Reroofing Methods for a Flat Roof


When a flat roof gets old, it tends to start leaking. Homeowners must decide whether to try to do repairs or get a new roof. If a roof has lived its life, it may be more economical to replace it. The material may be worn, and leaks may continue to appear. A flat roof must be durable and able to withstand extreme heat, freezing cold and hard rain. There is a variety of roofing systems for flat roofs that will protect your home from leaks for many years.

Single Ply Modified Rubber Roofing System

  • A single-ply rubber roof is a strong durable material made of rubber. The rolls of roofing are approximately 40 inches wide by 33 ft long. This covers one 10-by-10-foot section of the roof and is referred to as a "square." The old flat roof is removed down to the bare sheathing. Tarpaper is installed to the entire roof. Drip edge metal is installed around the entire edge perimeter and nailed down over the edges of the paper. Hot tar mops and hot tar rollers are used to spread the tar evenly on the paper, as the single ply rubber roofing is installed over the entire length of the roof. There is a 4-inch black overlap at the edge of each roll. The next roll of rubber is installed overlapping the black area. This process continues until the entire roof is covered. Roofing granules are sprinkled onto any small black areas on the roofing while the roof is still hot.

Tar and Gravel System

  • Tar and gravel roofs benefit from the gravel in two ways. The gravel is white in color and reflects the sun. It also is porous so it soaks up the water standing on the roof from a rain. The old roof is removed completely down to bare wood. Tar paper is installed over the entire deck, and drip edge metal fastened around the entire perimeter. Rolls of roofing membrane are applied to hot tar, which is poured underneath the material as it is rolled out. As the installation progresses, gravel is applied generously. The gravel does not cover the last strip of membrane applied, as it would interfere with the remaining material to be installed. The last two rolls of membrane are installed at the same time, and the gravel is applied as they are rolled out. As an alternative, a truck with a hydraulic lift can be used to pour the gravel onto the just completed membrane system.

Waterproof Membrane System

  • A waterproof membrane system consists of cloth rolled out in between a hardening system. The old roof is removed completely down to bare wood. Tar paper is installed over the entire deck, and drip edge metal fastened around the entire perimeter. A primer is applied to the surface and is given time to dry. A generous coat of a water-based pink adhesive is applied. A cloth material is rolled out as you apply the adhesive. At the same time, a large hand tool with a wide blade is used to work out any bubbles in the cloth. This is done to the entire roof. When dry, a final waterproof hardening seal coat is applied to finish the job.

Roll-Out Fiberglass Roofing System

  • A fiberglass roll-out roof is made of a tough sturdy material installed with a base of hot mopped tar. The old roof is removed completely down to bare wood. Tar paper is installed over the entire deck, and drip edge metal fastened around the entire perimeter. A fiberglass roll is 2 feet wide and is rolled over the length of the roof. The fiberglass strips overlap each other 2 inches. Hot tar is applied to the fiberglass as it is rolled out. When the roofing is hard and cool, fibered aluminum coating is applied to the entire surface with a paint roller.

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