The Brew Cabin

I know this is probably very basic - but I am an amateur! I have an area of 51 sq m which I want to random pave using 600 x 600, 300 x 300 and 600 x 300 slabs - how on earth do I work out how many i need of each size?

It's not as basic as you might think. You have to decide how 'random' your random layout will be. If you will use equal numbers of each size, then you total up the area of one of each, which in this case comes to (0.36 + 0.18 + 0.09) = 0.63m² and then divide the total area by that, which gives us 51/0.63 = 81 (roughly). So, you'd need 81 of each size, plus a few extra for breakages and wastage.

However, if you consider that using equal numbers of the smallest unit would end up looking too bitty, then you need to decide what ratio of sizes you think would look best. Maybe you could use 3 of the largest size to 2 of the mediums to 1 small, which, again, you convert to total area and use that to divide to whole area that is to be paved. In this example, you get...

(3 x 0.36) + (2 x 0.18) + (1 x 0.09) =

(1.08) + (0.36) + (0.09) =

1.53m²

51/1.53 = 33.3

....so you'd need...

(33.3 x 3) = 100 of the 600x600 = 36m²
(33.3 x 2) = 67 of the 600x300 = 12m²
(33.3 x 1) = 33 of the 300x300 = 3m²

Natcherally, you could elect to use a ratio of, say, 5:3:3 or 11:4:1 or whatever you think looks best, and so it becomes a matter of adapting the example shown above to your chosen ratio and then doing the sums.

How's that?

I think I love you !!!!! Thanks so much

OK now I know how many flags I need! ;)

Can you tell me how I work out how much grit sand and cement I need to order for the base?

Use the calculators I provide on the main website. In particular, the Bedding Mix calculator on the Mortars and Concretes page. :)