Concrete quantity help

johnnyroper

I am going to be building a small porch 2m wide by 1m deep.

I am thinking footings of half metre deep by half metre wide which I think would need 1 cubic metre of concrete??

Do my above workings out look correct and if so what would be most cost effective way of doing the concrete mix myself or get pre mixed delivered?

Thanks

crazyguy

Check hear : http://www.cemex.co.uk/re/re_co_ca.asp

lagi

Heres another, if you look at the amount of sand/cement your going to need. If you will be using a mixer you can work out how many mixer loads you will need to make this amount. Then workout access, costings, time and weigh up what would be more suitable.

If you haven't got a mixer then you would have to budget for hire, as you wouldn 't want to mix all that by hand.

http://www.source4me.co.uk/calculate_concrete_mix.php?tab=0

Tucker

You need to multiply the width and length of the trench in total and multiply that by the depth you are having.

Half a metre deep is alot of concrete for any footing. Most are 200 to 300mm or so.

If you are doing half a metre square and then running that over a trench length running 5 metres, that I would expect come to 1.25 cubic metres?

johnnyroper

thanks for the replies,so half a metre is too deep for a porch and i could use 300mm instead?

ab7167

200-300mm sounds a bit shallow to me. You could still be in made ground at that depth, I usually go a minimum of 400mm to give some protection against frost heave. Ultimately it depends on the soil you have, you could try digging a hole against the face of your house to see what footings the house has? You could ask local Building Control for guidance as well, I assume you will be applying for BR approval for your porch?

johnnyroper

ab7167 wrote: »

200-300mm sounds a bit shallow to me. You could still be in made ground at that depth, I usually go a minimum of 400mm to give some protection against frost heave. Ultimately it depends on the soil you have, you could try digging a hole against the face of your house to see what footings the house has? You could ask local Building Control for guidance as well, I assume you will be applying for BR approval for your porch?

i will be doing it properly as per the building regs,just sussing out rough costs at the minute.

fairly new house>5 years old the footings were put on piles assume the ground is a bit unstable round here?? thinking about it i am probably best to go deeper think i better check with building control.

Tucker

I was assuming he was digging out to the required depth and then building up on top of the footings with concrete block or trench block, to bring it to a slab height?

In which case 200 to 300 is all that would be needed for a 2 storey build subject to the ground being sound for BC.

ab7167

In that case, I don't disagree - I was thinking that base of footing 2-300mm below ground level was too shallow. Strip footings should be founded a minimum of 400mm below ground level to avoid frost heave. However, given that the rest of the house is piled, I would be wary that the ground @ 400mm bgl was adequate, and also wary of the possibility of differential settlement between the house and the porch with different foundation types.

Tucker

Yes, probably one of those projects that needs a trial dig, to see what ground you have.

I have to say though, the house being piled might not reflect the actual ground it is sat on. When doing larger estates, it's quite possible some of the development had ground that required piling. It's therefore likely the whole development was done in one way, to save building different ones to different specs.

My house is on raft foundations, as it the whole area. However, when I dug out for my extension, BC passed it for strip foundations becasue it was dense clay and didn't need to be on a raft at all. No doubt one or two trial digs they did in the area exposed some less solid ground, so the whole lot were done that way irrespective of the area it sat on.

joebob

We just bought some ready mixed concrete was £130 for a cubic metre. but ring around some quoted upto £180