quantities

[h12rpo]

Ok so to cast the top slab will a ton builders :-) bag of 'all in' do it? And how many bags of cement will i need for that?

Ta !

[slowfood]

1 ton should be around 1 cubic metre I would imagine, So times tour length, width and height in centremetres or millimetres and you'll know what you'll need, Less water the stronger the concrete, (Give it a good vibrate to get the air out-hammer the sides and use a sander with no paper ) Good luck

[cannyfradock]

Hey r2d2

Good advice from slowfood on vibrating the concrete. This will bring all the air bubbles to the surface, then can give the surface a float finish.

The actual materials needed depends on the size of your slab. Calculation is length x width x depth which will give you a cubic measurement....then x 2.2 will give you the dry materials. Or in laymans terms....if your slab is 120cm x 120cm this gives 1.4 square meters. multiply this by the depth (say 12cm for ex.).....1.4 x .12 = .168 meter cube.....you can round this off to .2m3(cube).

Multiply your cubic volume (.2) by 2.2 and this gives the dry material weight.... .2 x 2.2= .44ton. ....for ease round this up to .5ton.....or half a ton.

When you mix concrete using all-in you should use a ratio of 6 parts all-in to 1 part cement, so divide the half ton (.500kg by 7) which gives 7.1.(number of bags of cement needed)

A ton of all in is more than needed but is the cheapest way to buy it.....

I'm not very good at explaining things so if that was all jumbled. just post the dimensions and I'll calculate how much cement......chances are that you will need 7 or 8 bags.

Terry

[h12rpo]

I love your posts terry
My slab will be 160cm x 180cm at 10 or 12cm

So by my reckoning 1/2 ton of all in and 8 bags of cement .....thanks terry

Whilst i'm at it.......it looks like the top of my hearth floor will end up at 120cm off the floor.....does that sound about right ?

[cannyfradock]

...by my figures you are closer to 3/4 of a ton...including the cement. 8 bags should do.....maybe 9?

You are in the right ball park figure of the finished hearth height. The usual recommended finished hearth height is elbow height of the person working the oven which is between 1m 10cm and 1m 20cm.

Just out of interest, I always start my build by looking at the finished height and work backwards. I usually fix a piece of wood next to my build with markings of finished hearth height, I then make a mark where the insulation layer will end and where the slab height should come to. On the pic below is my "piece of wood"...or profile/datum. It's not so clear in the pic, but the piece of wood has a mark for each level of stage progression.



Your build is coming along fine. Please keep us updated with your progress.

Terry