shed foundation problem

[ctwatertrapper]

I'm in the beginning stages of contstructing a 12x16 shed. I had a plan to do 9 12'' sona tubes but the digging is getting pretty tough. Fortunately I got the four corners down below the frostline line (42''), but so far atleast 2 of the piers (outside middle) are right on some very big boulders. The location is on top of knoll and mostly sands and gravel so its well drained.

any alternatives you guys have done in a situation like this? its just going to be a storage shed for tools and equipment so nothing heavy going in there.

thanks!

[nytrapper23]

Can you just pour a floating pad? Here in ny we also have to go 42" if you are using poles. But we can also use the floating pad system,usually our inspectors will give you what thickness you need. I did one years ago , we had to do an 8" pad and had to haunch out the outsides to 12" . Then we just framed up the walls and built off the pad. I can't remember the exact size but it was a two car garage . I go by it everyday and it's still standing.

[ctwatertrapper]

theres ~2.5' elevation difference and its a very tough spot to get a machine into. rather not mess with a concrete pad... thinking about doubling up 2x12's for the frame on 6x6 posts and only using the four piers. In my town anything less than 200 square feet doesnt require a permit so i'm not worried about doing it to code but I do want a sturdy floor.

[nytrapper23]

Yes that would be a problem. Good luck. I'm sure you will come up with a solution .

[Tim bly]

Why not put the shead on green treated 6x6 posts like skids just level the ground under the skids and build the shead on top of the skids

[Admin]

For structures I say two things. Either go below the frostline or don't go in the ground at all. I have plenty of structures that sit on the surface of the ground and have no issues. Since this is just a shed, I would have just stayed above ground with it. However, since you already have some piers in, you are committed to continue with that process. If these "boulders" are big, you could rest the building on them. Doubling up the perimeter joist and only having corner post on a 12x16 shed will not workout for you. For a 12x16 structure you should have a center post on the load bearing walls. Even with a center post I would (at least) double up the perimeter joist that carry the weight. (This is the side of the building that the butt ends of the floor joist nail into and the rafter tails are on) When these sag, everything sags and becomes very noticeable. For a structure on piers I usually triple or quadruple the outside box on the load bear sides.

If you can't build directly on top of the boulder, can you step back a few feet and place the pier under the structure? If so. Place the pier there and cantilever the girder out past the pier. Doing this may allow you miss the boulder that is in the way. 

Also, 8" piers will be sufficient.


                          

[rick2]

Wish I could help but my father knew nothing about building and he passed that on too me.I made a bird house once.I ended up throwing it away.Beacuse the birds didnt like it.Now my wife is worried beacuse I got the saw out.I am going too make some cubby boxes.Who knows wat will happen:)

[ctwatertrapper]

thanks for the advice everyone. I took a step back and reevaluated my situation. I looked at all the projects i have going on (two sheds going up, milling, tree cutting, stump removing, gardens) and figured its time to call in some support from a friend with a backhoe. Cut down some more firewood and got us access to the locations. I think this will save me a lot of time and frustration...

man, wish I thought about this before I dug those four sonotubes holes down 42'' ...