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Posted: Wed Apr 27, 2016 9:52 pm
by Parched
I'm about to create a 5' x 10' garden shed base on soft-ish ground. I'm thinking I'll make it 4" thick, reinforce it using A142 reinforcing mesh and use a 1:5 cement : ballast mix. Will I need to dig the hole deeper and put hardcore in there also? And what's the purpose of hardcore please?
Posted: Thu Apr 28, 2016 12:07 am
by lutonlagerlout
make it 150mm thick and use C:30 readymix concrete with fibres,also make sure the mesh is inside the concrete or it can rust
sub base spreads load ,also you should use a damp proof membrane = DPM 1200 gauge
bulletproof!
knocking concrete up in a mixer is too hit and miss for me
LLL
Posted: Thu Apr 28, 2016 1:12 am
by Parched
The shed sits on timber bearers so the floor is wood and a couple of inches above the concrete. Is a DPM really required (& why)?
Posted: Thu Apr 28, 2016 6:39 pm
by rxbren
What's going in the shed?
My own is 8x6 shed (well kids for storing toys maybe convert to a playhouse) is on concrete lintels set on concrete
Posted: Thu Apr 28, 2016 6:57 pm
by Parched
Just a lawn mower, bikes, garden tools & clutter etc. and a cement mixer 
The ground is a bit soft so I want it to be strong to prevent cracking over time or frost damage etc. I guess it might tilt a little over time but that's better than cracking. My current line of thinking is hardcore (fairly small stuff that I've got lying around; 2" stones down to some pea shingle, 4" concrete with A142S mesh in the middle. Surely that will be enough? I was going to do 1:5 cement:ballast but on the cement bag (Blue Circle Mastercrete) is reckons 1:4 - a bit over the top do you think?
Posted: Thu Apr 28, 2016 7:14 pm
by seanandruby
Gen 3 concrete. Sounds like you will need sub base if dodgy sub soil. membrane is a must it keeps out ground salts etc: also stops the conctete drying out to quickly and weakening the slab.
Posted: Thu Apr 28, 2016 8:20 pm
by Parched
Gen 3 concrete - 1:6? Where does the membrane go, underneath the hardcore, or in between the hardcore and the concrete?
Posted: Thu Apr 28, 2016 8:42 pm
by seanandruby
Underneath the spacers, mesh and concrete.
Posted: Thu Apr 28, 2016 8:47 pm
by Parched
I was thinking the DPM would surely puncture on the hardcore, but I think I'm getting it - hardcore is the sub-base. So, dig down to firm ground, fill back up to the required level (less the thickness of the concrete) with sub-base, compact, put down DPM, fill with concrete (with the mesh in the middle). Is hardcore the sub-base? Would MOT1 do the job? Is it all getting a bit OTT for a shed base?
Posted: Fri Apr 29, 2016 10:45 am
by seanandruby
bible studies
Don't over think it m8 :;):
Posted: Sat Apr 30, 2016 4:36 pm
by Forestboy1978
rxbren wrote:What's going in the shed?
My own is 8x6 shed (well kids for storing toys maybe convert to a playhouse) is on concrete lintels set on concrete
That's a damn good idea. Why lintels though. I can't see steel reinforcement being necessary as it's already on concrete but I get the idea of propping it off the concrete base.
Either way, that base will never rot. One would hope anyway. Can't see what more you could possibly do to protect a shed base.
Posted: Sat Apr 30, 2016 5:11 pm
by rxbren
I just set the the lintels on some postcrete no subbase or anything
Bought the lintels as the cost difference between timber bearers and the lintels was minimal plus won't rot could have possibly put a bit dpm between the lintel and the shed but shed only cost me some felt and new roof so didn't bother
Actually thinking about it the shed is 10x7
Posted: Sun May 01, 2016 4:53 pm
by Forestboy1978
rxbren wrote:I just set the the lintels on some postcrete no subbase or anything
Bought the lintels as the cost difference between timber bearers and the lintels was minimal plus won't rot could have possibly put a bit dpm between the lintel and the shed but shed only cost me some felt and new roof so didn't bother
Actually thinking about it the shed is 10x7
Hmmm, I'm definitely stealing your idea lol.
I might modify it though.
What do you think about digging say for example for a 6x4 shed
6 x 4ft parallel channels 8 inches deep and 6-8 inches wide. Laying membrane in each and up the sides to the top. Tamping down 4 inches of hardcore. Topping that with 2 inches of postcrete and laying lintels on top and lining them up and levelling them.
Costs? £100.00 you reckon
That would be moderately cheap and doable in a day for 1 person I think and IMO effective IF 2 inches of postcrete is enough.....
Posted: Sun May 01, 2016 7:50 pm
by rxbren
To be fair used a few bags of postcrete, for the postcrete way the Hanson stuff is better as it has aggregate in it.
I only dug a spades width and worked from the highest point of where the shed was going to sit to allow enough depth for some concrete/postmix and show around 50mm of lintel. You don't really need masses of concrete underneath.
Spacing wise it all depends on the shed if it's a cheap b and q job with 50mmx50mm bearers on the base you'd probably want to be around 450mm centres for your lintels but if it's a thicker bearer on the shed floor you can go to 600mm or more
One point worth noting would be with the bearer approach you need to have the shed delivered as not all sheds have their floor bearers the same way so you could be in a position where you have laid your bearers the shed turns up and it's floor bearers are the same way.
Posted: Sun May 01, 2016 10:09 pm
by Forestboy1978
Wow, I was thinking 1 ft min would be needed but yeah you're prob right, it's not like it's a dance floor.
Put up a few sheds in my time but hadn't noticed about the direction of the bearers. Always presumed they'd fit them to the shortest lenght, being sheds are rarely square but food for thought.
Either way, 450mm makes it cheaper still.
It's def the way to go cos my mums is just on pallets on gravel and it's still going 30 years later. It'd dead now though and is getting replaced but it's not the floor that's gone. Concrete bases work but only seem to work if the base is the exact same size as the shed frame, i.e. sitting just inside of the tongue and groove so runoff misses the base. Obv this is cheaper and will work.
As I say. Stole 
Thanks