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Floating Base for Shed Q's

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  • May 22nd, 2019 6:40 pm
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Floating Base for Shed Q's

I will be building a wooden base for a lifetime shed for the the first time and I just have some questions.

The Plan: 12x8 base made out of 2x6 PT boards on 16" centers, with PT T&G groove plywood, resting on deck blocks. Plan was to dig out for each deck block 3-4" each and put crushed gravel underneath.

1) How many deck blocks for the 12' perimeter spans? (I was going with 4 each, 2 in the corners & 2 in the middle)
2) How many decks blocks for the 8' runs? Does each one need 1 in the middle? (total count for the base would be 19 with this arrangement)
3) Should I install blocking in a zig-zag pattern in the middle between the 8' joists?
4) Can deck blocks be partially buried to minimize the height of the base? I would like the 2x6 to be as close to the ground as possible without touching.
5) Nails only or joist hangers?

Thanks
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Dec 10, 2008
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8 blocks total. One in each corner, one in the middle of each 12' span, two in the middle (4ft span)

Install some blocking down the center

Use 5/4x6 instead of PT ply
Let's hug it out
Deal Addict
Jan 19, 2011
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6 blocks total, three on each 12' span (end, middle, end)

Joist hangers for the 8' joists, and blocking (edited) down the middle.

Anything more is overkill.
Last edited by fieldhousehandyman on May 20th, 2019 2:10 pm, edited 1 time in total.
"The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is."
Just a guy who dabbles in lots of stuff learning along the way. I do have opinions, and readily share them!
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fieldhousehandyman wrote: 6 blocks total, three on each 12' span (end, middle, end)

Joist hangers for the 8' joists, and block them down the middle.

Anything more is overkill.
You're still going to want a block or two in the centre.

At $10 a pop, it's cheap insurance.
Let's hug it out
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Dec 18, 2017
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London, On
fieldhousehandyman wrote: 6 blocks total, three on each 12' span (end, middle, end)

Joist hangers for the 8' joists, and block them down the middle.

Anything more is overkill.
I would go this route with 2x8 lumber, but since he is going 2x6, I would want a bit more support in the 8' spans, if even just a patio stone under each joist in the middle.
Deal Fanatic
Jan 25, 2007
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Paris
The idiot that did mine did 2x6 rim joists then this complicated 2x4 arrangement underneath then covered with fence board. I reinforced the front only and it’s stood now for 19 years.

The 2x4s are joists, then he ran 2x4s underneath the joists perpendicular every 4 feet. I think I have 5 deck blocks (corners and one in middle). Platform is 10x10.

Edit: I guess my point is that it’s hard to screw this up. Unlike a deck, won’t have much for live load and probably won’t have a tonne of snow sit on it in southern Ontario either.
[OP]
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Jerico wrote: The idiot that did mine did 2x6 rim joists then this complicated 2x4 arrangement underneath then covered with fence board. I reinforced the front only and it’s stood now for 19 years.

The 2x4s are joists, then he ran 2x4s underneath the joists perpendicular every 4 feet. I think I have 5 deck blocks (corners and one in middle). Platform is 10x10.

Edit: I guess my point is that it’s hard to screw this up. Unlike a deck, won’t have much for live load and probably won’t have a tonne of snow sit on it in southern Ontario either.
Totally agree, I could probably do whatever it would be fine but when doing a project for the first time I'd rather find out what the right/best way is. It's more for a learning experience then anything.
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And as RCGA and djeffery added, somewhat overkill is not a bad idea at all.

two or three blocks centered along the middle of the second, middle, and second last 8 foot lengths, provided they are all blocked, would be about the perfect amount of overkill.

6 blocks absolute minimum, 9 blocks ideal maximum, and definitely blocking between joists and joist hangers.

the one advantage to using fewer blocks is less hassle leveling them all.
"The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is."
Just a guy who dabbles in lots of stuff learning along the way. I do have opinions, and readily share them!
[OP]
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True good point about less hassle. Does anyone have any input about burying them partially and how close to the ground can / should the 2x6s be?
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I don't see a problem with putting the wood right down in the ground if you want to bring the floor as close to level as possible. The shed will probably be garbage before the wood rots (or you move by then).
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Jan 19, 2011
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You can bury them, and as long as there is daylight between all your joists and the ground, you are fine. I would keep approximately one inch minimum.
"The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is."
Just a guy who dabbles in lots of stuff learning along the way. I do have opinions, and readily share them!
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Jan 25, 2007
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adblink182 wrote: True good point about less hassle. Does anyone have any input about burying them partially and how close to the ground can / should the 2x6s be?
I’d keep it at least 1” off. The end cuts of wood absorb moisture like nobodies business.

My lower deck was done using blocks. I did beams but half the beam is 2x10 and the other half either 2x6 or 2x8 (I forget honestly) so it would set inside the block and no need for 4x4s. It’s 10x16 and 3 beams (along the 10 foot direction) 3 blocks each.
[OP]
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RCGA wrote: 8 blocks total. One in each corner, one in the middle of each 12' span, two in the middle (4ft span)

Install some blocking down the center

Use 5/4x6 instead of PT ply
Just curious why deck boards instead of ply?
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adblink182 wrote: Just curious why deck boards instead of ply?
If the shed has a plastic floor, it'll allow a bit more air circulation, and more importantly, prevent water from pooling between the floor and the boards. If it pools, there is only one way to dry, and that's downward. Even PT ply will rot if constantly wet.
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Be careful with that size of shed. Many municipalities have bylaws regarding square footage and need for a permit.
If you have dicks for neighbours, it can be costly. I've seen it happen in my town. The building department even went as far as asking for engineering specs for the 20 year old prefab shed. :facepalm:
[OP]
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Thankfully it's 108sq ft here, that's why I went with this one over the costco one, just that added space and still under the limit.

Makes sense about the deck boards, thanks
Newbie
Mar 28, 2008
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Toronto
I use only 2x6 with concrete block for every 4' for my deck (16x20) and it stay for 10 year without any problems. It did not move even a little. Just make sure that you dig a little and put gravel underneath of blocks to prevent heave. Also seal the cut if you use PT otherwise it will rot from those cut. I also did not let the wood touch the ground.

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