Concrete Base for Summer House - Some Advice Required

[diywoman]

Hiya,

I am new on here so be nice!
I am building a concrete base for a summer house. I don't want/can't afford the expense of having ready mixed concrete delivered plus would need to hire a pump as its down the other end of the garden! So my question is, how do I work out how many bags of sand and cement I need?

Measurements are 4.5m x 4.5m. Going for 3 inch deep hardcore and 3 inch deep of concrete. I thought it was a 1:5 ratio? I was ready about a C20 mix, would this be better??

this is my first job in a garden, more at home doing interiors! So any help is appreciated.

Thanks
DIYWoman

[welsh brickie]

you will need 2 ton bags of concrete mix and 10 cement, that's at 100mm thick. also lay a sheet of reinforcing mesh in the concrete
Its best to buy some 100mm x 25 timber and shutter the area to the size you want, level the timber and fix it to 50 x 25mm stakes nailed in the ground.
There are hire mix companies that will mix and barrow the concrete to where you want so will save you mixing it yourself, but you will need to lay it

[diywoman]

Great thank you. So that is for every 100mm depth of concrete?

[welsh brickie]

100mm thick concrete is the minimum you will need, also its best if the hardcore is compacted with a machine

[philipam]

Just wondering if you have done this yet, if so did you get more than half way across the base with just two tonnes of concrete mix???

At the very lest you would need four tonne of ballets to cover an area of this size at 100mm depth.