Footings in a 4' Frost Level Area

A GA.

There really is a reason for codes calling for that depth. You can always come by my house in January to see how I'm doing in the annual driveway gate lottery. The posts do not go below frost. They shift randomly each winter. Some winters I can't lock the gate. Some winters, I have to take the hinges loose to open it.

Knowing that concrete is terrible in tension, you did use re-bar, right? As long as you're not hanging a 600# gate off one, you should be fine.

lynlynch:

I would advice against that, experience dictates (i.e. I'm saying do as I say not as I do )

Last year I put up a sun sail (shade) on the east side of the house. 2 points connected to posts the other two to the house.

I told my girlfriend "hey, we can put a hammock up also, but she did'nt say anything about it......and my honey dew list was large so I did not push it. but I should have known better.

The day after I cemented, she said a hammock is a great idea.. So I reeinforce the posts with a cement column. I tried to seal it around the footing but we had clay and it was dry, its crappy when you swing a pick on it and it pings.......no that was no stone.

I did one that was alright, but on post two. I ran out of steam, and said good enough.

Well the next spring the post where I took the short cut, I had to do it right, because I could lean on it and it would rock. Frost can move mountains

see below might be hard to read

sun sail

post 1

post 2

So to the OP, either do it right or do it again, I was fortunate enough to be able to add to it. , I used rebar....and a hammer drill to tie it all together.

p911

OK, I live in the desert, this is Minn. I never go to Minn. in the winter. Did that two years ago. Was there for 6 days and the thermometer never got above 25°F during even the "hottest" part of the day. Snow everywhere. It never occurred to me that snow never melts there. Just gets piled up beside parking lots till spring. Why do people live there year round????????

It'll be 112°F here today.

I yield to the previous posters who have experience with the cold. Do as they say.

"It'll be 112°F here today." WOOF!

My yard thermometer does not read above 94⁰. I think it will, but it has not had to do so for the last four years.

Winter of 2008-2009, I had 100% snow coverage in my back yard for 6 months and 6 days. Not sure, I think there were about 12 days where the warm temp for the day was -25⁰F.

"Why do people live there year round????????" I've been pondering that very issue. Ah, it's not that bad. Gotta live somewhere.

"It'll be 112°F here today." WOOF!.......

they say its a dry heat.......so that makes it ok?

I agree with Phoenix911, you should go deeper than the frost level. I realize that your fence will not support a structure load because no building will be resting on it, so you need not meet any building code. But if you don't want it to move, get below the frost line. No amount of footing size or shape will prevent water from getting underneath all of the footing. If that water is too close to winter weather it will freeze.

The soil is like sponge will soak in under the footing. As others have said you need to go below the freeze or frost level. Moisture in the soil when it freezes causes it to expand. The process freezing and contraction loosens the soil will cause the post to shift around. What your bell shape may have done is made it worse. The soil inside the bell if it can not expand out may force the form up.

Here in Maine (and the snow does not melt until May at times) I go down a bit more than 4 ft. put crushed stone in the hole, THEN build my footing. My footings for things like you describe are usually about 6-8" thick and about 2 inches bigger than the post I'm setting on top of it (6" post = 10" footing width). Depth and drainage are key. If the brick corner post is for aesthetics, you might consider setting a solid post made of steel/iron or even plastic available today and then face it with the brick. I have not had one move yet (some have been in the ground for 10 years or more) Of course there's the advantage of having ledge around sometimes, and then you just go down to the ledge and call THAT your footing!

There is water everywhere under ground. Don't believe me? Take a large tarp and lay it over the ground this weekend with rocks holding down the edges and corners. In the morning wait until the sun has baked the dew off of the top of the tarp, and pull it up. Notice the damp ground underneath, the wetness on the bottom of the tarp (wasn't that ground dry when you put it down?), and the dry ground around the perimeter where the tarp was not!

People survive in the desert by pulling water out of the ground in a place that NEVER rains. It is called a solar still. You WILL get water under that footing, it WILL freeze, and your footing WILL tilt. I hate to be the bringer of bad news, but you must take up that footing and start over - down an additional 3' minimum. I would go to the 4'6" mark if you are in a 4' frost area if that fence is anywhere near traffic (a driveway).

I used to dig a lot of footings in the wintertime near semi traffic (15 mph max), and they would have the frost driven down 6 to 8 feet in the wintertime - we are in a 4' frost zone as well. I don't know the scientific explanation for it, but the traffic really packs in the frost! As long as you already have blisters from digging what's another 6 or 12 inches?

Somewhere in the back of your head logic is asking an obvious question that led you down the wrong path: "But people build garages and small buildings on slabs, and they don't fall down?" The key to the answer of that question is that it is properly called a FLOATING slab. It WILL move - and lots in the wintertime. If it is a far-flung building that you don't need to keep tightly shut and don't necessarily care about life expectancy you can do it, and save some money. However it won't last as long, especially if you skimp on rebar in the floor. It will crack in many places, and the walls will start moving independently, eventually shaking the building apart. If the slab is done right and ROBUST, it will all move together, and there will be times the walls won't be plumb and the floor won't be level, but as long as they all move together you won't notice or care.

A fence corner post is too tall and skinny for this to work without causing problems. Especially if it is a wrought iron fence. There is a lot of weight there, and lots of rigidity. The fence pieces and posts will work on each other until they tear each other apart. Your fence will be ready for recycling in 10 years, unless you are going for the haunted house looks!

If you have only limited time and ambition, I would recommend that you either drive in pipe corner posts (down 4 to 5' into the ground), or you get a back hoe to dig the footings that you desire down to 5' deep, dump in 6" of gravel, and slush in a footing 8" to a foot thick. Make the footing 1 to 2 feet larger than the corner post dimensions and be sure you put enough rebar to hold it all together. Not sure of the brick corner post you are building, but #4's at 12" oc ew is probably sufficient for that. I wouldn't go with less... Then you can build your brick column up from that. Backfill with clear stone if you have a good budget, or with site spoils if they are draining (sand, gravel, or something similar). You can fabric and throw down 6" of dirt at the top if you want grass to come right up to the edge of the post. If you don't fabric, the dirt will disappear and clog up the clear stone - you will be constantly filling in around the post, and eventually the clear stone will stop draining - potentially causing you headaches many years down the road.

If you do this right, you will have a beautiful fence you can be proud of forever. Screw it up and every time you drive by it you will mentally kick yourself yet again!

Best of luck with it - these sorts of projects are seriously enjoyable and full of satisfaction when they are done.

Well, even with all the off-topic whining about the heat or cold, I appreciate all the advice. Almost all of it good.

I saw a City of Minneapolis crew setting footings on Nicollet Avenue. Since they have done about 100 miles of iron fence with brick posts I thought I would ask them. The foreman said they go 1.21 meters (we are actually liberals up here, you can tell because even Public Works has gone metric).

I called and electric jack hammer's are $60.00 for 4 hours from Hiawatha Reddy Rents.

But why anybody does live here is a very good question.

Sucks, but it is $60 well spent.

Sorry...