12 x 16 Shed - Foundation Questions

[Egon]

Lay down some sidewalk blocks and build on those. Use Tapcon's to fasten plate.

Use the sidewalk blocks for the floor.

 

[J_J]

We just had built a 12 x 16 Gambrel shed with loft.

16 blocks laid out equally.

4 4 x 4 runners

2 x 6 joist 12 ft

2 x 6 16 ft sides

3/4 pt plywood.

Rest of the shed is standard.

Looks something like this.

 

[JPRambo]

I built similar a couple of years ago. I built floor in two sections. then I built wall sections and trusses all in Florida and transported to N. Georgia and assembled on a weekend with 3 helpers.

 

[Looking4new]

You are in Webster, NY right in the lake effect snow belt off Lake Ontario, I would do the roof on 16" centers, 1/2" plywood over them and skip shingles and go with steel.

 

[s219]

The size of the joists ultimately depends on what type of loads you want to support. You should also consider what type of decking is to be used and what spacings it supports (most structural T&G plywood decking assumes 12" or 16" spacing). When I had a summer job building pre-fab sheds in a factory, we used 2x6 12" on center with 3/4" T&G plywood for most of the shed floors, and would double up the plywood for the extra heavy duty versions. With 2x6 on 12" and two layers of 3/4" T&G, the sheds were rated to hold cars (and did that just fine). Economy sheds had a 2x4 floor and were fine for typical residential use (riding mowers, etc). All sheds had main skids running crosswise under the joists, and blocks were placed every 3-4' under the skids. With that arrangement, the joists weren't carrying much span anywhere, which is how 2x4 were sufficient in the economy sheds. Bottom line, the loads you want to carry will determine what joists are needed, what spacings, what blocking, etc. So what do you plan to store in the shed?

For blocks, you probably don't need to get fancy -- those deck supports you show are overpriced in my opinion. We used regular concrete blocks in 4", 6", and 8" sizes (whatever it took to accommodate uneven ground, with minimum of 4" block at the "high end" of the grade. Micro adjustments were made via shims to get the floors perfectly flat and level, and shims could be used at any time in the future to make adjustments if something settled. It's actually pretty easy to jack up a shed and adjust blocks, even those in the center. Wouldn't bother me at all, so I wouldn't feel obligated to span the joists edge to edge -- I'd much rather have support in the middle. When I built the shed at my last house, it had skids on the outside (actually, about 8" inset from the walls, so that they were hidden from view and blocks were not sticking out) and a skid in the center.

** Edit to add that the shed/blocking described by JJ and JPRambo is very much inline with what we used to do, so that is a good reference and photo to go by. Those sheds should have a very good floor load capacity. Notice how the edge runners are inset just a little bit to hide them and get the blocks out of the way.

 

[sld]

To get around codes here they are just built on 4x4 runners. I have one on a gravel base that hasn't moved in 10 years.

This is probably the easiest way to do it.

 

[Will_C]

I have a 12x24 garage that is on 4x4" runners- 4 of them. It sits on a foot thick pad of gravel. After 2 winters it has not moved at all- the overhead door, man door, and windows all work freely.

Will

 

[PILOON]

Couple of bags of pea gravel in the 4 corners to get level, 24" X 24" patio (flagstone) paver topped with the post bases you showed in earlier post.
That spreads the load nicely.

On 12 x 16 the 4 corners should suffice but if you anticipate heavy shed loading then go to six.
2 x 6 joists at 16" should be good, that or 2 x 8"s at 24".
If you plan on storing a tractor then go 2 X 8 @ 16".

I would lay a 6 mill poly underneath to minimize condensation.
Treated wood would also be advantageous to longevity.

 

[buckeyefarmer]

Most sheds are made to be placed above the ground and float on the ground, once you put in any kind of footings, it becomes a permanent structure. some people will level a gravel under the shed.
For mine I just placed blocks on the ground, so the tops were level with each other, and used PT 4x4's as runners across the blocks, then I built the shed on top. Has held up well in 17 yrs.

 

[Garandman]

Here is what I would do and it's just my opinion. You need to think carefully about what your actual soil conditions are, but frost heave is overrated.

I would make this a floating shed.

That's what they usually do around here.