Shingles have always been the common roofing material of the United States, and probably will continue to be for a number or years. While shingles are inflammable and not as durable as tiles or slates, the better qualities are sufficiently durable for the ordinary residence, and they may be treated so as not to take fire easily. They are also admirably adapted to color treatment, by means of stains, and many architects prefer them to slate on residences for this reason. The low cost of a shingle roof, as compared with a slate or tile roof, however, is probably the chief factor in their selection.
The best shingles are considered to be those made from cypress, redwood or cedar, in the order mentioned. Cypress shingles are probably more durable than redwood shingles, but their advantage in durability is offset by the slow-burning qualities of redwood, and also by the richer color of the latter wood, so that there is not much choice between the two woods.
The most common wood for shingles, however, is the cedar, which is considerably cheaper than cypress or redwood, and sufficiently durable when dipped in oil or stain. The old-fashioned split pine shingles were very durable, but the pine shingles now sold are inferior to cedar. Spruce shingles are also sold in some localities, but are not suitable for good work.
Practically all of the shingles now used have rough surfaces as they come from the saw.
Cedar and redwood shingles as commonly sawn are 16 inches long, while cypress shingles are usually 18 inches long, and may, therefore, have a greater exposure to the weather. Redwood shingles and the cedar shingles from the States of Washington and Oregon (which furnish most of the shingles used west of the Mississippi) are 5/16 inch thick at the butt; cypress shingles are usually sawn thicker, those used in Boston being 7/16 inch and ½ inch thick.
Ordinary roofing shingles are of random widths, varying from 2½ to 14 and sometimes 16 inches ; they are put up in bundles, usually four to the thousand. A "thousand" common shingles means the equivalent of 1,000 shingles 4 inches wide.
When shingles are to be laid to form a pattern, it is desirable and often necessary that they shall all be of the same width. For this purpose shingles of certain widths are bunched together and sold as "dimension shingles." The most common width for dimension shingles is 6 inches, although 4-inch and 5-inch shingles are carried in stock in many localities.
Dimension shingles are generally of the best quality and cost a little more than random widths.
In most cities dimension shingles with the butt sawn to various patterns are also carried in stock. Any suitable pattern can, how- • ever, be sawn from dimension shingles at a small expense.
Grading of Shingles. - Shingles are variously graded and marked by the manufacturers, the grades and marks differing for the different woods and in different localities.
The best quality of shingles should be free from sap, shakes and knots. The Washington and Oregon cedar is almost entirely free from all of these defects. In pine and cypress shingles small sound knots are permitted when not nearer than 8 inches to the butt end.
Unless the architect is familiar with the markings of the shingles in the local market, it is best to specify "the best quality," rather than the "first quality," as the terms are not synonymous, the best quality often being marked "Extra" or "Prime," while "first quality" may really be used to designate a quality not so good.
Durability. - In regard to the durability of shingles, an instance is on record where cypress shingles remained on the roof of a Virginia mansion, in a good state of preservation, for 104 years. Redwood shingles should remain in good condition for from 25 to 50 years, and if dipped in oil would probably last longer. Cedar shingles should last from 12 to 15 years with ordinary treatment, and if dipped in oil or creosote should last 25 years.
Paper Lining. - The roofs of all buildings that are to be plastered (at least in the Northern States) should be covered under the shingles by a layer of good strong waterproof paper. It is true that such a lining is apt to diminish the durability of the shingles (unless they are dipped all over) by causing them to sweat and rot on the under side, but this disadvantage is more than offset, in the Northern States, by the additional warmth obtained, and by preventing fine snow that may sift under the shingles from going farther.
Tarred felt has been much used for this purpose and answers very well, but there are waterproof papers which are more durable, as well as cleaner and better to handle.