Stone-coated or stone chip roofing tiles are made from an alloy of aluminum and zinc also as known as “Galvalume” or “Alu-zinc” metal sheets as the base metal for this roof covering.

In this article, we will not be focusing our attention over the advantages or disadvantages of this roof covering over long span aluminum, but will drive right into how we will determine the number of roofing tiles required for covering a roof. You can do this in preparation for a roof quote to be submitted by your roofing contractor, since many will submit a wide range of quantities for any one roof. I have seen many clients been short changed in quantity estimation and pricing on several roofing projects.

Stone-coated roofing tiles come in varying lengths of between 1100 mm and 1650 mm, but the most popular been the 1350 mm – 1400 mm range depending on the manufacturer. The standard width should be a 420 mm. During roof construction the purlins or battens are spaced at 365 mm (c/c) center to center and rafter at 1200 mm (c/c) center to center. We will be using factors derived from these numbers in determining the number of roofing tiles required for covering our roof.

For easy understanding, we will work on two popular roof types as examples;

1.  The simple gable roof and… 
2.  The hip roof types.

Accurate stone–coated roof tile estimation is based on a combination of roof measurements at the fascia, rafter, hip, rake and valley (gutter).

The two roof examples below will demonstrate how to use the formulas to arrive at the total number of sheets required for any roof style. The example roof dimensions are strictly hypothetical and not lifted from any real world construction scenario.


How to determine quantity of stone-coated (Alu-Zinc) roofing sheets

Rafter length divided by 0.365 = number of roof titles from fascia to ridge.

Roof length divided by 1.26 = number of ridge roof tile sheets from gable (rake) end to gable (rake) end.

Example 1: The simple gable roof

Gable roof

Roof length, 15 : 1.26 = 12 roof tile sheets across

Rafter length, 7:0.365 = 19 roof tile sheets rows up-Roof length, 15 : 1.26 = 12 roof tile sheets across

(Remember to round up to the nearest digit)


For this example, multiply 12×19 to determine the total number of roof tile sheets needed for one side of this gable roof. Multiply this by 2 to obtain the opposite and the total roof tiles required.


Total roof tile or sheets required will be; 12×19 = 228 tiles

For the opposite side, 228x 2 = 456 tiles

Example 2: The Hip Roof Type

In other to arrive at an accurate quantity of roof tiles for any simple hip roof style, we will use the formula and method in the example above (as a gable roof) and then we will calculate the additional tiles needed for the hip and or valleys by measuring the total length of all 4 hips, then multiply by 1.32. This equals the number of additional roof tile sheets to compensate for the cuts and bends at hips. Add together the total tile sheets including additional tile sheets for the hips to obtain total roof tiles sheets required for any hip roof.

1. Roof length 15 divided by 1.26 = 12 roof tiles sheets across

2. Rafter length 7 : 0.365 = 19 roof tiles sheets rows up

3. 12 x 19 = 228×2 = 456 total roof tiles

4. Hip length = 10m x 4= 40m

= 40m length of hip x 1.32

= 52.81 (round up)

= 53 additional roof tiles for cuts

Therefore total roofing tile sheets,

=456 tile sheets +53 (additional roof tiles at the hips)

=509 tile sheets

These are the basics in calculating the quantity required for using stone coated roofing tile for your roof covering. For more complex roof designs, you can section it out into these basics types above or if you don’t like calculations you can contact us

Contributed by: Akinola Richard