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Posted: Sun Sep 26, 2004 9:54 am
by Tichcooper
Morning,
I have a base of 4.2meter x 1.3meter - 70 mm deep. The base will be used for light traffic only (walking) If ordering 25kg ballast bags, approx how much would be required to fill this area, also how much Portland would be required.
Many thanks
TC
Posted: Sun Sep 26, 2004 5:02 pm
by Nigel Walker
The area you are working is 5.46m2 at a depth of 70mm. This equates to 0.38m3 - rounded up = 0.4m3. To accetane what tonnage you need - the formula I use is x 1.9 . Therefore you require 0.76 ton of ballast. You could either have 31 No. bags of 25kg or a Bulk Bag would come to between 800kg and 1000kg. The bulk bag would be a lot cheaper. 31 bags would cost approx £45 inc vat and the bulk bag would cost approx. £30 inc vat. You would also need 6-7 bags of cement at a mix ratio of 5:1
You would be better making the depth 100mm . This will give a better quality base and also you could use the full Bulk Bag of ballast
Ideally you would pop along to your local ReadyMix concrete plant and collect 0.4m3 of already mixed concrete - approx cost £35.00 inc vat. As not many people are able to do this, you could have it delivered, but the cost would be high as you would be paying a surcharge for delivery on part loading on a mixer wagon.
So get your mixer out and get batching !
Nigel
Posted: Sun Sep 26, 2004 8:12 pm
by Tichcooper
Many thanks for the reply Nigel. The reason its 70mm & not 100 is because the base is actually slabs. These are laid on sharp sand approx 50mm thick and have been down for over 3 years or so. The base is for a cat house made from mostly UPVC. I intend to lay tiles on the base when the construction is complete. It sounds a bit of a bodge job I know but do you think it will stand the test of time using this method or shall I start to re-think the whole job again.?
Regards
TC
Posted: Mon Sep 27, 2004 12:21 pm
by 84-1093879891
I wouldn't lay a concrete base over slabs (flags) - if they move at all, the concrete will crack. Much better to throw them out and lay a 100mm thick concrete base on a prepared sub-base.
There's a calculator on the main website that determines how much of what is needed to make sufficient concrete to cover a given area at a specific depth. I think you'd find it useful.