Advice required: Concrete base for workshop

[Jason Arthurs]

I'm in the process of planning to build a 10'x 12' shed at the bottom of my garden to be my workshop. The soil is a very heavy clay and at this time of year is quite sodden.

Most of the shed sites seem to state that a slab base is fine for most uses, but I'm concerned that whilst it maybe fine for a 6'x4' with a couple of bikes and a lawnmower I'm going to be using this on a daily basis and it will be storing and handling some quite heavy items. I don't particularly want it sinking into the clay.

I was considering a 11'x 13' concrete base around 4" thick, is this overkill (or insufficient)? Also considering the damp conditions how long will it take a base like that to set before I can construct a shed on it?

Regards, Jason.

[Dorothy Bradbury]

Cheaper... o Landscape base ground for runoff & lay down cheap gravel

---- ideally you want this quite steep o Lay down 4 parallel & equally sleepers

---- large air gap underneath prevents rotting

---- double stack the sleepers to get things level o Place shed on top

---- double base joists if very heavy loads inside

Roof... o If a flat roof, re-design to add 9" minimum tilt to it

---- that way even if it sags, it will still drain versus pool o Use larger overlapping eaves if you can

---- guttering will stop rain/solar warping of the siding

However 6-8 sleepers may be as expensive as concrete.

[Andrew Mawson]

bottom

daily

a/ The shed: Make it bigger than you think you will need they are always too small

b/ Assuming it's a wooden shed, lay one or two courses of bricks first with a dpc. This not only keeps the wood out of the damp but significantly increases your headroom

c/ Put a plastic membrane in the concrete to stop moisture rising inside

d/ Lay the base to stand proud by an inch or two from the surrounding garden and make it the size of the shed base, not larger, so water doesn't stand on it and run under

e/ Think how you will get power inside and where you want it - dead easy to lay a duct in the concrete but not so easy later.

f/ Don't 'back it into a corner' - you won't be able to get at the rear for maintenance

Best of luck.

AWEM

[John Rumm]

Any trees near it?

(roots magnify the problems a bit)

Stick 4-6" of hardcore under it and it will be fine! ;-)

(if there are lots of roots (like there were with my one) I would stick some rebar into the concrete as well)

Give it a week.

[Jason Arthurs]

Just to clarify, this will be a shed complete with wooden floor and bearers so the concrete is merely a hard standing for the shed.

Regards, Jason.

[Rumble]

Jason Arthurs said the following on 10/01/2006 17:24: Also considering the damp conditions how

Damp conditions have little to do with the time it will take for concrete to go off. You should, however, keep rain and frost off the newly-laid concrete for a few days.

A good rule of thumb is:

Walk on it after 24 hours Work on it after 48 hours Build on it after 7 days

Concrete continues to go off indefinitely, but notional maximum strength will be reached after 28 days.

[Douglas de Lacey]

Whatever else you do, consult and if necessary ask questions at the Brew Cabin.

Douglas de Lacey.