This is done by the yard square, and the dimensions are taken in feet and inches.
When a room consists of more than four quoins, the additional corners must be allowed at per foot run.
In measuring ceilings with ribs, the superficies must first be taken for the plain work ; then an allowance must be made for each mitre, and the ribs must be valued at so much per foot run, according to the girt, or by the foot superficial, allowing moulded work.
In measuring common work, the principal things to be observed are as follow : Glaziers' work is measured by the foot superficial, and the dimensions are taken in feet, tenths, hundredths, &c. For this purpose, their rules are generally divided into decimal parts, and their dimensions squared according to decimals.
Circular, or oval windows, are measured as if they were rectangular ; because in cutting the squares of glass there is a very great waste, and more time is expended than if the windows had been of a rectangular form.
This is generally done by the pound, or hundredweight.
Sheet lead, used in rooting, for glittering and valleys, is in weight from 71b. to 121b. per foot; and for ridges from 61b. to Slb.
The following table will show the weight of a foot, according to several thicknesses.
The thickness is set in tenths and hundredths of an inch, in the first vertical column ; and the weight opposite, in the same horizontal line, in the second vertical column on the right hand : the integers show the number of pounds avoirdupois, and the decimals the number of thousandth parts above the integer : so that the weight of a square foot of or .10 of an inch thick is Slb. and 899 thousandth
If the roof be equally hipped on all sides with a flat at top, and the plan of the building be rectangular, add the length and breadth of two adjoining sides at the eaves, and the length and breadth of two adjoining sides of the flat toge ther; multiply the sum by the breadth of the slope, and the product will give the area of the space that is covered.
Add the number of square feet produced by multiplying the girt of the roof by the length of a slate at the eaves, to the area, for the trouble of putting on the double row of slates; also add the number of square feet produced by mul tiplying the length of the hips by one foot in breadth, for the trouble of cutting the slates where they meet, to the said area ; and the sum will be the whole contents, so as to make a compensation for the trouble and waste of materials.
Example.—Suppose a house 40 feet 6 inches in width and 60 feet 3 inches in length ; the breadth of the slope 15 feet 9 inches, the breadth of the flat 12 feet, and the length 31 feet 9 inches.
Ft. In. 40 6 60 3 12 0 31 9 To this area add the allowances for workmanship and waste.
If there be no flat, add the two adjoining sides and twice the length of the ridge, for the length; multiply the sum by the breadth of the slope, for the area of the space covered ; then add the allowances as before.