Shop Build Question Post Protector or Tubular Frame

[pburchett]

I’m looking for some advice from folks here with real-world experience before I move forward on having a shop built.

I’m in central Kentucky, near Lexington, on flat ground. We get a steady breeze most days (8–11 mph on average), and my biggest concern is moisture—the water table is very high. I can’t dig a post hole without it filling with water before I’m done.

The building I’m planning is 24 x 32 with a 32 ft lean-to, and it will have a full concrete floor with a vapor barrier.

I’m considering three options:

1. A turn-key pole barn

2. A roof-only pole barn with concrete, (letting someone else do the hard part) and I finish the walls and install the garage doors myself.

I’m very familiar with pole barn construction, but in my case I would need the Post Protector system to prevent rot. Does anyone here have experience with post sleeves and wet ground? How well do they actually hold up long-term?



3. A tubular metal frame building like the carport-style structures, anchored to concrete

On the metal building option, I like that everything is anchored to the slab so there are no posts in the ground to rot. However, I do have concerns about durability. Given that we’re under constant wind load, do the screws tend to loosen over time? And how do those roll-up doors hold up? From my experience renting storage units, they seem pretty flimsy.

I’d really appreciate any insight.

Thanks in advance.

 

[m16ty]

I’d be concerned building any type of building on ground where the water table is that high. Maybe there are ways but that sounds insane to me.
As far as the type, those metal frame building are cheap. I’ve seen people put them up and they seem to do ok, but they aren’t near a sturdy as a well built post and frame building.

 

[Hemmjo]

Perma-Column. Precast concrete post bases.

 

[Jim.ME]

Slab with a thickened edge and rebar, with at least a foot high concrete curb wall on top of it with anchor provisions for accepting posts (wood or steel depending on your choice of building) keyed and doweled to the slab. The wall should be poured so the top of the wall can accept posts, i.e. anchor bolts or brackets depending on the post type. Side walls (wood/metal) stop at least 6 inches above the ground. The concrete curb wall on top of the slab keeps the bottom of the walls away from most of the ground moisture, external or internal.

Storage unit roll up doors don't compare to good commercial roll up door in quality or price. As usual good and cheap don't go together.

As always these days, you need to check local codes before deciding.

 

[DanielW]

The last couple of pole barns I've built, I've poured footings/sono-tubes for each post location, ending about a foot higher than ground level. When I pour the tubes, I set a heavy plate with some rebar or J-anchors welded on it into the concrete, flush with the top of the sono tube. I then have some simple L-brackets made, with 2.5" x 16" legs, 5.5" wide, from 1/4" steel. Weld two of these angles facing each other down to each embed plate to make a cradle for the post to sit in. Then a few pieces of threaded rod through the cradle/post.

It sounds complicated, but I actually find it easier than setting posts directly on a footing. Because the embed plates on the top of the footings are 8" or 10" square, you have a couple inches in any direction to fudge the position of the cradle on top of the footing before welding them down. So you don't have to worry about getting all your post holes/posts set perfectly in line - though you do still want to be within an inch or two. And once built, you have a full concrete footing for each post holding the post a foot above ground level. No wood in contact with the ground anywhere. It's pretty much doing what those precast post bases Hemmjo showed do. But this way you get a full footing poured with your tube (I usually go with 24" or 30" footing cones on the sono tubes), and also have a little more fudge factor.

I've seen the post sleeves, but I have my doubts about them. I would think that unless you really keep on top of having the top seam caulked tight around the wood, at some point that seam will open enough that water is going to wick between the sleeve and post via capillary action, and have no way to escape. I can't see how the sleeves are much better than putting a post directly in concrete. And it's pretty generally agreed (and I've certainly found it to be true) that a post placed directly in concrete will rot much faster than one placed in the soil, for the same reason as above (water wicking in between concrete & post, and never really being able to dry out thoroughly.

 

[DanielW]

Further to my last reply. Here's a sketch I made for someone else showing how I do it. This shows the embed plates in a slab-on-grade construction, but same idea.