Ballast / cement quantity required

mushtafa

mushtafa

mushtafa

Soldato
Joined
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West Sussex, UK
I'm trying to work out how much ballast and cement I need to order to make concrete for my shed base.

I've been recommended to go for a 4:1 mix.

I've worked it out I need to fill 1.062m3, so round it up to 1.1m3 is fine.

The ballast in bulk bags is 800kg, but I'm not sure what volume the bags are.

Can anyone help please?
 
Get a density and from that you can work out the volume. Generally you're looking at about 1.9t per cube.
 
would go a bit weaker for a shed base, for that sort of thing chuck in half a bag of cement a mix(with a small mixer)
i would guess that'll take a little more than 2 bulk bags of plant mix and 10 bags of cement, problem is 3 bulk bags will be way to much.
 
1m3 of concrete is about 2.5 tonnes in weight.
As above 6:1 or 7:1 is more than enough for a shed base.
Did you work out the quantity using a cube?
eg. 100mm thick will take 1m3 per 10m2
 
I found an online calculator which suggested I need 350kg cement and ~1900kg ballast. It sounded way off, but obviously not.

This plan is 95% right, but I still need to remove the old shed before I can take 100% correct measurements.

I make that 11.79m2. At 90mm thick it would be 1.062m3.

I've gone for 89mm thick just because that's the size of the CLS studwork I can use to build the mould.

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Sounds about right to me mate.
350kg cement and ~1900kg ballast is roughly 6:1 and with water added it wont be far off 2.4 tonnes

Have you looked for local aggregate suppliers? it may be cheaper to get 2 tonnes of ballast delivered and tipped off outside. it would also be easier to barrow it in as its a nightmare to shovel ballast out of a bag lol
 
B&Q do ballast for £40 per bulk bag including vat with free delivery over £100, might work out cheaper if your supplier are charging for delivery.
 
Mercenary Keyboard Warrior said:
Dont rule out ready mix, check a few places out locally, they will charge you for what you use
1.1m3 is fairly low amount but they will still probably give you a price which might be worth it depending if you want to spend hours mixing it etc
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Agreed, it's a similar amount i've done in the past and after a few hours of trying to mix it in a wheelbarrow (how hard could it be i thought!), i went and hired a mixer for the day. By the time you factor that into the cost premixed would've been similar in price and would've saved a lot of work.
 
Martynt74 said:
Agreed, it's a similar amount i've done in the past and after a few hours of trying to mix it in a wheelbarrow (how hard could it be i thought!), i went and hired a mixer for the day.
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haha! Yeah you definitely need any mixer for anything but a very small amount. Worth considering purchasing a used one off gumtree/facebook marketplace etc and punting it on when you are done. I actually made a profit doing this recently. Bought mixer for £170, used for a couple of days, sold for £215. Profit!
 
Only one company has got back to me regarding premix. Minimum cost was 2m3, plus delivery, plus VAT, just shy of £400!

I've looked at mixer hire, £25 for the day
 
mushtafa said:
Only one company has got back to me regarding premix. Minimum cost was 2m3, plus delivery, plus VAT, just shy of £400!

I've looked at mixer hire, £25 for the day
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Probably nearer £50 once vat and delivery fee each way is added, but still the cheapest way to go IMO. Lots of hire placed do a weekend deal for only a few pounds more than a 1 day hire, where they drop it off pm Fri and collect am Mon. It just takes the pressure off, rather than waiting for it to be delivered and then having to rush.
 
Is it for a wooden shed? I thought concrete bases were out of fashion, and the plastic bases were supposed to be better with regards to preventing damp etc
 
Armageus said:
Is it for a wooden shed? I thought concrete bases were out of fashion, and the plastic bases were supposed to be better with regards to preventing damp etc
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Yeah, I'll build a wooden shed. I've never seen a plastic shed base, but at least a concrete one will be exact measurements and last forever
 
assume your going to stick a DPM under it?
Are you connecting it to the house and as such are you putting in some kind of seal/flashing between the shed and the house

I only mention as its sounding more like a permanent outbuilding as opposed to a shed if this is the case and whilst it may not be an issue to you, only your deeds, local planning etc would tell you if there was any issues with that

The fact that you show no wall against the house makes me assume the house wall is forming the "back" wall of the shed?
 
Yeah, being built onto the side of the house. (I was planning on lining that wall with OSB/ply so it won't remain bare brickwork).

I will add flashing as required to seal the roof against the house. I don't need anything between the stud wall and the house though do I?

I was going to add a damp proof between the shed base and timber walls, and shed base to house wall. Is this enough? (I'll do some more research).

As far as I know it shouldn't need any permissions as it's under the height limits.
 
It doesn't really matter. An individual is less interested in cost differences so you might as well go for something that cures quickly.

Just make sure you hire a mixer. Makes much better quality concrete if you mix it properly.
 
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