Repairing Flat Roof Tar & Pea Stones

Built-Up Roof Basics

• Flat roofs are a type of built-up roof, sometimes called BUR by building professionals. The term "flat roof" actually refers to low-slope roofs; a truly flat roof would collect water and quickly deteriorate. In practice, "flat" roofs gently slope toward edges or drains that shed water from the roof's surface. Like standard roofs, built-up roofs sit on top of a roof deck and underlayment materials. Above the underlayment, builders place rigid insulation panels and overlapping layers of roofing felts or asphalt-impregnated fabrics. Roofers bind the separate layers with tar, also called asphalt or bitumen. Gravel and asphalt form the final, protective layer of many flat roofs.

Demolish or Patch?

• The first step in repairing a tar and gravel flat roof is to determine whether you should simply patch the damaged area or demolish and replace the roof. Although temporary, properly installed patches can last several years. If you must quickly repair a leak during a storm, then patching is the only option. If conditions allow you to replace a roof, you should carefully inspect the roof's condition before embarking on such an extensive project. In general, loose gravel and cracked or peeling tar indicate that the roof covering requires replacement. However, if the damaged gravel and tar is isolated to a small area, a patch may suffice.

Removing and Replacing Tar and Gravel

• Removing tar and gravel roof surfaces is difficult, time-consuming work. Roofers usually use hand tools, such as roofing shovels and spud bars to pry and scoop damaged tar and gravel from a roof surface. Most building professionals replace old tar and gravel roofs with a smooth-surfaced membrane, usually rubber or asphalt fabrics.

Patching Under Wet Conditions

• Roof covering manufacturers offer "wet patch" compounds for emergency flat roof repairs. Wet patch is an asphalt product that hardens under moist conditions. Many varieties harden when fully submerged in water. Wet patch resembles a thick paste. Roofers typically apply the compound with trowels or putty knives.

Flashing and Other Sheet Metal

• Flashing and other sheet metal caps protect a flat roof's edges and drains. Flashing shape and size varies according to the roof's design; some pieces are 90-degree angles, others are 45-degree angles or three-sided forms. If you must repair a flat roof's flashing, remember that these protective metal pieces should overlap the roof's base layers and sit beneath the roof's exposed tar and gravel layer.