It is currently 29 Mar 2024, 13:37

Concrete slab

Roll up, roll up. Here you will find everything from new workshop designs, through builds to completed workshop tours. All magnificently overseen by our own Mike G and his tremendously thorough 'Shed' design and generous advice.

Concrete slab

Postby Deejay » 16 May 2021, 10:21

Morning all

I have a steel garden shed, similar to this ...

https://www.argos.co.uk/product/6554543 ... hed:3:49:1

I need to move it, and want to put it on a concrete slab. It holds only garden tools so there will be little weight for the slab to carry. It will be about three inches thick and have steel mesh near the bottom reinforce it.

My question is , how much (lateral) space should I leave between the shuttering and the ends of the reinforcing metal ?

Cheers

Dave
User avatar
Deejay
Sapling
 
Posts: 428
Joined: 22 Jul 2014, 09:36
Location: Wiltshire
Name: Dave

Re: Concrete slab

Postby AJB Temple » 16 May 2021, 10:38

Interesting question. I have always left enough so that there is no chance of the mesh poking out of the slab, 50mm or so. I would be interested if there is a technical answer. I may well try fibrous mix next time I do a slab.
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5436
Joined: 15 Apr 2019, 09:04
Name:

Re: Concrete slab

Postby 9fingers » 16 May 2021, 11:10

I'd say that unless you have a specific soil type problem etc that there would be no need for steel in an under shed slab.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10043
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: Concrete slab

Postby Deejay » 16 May 2021, 11:50

Morning Bob

It is the soil conditions. The ground surrounding my house is 'made up' with topsoil. I am told that my part of this 1989 estate needed very deep foundations due to soil conditions. My next door neighbour needed piling to build a brick extension.

There is evidence of settlement of the added soil where a slabbed area meets the house brickwork. So, for the extra twenty odd quid, I will use reinforcing mesh in the hope that if the slab moves it will be in one piece, and will not crack.

About 50 mm was what I was thinking AJB, far enough from the edge to stop any rusting of the steel but close enough to provide support for the screws to hold the shed down.

Cheers

Dave
User avatar
Deejay
Sapling
 
Posts: 428
Joined: 22 Jul 2014, 09:36
Location: Wiltshire
Name: Dave

Re: Concrete slab

Postby AJB Temple » 16 May 2021, 12:22

So in essence your plan is to make a raft. Your reasoning for adding steel, which is cheap, is wise I think and in your shoes I would probably do steel top and bottom of the slab and make sure your mix is suitable.

Ah, just saw you plan only 3 inches. I would do it a bit thicker, but I do tend to over build.

For the first time ever, I have a couple of superficial cracks in the top of my latest slab. I am pretty sure this was caused by secondary mag float of the top when it had gone off a bit too much. Annoyed with myself.
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5436
Joined: 15 Apr 2019, 09:04
Name:

Re: Concrete slab

Postby Mike G » 16 May 2021, 14:05

There is nothing to be gained from having steel in a 3 inch slab. It needs to be 25mm up from the bottom (and 50 from the edges, as has been said), and that puts it close to the line of neutrality in the middle of the slab where it is neither in tension nor compression, no matter what happens to the slab. You should never really cast up a slab under 4 inches thick, and in that case, the steel will be doing its job nicely.
User avatar
Mike G
Sequoia
 
Posts: 9838
Joined: 30 Jul 2014, 22:36
Location: Suffolk
Name:

Re: Concrete slab

Postby Deejay » 16 May 2021, 15:56

Thanks Mike.

Four inches it is then.

Cheers

Dave
User avatar
Deejay
Sapling
 
Posts: 428
Joined: 22 Jul 2014, 09:36
Location: Wiltshire
Name: Dave

Re: Concrete slab

Postby Woodster » 16 May 2021, 16:51

Over the years we’ve had several sheds that have just been sat on concrete pavers. A 8’ x 6’ was sat on pavers at one property for over 11 years until we took it apart to move to a new house. Our current 10’ x 8’ has been sitting on pavers for nearly 8 years and the base looks fine. The shed company levelled the lawn, tamped some sand and gravel down then just laid about 8 large pavers on top. There are gaps between the pavers but hard to tell how much now as the sheds been down so long. At one property we inherited a large shed that looked like it was many years old. I think it even had creosote on it. It was sat directly on the dirt and a bit the worse for wear but I still managed to park my little lawn tractor in it.
User avatar
Woodster
Old Oak
 
Posts: 2558
Joined: 26 Jan 2017, 13:17
Location: Dorset
Name:


Return to Workshop Builds

Who is online

Users browsing this forum: No registered users and 11 guests