Anchoring posts for metal building?

I am going to have some power poles milled into posts for metal building. Trying to decide whether to mount posts to concrete floor, over footing, or set them in concrete. Does anyone have experience mounting posts on top of concrete? If so what method/brackets did you use?

Based off what I've seen with pole buildings that anchor the post in the concrete, I would go with anchoring them on top of the concrete. Every older pole building I have seen with the post anchored in the concrete has showed them rotting off at slab height over time.
JMO

I would also put them on top of slab. We always use Simpson ABU66Z 6x6 Post Base. Also meets our building codes. Come in various sizes, either preset anchor bolts when pouring slab or use red heads if pre-existing slab

X2

Thanks for posting, I need to do the same and those above grade post holders look perfect.

Im not a builder but I do site work for such, Lately we have been required to have anchor footings and large anchor bolts on the ends of buildings built on a slab. This is for wind lift. This has been on residential only so far. Something to consider.

Thanks all!

I’m about 100% on going on top of concrete. I have set poles in concrete before and know how to plumb them up. I’m a little concerned about how to set the brackets in wet concrete correctly to be sure the posts end up plumb. Any tips there?

I struggled with this when I built my barn. Instead of poles having contact with concrete or ground, I imbedded u bolts in the concrete slab's haunch. Then simple walls attach to the floor plate. I also put a base sheet between the plate and concrete slab to eliminate any abrasion between the wood and concrete floor.

A new (last 20 yrs.) method used here is drilled 8 in. hole below frost line. Soni-tube (heavy cardboard tube) placed in hole extending 15 in. above grade. Fill with concrete to 10 in. above grade. While concrete is still wet place metal 6x6 holders for posts into top of concrete. The holders have metal rods with anchors to hold posts in place after concrete sets. Now you have concrete pillars with wood posts above grade. On my two 6 yr. old barns they are rated for 120mph. winds. Good luck.
Case.

I have used the above brackets but only for supporting center span locations.
On a corner I would prefer to set the post in concrete. Pressure treated or cedar posts at least 4 feet down.

On the other hand......it is a lot easier to locate the post for squaring if you locate it on top of the slab. If you go that route I would be certain to use a redhead on either side of the post. You haven't said how deep your concrete is or how tall these posts will be. Lots of leverage at the top of the post. !

I would also epoxy the redheads in place even though they don't necessarily require it

That’s kind of what I’m thinking case. Just without the tube and extension.

Heres the poop White. I’m planning on pouring a footing under where the posts are going, 4’ deep 6”-8” diameter with larger pad on top and a 1/2” rebar rod running the full depth. Posts will be 18’ tall. Only about 20’x20’ of the 40x60 will have a floor 5 1/2” thick.

I've done posts on top of footings with the Simpson post bases shown above, anchor bolts in the footings. I like to bring the sonotubes flush with the top of the slab to create a joint where the footing and slab can move. In NJ, we get freeze/thaw cycles all winter. Although it rarely happens, slabs can heave in the winter. I don't want the slab tied to the footing. In NE, I'm assuming that once the ground is frozen, it's frozen until Spring. Maybe slabs don't move there.

did you notch the post or is that 3 foot sections of post. Never seen that done .

I’m building it in NW Ontario so frost should stay all winter. Do you put an expansion joint wrap around the tube, or just use the tube to keep it separate from the slab?

I notched all the post. They are all true 6”x6” Amish rough cut hemlock. I wanted my hemlock siding flush on the inside.

My pole barn has posts concreted in the ground. Posts are made from 3 pressure treated 2x6's bolted together to form a 6x6 post. A standard 6x6 post does not get the treatment all the way into the center and thus rots from the inside out. Barn was built in 1995 in a wet spot and all posts are still as solid as new.
Trapset: if you are milling power poles make sure they are treated all the way thru. Poles around here are not..

My sawmill produces and treats residential telephone poles along with fence posts. If your solid 6x6 posts are not treated 100% three things, log was too big for milling a 6x6 (too much heartwood for diameter)
Wrong treatment chemical (non-human contact) Decks and railings of treated wood is treated different than posts. Third, moisture content too high prior to treating, pressure vessel pressure too low or time in vessel too short. Log size for a pole barn post should be just larger than finished post, that gives minimum heartwood. A straight 10 inch log should be used for a 6x6 post. All my timber is laser sorted to big end small end diameter. We do bore/core testing to certify.

But you will have a continuous footing around the entire 40x60 perimeter ?

Thanks

We weren’t planning on going all the way around with concrete White. We’re thinking about just pouring where the posts are then using ground contact treated 2x6 around the bottom and crushed stone inside except where the 20x30 slab part is.

I’m not against a footing all the way around, just not sure what it would accomplish. I think all the weight will be on the posts, therefore, the footing under them. Unless I’m missing something.

Well the way I look at it is this..............unless I completely misunderstand your project.......which is entirely possible.



The walls are going to support the weight of the roof. Not the corners. The walls need to transfer that weight to the ground.

If 60 feet is the long dimension.......surely there is some variation in the ground surface over that distance. If your wall is bearing on that uneven surface it will eventually conform to that uneven surface.....dips and peaks in the wall and the roof eventually.

I would much prefer to start with an absolutely level surface (concrete) to stand my wall on. It will make it easier to build, easier to roof, and way less maintenance over the long term.

Especially in a climate where the ground freezes all winter. When the ground freezes here it keeps moving all winter. I can see places in my house that show up to 3/8" displacement by February. It returns to 'normal' by July 4th.
If you are on a continuous footing you will still see movement but not differential movement because the entire footing moves together.

Cold climate building can really present some conundrums to a guy.

I didn’t explain the project very well. It is actually kind of pole barn style. Poles every 8’ connected with 2x8 inside and out around top. Trusses will sit on posts and 2x8s. Then 2x6 nailers aroun outside for metal to be attached to. Actual walls shouldn’t be providing any support, if all goes right.

I was debating whether to set the posts in concrete or set them on top of individual concrete footings. I think I’ve decided to go the “on top” route. Just need to figure out which brackets to use and wether to wet set or red head them in. The wet set seems kind of precise and permanent, as well as kinda busy trying to pour 26 footings and set mounts all at the same time. Whereas red heads could be done after and with oblong mount holes in the brackets, be a little more adjustable.

With my layout skills somewhat lacking, I like your idea of the Redhead being tweaked some. I don't think your strength would be less.

I would make sure your building code allows for posts to be set on top of the concrete. I believe I was told they have to be buried to help with lateral support. Also you don't have to pour concrete around them but you will need it for the footings.

look up "ladder framing"

I would use 5/8” x 8” titan bolts instead of redheads. Thats usually code for me around my parts and the brackets shown at the beginning of this thread have a hole the allows for adjustment. I looks like a very wide V type of hole. That said the wet set is way better. When i have done this it has been with sonotubes. Just set some string lines and you can literally screw into the tune to hold and cribbing for your bracket. Sounds like a fun build

Aha ! Not at all what I was envisioning !!

That plan should work but I'd use loooong red heads and still use epoxy.

When putting up one of our storage buildings last year the posts were put in the ground within the edge of othe slabs perimeter first. Then the slabs poured around the posts but a barrier was wrapped around the posts so the concrete could not come in contact to the wood.

The design engineer said the raw concreted touching the posts has ingredients that would eventually eat the posts. No matter the wood. We’re wood walls on top of the concrete, the concrete would have been troweled and surface finished which helps seal in the chemicals plus a sealer coat or roll out sill sealer between the two materials would prevent as well.

Osky

Got it, thanks guys! Appreciate the tips.

No codes where I’m building it but nice to know what some of the codes are other places for footings etc. Codes can be a pita but can save you from yourself in some cases, or save me from me is a better way to put it. Lol

So DT, you have your wet set brackets in place when forming then just pour under and around them?

Yup. Its common practice for me to set most anchors and the bracket/post before pouring. Not my idea, the engineers. I havent used these because usually mine are custom but this is what i would get for your application, and tie it into the other bar. Bucket. Also, it might be worth doing a monolithic slab of sort. Single pour with deeper perimeters that act as a footing. Excavate your hole and prep. Throw your bar in and tie it up. Get your buckets and locate where they need to be. When you tie them into the bar get a good elevation. Then plumb and straighten from a line and brace outside of mud with anything. 2x concrete stakes etc. Make sure you like your locations and they aren’t going to move and poor. Then just plop your posts in and plumb. Some might say this is harder, but doing it right usually is. The first photo is a passive house and the porch had custom rail tie posts that had a flange to flange connection. I set my flange for the concrete guys to pour and then we placed and bolted the rail tie post on top of that. Oak beam construction roof. The measurements had to be nuts and you make them such. Second photo is another project im leading. We beeded hold down units in all the corners. 1” allthread to line up inside a triple pack of 2x. People think its hard to nail this sort of thing but if you do the right prep its not bad. Its really the same and throwing the post in the mud. But better

I would use these.

Those look nice S2, but it’s think they’d cost more than the post. lol

DT, with that much adjustment in the first brackets, I wonder if I could use 5/8” ready rod set into the concrete. I might be over thinking it. We plan on having an elevation system on site for footings so I’d really just need a string line for placement of wet set brackets. When you say your using custom brackets, are you welding up your own?

Those brackets dont have much more space for anything other than a bolt head. It looks like a big lag with a regular hex drive head. If your dead set on those, pour, let the mud dry as long as you can, and drill a hole for a titan

10/4, Thanks. Not dead set at all. Leaning towards wet set like you described earlier. Have you ever heard of anyone welding up their own brackets?

Oh ya. Thats what the company i work for does all the time. We do a lot of what we call knife plates. 1/2” plate steel welded into a T. Then we mortice that into the post or beam. Let me know if you want tricks for the location of the drift pins or bolts. Always a hurdle getting it all lined up to fit snug. Our drift pins are usually 5/8” to 3/4”. You could weld bar onto the bottom like Schweg’s photo

Is the T bracket and mortise more for looks or is it stronger also? On this project, I’m looking for function and simplicity over form, for sure. I wonder if could find some red iron deep channel iron I could cut into U shapes and weld anchors on bottom. Even if the channel wasn’t exactly a 5.5 in ID, I could mill the posts whatever dimensions I needed to fit snug inside.

I think that would be a great project and save you some money. We do it for structural integrity, but also, it has an aesthetic appeal. Its really new wave mortise and tenon type stuff, but with way more steel. Steel is in...

That said, if you welded a T and had bar out the bottom that would work. Its not hard to mortise out the channel. Start with a circular saw, hog with a chainsaw, and finish with a chisel. But for your application just cut it out, place the beam on it (and you'll have a little play depending which way you orient the T), the drill 3-4 holes the exact diameter or a few thousandths over the dil of you rod. Get steel rod, cut to length, chamfer the edges and send em home. There is a million ways...

I like the T type bracket idea a lot. It would be nice to have the holes in the metal pre drilled but I think it would be hard, later, to hit the bracket holes when drilling the posts on site. Have you ever used T type with pre drilled holes D.T.?

Maybe a guide plate with holes in the same spots as the mortised in bracket could be set outside the post and drilled through. Might have a better chance of hitting the holes that way.

I primarily use the T brackets or knife plates with pre drilled holes. Honestly, id like them not to be pre-drilled and just send one bit through and call it good, but sometimes you can't have it all. In your application you wouldn't have to worry about cutting fluid on your wood. We use some fancy stuff and it has to stay that way so pre-drilled holes help in 1/2" steel. You will need it when you hit steel. I usually have a few squares on some clamps so i can sight X and Y to make sure my holes are relatively square to the piece.

There is a theory that offsetting your holes a tiny bit in the right direction will "suck it in" tight. Don't bother, wood moves and generally shrinks when your done with it. I've wasted a lot of time for no good reason

Got ya, thanks!

Is 1/2” the thinnest knife plate you think I could use with 18’ posts?