Levelling an existing concrete shed base

[S&J]

My husband and I are looking to install a new shed or cabin and need some advice. We've looked at lots of information on this site and while we can find answers to some of the queries, some definitive advice would be much appreciated.

We have recently removed an old garage which stood on a concrete base. Once removed we realised that the concrete base is in three different levels: the floor is the lowest level, with the surrounding areas starting higher than the garage floor and sloping away.

Our initial plan had been to install a new shed or cabin directly on to the concrete but the differing levels won't allow this. So, we're after any advice regarding how we can create a level base for the new construction. We thought the most obvious solution was to level using concrete over the existing concrete work however this is proving to be very expensive as it's not something we could undertake ourselves. So in the interests of cost we are looking for an alternative solution.

My husband thinks we may be able to create a frame in the same way as you would if you were installing decking as this would allow us to overcome the differences in levels of the current base. We could then use this frame to support the new shed following which we would deck the surrounding area. However, we have no idea if this would work and are open to any alternative suggestions.

Thanks in advance!

 

[23vc]

I assume you're talking about a large volume of concrete required to fill it, if it was say 1 or 2 cubic metre that wouldn't be that hard or expensive to mix with a hired mixer if you order a few bulk bags of balast.
Otherwise you can frame it like you would for decking but make sure you fix the 4x2 or 6x2 or whatever you're using to the concrete with suitable fixings (eg drill and bolt it) or even break holes in it and set posts in concrete which are then bolted to the deck frame.

 

[S&J]

Thanks for the reply. I should have said.... The concrete is about 17 feet by 13 feet so a large area to level.

 

[Tigercubrider]

How much of a level difference is there?

there is the heck of a difference between 17x13 feet 1" deep or 12" deep

 

[S&J]

Probably 6 inches from the highest point in the middle to the lowest points.

 

[r896neo]

Your decking idea is fine as long as you don't mind it being up in the sky a bit.

Simply use timber posts which sit on the concrete would be easiest. I don't see the need to bolt it down or even break holes in a perfectly good base simply to fill them back up with concrete....

 

[23vc]

Fair enuff, I was thinking strong winds but then I don't know how big this shed is

 

[S&J]

Thanks for all the advice. It's quite a sheltered area so wind won't be an issue. Plus the current concrete is slightly raised so an additional few inches in height won't make much difference.

 

[S&J]

Thanks for the precious advice but I'd like clarity on one point.

We've now roughly planned how to approach this and have been to a builders merchant to get a quote for the materials. They suggested it would be better to deck the whole area and put the shed (with joist spacers for air flow) on to the decking.

But we don't see the point in decking an 8' x 10' area simply to put a shed on top and think our initial idea of putting the shed on to the frame joists with decking around is better.

Any views?

 

[r896neo]

No your hunch is right not only is it a waste of time and money but its an actively bad idea.

You want nice free moving air under there and decking it will simply reduce ventilation and hold more moisture.

Put it straight on the joists

 

[S&J]

Thank you.