Shed on sloping tarmac

[petej42]

Looking for a bit of advice on building a shed
I'm planning on building an 8 x 12 foot shed on sloping tarmac. Between the highest and lowest point is about 18 inches and all four corners need to be supported by different lengths.

What sized timber would be best for the frame? 6x2 or would 4x2 be enough
What is the best way of supporting the legs, I'm guessing direct to the tarmac is a no-no as tarmac can be soft, but I was thinking of a concrete block leveled with cement or even just building small concrete piers to provide a level surface.

Or is there a other approach

Thanks

 

[foxhole]

Sounds ok , there is also a large range of adjustable supports or ground screws for shed base support .

 

[petej42]

Thanks, my concern with the ground screws is their being on sloping tarmac and needing to be 18inches tall. I Could of course build a small pier so shorter ones would be needed

 

[foxhole]

Thanks, my concern with the ground screws is their being on sloping tarmac and needing to be 18inches tall. I Could of course build a small pier so shorter ones would be needed

Not a problem , a 1200mm ground screw would easily achieve you 18” height , lots of sizes available .

 

[simplesteve]

I would build piers, let them go off/dry out/move slightly, then put a concrete slab on top of each one and use this stage as your final ' levelling out'. Have your lengths of framing to hand when you're doing this.
It's just a personal thing, and probably wrong, but I just wouldn't trust the thread on a n adjustable leg for all those years with all that weight.....?

 

[bigbaldbloke]

I’d go 6x2 for peace of mind, especially with that size and the slope. 4x2 can flex a bit more than you’d like over time. For the legs, don’t sit them straight on the tarmac, it’ll shift and sink. Concrete blocks or small poured piers are a good shout, keeps everything level and off the ground. I’ve done similar with deck blocks and they’ve held up fine.

 

[petej42]

I would build piers, let them go off/dry out/move slightly, then put a concrete slab on top of each one and use this stage as your final ' levelling out'. Have your lengths of framing to hand when you're doing this.
It's just a personal thing, and probably wrong, but I just wouldn't trust the thread on a n adjustable leg for all those years with all that weight.....?

Must admit, i too am a bit suspect about the adjustable legs, especially as one needs to ge about 18 inches. We could build a pier of course, then sit a small adjustable leg on top but then again, may as well just put a pier in of the right lengtjh

 

[petej42]

I’d go 6x2 for peace of mind, especially with that size and the slope. 4x2 can flex a bit more than you’d like over time. For the legs, don’t sit them straight on the tarmac, it’ll shift and sink. Concrete blocks or small poured piers are a good shout, keeps everything level and off the ground. I’ve done similar with deck blocks and they’ve held up fine.

Yeah, I thought as much with the tarmac. I have given it a good thump with a hammer and it seemed solid enough, but there is a lot of weight in an 8x12 shed. Think we will go with the piers. We're going for the 6x2 as well. 4x2 would probably have been OK if it were being placed on level ground, but since there is a slope,6x2 seems the sensible option

 

[simplesteve]

I would have went 4x4 on the base framing. That's not gonna flex in any direction.

 

[petej42]

I would have went 4x4 on the base framing. That's not gonna flex in any direction.

We've actually gone for the 6x2 and using 6x2 cross members and noggings which should prevent any flexing. The piers will be 4x4 or 6x4 (2 of 6x2) and plenty of them to minimise any "bounce"