All canvas must weigh, when thoroughly dry, 10 ounces to the square yard, and must not lose over 5 per cent of its dry weight after being soaked in water 10 hours and so rubbed as to take out all matter soluble in water. It is to be laid dry, stretched tight, all edges to be lapped 1 inch and tacked with 3/4-inch tacks set | inch apart.

In all places where the roof meets a vertical surface, three-cornered strips 1 1/2 inches by 1 1/2 inches are to be nailed, and the canvas is to be carried up over them and 8 inches on the vertical wall. If such wall is of masonry, there will be a 1 1/8 inch by 2 1/2 inch dressed strip bolted by expansion bolts set 3 feet apart under the projecting ledge of brick; and canvas is to be tacked to the under side of this strip as at other places.

After the entire roof is covered and the canvas swept clean, it is to be soaked with water, and, when thoroughly wet, is to be rubbed full of stiff paint composed of white lead and raw oil in proportions of 100 pounds of lead to 3 1/2 gallons of oil. After this is dry and the surface hard, and not less than five days after the first application, the roof and all exposed surfaces of wood strips in connection therewith are to have two coats of white lead and oil paint.