Calculating materials needed for wall footing.

[Probs]

Hi folks,

As I'm sure many of you do this for a living or indeed more frequently than me maybe you can help me out I'm looking for an easy way to calculate how much cemement/all-in-ballast I would need for foundations of a given size.

Does anyone have a formula that they use for this ?

I'm looking to use cement and ballast at a ratio of 1:6.

Thanks chaps,

- Jamie

[lutonlagerlout]

for 1 bulk bag of ballast you will need 5 bags of cement

i.e. 850 kg ballast : 125kg cement i know this doesnt sound quite right but believe me it works ,the cement and ballast have different densities etc
cheers LLL

[Probs]

Thanks Luton but I think you might have miss-understood my question

I know how to work out the ratios but I'm struggling to work out for instance how much I would need for say a footing which is 3m long 1 foot wide and 1 foot deep. I.e. would 1 25kg cement bag + 6 25k ballast bags do the job ?

Is there any easy way of working this out ?

Thanks again,

- Jamie

[matt h]

area in cubic metres = apprx 0.3
go to main site and use tables already setout for you to calculate your particular mix.. easy if you can read:p

[Mikey_C]

having worked out your cubic meters required (LxWxH, all in meters), you then need

your looking for the C20 concrete calculator

if using ballast, add grit sand and gravel weights together.

[lutonlagerlout]

i would go 3 m by .4m by .4 m a wall shoulkd have a foudation at least 10mm wider than the wall so if its a 225 wall then the foundation should be 425 wide

for this 1 bulk bag of ballast and 5 bags of opc will suffice

rgr that?


LLL :;):

[Rich H]

Should be bang on. 0.4 x 0.4 x 3.0 = 1.05t ~ 0.85 + (0.25 x 5) = 0.975t

[Bob_A]

if using ballast, add grit sand and gravel weights together.

That sounds logical yet many online calculators say that when you use all in ballast the weight required is actually less than the weight of adding sand/aggregate together.

There are a number of sites with calculators that do that, here's a few

http://www.diyhelp.org.uk/estimatorsPages/concreteBallast.php
http://www.diyhelp.org.uk/estimatorsPages/concreteNonBallast.php

http://www.source4me.co.uk/calculate_concrete_mix.htm

http://www.workswright.co.uk/maths/maths.shtml


Why do they suggest that you need a bit less when using ballast?

[Mikey_C]

in the words of the dragons den, just to let you know where I am "I'm out", apart form the fact that "all in ballast" as discussed on this site can be an uncontrolled "doesn't conform to any particular specification", I couldn't offer any suggestion why less ballast is required. Hopefully one of the pros on here can.

However, are you worried about under ordering on quantities or are trying to get a perfect mix?

If it is the later you should be looking at computer controlled on site mixing trucks or ready mix, not throwing ballast and cement at a mixer with the usual inherent errors.

If it is the former I am guessing you putting something on this footing and will require cement for this and ballast is always handy on a working site.

[lutonlagerlout]

a normal builder's mixer holds about 1 big barrowfull of concrete
you get 10 of these out of a bulk bag ,so you use 12.5 kg (half a bag) of cement, roughly 8-10 pints of water (half a bucket) and about 12-14 shovels of ballast (depending on shovel size)
abracadabra foundation mix concrete!!!

LLL

[Bob_A]

If it is the former I am guessing you putting something on this footing and will require cement for this and ballast is always handy on a working site.

It is the former, the mix doesn't have to be accurate and like you say it's always best to over order. ballast doesn't go off so it will get used eventually.

I'd like to find the answer to this one, not because it's important but because it's bugging me.

[Mikey_C]

ahh! the thirst for knowledge. more than acceptable, let us know when you find the answer.

[Probs]

Hi folks,

JUst managed to get some time to check the site, Firstly I'd like to say thanks for all the replies the link to the calculator on http://www.source4me.co.uk/calculate_concrete_mix.htm has been extremely useful. At least to confirm what sort of quantitys I should be looking for.

Secondly it gives me an idea of how much cash I should be looking to spend and of course how much humping and dumping I'm going to be doing

Since I'm looking for a relativly small amout of concrete (Just under 1.5 m sq) would it be cheap to have that amount ready mixed and pumped to where I want it ?

Or would it be considerably cheaper to buy and mix it myself ?

Thanks again folks, I hope your associated weekends are going better than mine !

- Jamie

[matt h]

small amount do it yrself. Isnt it 1.5 cubic metres?:)

[Probs]

Yeah sorry. Typo !

Problem with mixing it myself is getting it to the location. It's a midterrace house so a lot of barrowing to do, I'm just worried it'll start drying out and stuff ...