Natural Stone Estimating Made Easy
Posted in Estimating Posted on July 14, 2015
People love natural stone for its beauty, durability and… well, its natural-ness. Every piece of stone is unique, which is great for the finished appearance but can make determining your material needs tricky. Estimating natural stone shouldn’t be the hardest part of your day. Here’s how to do it in 60 seconds or less.
Let’s start with the basics. A cubic foot of limestone weighs about 165 lbs. Knowing this, you can figure out how much to order of any limestone product sold by weight. Just figure out your cubic footage and multiply it by 165. Most of the time, however, there are shortcuts that make estimating even easier.
How many pieces of armourstone do you need to build a 50’ x 8’ wall? It doesn’t matter. Armourstone is sold by weight so it’s necessary to convert the square face footage of the wall into tons, not pieces. A piece of armourstone that is approximately 3’ long by 2’ high by 2’ deep has 6 square face feet (3 x 2) and weighs about a ton. So:
Square face footage of the wall (l x h) ÷ 6 = # of tons of armourstone needed
In our example, there are 400 square face feet in the wall (50 x 8), which requires approximately 67 tons of armourstone (400 ÷ 6).
Building stone is estimated in much the same way as armourstone. Building stone with a 4” bed depth weighs approximately 50 lbs per square foot. That means 1 ton of building stone will cover about 40 square feet of wall. So:
Square face footage of the wall (l x h) ÷ 40 = # of tons of building stone needed
If we use the wall from our previous example, 400 square face feet of wall would require approximately 10 tons of building stone (400 ÷ 40).
Wall stone typically has an 8” bed depth. Because it’s twice as deep as building stone (and, therefore, twice as heavy), one ton only covers half as much... 20 square feet. So:
Square face footage of the wall (l x h) ÷ 20 = # of tons of wall stone needed
If we needed 10 tons of building stone for the wall in our example, we’ll need 20 tons of wall stone (400 ÷ 20).
The method of ordering flagstone varies, depending on the type. Square cut flagstone is sold by the square foot so no further calculations are required. Random flagstone is sold by the ton and coverage depends on the thickness of the stone (see chart).
Imagine you are estimating a 25’ x 30’ patio. If your design calls for square cut flagstone, you need only order 750 square feet (25 x 30). If you are using random flagstone, the calculation is simply:
Total square footage (l x w) ÷ Coverage (based on flagstone thickness) = # of tons of flagstone needed
From the chart, we know that one ton of 2” thick flagstone covers about 80 square feet. So, for a 25’ x 30’ patio using 2” thick stone, we would need 9.5 tons of random flagstone (750 ÷ 80).