How much does slate weigh?

Slate Coverage

To calculate the weight per per m², we must first know how many slates the roof will require. This table explains the required measurements for effective coverage.

*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.*
Slate Coverage
Slate Size	Lap mm
(Nominal) mm	50	65	75	80	90	100	110	115	120	130	140	150
600 x 300	12.1	12.5	12.7	12.8	13.1	13.3	13.6	13.7	13.9	14.2	14.5	14.8
500 x 300	14.8	15.3	15.7	15.9	16.3	16.7	17.1	17.3	17.5	18.0	18.5	19.0
500 x 250	17.8	18.4	18.8	19.0	19.5	20.0	20.5	20.8	21.0	21.6	22.2
450 x 300	16.7	17.3	17.8	18.0	18.5	19.0	19.6	19.9	20.2	20.8	21.5
400 x 250	20.2	20.8	21.3	21.6	22.2	22.9	23.5	23.9	24.2	25.0	25.8
450 x 230	21.7	22.6	23.2	23.5	24.2	24.8	25.6	26.0	26.3	27.2	28.1
400 x 300	19.0	19.9	20.5	20.8	21.5	22.2	23.0	23.4	23.8
400 x 250	22.9	23.9	24.6	25.0	25.8	26.7	27.6	28.1	28.6
400 x 200	28.6	29.9	30.8	31.3	32.3	33.3	34.5	35.1	35.7
350 x 300	22.2	23.4	24.2	24.7	25.6	26.7	27.8
350 x 250	26.7	28.1	29.1	29.6	30.8	32.0	33.3
350 x 200	33.3	35.1	36.4	37.0	38.5	40.0	41.7
320 x 220	33.7	35.7	37.1	37.9	39.5	41.3	43.3
320 x 180	41.2	43.6	45.4	46.3	48.3	50.5	53.0
300 x 200	40.0	42.6	44.4	45.5	47.6	50.0
300 x 150	53.3	56.7	59.3	60.6	63.5	66.7

Weight per square meter

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.

Weight per slate in kilogrammes

In this table you can find the weights for the most common slate sizes and formats.

Weight per slate in Kilogrammes
Slate size	Thickness
(Nominal) mm	4-5mm	6-7mm
600 x 300	2.495	3.899
500 x 300	2.416	3.290
500 x 250	1.889	2.760
460 x 220	1.266	1.848
400 x 300	1.784	2.690
400 x 200	1.098	1.809
350 x 200	0.910	1.675
300 x 200	0.896	1.138