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View Full Version : Best way to secure a round post on concrete base



bluedog225
09-23-2010, 04:28 PM
I'm trying to set a round post (a log) on a concrete base (sonotube) for a small pole barn-type structure. Concrete to ground level and post above ground. The posts will average around 8 inches at the base. I'm having a hard time figuring out how to secure the posts against lateral and lifting forces.

The best I can come up with is a bolt out of the concrete and a "U" shaped iron strap.

Other than just burying the post, is there an easier/better way to do this?

Thanks

Tom

switters
09-23-2010, 04:30 PM
http://www.decks.com/articles.aspx?articleid=306

bluedog225
09-23-2010, 04:40 PM
Thanks. I should have said 8 inches diameter at the base. So the standard post base will not work.

Paul Pless
09-23-2010, 04:43 PM
Thanks. I should have said 8 inches diameter at the base. I'd cut two opposing sides square with a skil saw at the bottom, then use a standard two piece tie-down like switters posted. Failing that a I'd use a large section angle iron.

switters
09-23-2010, 05:02 PM
The point is that the post does not bear on the concrete, trapping moisture and rotting out.

tomlarkin
09-23-2010, 05:05 PM
I'd run 3 or 4 long galvanized lag bolts into the base of the post, protruding 6 inches or so. Place large washers on each. When you're setting the post, block it up so there's an inch or so above the concrete. This keeps the butt out of the water and will help the post last longer. It wouldn't hurt to paint some wood preservative on before setting the posts.

Paul Girouard
09-23-2010, 05:14 PM
A knife hanger or strap.

Hopefully you haven't poured the concrete yet?

A flat strap poured into the concrete , use a chain saw to cut a "scabbard " / plunge cut into the bottom of the post , thru bolt the post to the metal strap.

I'll be doing some thing similar in the next few weeks, although the knife hanger / bracket I'll be using has a 7 3/4" square flat base and a 4" wide x 12" long strap off the top. It will be bolted down by boring 4 each 5/8" dia. holes into existing concrete with 1/2" SS threaded rod epoxied in to the bored holes.


You might be able to do a similar thing althought with only a 8" concrete post base your bolts into the concrete would be a bit close to the edge of the concrete base.

Paul Girouard
09-23-2010, 05:20 PM
Or a Simpson type hardware made for this application,

1088


Other types found here: http://www.strongtie.com/products/categories/post_bases.html


The type that are poured in tend to have higher strength ratings for both uplift and lateral support.

The Knife type hold downs we get made up to our spec's generally out of 316 SS.

paul oman
09-23-2010, 05:40 PM
bottomless bucket with epoxy sand slurry - post in the bucket, bucket on the slab.

bluedog225
09-23-2010, 05:57 PM
I'd run 3 or 4 long galvanized lag bolts into the base of the post, protruding 6 inches or so. Place large washers on each. When you're setting the post, block it up so there's an inch or so above the concrete. This keeps the butt out of the water and will help the post last longer. It wouldn't hurt to paint some wood preservative on before setting the posts.

Thanks. Would I need to get the bolt heads pretty close to or tied to the rebar to keep them from pulling the top of the concrete peir off?

bluedog225
09-23-2010, 05:58 PM
Or a Simpson type hardware made for this application,

1088


Other types found here: http://www.strongtie.com/products/categories/post_bases.html


The type that are poured in tend to have higher strength ratings for both uplift and lateral support.

The Knife type hold downs we get made up to our spec's generally out of 316 SS.

Thanks. I didn't realize I could order them that large.

delecta
09-23-2010, 06:53 PM
I'm going to assume that you haven't poured yet, Get some 1/2"X2" flat stock. Have them cut into 12" and 4" pieces and have the 4" piece welded on one end to make a "T". Blow a 1" hole on the top and set them into the concrete, plumb. Six inches above grade with a nice 1" hole. Drill out the bottom of the log with a 5/8 bit, make a mortise. Drill the one inch hole in the log and drive a broom stick through. You could use a dowel if you want :)

tomlarkin
09-23-2010, 07:29 PM
Thanks. Would I need to get the bolt heads pretty close to or tied to the rebar to keep them from pulling the top of the concrete peir off?

As long as they protrude a few inches below the top of your rebar I think you'd be safe. I don't think you'll have room to get in there to tie them off.

Donn, you're right that threads going with the grain aren't especially strong, but in this case, with enough thread, and 3 or 4 bolts, it should be more than strong enough. It would take a lot of lifting force to rip them out.

gibetheridge
09-23-2010, 08:07 PM
I got good results on previously poured concrete posts by hammer drilling a 1 1/2" hole in the concrete 12 inches deep, then drilling a 1/2" hole 24" up into the center of the log post. I then ground a bit of a bevel on the end of a 34" piece of hot dipped 5/8" threaded rod and sledge hammered 24" of it into the end of the log. After applying several coats of wood preservative to the end grain I filled the hole in the concrete 1/2 full of expanding grout and laid 2 layers of roll roofing on top and let the log and pin down onto that, turning the log a couple of times to seat it in any squeezed out grout. Bracing held the log plumb whilethe grout hardened, and excess roll roofing was trimmed later.

If the bottom of the post is going to be anywhere near grade you should make sure to design in considerable overhang to the roof in order to keep the log end as dry as possible.