Shed skid placement for heavier loads?

[brass89]

Hi all. Planning on an 8x12 shed/workshop. The original plan was gravel under solid 8x16x4 blocks to support pressure treated 4x4 skids 12ft long. 2x6 pressure treated 16" o.c. with 3/4 pressure treated ply. I have a tool chest currently in storage that would be much more convenient if it could find a home in this shed. I'm not so confident that 2x6's spanning 4ft are sturdy enough. Some sheds use just 2 skids, some use 3 - has anyone ever used a 4th offset?

Typically if 4 skids were used (assuming the walls were directly over the outer skids not cantilevered), they'd be evenly spaced every 24" o.c. Would it be detrimental to have them 'unevenly' spaced, such as one skid either end, one in the center, and a 4th between one side and center skid to cut that 2x6 span down to 24"?

Even if I did this, would it support a tool chest? (roughly 20" deep, 32" wide, around 60" tall - typical mac mechanics tool chest). The rest of the shed would be just general storage, shelving, an 8ft workbench / assembly table down the other side. This wouldn't be right away, if/when I moved the tool chest into the shed I'd see about adding another piece of ply underneath or solid boards under the casters - not just relying on the single 3/4 sheeting. But I can't do that if there isn't enough foundation support in place to begin with and now would be the time to put it in. No clue how much it weighs loaded, if I had to guess I'd say a good 300lbs empty. Obviously a solid concrete floor would be best but it's not an option right now. Any suggestions? Thanks.

Here is an example of what I'm referring to trying -

 

[bad_idea]

I just built an 8x16 this summer on skids. (4) 4x4x16' skids spaced evenly resting on cinder blocks. I used 2x4s 12" OC for the floor joist because they only span 2' or so. This is my second shed, I learned w/ the first one to put something under heavier items. I have a couple shelving units in there that started to punch holes in the 3/4" plywood floor. Too much load concentrated in such a small area.

I would space the skids evenly and then use 2x4s layed on their side on the floor, under the toolchest wheels.

 

[brass89]

Hi bad_idea, thanks for the reply. I wasn't sure about the uneven skid placement idea I had, might be ok for stationary but if I ever did have to move it I think it'd cause all kinds of issues with uneven drag etc. I'm surprised your shelving did that, although it probably depends on the weight stored on it. Something to think about when I build.

If I use 3 skids evenly spaced, I'll have a skid right up the middle to support underneath solid blocking giving something to screw the plywood sheets to along the seam where they meet. If using 4 skids, would unsupported solid blocking work for a seam right up the middle of the floor? (since there will no longer be a 12ft skid centered under the middle of the floor) - or would I then need to cut/adjust my plywood sheets to match the skids? (1/2 sheet along either side of a centered full sheet, as opposed to 2 sheets side by side) Thanks

 

[bad_idea]

The 4x4 skids support the floor joists, the floor joists support the plywood. The plywood will be nailed to the floor joists, so the skid placement should have no impact on plywood spacing. Off center skids shouldn't affect dragging the shed around too much. The shelving unit had around 700 lbs on it. Check out these video series, I found them useful in building my shed. I am not a carpenter, but mine turned out good.

 

[brass89]

Hi bad_idea, thanks again for the reply. I know what you're saying about the plywood being screwed to the joists. My only concern was where two sheets meet. I've tried to diagram what I'm talking about - thinking I should use blocking to provide a nailing surface along the seam where 2 sheets **** together (since it's an edge). Original blocking was planned in plain brown (resting on 4x4, blocking between each 2x6 joist) - but maybe the blocking in red should be added as well? Normally this wouldn't be an issue with something like T&G, but unfortunately I can't find any pressure treated T&G. Maybe it doesn't exist? There's stuff like plytanium or whatever tongue and groove subflooring, there's T&G osb subfloor. But as soon as I move to pressure treated that's no longer an option from either h.d. or lowes - at least in my area anyway.

I know a lot of people opt for T&G that's rated as exposure 1, but as I understand that's only for temporary exposure to elements (ie will survive a couple of rains during the build). In my particular area, humidity can be a beast. This last summer, most days were 60% humidity and higher, and during winter I'm sure some snow will get tracked in. In any case, there's no interlocking between the sheets where they join so I'm thinking they'll need screwed down well along where the edges meet in the middle. (I'm opting for pressure treated 4x4x12 skids, pt 2x6 joists, pt 3/4 ply and pt 2x4's for the sills of the wall framing at the floor.) Thanks for all your input.