TALK: BRICK AND STONE. This work in practical estimates furnishes excellent opportunity to develop the pupil's reasoning power. As simple problems made without the use of pencil and paper. Again, let us say, give much oral work as the pupil goes along. When he once understands the why in the work of any class of problems, let the oral work come in to fix it permanently and clear up any haze that is apt to linger on the borders of his mental pictures. Facts That Should be Known about Brick and Stone. 1. Bricks vary in size but generally are 8 in. × 4 in. × 2 in. 2. We estimate about 22 bricks with mortar to a cubic foot. Allow of the space for mortar. 3. Bricklayers are paid by the day, by the job, or by the number of thousand laid. 4. Stone work is estimated by the perch. Ordinarily a perch is considered to be 25 cubic feet. 5. In estimating labor on stone work, the general custom is to measure the corners twice and to deduct one half of the openings. 6. One cord of stone makes about 100 cubic feet of wall. PROBLEM: Estimate the number of bricks needed to lay a wall 160 ft. long, 9 ft. high, and 20 in. thick. = Number of cu. ft. in wall 13 × 9 × 160 = 2400. If 22 bricks are needed per cubic foot, for 2400 cubic feet of wall, 2400 × 22 bricks, or 52,800 bricks, are needed. PROBLEM: How many cords of stone are needed for the walls of a building 40 ft. x 60 ft., if the walls are 2 ft. thick and 10 ft. high? NOTE. Draw a picture of the above. SOLUTION: 2 walls, each 60 ft. x 10 ft. x 2 ft. contain 2400 cu. ft. 2 walls, allowing for corners, contain 2 × 36 × 10 × 2 cu. ft., or 1440 cu. ft. 2400 cu. ft.+ 1440 cu. Since a cord of stone makes about 100 cubic feet of wall, there are needed about 39 cords of stone. NOTE. Make clear how you figure two walls only 36 feet long. The sign X is to be read "by" in some cases here. TALK: LATHS AND SHINGLES. Tell the pupils what is meant by laying shingles "4 inches to the weather." Show shingles wider than four inches and some less than four inches in width. Explain that they are estimated four inches wide in figuring the number to a bunch, and in finding the required number for a given surface. Facts That Should be Known about Laths and Shingles. 1. Laths are 4 ft. long, 1 inches wide, and are usually laid of an inch apart at the sides. 2. 50 laths make a bunch or bundle. 3. Allowing for waste, a bunch of laths will cover about 3 square yards. 4. Lathing is estimated by the square yard. About one half of the surface of openings is deducted. Plastering also is estimated by the square yard and only one half of the surface of openings is charged. 5. A bunch or bundle of shingles contains 250. 6. Shingles are 16 inches long, are considered 4 inches wide in estimates, and are laid 3 or 4 inches to the weather. 7. 1000 shingles are called a square of shingles, and will lay about 100 square feet, 4 inches to the weather. 8. Lumber dealers will not sell a part of a bunch. PROBLEM: The sides of a gable roof are 12 ft. x 20 ft. How many shingles laid 4 in. to the weather are needed to cover it! SOLUTION: One side. How many in a row? Each shingle is estimated 4 in. wide. There will be 3 shingles to each foot, or 60 shingles in each row. How many rows? Each row covers 4 in. of exposed surface. Then there are 3 rows to a foot, or 36 rows on a side. How many shingles? If one row contains 60 shingles, 36 rows contain 36 60 shingles, or 2160 shingles. Both sides. Since there are 2 sides to the roof, it will take 2 × 2160 shingles, or 4320 shingles. ANOTHER SOLUTION (equally as good and simpler): 1 sq. ft. of roof surface requires 3 shingles in width and 3 in length, or 9 shingles. On each side of roof there are 12 × 20 sq. ft., or 240 sq. ft. of roof surface. On both sides there are 2 × 240 sq. ft., or 480 sq. ft. of roof surface. If we estimate 9 shingles per square foot, it will need 480 × 9 shingles = 4320 shingles. To estimate the number of shingles required for a roof, when laid 4 in. to the weather, Multiply the number of square feet of roof surface by 9. It is easy to see why the above is true. Each shingle is 4 in. wide and 4 in. only of its length are left exposed, hence it covers 16 sq. in., or of a square foot. 9 shingles will cover a square foot. If laid 3 in. to the weather, 12 shingles will be required to cover a square foot, so, in that case, multiply the number of square feet of roof surface by 12. PROBLEM: How many shingles are needed for a gable roof 15 ft. by 30 ft., shingles to be laid 4 in. to the weather! SOLUTION: 215 × 30 sq. ft. = 900 sq. ft. roof surface. Another way to estimate easily and quickly the number of shingles required for a roof, when laid 4 in. to the weather, is, Allow 1000 shingles to each 100 square feet of roof surface. PROBLEM: How many shingles laid 4 in. to the weather are needed for both sides of a roof 20 ft. by 40 ft.? SOLUTION: 220 × 40 sq. ft. 1600 sq. ft. of roof surface. PROBLEM: = = When one bundle of shingles is allowed for 25 sq. ft., how many bundles will be required for a gable roof 22 ft. by 16 ft., and what will be the cost at $2.75 per M.? SOLUTION: 2× 22 × 16 sq. ft. = 704 sq. ft. on both sides. 704+25 = 28, or 29 bundles of shingles required. 250 × 29 = 7250, the number of shingles required, or 7.25 M. shingles. 7.25 $2.75 = $19.94, cost of shingles. |