Need some advice on Concrete

[Marc]

Hi,

I am laying about 3 metres square of concrete in my garden (extending the existing concrete patio).

I was thinking of using the ready mixed concrete bags you can buy. however i noticed the exiitng concrete has some very large stone gravel in it. Is it better for me to buy the mix separately? and what size gravel should I use?

Also do I need a bed or can I lay the concrete straight onto the earth?

Many Thanks

Marc

[marson]

I would say if you are concerned about getting the optimal concrete mix, you should order it pre mixed. You will have to pay for a small load, but you will save a ton of work. Otherwise, if it's just a patio and not the front lawn of the White House or something, you could use pre mixed bags. Your mix won't be as consistent, but it will be good enough. Don't know what you mean by "large stones". Typically, concrete for such applications has "3/4- aggregate--that is a portion of the aggregate contains rock that are 3/4" or less. Sacrete will also have aggregate, so it should be fine. I wouldn't recommend mixing your own. It's a ton of work, you will have to come up with aggregate, and your mix will be even more inconsistent than pre bagged.

Whether you need to lay a "bed" depends on local conditions. If you have well drained sandy soil it isn't necessary. If you have clay soil and live where the ground freezes, then you definitely need a layer of sand.

[Marc]

Thank for the advice,

I think i will buy pre mixed bags and add water myself using a hired mixer.

The pre mix didint seem to have very large stones in it thats all

[RicodJour]

You may want to re-examine your plan. You said the area was 3 meters on a side - roughly 100 square feet. Figure 4" thick slab - that's about 33 cubic feet. If you use 80 pound bags of concrete mix, you'll need 33/.6, or about 55 bags. Price the bags, the rental cost and put _some_ value on your time (include fetching and returning the mixer in your time calcs). Even with a short load of concrete I'd be shocked if the bags weren't a lot more money. They're definitely a lot more work.

The way you should go:

The way you're thinking of going: R

[marson]

I was thinking he meant 3 square meters rather than three meters square. If it is the latter, then I definitely agree that the OP should use a ready mix truck.

[Marc]

going:

Thanks, its only a small area 1 x 3 m

[RicodJour]

1 m x 3 m meters is 3 square meters. 3 meters square is 3 m x 3m. Small change, big difference. R