How do you calculate how much hard core you need?

Kashkai

As the title states, I want to order some fill material (probably 804 - a sand/gravel mix) to use as a base for a patio. However, I have no idea how I go about calculating how much I'll need. I don't want to end up ordering too little and then having to get more in or worse, ordering too much and having a pile of fill left lying around. Perhaps I'm cynical but I think if I leave it up to the supplier, he'll deliver more than I need and I'll end up with excess material that I won't need/be able to dispose of.

I have 2 areas that need the base:

60 sq metres for the patio and 45 sq metres for a base for a metal shed.

Thanks in advance.

Minder

From here 804 granular subbase is approximately 2.3 tonnes per cubic metre when compacted. You need to decide how thick the subbase will be for the two areas then work out the tonnage from there.

Thickness x 105 sq m = cubic metres x 2.3 tonnes/cu m = tonnes.

You place your order in tonnes. The delivery ticket should have the tonnage of material on it. A typical 8 wheeler wagon has a capacity of 15 cubic metres. 804 subbase is approx 1.6 tonnes per cubic metre in the loose, so a wagon is about 24 tonnes if full, and as they are never full, expect about 20 tonne per load. I say this because the supplier will probably charge a fresh air charge for any load not full.

BTW 20 tonne will give you a layer about 80mm thick, or 3 inches.

If you are happy that the area is flat and you know the thickness you need, you can work up the volume and tonnage.

If the area is up and down like a rice pudding, stake it out into a grid and run string lines across the grid at the finished level you need. Dip off the string lines with a measuring tape and calculate the volume of each box in the grid.

(Sorry if any of that is teaching your granny to suck eggs).

RKQ

This site might prove useful, you will need to know length by width by depth required. Lots of different calculators:-
http://www.pavingexpert.com/calcall.htme

Aeneas

Prosperous Dave wrote: »

As the title states, I want to order some fill material (probably 804 - a sand/gravel mix) to use as a base for a patio. However, I have no idea how I go about calculating how much I'll need. I don't want to end up ordering too little and then having to get more in or worse, ordering too much and having a pile of fill left lying around. Perhaps I'm cynical but I think if I leave it up to the supplier, he'll deliver more than I need and I'll end up with excess material that I won't need/be able to dispose of.

I have 2 areas that need the base:

60 sq metres for the patio and 45 sq metres for a base for a metal shed.

Thanks in advance.

I have used two sites in the past to help me calculate the amount of crushed rock I might need for filling: SI Metric.co.uk and Reade Advanced Materials. Both give weight/volume ratios for crushed limestone and sandstone - one in kg per cu.m the other (an American site) in lbs per cu.ft. I have found them to be pretty accurate when I got my own volumes right. Their figures seem pretty similar to Roadstone's site which I was unaware of and is probably best for Irish conditions.

Kashkai

Thanks for all the advice lads - much appreciated.

David