Concrete for small shed

[legodude]

Hi All,
I'm thinking of adding a small shed in the backyard to store tools, air compressor, bikes, etc. Approx 50-60sq ft. I'm looking to hire someone off craigslist to do a concrete slab for the base, and am looking for some guidance from the group. How thick should such a slab be? Rebar? Does it need a footer?

I don't need something that will last 100 yrs, but I would like it to not be a total mess after one winter.

I'm in southeast Michigan.

thanks
mike

 

[Chaz]

I'd just frame a 3 1/2 inch slab on top of the ground to keep the shed from touching the dirt. The ground will freeze under it, but it wont move much, if at all. That's only about a 6x8 slab.... pretty small

 

[hh76]

Won't need any footing, just slab on grade. 3 1/2" is fine, and I'd use wire mesh or rebar. Clear off the turf, and a couple inches of top soil, form it up, get a load of gravel, compact that and pour.

 

[elav]

See if you can find a place that rents trailers with pre-mix concrete. The smallest they typically sell is 1 cubic yard. 1 cubic yard will get you 60 sq ft at 4" with a little to spare. As mentioned above use wire mesh and have a base of crushed agg.

 

[Sureshot]

We did small stuff like that on the farm when I was a kid and went right over the grass and it lasted 30+ years already. As was suggested frame it with 2x4's and peg it in place. The pegs will keep it from moving and the 2x4's from bowing out. Be sure to put the pegs below the top of the frame so you can screed(level) the concrete. Trowel smooth. Very easy DIY project. I am sure youtube has many vids.

Here is a basic one.

 

[rancherbill]

Put s piece of plastic on the ground before the concrete, it will stop ground moisture from wicking through the concrete. It will reduce rust on your storage items.

 

[theoldwizard1]

If you find some decent paving brick/patio stone, you could just use them, if you remove the turf and compact and level with at least 2" of gravel. I would use pressure treated 2x4 staked into the ground around the perimeter to keep them from moving.

Do NOT use those crappy 1", mostly gravel, 6x12 (?), patio stone. If you look sideways at them they crack/crumble.

 

[Ron Fletcher]

Or you can do something similar to what I did. I added 3' onto an already 5x10 foot slab to make it 8x10. I just made small forms about 2'x3' out of 2x6s and nailed them to the existing slab. It took about 1 1/2 -2 bags to fill each one of the five holes. I did one or two each day because I only had a small wheelbarrow........So, if you are going to do a slab that is about 7x7, just divide it into quarters with your 2x6s. Then just do a little each day. When one quarter is done, wait a day or two and then do the next one. Leave the 2x6s when you are done. It won't hurt a thing. Mine have been there for years and it never bothered them.

 

[Ron Fletcher]

And by the way, welcome to the board.

 

[zorty]

Another first timer in SE Michigan looking to expand on this question, hopefully without hijacking the thread. I'm looking to expand an existing single car garage outward about 4 feet for workshop space similar to what it sounds like Ron Fletcher did. Existing size is about 8.5' by 18', and the extra slab I'd be needing would be about 4' by 18' (roughly about a yard of concrete being added if my math is right). Am I safe following the same thickness, wire mesh, etc. advice for legodude? Is this a size that's small enough to do myself like SureShot and hh76 suggested, or should I farm it out?

 

[boiler7904]

What does the City of AA have to say about concrete foundations for a shed? Most towns allow sheds up to 100 sf to be built without a permit as long as they don't have a concrete foundation - they're considered temporary structures. Concrete foundation or larger than 100 sf puts you into permanent structure territory which means a permit and inspections. Either way, make sure you know where your lot lines, setbacks, and easements are before you start construction so you don't run into problems later on.

Personally, for 50 or 60 sf I'd build a pressure treated wood platform on either pressure treated wood skids or concrete pier blocks. Cheaper and faster to build shouldn't be a long term durability issue. It isn't like you're parking a car or heavy garden tractor in something that small.

 

[Vettman]

I built this shed in 1996. Local concrete guy poured and finished the pad (8' X 12') and set the bolts. He charged me $200.00. It was poured on level compacted soil, framed with 2X6's. The dimensions were such that the siding came out even for 96 sq. ft. It cost a total of $800.00, but I used scrap sheathing from nearby home construction, and I had the door. Some of the material the carpenters were throwing away was better than what I could buy. If they didn't want to pull nails, they discarded the scrap in a dumpster.

 

[ddawg16]

What does the City of AA have to say about concrete foundations for a shed? Most towns allow sheds up to 100 sf to be built without a permit as long as they don't have a concrete foundation - they're considered temporary structures. Concrete foundation or larger than 100 sf puts you into permanent structure territory which means a permit and inspections. Either way, make sure you know where your lot lines, setbacks, and easements are before you start construction so you don't run into problems later on.

Personally, for 50 or 60 sf I'd build a pressure treated wood platform on either pressure treated wood skids or concrete pier blocks. Cheaper and faster to build shouldn't be a long term durability issue. It isn't like you're parking a car or heavy garden tractor in something that small.

VERY important point.

Some other comments....if you do use concrete...yes to doing it above grade...it will keep water out.

12x12 pavers would also work well on a good compacted base of sand and gravel...make sure you put down 6mil plastic to keep moisture away.

So....do your homework with the city and see what they say about the pad. I'm willing to bet that it would require a permit. If so, then just do the PT floor on top of pavers or just a border of cinder block.

 

[Sureshot]

Another first timer in SE Michigan looking to expand on this question, hopefully without hijacking the thread. I'm looking to expand an existing single car garage outward about 4 feet for workshop space similar to what it sounds like Ron Fletcher did. Existing size is about 8.5' by 18', and the extra slab I'd be needing would be about 4' by 18' (roughly about a yard of concrete being added if my math is right). Am I safe following the same thickness, wire mesh, etc. advice for legodude? Is this a size that's small enough to do myself like SureShot and hh76 suggested, or should I farm it out?

This is a whole other scenario. Start a thread with pics etc. And no I doubt you can get away with cheating so much. You will likely want the slabs tied together and ??????????????

Welcome to GJ

 

[legodude]

Thanks for the helpful comments everyone.

I already have an email in to the AA city office to figure out the permitting requirements.

One possibility that was brought up would apply to me too: I could position the slab such that it ties into my garage slab and then just have to build 3 walls for the shed/garage extension.

If I tie into the existing garage slab, would I do something like drill some holes for rebar to connect them?

I tend to feel that a lot of this will depend on what the city says.

But I can already start to get a better idea of pricing from the contractors, so thanks.

*mike

 

[BFBOB]

One thing about cities - they do have rules. One I came across allowed a 100 sq' slab plus shed with no permit. Had planned a 10x12, but it was worth the hassle reduction to make it 10x10. There are also probably setback requirements. Min. of 10' from property line or any other building in this case. That would preclude butting it up to the garage. If you wanted to do that, it would probably be reclassified as a garage addition with all that entails.
In my case, it didn't need to be particularly weathertight, just roofed, so I built it inside the corner of a 6' board privacy fence, matching the color and pitch of the roof of the house and matching the siding of the shed to the fence boards. I started with just a gravel floor - fortunately, as it turned out. City came in with its setbacks and the shed had to be moved to the nearest level spot which was far enough downhill the only option for the floor was concrete.
You wouldn't believe how heavy a 12x12 shingled roof structure is, but I moved it the 30' single handed with no power equipment.
So, yes, check with your city before building!

 

[Sureshot]

Thanks for the helpful comments everyone.

I already have an email in to the AA city office to figure out the permitting requirements.

One possibility that was brought up would apply to me too: I could position the slab such that it ties into my garage slab and then just have to build 3 walls for the shed/garage extension.

If I tie into the existing garage slab, would I do something like drill some holes for rebar to connect them?

I tend to feel that a lot of this will depend on what the city says.

But I can already start to get a better idea of pricing from the contractors, so thanks.

*mike

If your intent is to simplify or reduce cost by tieing into your garage I would forget it. Much easier and faster to build an independent structure. Likely many less code issues etc.

I have a small shed I keep fuel pails and propane tanks in. Some stuff is best left away from the "real" garage.

 

[38Chevy454]

Make your new shed 10 x 10, or whatever the city limit is. Just like we say about a detached shop, you will fill it up! Start at the biggest they allow.

 

[bczygan]

Here's what you do for any shed, step by step.
Find out who has jurisdiction for your location for zoning.
Look on their website for a zoning map and determine the zoning for your particular lot.
Look on their website for the zoning rules for your particular zoning. Especially read everything concerning accessory buildings. You may only be allowed one, and if you have a detached garage, no shed would be allowed. It will also tell you height, maximum size, maximum lot coverage for all buildings or hard surfaces, percent of rear yard coverage allowed, where height is measured to, setbacks etc.
These rules will tell you everything about what you can build. Size, location, setbacks etc.
If you build something that doesn't need permits, it still needs to be sized and located as required by zoning, and also must be built to meet the building code, even though it won't be inspected.
If you need to build something that requires permits, then you need to talk to the building department.
Check your plot plan and legal description or mortgage survey for any easements.
Call Miss Dig to mark any underground utilities.

Addressing your concrete questions. Surface prep is critical. Remove all organic matter (Grass and topsoil) and provide a pad of compacted material to slightly above surrounding grade. Make sure surrounding grade slopes away from the shed for positive drainage. I did and 8'x12' shed with a 4" slab. Had to wheelbarrow 40' from the truck. It was more than I could place and finish. Ended up with a bit of a cold joint in the middle. Would recommend help for anything over 50 or 60 SF. That is for delivered material. For hand mixing, I wouldn't do over 10 SF. Always use mesh. Cheap insurance. Use a concrete slab where you can. A much better base and easier to access with wheeled items. Use a plastic barrier under the concrete. 4 mil Visqueen minimum. Set J type anchor bolts in the slab to anchor the walls to.

 

[fiaroadster]

My son lives in A2 as well and wants to do exactly what you propose (small shed/concrete floor). Please post what you find out.
thxs

 

[01ssreda4]

I've seen 6 mil plastic left outside. The quality and weather resistance is for ****. I put it under a bay slab of 12x24 and feel like an idiot for doing it. It won't last under those conditions.