Paper Roofs.
Although, as intimated in a former page, in covering our imaginary dwelling with tiles or slates, we may seem to have done all that is necessary in respect to “roofing,” yet we should leave our subject only half treated if we were to omit mention of other contrivances which have been partially acted on; such as the use of paper, of asphaltum, and various other substances.
About thirty years ago, Mr. Loudon published a pamphlet, in which he described the mode of preparing paper for roofs, and discussed the various arguments for and against its adoption. His description had immediate relation to a series of paper roofs in a large farm at Tew Lodge, in Oxfordshire, and comprised the following among other particulars.
Paper roofs may be made very flat, being raised no higher than just sufficient for throwing off the water. Instead of tile, slate, or thatch, they are covered with paper, prepared by immersion in a mixture of tar and pitch. In the first place, pieces of wood called “couples,” are laid across the walls of the building, rising two inches and a half to the foot to obtain a drainage obliquity; these couples vary from two or three to six inches square, according to the size of the roof. On the couples are placed horizontal rafters, about two inches square; the distance between the couples being from five to eight feet, and between the rafters about eighteen inches; the couples are nailed to the wall plate, and the rafters to the couples. At Tew Lodge, the rafters used were young larch-trees, sawn up the middle, cut to the proper lengths, and prepared so that the upper surface should be level. On the rafters are placed thin boards, from a half to five-eighths of an inch in thickness; these boards are nailed to the rafters, not horizontally as for slating, but in a direction from the eaves to the ridge of the roof. In some cases substitutes for thin boards may be used; such as close copse-wood hurdles, plastered over; or common plaster-laths.
The paper employed may be any common, coarse, strong kind; that kind used by button-makers being favourable for the purpose. It is prepared as follows: a boiler or cauldron, three feet wide by two deep, placed over a fire, is filled to within six inches of the top with tar and pitch, in the proportion of three parts of the former to one of the latter; the fire being applied and the mixture made to boil, the paper is immersed in it one sheet at a time, and then laid in a stack or pile with such a slope as to allow it to drain, a little grease of any kind being placed between the sheets to prevent their adhering; and when dry the paper is similarly treated a second time. The paper thus prepared is then nailed down to the roof. The workman begins at the eaves, and allows three inches for being turned down and nailed underneath the end of the board, which boards project an inch over the first rafter. If the paper be common, coarse, wrapping paper, it is laid on much the same as slate, so that when finished it will remain in double thickness all over the roof; but if thicker paper be employed, it is only made to overlap about three inches in each layer. Every sheet is fixed down with four nails about an inch in length, having broad flat heads.
On the paper thus fixed is laid a composition consisting of two parts of tar to one of pitch, thickened to the consistence of paste, with equal parts of whiting and powdered charcoal. The composition being well boiled and kept constantly stirred, it is spread over the roof with a hempen mop as quickly as possible on account of the speedy cooling. When properly laid on and dried, the composition totally conceals the joints of the paper, and forms a smooth and glossy black covering an eighth of an inch in thickness. Sometimes, while the composition is yet wet, sand, dust, or ashes are strewed on, to increase the substance, and shield the composition from the action of the sun.
Mr. Loudon enumerates as the advantages of this roof—economy, durability, and elegance. The economy is shown by the circumstance that, on account of the lightness of the paper, less massive walls and timbers are required than for other kinds of roof. The expense at Tew Lodge was from fourpence to tenpence per square foot, everything included. It is one result of the flatness of the roof, that ten square feet will cover as much as fourteen feet at the usual pitch of slated roofs. As to the durability, many proofs are adduced to support it. A paper roof to a church at Dunfermline remained forty years without requiring any repairs; and several warehouses at Greenock, Deal, Dover, and Canterbury, had paper roofs, which were known to stand from ten to twenty years. Mr. Loudon considered that, from the flatness of the roofs, and from other circumstances connected with the appearance of the prepared sheets, the paper roofs were more fitted to join harmoniously with certain styles of architecture than slated roofs.
Objections have been made to this kind of roof, on the ground that it is liable to be blown off by high wind, and still more that it is very inflammable. With regard to the former, Mr. Loudon states that if the roof be properly made there is little danger of its being removed by high wind. In reference to the second objection, he states:—“They seem to me not so liable to set fire to as thatch. Pitch (especially if coated over with sand or smithy ashes) will not be lighted by a spark, nor even by the application of a slender flame, as will that material; though, on the other hand, when lighted, it will unquestionably burn with greater velocity than any species of thatching.... In the steward’s house and men’s lodge wood is constantly used as fuel, which, though more dangerous for emitting sparks than coal, yet no accident has or is ever likely to happen to the roof. In my house, where coals were chiefly used, the chimneys have been repeatedly set on fire to clean them, without the least accident happening to the roof.”
Many years afterwards, when Mr. Loudon published his elaborate Encyclopædia of Cottage, Farm, and Villa Architecture, he briefly sketched some of the forms of roof which have more or less recently come into use. These we must here notice.