Advice for foundation for a large shed

[Lhorn]

I've decided to put up a large shed/garage type structure to store an extra car out of the elements and give me a little more storage for supplies etc. It's one that is available through Costco (only one big enough to store a car) and is basically a plastic type material with a metal frame. I'm comfortable that it will suit my needs (I decided not to add on another garage stall because of cost and other reasons.)

It will be placed next to my current garage under a very large tree. I'd rather not pour concrete because of cost and because I'd likely damage the tree roots, so per the manufacturer's recommendations, it can be assembled on a bed of pea gravel. This area has a gentle but noticable stope. Not knowing anything about construction, what's the best way to do this? Should I dig into the slope to bring the high part down to the level of the low part, then fill with gravel? How deep should the gravel be? Would the quickest way to do this be rent a tiller to pull up the dirt and haul it away? For better drainage should the gravel bed be elevated a bit and contained in a perimeter of treated wood? I'm sure the manufacturer will have a recommendation but this shed comes with some sort of a plastic or rubber floor - should some form of a plastic moisture barrier be installed?

Any other advice is welcome. Thanks as always

 

[babzog]

I just put one up (not the costco one, a shelterlogic I picked up on kijiji) a month ago or so to hide the tractor and steel. What I did was to clear the area first, removing tree stumps, saplings, etc. Then leveled the area as best I could. After that, I ordered two dumptruck loads - one of pitrun to fill the area and build it up, another of 7/8" gravel for a topcoat. The gravel, once leveled, makes a nice base on which to erect the temp garage and drains well. Put up the garage (with my BIL, in the pouring rain) using the supplied 15" anchors. Screwed down into the gravel and pitrun, they're not going anywhere as far as I can tell.

No plastic or anything else... while the sides seal against the ground fairly well, you're gonna have an opening under the doors... snow, etc is gonna blow in there and you don't really want water accumulating in the shelter.

 

[MScott]

Not sure where you live, Lhorn, but you both should be aware that these sheds will collapse under a heavy snow load and you should be prepared to clear them off after a substantial drop. Mine had heavy 2"+ frame members and they still broke (and dropped on the car stored inside.)

 

[magnusk750]

Make shure you make the ground with a slope outwards from thed, at least some 3 feet to lead rain and moisture away. (Sorry, for my english but I think it understandable.)

 

[Lhorn]

Thanks for the advice. I live in northern california so snow is not a problem at all. Nor is much wind. The place I will erect this is pretty sheltered by a big treee so sun damage will also be lessened. It rains a lot in the winter and the ground gets pretty waterlogged so I want to make sure drainage is adequate. Any idea how deep I should make the gravel bed?

Thanks

 

[motofly196]

I would stay away from pea gravel...it won't compact, and always stays "loose". If you really need gravel, and plan on moving a vehicle in and out of the shed, I would suggest 5/8" minus. It compacts well, and vehicle tires don't sink in if left for an extended amount of time. It will work even better if you rent or borrow a plate compactor and go over it a few times sprinkling water on it as you compact. 3-4" of material would do for a vehicle.

Scott

 

[Lhorn]

Thanks for the advice.