Hello,

while a slab on an even or flat surface is not a big problem, I am having difficulties figuring out how to do a slap on a slight slope.
I am trying to do a 16'x18' slab for a shed. The difference from top to bottom is about 2' to 2 1/2'.
Any input from the specialists?

 

You need a mostly level slab for your shed. Least expensive is to level the site. You can cut down the high side. Build up the low side or a combination of both. Sometimes a retaining wall is needed.

 

I was afraid of that someone would mention retaining wall. This will make it more difficult and expensive. Darn.

 

There are a couple ways to do this!

Having just build a garage on a slope, we worked down the slab area so that it was flat with the low side, about 2' also, and created a swale around the slab, thus keeping the slab on virgin, non-compacted soil.

You can always do the same and install a retaining wall/bolder wall on the high side.

 

IMO how you do it is based on where you wnt the entry and how you want that to work. Start with the location of the door , determine the floor elevation should be at that point, then level it out from there.

 

Starting at the door is good advice. Without being there it's hard to be specific but there is no reason you shouldn't be able to get a skid loader in there and excavate for your pad. If the door is on the low side, fine. But after the pad has been poured level, put concrete block walls around the perimeter of the pad and build your walls on that. You need to keep your walls and siding up above grade. And if your door isn't going to be on the lowest side you will need to do some excavating and grading anyway.

That being said, you will need to check with your local building inspector because a 16x18 shed is big enough that it probably requires a footing and building inspections along the way... Not just a shed on a pad.

 

In our state anything under 250 sq ft is exempt from needing a permit as the assumption is that it's most likely a small shed kit or plastic shed with no footing required.

 

In my area several factors like size and if it is a permenant structure affect whether or not permits are needed. Pouring concrete is a determining factor that makes it a permenant structure and subject to zoning and building codes and inspections. Compare to the same shed built on a wood pallet base which is considered moveable/temporary and doesn't need permits.

In my area they don't go by square footage to determine size. Instead if any dimension exceeds 12' then you need a permit.