# how many keystones do i need? (formula)

Discussion in 'Landscape Architecture and Design' started by yergus, Aug 29, 2001.

1. ### yergusLawnSite Memberfrom MissouriMessages: 146

i need a formula for estimating how many keystone blocks i need for a project. let me set up a example and see if you can help me figure out how many stones i will need as well as how you came up with that figure.
key stone blocks 4 X18X 8
wall= 125 feet wants even with ground on top of terrain
left side is ground level, two feet out there is a nine inch drop, twelve feet further it drops to forteen feet, twenty feet further the terain raised nine inches and stays that way til the end,
please draw this out, figure how many stones i will need and how you came up with that formula.
i can come up close each time, but i use a reduculus formula that takes forever and a day to get it.
i know there has to be an easy, faster way

2. ### paulLawnsite Addictfrom Chicago,Ill.Messages: 1,625

Can you say "Structural Engineer"!!!
You have about 1750 face feet of wall 125'X 14'=1750 Sq ft.
This is a rough and dirty estimate, reason is I don't know the slope that you have on your drops and I don't know the soils you have!

Remember you are going to have to have this wall engineered!!!
DON'T GO BUILDING THIS WALL WITHOUT IT!!!!!

3. ### StonehengeLawnSite Bronze Memberfrom MidwestMessages: 1,276

First of all - what Paul said.

Second, for a wall that big, you needn't worry about pinning down the exact number of block. That can change come install time anyway. Just get it close and add in some extra for good measure.

And remember, the exposed height of the wall is not the total height of the wall. You will have several courses buried on much of this wall.