prefab shed foundation

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  #1  
Old 01-01-06, 04:54 PM
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prefab shed foundation

So I took the easy way out and bought a 10x14 shed that is being delivered Tuesday. The guys said that it can rest right on the ground without any foundation if I prefer - they will level it. But said even better would be buying about 20 1x1 pavers to use under the runners. The building has 5 pressure treated 4x4's running underneath. They said 20 pavers would allow 4 pavers per runner and provide more than adequate support. My questions are:

1- Does this sound like an adequate foundation? I know I see all sorts of buildings "on blocks" - just don't want to have any problems in the future.

2- Should I remove the grass where the building will sit? This would allow the building to bare directly on the soil rather than my somewhaty suishy St. Sug grass!

Thanks in advance!
 
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  #2  
Old 01-01-06, 06:32 PM
Join Date: Mar 2005
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prefab shed foundation

Anything would be better than setting your shed supports on soil or grass. What you use will depend on how much you wan to spend.

A concrete slab is the most expensive and time consuming to install.

Concrete slabs or pavers would be more economical. Remove the grass where you plant to put the concrete and spread some fine sand (1" deep or so) for leveling allow them to level the shed.

If you but 12"x12" pavers you be paying more than you would if you bought 4x8x16 solid block.

Dick
 
  #3  
Old 01-02-06, 03:41 AM
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Thanks for the reply. I thought about the solid block, but it gives less surface area - so I get more bearing area with the pavers (assuming the same number of each) than I do with the solid blocks. But, the blocks would give me a higher footing which may help if I only remove the grass where I'm putting them and not underneath the entire building. Hadn't really thought about the sand. May have to get some. I live in coastal NC and we have a really thick layer of topsoil that could compact over time.
 
  #4  
Old 01-02-06, 12:40 PM
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prefab shed foundation

You lay the 4x8x16 block on the face (8x16). Almost the same area area (which is really not that important) as the 12x12 pavers. This will give you 3 5/8" thick concrete. What is the thickness of the pavers?

Since they are 12 x 12, I would assume they are not the same stregth as a real interlocking paving stone (8000 psi).

Dick
 
  #5  
Old 01-02-06, 03:44 PM
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Hmmm...concrete strength. Haven't even thought about that. I'm sure you are right - certainly not 8000 psi for a paver - I'd be surprised if it was 3000 psi. I had no idea that a typical block was 8000 - I'm a civil engineer and about the highest strength we ever spec is 4000 - but this is typically for parking lots, sidewalks, etc.

What about the deck blocks? The pyramid shaped blocks that a 4x4 fits in the top of? I was even thinking that 9 of these may be enough. Put 3 blocks on the 1st, 3rd and 5th 4x4 row of the 5 rows of 4x4. That gives only a 7' span for the 4x4's. I would go ahead and get 15 total blocks and do 3 on each 4x4, but this seems like overkill and like it would be difficult to level. If you used the 4x8x12, would you still use the originally proposed 4 on each 4x4 for 20 total blocks?

Thanks for the opinions! I really appreciate it!
 
  #6  
Old 01-02-06, 04:47 PM
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prefab shed foundation

A true concrete paver (interlocking, various shapes, maximum dimension, 2 1/4" to 3 5/8" inches) has a minimum required compressive strength of 8000 psi according to ASTM standards. The units are tested on the flat.

A 12x12 paver could be almost any strength since they are usually more of a retail item.

Concrete block (hollow) has a minimum conpressive stregth of 1900 psi when tested vertically. the aspect ration reduces the actual concrete stregth to this indicated value. Actual strengths are usually 40% to 60% over minimum, because it is too difficult to make a low strength unit. Special strengths are made for loadbearing masonry buildings (no stee or columns) of over 20 stories using 6" hollow block walls with some grout and steel.

With your loads, concrete strength is immaterial. Just use what fits your purpose. The solid 4x8x16 is probably the most readily available at a low cost. - You don't need many block and you gas and car cost for getting the block may be more than the block.

Dick
 
  #7  
Old 01-03-06, 07:52 AM
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My preference would still be a 3" concrete slab, but like Concretemasonry said, it would be more expensive and take longer to install. But the upside is that it will last longer than the shed. And wood floors with little or no ventaltion under them don't last all that long.

Forget the Dek Blocks. The 4X8X16 will work just as well and cost about 1/5 of what the Dek Blocks would be.
 
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