natural slate roofing
NATURAL SLATE
COVERAGE AND WEIGHTS

SLATE COVERAGE

This table explains the required measurements for effective coverage.

Slate Coverage
Slate SizeLap mm
(Nominal) mm5065758090100110115120130140150
600 x 30012.112.512.712.813.113.313.613.713.914.214.514.8
500 x 30014.815.315.715.916.316.717.117.317.518.018.519.0
500 x 25017.818.418.819.019.520.020.520.821.021.622.2
450 x 30016.717.317.818.018.519.019.619.920.220.821.5
400 x 25020.220.821.321.622.222.923.523.924.225.025.8
450 x 23021.722.623.223.524.224.825.626.026.327.228.1
400 x 30019.019.920.520.821.522.223.023.423.8
400 x 25022.923.924.625.025.826.727.628.128.6
400 x 20028.629.930.831.332.333.334.535.135.7
350 x 30022.223.424.224.725.626.727.8
350 x 25026.728.129.129.630.832.033.3
350 x 20033.335.136.437.038.540.041.7
320 x 22033.735.737.137.939.541.343.3
320 x 18041.243.645.446.348.350.553.0
300 x 20040.042.644.445.547.650.0
300 x 15053.356.759.360.663.566.7

The values shown in the Slate Coverage chart above are calculated using nominal sizes and incorporate a 5mm jointing gap. We recommend the addition of at least 5% wastage allowance.

Weight per square metre

To calculate the weight per square metre, simply multiply the weight per slate given below by the number of slates per square metre for the same slate listed above.

For example; 500 x 250mm slate (4–5mm thick) = 1.889 kg x 18.8 (at 75mm lap) = 35.51kg per square metre.

slate weight detail

Weight per Slate in Grammes

Weight per slate in Grammes
Slate sizeThickness
(Nominal) mm4-5mm6-7mm
600 x 3002.4953.899
500 x 3002.4163.290
500 x 2501.8892.760
460 x 2201.2661.848
400 x 3001.7842.690
400 x 2001.0981.809
350 x 2000.9101.675
300 x 2000.8961.138