bolts are thick enough?
-I couldn't decide on their lengths. If I use lags to go in lengthwise with the 2 by 4, and bolts to go through widthwise (ie, parallel with the trellis), what lengths do you recommend for these lags/bolts?
-I couldn't decide how many lags/bolts I should use.

About the only thing I was able to figure out on my own is the [galvanized] washers to use with the [galvanized] lags and bolts. Yay for me.

Maybe it was just too long of a day at work, or maybe I was too hungry at the time. Or maybe I was too preoccupied with trying to figure out why I can't get rid of my ugly slice.

lefty--I'm hesitant to go with your Simpson recommendation considering the height of the trellis, and the fact that the non-pressure treated would has been embedded in concrete for the past few years. Had they used pressure treated 4x4s, I'd definitely lean towards your idea.

I also came across another disappointing finding: The legs are kind of bowed. So, if I go with the angle bracket approach, I definitely have to preassemble them to the trellis, and situate everything before pouring the concrete.

Considering the mess I've described in this post so far, do you guys now think I should just scrap the angle bracket approach and set the trellis directly in the concrete like the landscapers did?
 
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Old 09-13-07, 10:44 PM
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The simplest (and longest lasting) solution might be to scrape the entire trellis frame, saving only the lattice panel, and have a VINYL frame made for it. THAT you can embed the legs of directly into the concrete, No additional bracing would be needed.

Getting the angle iron or post bases set to line up PERFECTLY with your existing frame is definitely going to cut into your time on the course. And iron, especially angle iron, is not at all forgiving.

Wood, even PT, set in concrete, is going to rot in about 10 years.

Go see one of the local shops tht makes vinyl fencing.
 
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Old 09-14-07, 05:41 AM
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zinc-plated will work fine. zinc is the main ingredient in hot dipped galvanizing, it's just a cheaper way to do it.

If you buy lags, 1/4" would be a bit small. You might want 3 per side... 5/16 x 1 1/2" or 3/8 x 1 1/2. If you want bolts, you'd need some 5/16 x 2" or 3/8 x 2 and some 5/16 x 4" and 3/8 x 4". If the legs are a little bowed, the bolts will be a better choice because you will be able to tighten them to the angle iron better.

Putting the angle irons onto the trellis first might be the most simple for you. In that case, it would work best if your angle irons just ran right to the bottom of your hole and into the dirt (so that the trellis doesn't sink down into the cement). Forget bending the angles on the angle iron. Just stake the thing up straight and add cement around it.

Keeping the legs of the trellis above ground where you can keep the legs painted will help it last longer.
 
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Old 09-14-07, 09:47 PM
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Heh heh--thanks for your persistence and patience while helping me out. I really appreciate it.

Originally Posted by XSleeper View Post
...If you want bolts, you'd need some 5/16 x 2" or 3/8 x 2 and some 5/16 x 4" and 3/8 x 4"...
I'd like to go with your bolt suggestion because I do want the angle irons as flush as possible with the legs. I tend to over-tighten things, so I also like the fact that it eliminates the chance I'll strip the wood by not using lags.

For the 4" bolts, do you suggest I create pre-drilled holes all the way through the "4-inch side" of the two by fours? If so, doesn't this seem like a lot of drilling to the point where it might actually compromise the structural integrity of the legs? Maybe I should use lags for the "lengthwise" part (after I pre-drill pilot holes, of course), and bolts for the "widthwise" part? (Am I making sense?)

Thanks again, and I hope you guys have a nice, relaxing, house-work-free weekend.
 
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Old 09-14-07, 10:22 PM
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3" lags into the 3 1/2" thick part sounds like a good idea... more wood for the lag to bite into on that side. And I don't think a 5/16" or 3/8" hole will weaken a 2x4 enough to worry about it, but it does make sense to bolt through the narrow side, lag into the wide side. The holes you drill for the bolts will be barely larger than the bolt. The holes you drill for the lags will be roughly 1/8" smaller than the lag, so that the lags will be tight, and shouldn't strip.

You're very welcome- hope it turns out the way you planned- and I hope I have a relaxing weekend too. Saturday morning I'll be working on creating my own crown moulding jig for a job next week! (Recreational woodworking) LOL
 
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Old 09-18-07, 10:16 PM
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Could you share some tips on the proper method for mixing (and testing the consistency) of "ready-mix" post hole concrete? I bought four 50 lb bags of this stuff for now. (I'll probably need more, but the hardware store is just down the street and I'd rather not get stuck with too much concrete mix.)

I know all I have to do is add water, but I've never worked with concrete before. I'm under the impression that it's better to pre-mix it in my 5 gallon bucket instead of trying to mix it in the 2 holes I dug. Any tips are greatly appreciated.

Thanks again!
 
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Old 09-18-07, 10:33 PM
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must_golf_more,

Don't try mixing it in a 5 gallon bucket -- USE A WHEELBARROW!!

A 50# bag is about 1/2 cu. ft. Meausre your holes and figure out how much you need.

Pour the bag into the wheelbarrow and add a little water. Mix that with a hoe. Add a little more water and mix it some more. You want to keep the mix on the dry side. You can always add more water and not hurt it. If you get it too wet, you have destroyed the concrete. When the mix is right, all of the dry material is totally mixed in and you will have no water standing on top. It will be about the consistancy of cake mix batter. (Runnier than cookie dough, but no where near anything that resembles a soup!!)

(I don't know just how to describe it, I just know when it's RIGHT!!) It shouldn't stick to the hoe, but it won't be runny and wet.

But, then too, it's only going to be used as a footing for the trellis. If you get it a bit too wet or a bit too dry, it WON'T be the end of the world. A good place to learn how to mix it!!

And don't worry about buying too much. As long as the sacks are in new condition, you can always return them!
 
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