frost an a pole building?

[CalG]

I put up a small car park a few years ago. Its about 28 X32.
Sinking the holes for the posts in one corner was wet going, and hit ledge about 3 feet down. I thought OK, and set the post on the stone.
But now, as the years pass, It's apparent that that one corner is lifting. I assume by the frost action, based on the wetness. Not too bad, call it 4 inches.

Just to note, The uphill grounds, only two feet from the posts, was dug and a drain pipe installed. of course this ended up being HIGHER than the post footing when ledge was hit. But the drain should carry away most of the surface water.

Should the post be re-sunk and the hole lined with coarse gravel to allow the soil to move with the water laden frost?

Or???

Open to suggestions

 

[skyhook]

Look up " techno posts " in google under images. I would ( if possible ) clean the hole out and install one of the techno posts as far below the frost line as you can, re-position your post on top and secure it to the techno post somehow, cover up and it should be good. You can get these at any local hardware store.

 

[777777]

Skyhook, have you used the techno posts and are they cost effective ?

 

[CalG]

Look up " techno posts " in google under images. I would ( if possible ) clean the hole out and install one of the techno posts as far below the frost line as you can, re-position your post on top and secure it to the techno post somehow, cover up and it should be good. You can get these at any local hardware store.

Well, that solid ledge is going to make getting below frost level a job for a ram hoe. And If I go that way, a PT post down 4 feet seems to work just fine. At least that appears to be the case for the other posts holding up the car park.

I don't feel those techno posts are the solution for this situation. But I had thought to put a split PVC pipe sleeve around the post. Something slippery for the frost to work on.

 

[skyhook]

Skyhook, have you used the techno posts and are they cost effective ?

Yes I have, there about $40 bucks or so a piece, the key is to stop the frost from lifting and these post's did the job for me on my front deck. In the past it was just mounted on blocks and the frost would lift my deck, after installing these ( myself ) it would no longer lift. They come in 36" or 48" lengths. I went about 3 1/2 feet down.

 

[skyhook]

Well, that solid ledge is going to make getting below frost level a job for a ram hoe. And If I go that way, a PT post down 4 feet seems to work just fine. At least that appears to be the case for the other posts holding up the car park.

I don't feel those techno posts are the solution for this situation. But I had thought to put a split PVC pipe sleeve around the post. Something slippery for the frost to work on.

I hear ya, whatever works for you.....:thumbsup: but if the frost is lifting that stone that your post is on, one way or another, you'll have to break through.

 

[Billrog]

Jack the other 3 posts up 4" and call it a day.

 

[CalG]

I hear ya, whatever works for you.....:thumbsup: but if the frost is lifting that stone that your post is on, one way or another, you'll have to break through.

Nah! That "stone" that the post is sitting on likely spreads at least 50 feet each way but up. Sometimes we call it ledge, but it's just a stone with no edges.

One thing for sure, It does not move with the seasons. ;-) I've got lots of it, if you need some, come and get it!

 

[skyhook]

Jack the other 3 posts up 4" and call it a day.

Good idea, or lift that corner of the roof to compensate.

 

[ishiboo]

Techno should make a SSQA driver, as well as perhaps a mast-based 3-point unit for a tractor. Would probably make these pilings a lot more reasonable/accessible for people.

 

[GLyford]

How about digging down to the ledge, and clearing off the bottom of the hole with a shop vac for clean access to the ledge. Use a hammer drill to drill a couple 3/4" holes, and use the epoxy set 5/8 threaded rod anchors.

Then use the heaviest reinforcing "z-rated" strap you can find, I'm thinking something like this
Simpson Strong-Tie Z-MAX 18 in. Galvanized Medium Strap-MSTA18Z - The Home Depot
or this
Simpson Strong-Tie DTT ZMAX 14-Gauge Galvanized Deck Tension Tie-DTT1Z - The Home Depot
to bolt it down.

The potential problem I can see is what if it's not the ice and frost grabbing the sides of the post (as your PVC idea would protect you from) but layers forming between the ledge and the bottom of the post simply jacking it up from the bottom? In that case, I'm not sure even straps would help you, the frost might be strong enough to rip the wood free from straps.

If frost can pull out EVERY guard rail end on I-80 through western PA, it can get some force behind it.

Is the ledge dead flat or at an angle at the bottom of the hole? If it is at an angle, can you do anything like cutting grooves or something to encourage the water to keep going past the post, and not linger? Maybe widen the downslope side of the hole just above the ledge and fill with extra gravel?

Just spitballing ideas here, feel free to shoot any of them down that you know won't work, because that might spark the next one that will.

 

[Ford850]

Did you add uplift cleats to the posts when you built it?

 

[Apsterbobed]

If you are truly on ledge then it doesn't move, I would dig down to the ledge and then dig a drain away from the post to give the water a place to go. Put in a drain pipe and or stone and tie it into the drain you alreay have. Put just enough stone in the bottom of the hole to get it level. Then put a precast frost post in and back fill with stone. Next try to fix the water problem above grade, slope away from the building, add a gutter, put a berm on the up hill to redirect runoff away before it gets to the building. You don't need to do all these things just do what makes the most sense for your building and surrounding land. You have 2 problems working against you, water and lack of depth. The frost post will help but should be below the frost line (4+ feet) so I doubt it will solve your problem alone, the shape of the post helps keep the frost from getting a hold of it but if the water is under it I'm not sure the shape can completely hold it down. Keeping the water away and giving it a way to leave will reduce the frost movement in the ground so there will be less force on the post.

This is a frost post:
http://americanconcrete.com/Frost%20Post%20and%20Pads/Standard%20Frost%20Posts-Catalog%20Vertical.pdf

 

[CalG]

Great ideas, Thanks to all.

Depth is the issue. I've ditched, trenched, placed perf pipe, and filled the slope above with stone and rubble.

But stopping the movement of water over the surface of the ledge is not an easy accomplishment.

Prefab solutions need depth. That is in short supply. My comment on 3 feet is generous.
I have thought to place a second drain below the post, but I've never heard of a situation where drying soil down slope has limited frost action uphill

The ground shows dampness with the spring time. When it dries, I'll dig it out and reline the hole. the car park really could give a hoot, it's just that a certain angles, It looks funny.

 

[Apsterbobed]

It sounds like you have already done what you can about the water wich is good. If you don't think a precast will work then I would think about epoxy and forming your own pier. Drill 4 or 5, 12 to 18 inch holes in the ledge and epoxy in rebar long enough to make it almost to the surface. Then form your own pyramid shaped colum and put in some type of anchor at the top. When done put an apron of 2" foam board around the concrete sloping it away from the post one 4'x4' sheet should be enough, then cover with 6 to 8 inches of top soil / gravel to get you to finished grade.

 

[GLyford]

Oh yeah, that whole "frost protected shallow foundation" thing, forgot about those. How about putting a layer of 2" foam, about 6" under the surface to protect it from UV and casual damage, all around the post?