Shed slab - will this work?

Greetings,

I am currently digging for my shed slab. 10x12, in Minnesota. In all the reading I've done (both online and in books), I come across a lot of conflicting information. Here's what I plan to do, and I'd appreciate if any of you experts could weigh in on it:

I have made the forms, squared them, and staked them out. I dug a 8" deep trench for a one foot wide footer around the entire slab. This leaves 2" for gravel/sand and 6" for the slab footing. The inside is dug to 6" deep for 2" gravel and 4" slab. I plan to put rebar in the footers.

Is this deep enough? I will have to worry about frost, etc., but it's just a shed and I don't want to go overkill on it. Should I put gravel/sand in the footer trench? I've seen people recommend only putting it in the 4" floor area. Will class 5 suffice for this base? Finally, for the base material, do I need to rent a jumping jack or vibrating plate compactor or is this not necessary?

Again, I've got the site dug, but before I order the mix I want to make sure it's adequate...

Thanks in advance!
Pat

 

Pat -

Since you are building a shed with a floating slab, you do not have to worry about the frost depth. Since you are not over the magical 120 sf, you probably are not under any code requirements, but there might be local requirements.

Can you imagine going down 4 or 5 feet for a shed?

Personally, I would put a few inches (2"-4") of the Class 5 base material in both the footing and slab areas since, you will have to get something delivered anyway. Your delivery will cost as much as the material. Rent a plate compactor to compact everything.

I just had an exposed aggregate pation put in and the contractor does not use anything but the Class 5 base material since it is better and easier to work with.

The rebar around the perimeter is good. Put some 6x6 mesh in the slab area and over the "footing" area to get extra flexural strength and eliminate cracks. Fiber mesh will not be as effective for this. If getting a small amount of mesh is difficult, use some small rebar 12" on center.

Pour all the concrete at once and do not forget the anchor bolts. Make sure it is very square. Keep the slab high enough above grade to keep things high and dry. It is better to be too high than too low (less digging also).

Good luck!!

Dick

 

Hi Dick,

I appreciate the reply! Your advice sounds good, and I've already talked with the city about permits. I was actually going to go bigger and get a permit, but then setbacks would have applied (unless I got variances from neighbors... lot of work involved) and I really wanted to tuck this away in a corner of my yard, so I went with the max size w/o permit. It's right up against my property line, and nicely hidden with some nearby pines.

I'll try to get some mesh for the middle of the slab, and plan to put it near the center of the 4" depth (i.e., 2" down from surface)?

I'll have an experienced friend helping me with the pour, as well as many extra hands for wheelbarrowing from the truck to the forms, but I have one more question about the details:

When inserting the J-bolts, isn't there a void created where the "hook" part of the bolt goes into the concrete? If so, do I just fill with a bit of mix and trowel smooth? I've never done any foundation type concrete work, but have done many small jobs. I plan to make a checklist to use during the pour so as to not forget any key things... like the bolts... - I think organization will be key during this.

Thanks again for the help, I appreciate pros like you taking the time to help those of us without that amout of experience.

Regards,
Pat

 

Pat -

The mesh is best in the bottom half of the concrete. Just keep it off the ground. You will have to pull it up once in a while, but the exact location is not critiacal.

Just fill around the bolt when you finish.

My son went through the same 120 sf barrier as you. He went with a 10 x 12 also, but had 10' walls for extra space up high. Since he tucked in a corner behind the garage and next to the house the height kind of fits in since he had the same siding, roof slope and shingles as the house.

Dick

 

Just jiggle the anchor bolts, and the hole should fill. Also remember that if you dig too enthusiastically, it is better to back fill with the base, not dirt. Undisturbed soil should be at the bottom, always.