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!

 

Have you thought about putting down some type of pavers?

 

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.

 

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.

 

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?

 

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.