Frost heaving

[nate379]

2009 I started on a 16x20 storage shed in my yard that I finished last summer.

Winter 2009/2010 it was all framed with a roof, just no doors put in or siding and nothing done to the inside.

The shed sits on a compacted gravel pad (several hours with a plate compactor) that was leveled. I put down 4 4x6s that span the 20ft length and then built a 2x8 O.C. floor on that.

I don't have any photos of it right now, but here is a photo of the pad:

I was clearing snow today and it looked like the shed was leaning a bit to one side. Grabbed a level out of curiousity and it's sitting about 2" low on the left side in the photo.

I'm hoping it's just the frost that shifted it, but I'm not sure why it would do it now and I have no movement at all before??
I'm not "too" worried about it as long as it will go back to level once everything thaws... is that usually the case? I know the heaves that get in the roads smooth out at least.

 

[smoke show]

Is that area excavated, or is the gravel pad just sitting on the topsoil?

just askin.

 

[nate379]

Few inches of topsoil, but it's all gravel under that on the whole property.

 

[smoke show]

I would never build a structure that big on topsoil.

But thats just me.

 

[mrjohneel]

Well, I'm not a carpenter but I did build two decks in Mass. and helped a friend construct an addition on a foundation he had poured, and your foundation is something that probably would be subjected to lots of heaving and distortion here (never mind code) and I think it would be even more likely to fail in Alaska. I hope I'm wrong! But even for a shed that small I think you'd have to have some deeper footings. Good luck!

 

[Valhalla]

Hindsight is always 20-20.
Jack it up a bit and level it out in the spring.
Lessons learned in life. Don't sweat it!

 

[barn burner]

I build sheds and outdoor structures for a living. If it's not on a frost proof permanent foundation, it'll move some. But I wouldn't worry, where's it going to go? I've put hundreds of sheds just on cap block sitting directly on the ground. A gravel pad will help some with the heaving and settling but won't totally eliminate it. If it doesn't go down, you can always use a car jack and throw some treated shims under it to get it back to level.

 

[nate379]

How would you build it? It's not on topsoil, that is gravel in the pic. 1" minus road base.

I would never build a structure that big on topsoil.

But thats just me.

If I lived in the south I would have dug to frost line, but here that is 12ft.

 

[Frozen Canuck]

You really have limited choices here Nate. One either digs down to a level below the frost line & builds a foundation that will resist the effects of said frost (think way more $ than the entire cost of this structure) or one simply places the structure on the ground & either lives with or corrects annually the effects of the frost heaves on the structure. Sorry to give you the bad news, if the structure has windows & doors you will get good at leveling it out just to keep those operating properly in the future. Good news is you did not waste money on a halfway measure, say a 4' deep foundation that the frost would have picked up & threw around as well.

 

[bogydave]

This year was colder than the "norm".
I'm noticing frost heaves in many of the roads that haven't been there before. In the 90s, many fire hydrants in Anchorage froze (12' deep) & broke, several flooded icy streets.
Anytime I put sonotubes for decks, corner pier blocks for the wood shed, even the green house gravel base, I dig down to good gravel & compact & back fill with gravel for drainage.
Big circle of 2" blue board 6" below the soil level around the sonotubes.
Going down to gravel, blue board insulation & using rain gutters to keep the water away helps prevent frost heaves.

 

[nate379]

Yeah I have gutters on it as well. It's just bugging me that it did it this year and not last year. I sure hope it settles back down because I'm not sure I can easily jack it up. Lot of blood sweet and a few smashed fingers went into it. I don't know how the heck they can frame up a whole house in just 2-3 days cause it took me about 5 months of weekends and before/after work here and there to build it.

 

[ironpony]

very nice job, well done
but without a proper foundation it is going to move
when I placed mine it moved around the first couple years
just shimmed it here and there to keep the doors working
and then I decided where it was going to stay
put in a foundation and placed the building on it
level ever since

 

[smoke show]

How would you build it? It's not on topsoil, that is gravel in the pic. 1" minus road base.

I would never build a structure that big on topsoil.

But thats just me.

If I lived in the south I would have dug to frost line, but here that is 12ft.

Usually remove the topsoil untill we reach clay or whatever lies beneath.

But we're a fry car from AK.

 

[Jack Straw]

Great job!

When I build a small shed I put 4 blocks down, 1 for each corner. If I have to adjust it in the future it's no big deal. I don't know if you could do that with a garage that gig.

 

[bogydave]

Great job! Like the trusses.
I see yo insulated & have a gas line to the shed. What temp do you keep it at?
If it goes back to level, you should be OK, not sheet rock to crack. It gives enough to be able to withstand some movement & not damage anything.
As long as the gas line & the electrical have a flex connection, I would worry about it.
Well built & should last many years. It's handled some tough wind storms, that proves it's well made.
That one cottonwood that's close, would be fire wood soon, much taller & the tops like to break. Maybe it' not on the wind side, but the mess they make was enough that I got rid of all of mine

Nice looking shed, Can't wait to see the future wood shed

 

[nate379]

That's an air line that goes to the garage, I put a 60 gal compressor in the shed. I insulated it cause insulation is fairly cheap and it was easy to do while I was at it before I put up shelving and moved everything in. Figured may as well vs wish I had.

I should have cut that cottonwood before I built the shed but it's on my neighbors land and at the time we were not getting along. I'm not comfortable enough with my felling skills to drop it and not hit the shed so will have to pay for someone to do it.

 

[nate379]

I noticed yesterday that my 2 conduits on the left side (grey pipes) are came unglued and the pipe pulled away from the LB. There's enough slack in the wire and the air line that it didn't damage anything.

This tells me though that the left side lifted up some and it's not the right side that sank... a little bit better deal. I have a sinkhole in the yard and I was a bit worried there was another one under the shed.

The sinkhole... the best I can figure is when the contractor cleared the lots they just dug a hole and stuffed all the junk into it. I might rent a roller this summer to sink it in and then fill it with topsoil... again.

 

[Swedishchef]

I never thought I would say this: I have shed envy Nate.

I plan on building a 16X20 shed myself. If you don't mind me asking, what was the total cost?

Very nice shed and glad t o hear it didn't shift too much.

ANdrew

 

[Dune]

How would you build it? It's not on topsoil, that is gravel in the pic. 1" minus road base.

I would never build a structure that big on topsoil.

But thats just me.

If I lived in the south I would have dug to frost line, but here that is 12ft.

Google "alaskan floating slab"

 

[nate379]

Where I live there they don't allow any buildings on the property beyond house, garage and a "shed". A shed being a "temp" building. That is the reason I built it with a wood floor with skids.

I may have been able to have that waived but I didn't want to end up asking too many questions and then being told NO at all to my shed. I think the intent of allowing a shed is more a small unit to store a few mowers, not a "2nd garage".

I could have poured a slab and then set the shed on that but that would have added another $1200 or so to the cost of the build.

The thing with a slab is that if there is no heat put into it, the frost will still get under it the same as my gravel pad.

Swedishchef it was around $10k all said and done. It could be built for less in the lower 48, building materials are more expensive up here.

 

[greg13]

At the very least I would have sunk below the frostline piers to support it, not a lot more money.

 

[nate379]

Yes, quite a bit of money. I had looked into it and it was going to be about $300 per pier. If I had done 12 of them (3 per skid) that would have been about $3600.

 

[greg13]

$300 per pier??? What are you buying gold plated? A treated 6x6 should work fine or go the extra and pour concrete with a sonotube. 4' deep hole x 12" dia. would be plenty. I know prices are higher up there, but here it should be less than $100/hole. My concern would be with no below the frost line support it may get twisted up in cold weather, I see it all the time with Mobile Homes.

 

[nate379]

That was the price for using drill stem pipe knocked in the ground with a truck mounted hammer It's was $25/ft labor/materials. Frost depth is 12ft.

 

[greg13]

OK, I hang my head in shame, I forgot about the fact that your frost line is a WHOLE LOT deeper than ours.