Pole barn...anchor posts?

marrt · Dec 3, 2007

I'm building a 30" x 36" pole barn style garage. There are 26 posts in total. My question...do I need to anchor the posts to their concrete pads? The posts are all just sitting on their respective pads (to minimize rot) and will have, on average, about 18" of fill. I'm a little concerned about "up lift" from severe weather conditions. The anchors will cost about $600 for materials alone. Money well spent, or just wasted?

claridon · Dec 3, 2007

A few years ago I built my pole constructed shop using pressure treated 4X6 posts. We set the posts on a 6" concrete pad in the bottom of a 42" hole. To resist "heaving" out of the hole we nailed (2) 2"x6"x6" pressure treated "cleats" on opposite sides of each post; bottom of cleat was flush with the bottom of the post. I've had no problems with any vertical movement of the posts. We can see temperatures below zero here in January/February. Cleats are required by our county building inspector in all pole building construction. No anchors were required or used.
-Len

Erik_in_Hoyt · Dec 5, 2007

I built a 24X48 pole barn for a neighbor about 10 years ago, set the posts about 36" deep and there's been no problem with heaving.
All I did was punch 12" wide holes and put rocks in the bottom for drainage -- no concrete cookie -- and it's doing fine -- but we also poured some concrete around the posts and have 24" eaves to help keep the area at the bottom of the walls dry.

MarkV · Dec 5, 2007

At 18” deep are you deep enough to be below the local frost line? Around here we would normally go about 48” and the friction of the ground against the pole prevents up lift do to high wind.

MarkV

ToadHill · Dec 5, 2007

I poured mine 48" deep and 6" above the grade, put 2 pieces of flat iron into the wet cement with 2 holes drilled in each. I mounted the polls on the cement with a sheet of aluminum below to stop wicking any moisture and lag screwed the polls in. My neighbor asked me if I was building it to last 3 centuries.

radman1 · Dec 5, 2007

claridon said:
A few years ago I built my pole constructed shop using pressure treated 4X6 posts. We set the posts on a 6" concrete pad in the bottom of a 42" hole. To resist "heaving" out of the hole we nailed (2) 2"x6"x6" pressure treated "cleats" on opposite sides of each post; bottom of cleat was flush with the bottom of the post. I've had no problems with any vertical movement of the posts. We can see temperatures below zero here in January/February. Cleats are required by our county building inspector in all pole building construction. No anchors were required or used.
-Len

That is exactly what I did.

WVBill · Dec 6, 2007

I'm in the eastern panhandle of WV and built a 32' x 40' pole barn about 7 years ago. I went 54" deep on my holes - put in 6" gravel and set my poles on top of that then filled holes with concrete. (I know - there's the concrete or earth backfill debate).

The reasearch I did in advance of building advised:
1) poles should be set below the frost line in your area (30" here in Jefferson County WV)
2) pole depth is determined by the size of the building sides, the roof overhang and the diameter of the poles. Pole depth primarily resists uplift generated from wind on the sides of the building and under the eaves. Pole resistance is a function of the surface area of the pole in contact with the backfill. There are books on pole buildings (I got mine from Amazon.dom) that have reference tables for detemining how deep you should put your poles with adjustments if you use cleats or anchors. I'm pretty sure from what I remember of the tables that 18" isn't deep enough even with anchors.

Amazon.com: Practical Pole Building Construction: With Plans for Barns, Cabins, & Outbuildings: Books: Leigh Seddon

Amazon.com: Building Small Barns, Sheds & Shelters: Books: Monte Burch

Amazon.com: Monte Burch's Pole Building Projects: Over 25 Low-Cost Plans: Books: Monte Burch

Hope this helps - be sure to post pictures of your buinding progress.

WVBill

marrt · Dec 8, 2007

The frost depth where I live is 24". We dug down about 30" in most areas. There are 26 posts in my 30 x 36 building. On average, the posts are 5 feet apart. On closer inspection, the 18" number I mentioned above is only for a few holes with extra concrete. I will measure each hole tomorrow for my own curiosity.

Regarding the hold down brackets, they are not readily available with the proper amount of galvanization for treated lumber. They now have to be special ordered with a 4 to 6 week wait. I did find 11 brackets that were old inventory at the lumber yard with the correct amount of galvanization. I installed those around the perimeter. Regarding the use of a treated lumber sleeve, that isn't easy to accomplish ether. Most commonly available 2x lumber only has a .10 treatment. Lumber placed below grade should have a .31 treatment. This is a special order and the lumber yard will not order the small quantity I need.

Most pole barns are build with poles on 8' center. With no openings, that would be 16 posts around the perimeter for my building (132 / 8). With 11 posts anchored, I should be ok I hope.

2manyrocks · Dec 8, 2007

The pole building book I have was written before the change in pressure treating, but one of the suggestions is to insert lag bolts in the pole below ground and then pour concrete. Maybe there are some very well galvanized lag bolts available. Seems like the other suggestion I've come across is that the edgs of the hole be smooth so the frost doesn't get a better bite on the whole thing.