New (larger) shed

Here in Pensacola, FL, Hurricane Ivan took out
my 8X10 shed. It would have made it, if it weren't
for the three pine trees that decided to fall directly on
top of it.
Anyway, I've since completely demolished it, down
to the 8X10 concrete slab. I thought this might be a good
time, instead of putting up with the small shed, to enlarge it to 12X12. Now for my question for the knowledgeable ones:
- If I want a larger concrete slab, do I have to demolish the existing smaller slab or can I simply frame out the larger size while using the existing slab as part of the new
foundation? I was concerned about one part of the two
slab foundation settling, thus wreaking havoc on the fame.
If it's feasible I'd like to add on to the existing slab. I demolished a concrete patio a while back, it was'nt fun..
- Would it be better use 6X6 posts as a foundation for
the new (plywood) flooring? Essentially the old slab would remain under the wooden floor, but play no part in the structural integrity of the shed? My only concern about this is the height of the floor.
Does anyone have a better idea or comments about
my two ideas above?
Thanks/Lew
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jack wrote:

Check zoning. Many places have MUCH stricter requirements for anything over 100 square feet.
If you're going to add to the foundation, I'd build a foundation around the existing slab to support the building, then fill in the gap between the foundation and the slab with concrete. At that point your pouring a floor instead of a foundation.
Brad
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Brad Bruce wrote:

I'd go along with that, and it would be ideal to have the 8x10 in the middle. If not in the middle then just inside the new wall in one corner. But 12x12 isn't that much bigger, so I wouldn't worry even if the op used the 8x10 as a corner of the new floor
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I would recommend using the existing slab and adding on in the direction of choice. If it was properly installed originally it should be stable. You can pin the slabs together with slab ties. essentially drilling into existing slab about 6-8 inches every foot or two and using an epoxy to glue re-bar into the holes. When you pour the new slab it will tie the slabs together and they should not move especially since you don't have to worry about frost. Do check with the local code as far as requirements. Larger buildings may require muuuuuch more hurricane proofing. My local full permit cutoff was 100sf and above, but they changed it to 200sf and above. Now I have what looks like a one car garage next to my pool and my inspector says its just a garden shed. :-)
Wood floors are not necessary if you already have a slab and concrete gives you a good mounting surface to anchor that thing.
Good luck,
Matt
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jack writes:

Hey, those pines were the only thing keeping it from flying away! <gd&r>

Disclaimer. Dunno nothing about Pensacola soil conditions so my advice is worth about 25 cents on the dollar but . . .

Were I you, and the original slab hadn't settled noticeably, I'd prepare a concrete for for the size of the new footprint, undercut the original slab about 3-4 inches in and 4-6 inches under on the side(s) where you intend to add on. You can run the rebar or wire into the undercuts and pour. I'm guessing you've got pretty good drainage and zero worry of frost heaves. If one or the other assumption is wrong you might care to hedge your bets by digging and pouring pit footings at appropriate intervals.
I'm also guessing that at 12x12 you'll not be putting anything denser than a 12 hp lawn tractor in the new shed.
Best,
Marc
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Depends on what you're doing with/in the shed. If you're storing a lot of small stuff, you could build something like the old shed with studs on 24" spacing, and the attach 2' bump-outs like window-bays on three sides. This allows you to use the same pad, but gives you a shed that looks something like a camping trailer...
Speaking of which, you could always just drop an enclosed trailer on the pad.
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