Exposure of each slate will equal the length of a slate diminished by 3" (the usual amount of lap) divided by 2, multiplied by the width of the slate.

To determine the number of slates required, divide the area to be covered by the exposure of each slate as determined just above.

Example - Determine the number of 6"X 12" slates required to cover a surface 16'X20'.

Solution - 12"- 3"/2 X6"=27 sq. in..

16X20X144" / 27 = 1707 slates.

## Table Of Slates Per Square Of 100 Feet

 Size Length of Expos. No. Req. Nails Req. 6"X12" 4½" 533 3.8 lbs. 7"X14" 5½" 377 2.66 8"X16' 6½" 277 2 9"X18" 7½" 214 1.5

## Analysis Of Cost Factors Per Square. (100 Sq. Ft.)

Slate, @.....................................................

Slater, 8 hrs., @..............................................

Roofing Paper, @.............................................

Placing paper, 20 min..........................................

Nails, 2 lbs. (8"xl6" slate) @...................................

Total.....................................................\$

Metal work extra.