Concrete Slab for workshop base - Novice needs help

[NickCurtis62]

Total novice at this so bear with me.

Have an area measuring 10m x 3.7m that i want to use for a workshop base (75mm deep).
On the ground is already a a mix of 30-40mm mix of what looks like flint chippings which has
a depth of between 40-50mm, so hopefully ok to lay the concrete on top of.

My questions are (having been quoted over £400 for a ready mix delivery!)
1. What quantity of sand and gravel would i need for the area in question?
2. What type of sand?
3. What type of gravel?
4. Would it need any steel mesh?
Thanks in anticipation

 

[tomfe]

You'll want more hardcore down, if what's down is really old and stable you might get away with it.
£400 is an alright price, unless you have a tractor with a mixer you aren't going to mix that by hand.
You can put some steel in it if you want it will help with cracking (a142 or go bigger).
Due to the size you need building regs, what have they said about the base?

 

[Bilabong007]

In my very limited experience having mixed about half a cube of concrete, I agree with tomfe that mixing that amount would take ages and be backbreaking work

You can google concrete calculators for the amounts you need and either buy ballast (sand and aggregate premixed) or sand and agg separate. Your going to need lots of it and it won't be as cheap as you may think

Graeme

One here http://www.source4me.co.uk/calculate_concrete_mix.php

Estimated volume of concrete: 97.998 cubic feet or 3.63 cubic yards or 2.775 cubic meters.
Total weight if using pre-mixed concrete*: 13,033.761 lbs or 5,910.75 kg.
From Http://www.calculator.net/concrete-...t=centimeter&slabquantity=1&slabcal=Calculate

 

[nickjb]

I'd go with the readymix. £400 isn't too bad. Having recently laid a slightly smaller slab it was hard enough work shifting it around and getting it level. I wouldn't have wanted to add doing the mixing as well.

75mm of concrete on 40mm of chippings sounds a bit thin to me. Mine is way more than that. I'm just a DIYer though so maybe erred on the side of caution.

 

[tomfe]

I work on, 0.5 cubic of concrete ismax for mixing by hand, 2 cubes for mixer, 4 for PTO.
Ready mix is around £100+ per cubic metre. You generally can get the materials for about 75 per meter = not worth it.
Depending on what you are going to do in your workshop will greatly dictate the thickness of slab you need. It could be 100mm but cars etc you want at least 150mm.