353. - Cover all boarding that is to be slated with tarred felt, weighing 20 pounds to the square (Neponset black building paper), well overlapped previous to slating. Cover all inclinations of the (front) roof, also roofs and cheeks of dormers with the best quality of Brownville, Me., (Peach Bottom, No. 1 Bangor) blue black slate, (or Granville, N. Y., red slate), 8x16 inches in size on dormers, and . 10x20 inches on the roof.
The slates are to be laid with a double lap and (3), (2½) or (2-inch) head cover, and secured with two tinned or galvanized nails to each slate. All slates to have smooth split surfaces, out of wind, with edges and tails cut or sawn straight and square. All slates more than 3/16-inch thick are to have the nail holes drilled and counter-sunk. The eaves and ridge courses to be double. Slates to be cut close to the hip-and ridge poles, and to a straight line in the valleys.
Rendering.* - All slates for a distance of 2 feet each side of valleys and 1 foot each side of hips, chimneys and rising parts, the last two courses at ridges and the first four courses, at the eaves, to be thoroughly rendered with (Purcell's) elastic cement (or slaters' cement).
All the slates on the flat slope over------ - are to be rendered at the joints over the nail holes and an inch under the tail with the same cement, using 40 pounds to each 100 square feet.
Valleys. - Line the valleys with strips of (tin, 14 ounce zinc, 16 ounce copper), 20 inches (18 inches) wide, with end joints locked and soldered, and the edges nailed to the roof with galvanized nails every 12 inches.
[If tin lining is used, it should be pointed on underside.]
Flash in the best manner around all (scuttles, skylights, dormers and masonry) coming in connection with the roof with (Merchant's or Taylor's old style IX. tin, 14 ounce zinc or 16 ounce copper) 7 inches wide, turned up 3 ½ inches.
* A great deal of slate roofing is done without any rendering at all. For good work, however, the slates at hips, ridges and valleys should be bedded in elastic or slaters' cement, and if the roof is less than " one-third" pitch, all of the slates should be rendered as in second paragraph.
Aprons. - Put on aprons of the same material 10 inches wide, at the top of lower sections of roof coming against walls, or roofs of a different pitch. Put apron under dormer window sills, nailed to inside of sill and extended 3 inches on the slates.
Counter-flash all under flashings against masonry with (4 or 3 pound sheet lead or 16 ounce copper), worked 2 inches into the joints of the masonry, cemented in with slaters' (Purcell's elastic) cement and brought down to within ½-inch of the slate. Counter-flashing to be stepped on the rakes.
Cresting Finials and Hip Rolls. - These will be furnished and put on by the metal worker.