Smooth-surfaced roll roofings are less expensive than mineral-surfaced but do not weather as well because the asphalt coatings are not protected by mineral granules from the action of sunlight.
If properly maintained, however, they should render satisfactory service. Lightweight smooth-surfaced roll roofings are used for temporary structures and as underlay materials for other roof coverings, such as slate, tile, and cement-asbestos shingles. Instruction sheets, nails, metal caps, and lap cement are furnished by the manufacturer with each roll of smooth-surfaced roll roofing.
To render the best service, smooth-surfaced roll roofings should be recoated at regular intervals with bituminous roof coating. Seams that have opened should be recemented and any small holes in the covering filled with flashing cement. Loose nails should be pulled, resulting holes sealed with flashing cement, and new nails driven where necessary.
Coating materials are usually composed of an asphaltic base and mineral filler, thinned to heavy brushing consistency with a volatile solvent. Fatty acid pitch-base coatings are also available. Manufacturer’s directions on the container should be followed in the application of these bituminous coatings.
Smooth-surfaced roll roofing may be applied over other roofing materials, provided the surface of the old covering is in reasonably good condition. If not, the worn roofing should be removed, the roof deck prepared in the same manner as for asphalt shingles, and the roll roofing applied according to the manufacturer’s directions.