A square of slate is 100 superficial feet. In measuring, the width of the eaves is allowed at the widest part. Hips, valleys, and cutting are to be measured lineal, and 6 inches width extra is allowed. The thickness of slates ranges from 3/16 to 5/16 of an inch, and their weight varies from 2.6 to 4.5 lbs, per square foot. The lap of slates varies from 2 to 4 inches. The standard is assumed to be 3 inches. The pitch of a slate roof should not be less than 1 in. height to 4 in. length.
| Size |
#Slate |
Wght pr sq(approx) |
Size |
#Slate |
Wght pr sq(approx) |
| 12x6 |
533 |
850 lbs |
18x11 |
174 |
650 lbs |
| 12x7 |
457 |
20x10 |
169 |
| 12x8 |
400 |
20x11 |
154 |
| 14x7 |
374 |
750 lbs |
20x12 |
141 |
| 14x8 |
327 |
22x11 |
138 |
| 14x9 |
291 |
22x12 |
126 |
675 lbs |
| 16x8 |
277 |
650 lbs |
22x13 |
116 |
| 16x9 |
246 |
24x12 |
114 |
| 16x10 |
221 |
24x13 |
105 |
| 18x9 |
213 |
24x14 |
98 |
| 18x10 |
192 |
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