List of Materials & Steps for a Built-Up Roof on a Flat Roof

About Built-Up Roofs

• The traditional built-up roof is made from tar and gravel, applied in three or more layers of waterproof material with alternating plies of hot tar and fine river stones, according to writer Max Alexander of the This Old House website. Originally made with tar paper, these roofs are now made with a variety of advanced materials, such as fiberglass, that give the roof more durability and water resistance. Advantages of built-up roofs include good fire resistance due to the gravel and an attractive appearance. It is one of the cheapest types of roofs for flat-roofed buildings and is easy to repair.

Built-Up Roofing on Flat Roofs

• Built-up roofing is easy to install on flat roofs because they are less hazardous to work on than sloped roofs and hold the materials securely as they cure. Generally a base sheet is used as the bottom layer and fastened to the roof structure mechanically. Asphalt and gravel are then applied to the roof in layer after layer to make a solid surface to repel water from the roof surface. Plastomer coatings may also be used to give the roof more flexibility than a simple asphalt surface. Both hot and cold asphalt is used for built-up roofing.

Materials Required for Built-Up Roofing

• Built-up roofing is done in a number of ways, but the easiest for do-it-yourselfers is the cold-asphalt application method. This method uses an adhesive, roll roofing material, nails and asphalt cement applied in multiple layers. A reflective coating can then be applied after the roofing has cured to provide “cool roof” capability for better energy efficiency.

Steps for Installing a Built-Up Roof

• The roof must first be repaired before applying the new roofing materials, with all blister, buckles and raised edges flattened. Flashings, drains and vents should be in good condition. The adhesive is applied to a clean roof, and rolled roofing applied securely with nails. More adhesive is applied and then the asphalt emulsion compound. This compound is allowed to dry for 7 to 10 days. A reflective coating may then be applied.