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How did this go? Round here the volumetric boys are the way forward for jobs like this. Mixed to a consistency you want on site and also don't mind waiting for you to barrow. Last time did a barrow job the customer was so shit at narrowing that the driver taught him how to operate the machine and jumped on barrow with me! Earned his drink that day.

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A foot really????? That is some serious concrete depth.


4m x 2.5 at 8inches deep needs two ton of ballast (sand gavel mix) and 12 bags of cement.


So for a foot deep (12 inches), another ton and about 5 bags which would be 3 ton of sand/gravel mix and 17 bags of cement.


But lad, that is some serious friggin concrete depth, honestly! :icon_eek:


Don't you worry about mixing that, get a buddy. It takes 3 hours to mix, tamper and float 4m x 2.5 at 4 inches deep. Add another two hours for depth but the same time to tamper and float. It is an easy job, just make sure you have a board to shovel your open bags of cement from.


Remember to pick your weather if using an electric mixer or having open bags of cement. Rain will feck everything up! Honestly! Water and electrics and water and cement do not go! lol


Try to get your sand gravel mix hi-abed up to the level you are working so you don't have to wheel your barrow up steps.


Make sure you spend a good amount of time shuttering off using timbers or fabricated shuttering. If using timbers run a brush of cooking oil along the timbers before laying concrete so they come off easy.


Have everything ready, shovels, float, powerfloat, rags, rake, mixing board, ballast beside your mixer and a good ramp in and out of your form.


If you are going that depth you are going to need an agle grinder and rebars. I mean cut length of steel rods tied together like a grid to re-enforce the concrete.


Get a good hardworking buddy and if you start that job at 10am you guys will be finished by 6pm no problem. Ready to do your finsihing touches before nightime sets in.


Don't worry about an outside tap............your mix should be nice and coarse. A bucket filled from a kitchen tap will do....inconvenient but as long as you can get in and out without taking your dirty shoes off each time and your grand. Takes very little water each time for the mixer, wait you see. Too much water and the sloppy concrete will be flying out spilling everywhere. So just small drops at a time.


Make sure you have enough bags of cement because if you run out and not finished then you are screwed. You can add concrete to the form at a later date but it will compromise the structure strength.


1 cement x 3 ballast (when ya can).......1:4 if under pressure and if running out.....ahem cough cough.....1:5........but mix it with all the other stuff you have just thrown into the form. Meaning keep the 1:5 for the end....if you can.

I have never heard so much drivel.


17 bags of cement to mix 3 cube .??????? Do you realise 3 cube of concrete is over 7 ton ?What bloody mix do you lads do, your calculations are miles out, and don't even add up, you say a 1:5 mix at worst case scenario, so that's nearly a ton of cement not 17 bags ? for Christ sake don't drop anything on it as the slab will crack.


You need,

960 kg of cement = 38 bags

5.4 ton of ballast

900 litres of water


That will mix you 3 cubic metres of a c20 mix


But, why oh why are you going 300mm deep, that's quite ridiculous, if your building as a raft, then by all means put a deeper toe on the slab where the walls/structure will be bearing, but the centre only needs to be a maximum of 150mm, even 100mm would be OK.

Seriously, I build grain stores that hold thousands of tons, have artics on them, tractors and trailers, and they are only 8 inches this at most, usually only 6 inches deep.


If I am honest, I would seek some advice from a builder/construction person as it seems your making a few guesses on this job.


Membrane, insulation ? Planning ?

spot on mate,some people do talk bollocks on subjects theyvno nothing sbout.taking water from kitchen sink ffs.

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Think it 2as called jablight for the cavity the bricky supplied it he got it off site

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Looks good lee. Just doing a slab myself for a bit more shed space. 3m x 10m doing it in 4 sections. A bit of cowboy concrete work mixing it with the digger. :laugh:





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Bit of overkill for making opinel knives. Lol. Must be for the right surround pics. Jok.

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