concrete, mortar or screed?

[BrokenBiker]

my grandmother rang me earlier with a rather strange question. can I gut the base of her wooden shed out and then cement a new floor in, as apparently it is rotting from damp and its the 2nd base she has had.

when I cut the floor out I noticed that it is pretty much just resting on a few scattered breeze block that are sitting on mud and a few puddles.

so the question is, what is best to use to fill this all in. area to cover is 6x8 foot and depth varies from around 5 inches at deepest to around 3 inches at shallowest area.

do I just mix up some mortar (4 sand:1 cement), get some ready mix concrete, make my own concrete or use screed (1 sand:1 cement)

which ever route I go I also need to know how much of each bit to buy ie cement, sand, aggregate and so on

 

[the snooper]

concrete for sure 5 to 1 is good enough for a drive so you should get away with a weaker mix
with a wooden shed its best to have either a concrete base or good solid pavers with some bricks to raise shed from floor to allow good air circulation if you sit the shed straight onto concrete or similar it will just soak up the rain

 

[BrokenBiker]

concrete for sure 5 to 1 is good enough for a drive so you should get away with a weaker mix

cheers when you say 5:1 what do you mean? I haven't concreted anything before, only ever mixed mortar for laying slabs after the concrete was brought in on a mixer

 

[the snooper]

5 parts sand and gravel 1 part cement

 

[BrokenBiker]

cheers. will the bags of ballast be ok as sand/gravel substitute?

 

[the snooper]

you need the sand and gravel mix for concrete

 

[BrokenBiker]

http://www.diy.com/nav/build/buildi...llast-Natural-Large-bag-9273144?skuId=9282844 this is the stuff I am talking about.

also how do I work out how much cement sand/gravel mix I will need to buy to mix the volume I need for the shed floor?

 

[dan.taylor.1]

If the bricks it was Sat on had a plastic damp proof membrane between them and the wood I bet it wouldn't rot anywhere near as quick.

But concrete is better anyhow you can buy plant mix which is sand and gravel so y ou just add cement and water. Most builders supply type places stock it (homebase and the likes may even have it but at a cost!)

Volume wise, take your area in sq meter, multiply by depth (0.15 for 150mm) and it'll give you the amount in sq meter, most builders type bags give you coverage on them.

Dan

 

[dan.taylor.1]

Yes that stuff you posted is like plant mix. Add cement and water and mix.

Dan

 

[BrokenBiker]

cheers.

so how much will a 25kg bag of cement and enough of that ballast to mix 5:1 make in terms of coverage at say 3 inches thick?

 

[Robotstar5]

I've got my sheds on sacrificial 3"x2" tanellised (sp?) timber so when they rot, just slide out and replace, although after 9 years there's no sign of rot.

 

[Pete.]

For a garden shed you don't really need anything more than a sharp sand & cement screed. That's what I put down for my first small workshop, it's long since gone and a kids trampoline now sits on that base which is still sound 8 or 10 years later and open to the weather. Put some poly down to keep it from pulling moisture out of the ground first then just knock up your mix.

 

[BrokenBiker]

cheers, will be finishing cutting out the floor tomorrow so will be able to take more accurate measurements.

anyone know how to work out how much I need to buy to mix enough concrete with a 5:1 as that is what she has decided she wants and as she is paying im not gonna argue.

 

[the snooper]

if you had an even depth you could work out the area into cubic meters then simply speak to the merchants supplying the materials

 

[Rig Pig]

If you haven't got a mixer don't even think about mixing it by hand, the last big base I did by hand nearly killed me! Serious graft!! Rent or borrow one

 

[norlander]

If you haven't got a mixer don't even think about mixing it by hand, the last big base I did by hand nearly killed me! Serious graft!! Rent or borrow one

+1on that and a barrow to shift stuff about and maybe a scaffold board to run the barrow up to the shed doorway if needed.
Its easy to drop a spherical object and say hello to Ernie when concreting not to mention mashing a disc in your back.
Something to tamp the concrete in useful as well.

 

[Pete.]

That's the beauty of screed, mix it dry until it's an ever colour then bung it in. Very little water needed (none if you don't use a DPM) and much less work. Not that it's a large area anyway.

6'x8'x4" thick is about 16 cubic feet or just under half a cubic metre, which is more than a ton of good concrete, a bit lighter for screed. Figure about 40-50 bags of sand/ballast and cement at a guess, perhaps a bit more. Cheapest way to get it is have the builders merchant drop off a ton of ballast I should think. I would certainly not relish knocking that up by hand.

 

[BrokenBiker]

so a ton of ballast and a fifth of a ton of cement? Or half a ton of sand and half a ton of cement?

what is a dpm?

 

[brightspark]

so a ton of ballast and a fifth of a ton of cement? Or half a ton of sand and half a ton of cement?

what is a dpm?

damp proof membrane a polly sheet . most general purpose concrete mixes are 3 . 2 . 1 as in -3 gravel 2 sand and 1 cement

 

[BrokenBiker]

Ah, wont be doing that just filling it up so she has a solid level floor that wont rot