concrete slab for shed height problem


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Old 09-18-13, 04:55 PM
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concrete slab for shed height problem

I have recently rebuilt the front deck on my house. The Deck was built in a manner where it is entirely waterproof so the space underneath could be used as a usable work area for me.

I have fully enclosed the area under the deck into a glorified work area and storage shed. There is no major weight being placed in there mostly just foot traffic and maybe a snowblower.

The base of the enclosure was done using green board. The "shed" floor is currently filled with several inches pea gravel. The pea gravel is a horrible surface. Screws, tools, and other items constantly disappear in it. Not to mention keeping my work bench level is near impossible.

I would like to pour concrete in there using the green board framing as the basis for my forms. The problem is that currently the shed ceiling height is a bit higher than 6'8". So I would like to pour the smallest depth of concrete possible so I can continue to comfortable use the shed.

What is the shortest depth I can do that will hold?
What can I do to minimize cracking and such?
Is there a specific kind of concrete that does better with a smaller depth?

The other question is that I do currently have several inches of pea gravel already there, do I need that much? Could I pull it out and replace it with just a bit of sand?

I do live in an area that has long winters although the temperatures don't often get below 0.

thanks!
 
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Old 09-18-13, 07:26 PM
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Have you thought about putting down some type of pavers?
 
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Old 09-18-13, 09:09 PM
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Pea stone will not compact so it would need to go.
4" of concrete in my option would be the minimum I would trust to not crack.
I'd make some local calls to concrete finisher if you want a nice flat crack free floor.
I'd also add a vapor barrier to keep the moisture from coming up through the floor.
 
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Old 09-19-13, 08:44 AM
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Any thickness of concrete will crack if certain precautions aren't taken.

For a lightly-loaded workshop area, I wouldn't be afraid to go with just 3" of concrete, placed on at least 1" of well-compacted gravel (with rock and fines in it). Get rid of all of the pea gravel, and use a good, dense concrete mix. If you're batching with a pre-bagged product, you might try Quikrete 5000--easy to work with, and good strength. Make sure to install adequate control joints, such that you determine where the cracks (if any show up) will occur.
 
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Old 09-19-13, 09:54 AM
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Thanks for the replies. 3" might work. Any bigger and my head room becomes an issue.

I am assuming I should use wire mesh?

Would it help to use this fiber reinforced concrete as well?
 
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Old 09-19-13, 01:04 PM
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I've not had positive experiences using fibers as concrete reinforcement, so that's your call. Wire mesh would help if/when the slab is subject to settling and heaving, keeping the separated pieces tied together. Placement of same in a thin slab is very critical--too close to the surface and it can protrude, and be hard to push back down (without going too far down); laying on the gravel base, it won't do any good.
 
 

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