How to Apply a Flat Roof Coating

What You'll Need
Push broom
Paint roller
Rubber membrane
Rubber membrane adhesive
Liquid flat roof coating
Seam tape
Surface cleaner
Clean rags
Tape measure

A flat roof coating provides extra protection from pooling water and other elements. The majority of flat roofs you see will have a layer of gravel on the surface, there to push water to the drains. The problem with gravel is that it makes pinpointing leaks impossible. There are two popular flat roof coating methods that are much better than gravel. The first is a rubber membrane which is installed directly to the top of the flat roof. It allows you to see leaks easily while preventing pooling water. The other flat roof coating is a liquid such as polyurethane. Follow the simple steps below to apply both types of coating.

Step 1 – Clean the Flat Roof

When you apply any flat roof coating, the roof needs to be relatively clean for the coating to adhere to the surface. Use the push broom and sweep the flat roof as clean as possible. Dispose of the debris in a garbage bag or use a vacuum cleaner to suck it up. Another option is to powerwash the surface and scrub it down with a stiff-bristled brush and surface cleaner.

Step 2 – Select a Flat Roof Coating

Choosing a flat roof coating is not that easy because there are many quality products on the market. A rubber membrane is easy to install, relatively inexpensive and will outlast many other products. Liquid flat roof coating has various properties including sealing existing areas that are leaking. Some can be applied in very cold (and hot) weather conditions whereas others are more temperamental. Application is very simple but time consuming.

Step 3 – Applying Liquid Coating

Once the flat is cleaned off, you can begin to apply the liquid coating. Make sure to consult the directions on the container to know how long it takes to dry and any temperature considerations. Begin at one of the car corner of the flat roof and work in smaller sections. Use a paintbrush to apply it as you would paint. Pay close attention to applying the coating where the roof meets the sides.

Continue in this manner until the roof is covered. The last corner should be the one to be finished last. Do not neglect vents, pipes or chimneys by painting the coating around these areas.

Step 4 – Install Rubber Membrane

Use a tape measure and measure the length and width of the flat roof and cut the membrane to fit. Lay it on the roof making sure the edges are flush to the sides and that each piece is flush to the previous piece of membrane. Fold one section in half and paint the membrane adhesive to the roof as well as the membrane. Fold the membrane back, and use the roller brush to remove air bubbles.

Continue until the roof is covered, and then seal the seams with the seam tape. Roll the air bubbles out of the seam tape as well.