12 x 16 Shed - Foundation Questions

[dave1949]

Its not the temperature but the water content that decides frost heave. Our driveway is wet gravel and will heave 6" above the lawn that is not plowed so has a lot less frost.
Been to Webster once and stayed in a very wet campground for one night. If there was any way to pour a floating slab that is the route I would take. Other than that a regular floor sitting on a pair of PT beams about 10 feet apart with a foot of overhang at each side.

I agree. The ground moisture content and exposure is the key to how much heave will take place. Our driveway does the same thing every year.

A layer of 2" foundation wall styrofoam insulation will stop frost penetration. If you dig out 12" of soil, lay the foam boards down with a 2' border extending outside the perimeter of the shed, then build back up with washed stones (no fines) to above grade level 4" to 6", I think it would stop heaving in a wet area.

I have a foam apron around the outside of our house. This year we had a 10" high heave in the driveway starting at the outside edge of the foam board. Very abrupt and distinct line between foam and no foam. Besides being plowed and getting maximum air exposure, our driveway has slopes that drain to it on one side.

 

[blucoondawg]

I tend to use the blocks under the corners plan and it's a pain because it's always sinking no matter how much of a pad I put under the block. Also in a 12 foot span my shed sags even with double 2x's spanning, I plan to convert to the runner method with 6x6 runners. I'll box blade off the top soil and lay a nice road base pad to place the shed on

 

[dmbtree82]

I built a 12x16 in NE Pennsylvania a year and a half ago. Mine is on three skids and each skid has 4 support points of block under it. The four corner ones are tubes with concrete and 4x4 posts. There is about 1.5' of elevation change from the front to back of my shed. Its been through two winters and seems fine. 2x4 walls and gambrel trusses 16" OC, 2x6 floor joists 16" OC, and a double layer of 3/4" PT plywood on the floor. I have an ATV, JD 1025r and a whole lot of other stuff in there as well.

 

[newbury]

I built a 12x16 in NE Pennsylvania a year and a half ago. Mine is on three skids and each skid has 4 support points of block under it. The four corner ones are tubes with concrete and 4x4 posts. There is about 1.5' of elevation change from the front to back of my shed. Its been through two winters and seems fine. 2x4 walls and gambrel trusses 16" OC, 2x6 floor joists 16" OC, and a double layer of 3/4" PT plywood on the floor. I have an ATV, JD 1025r and a whole lot of other stuff in there as well.

How big are your tubes?

I'm in Northern Virginia and building a 12x20 shed. I had been planning on using three 4x4 PT runners for the 20' dimension, supporting them at the ends and in the middle with 12" concrete tubes, and in between with paver type blocks on gravel pads, similar to:


This will let me drill 9 holes with my lightly used PHD

Is 12" overkill?

Also should I sink some rebar in the concrete?
I have not been able to find any guidelines for size of tube needed.

 

[check]

I love PT 6 x 6, so I would just throw three of them down lengthwise on top of a good gravel base. And just make sure that your 2 x 6 joists are well attached to the six by sixes, and I would space them a foot apart. (I never did like the 16 inch OC spacing, and you will only use an extra five by sixes to cover the 20 foot length if you space them 12 inches apart.). With 12" oc spacing, you also have more flexibility with respect to where you put your plywood joints.

A nice, easy project, with good dimensions. I build a 10 x 20 concrete pad to put my plastic shed on, and I wish I had made it 12 feet wide, because 10 ft. makes it real tight in there when I park my double Sea-Doo trailerfor the winter.

 

[Walt 2002]

Shed on skids here also escapes being taxed - so far.

Walt Conner

 

[dmbtree82]

I only used 8 inch tubes for mine, but you're going a good deal larger. It also depends on what you plan to put in there I would guess.

 

[mike69440]

Make a Gravel, hard pack trench footing, add perimeter drainage and lay large Patio Blocks for floor. Pack everything down well with a tamper.
Make some Blocks to space every 32" and double plate 2 x PT as the Plate with the block below the PT so to limit ground contact.

Frost wont hurt it a bit if done well.

Roof with overhang will help keep walls dry.

 

[mike69440]

Make a Gravel, hard pack trench footing, add perimeter drainage and lay large Patio Blocks for floor. Pack everything down well with a tamper.
Make some Blocks to space every 32" and double plate 2 x PT as the Plate with the block below the PT so to limit ground contact.

Frost wont hurt it a bit if done well.

Roof with overhang will help keep walls dry.