How to Install a Flat Roof Membrane

What You'll Need
Flat roof membrane
Membrane adhesive
Roller brush
Plywood (optional)
Saw (optional)
Roofing nails (optional)
Pencil (optional)
Seam tape
Oil-free soap
Tape measure

A flat roof membrane is made out of a synthetic rubber and other compounds designed to move water from the roof, and they are also UV-resistant. Gravel on a flat roof does the same thing but is less effective. The flat roof membrane also makes finding a leak very easy whereas with gravel, it’s virtually impossible. Follow the simple steps below to install your own flat roof membrane.

Step 1 – Roof Preparation

A flat roof membrane is actually glued to the roof, but for the adhesive to bond well, the roof needs to be cleaned. Since the flat roof membrane is often installed on top of shingles, use a product that is recommended for the specific shingles that you have. If you are installing it prior to shingles being placed, clean the roof using water mixed with a few drops of oil-free soap. Let the roof dry before continuing.

If the current roof has gravel, then you can either remove the gravel (which is very labor intensive) or you can cover it. If you choose to cover the gravel, lay sheets of plywood directly on top of the gravel. Cut the plywood as needed to make an even fit, and then hammer the sheets in place with roofing nails. You want a tight connection between the membrane and the roof. Installing it on top of gravel creates too many air pockets.

Step 2 – Fitting the Membrane

The flat roof membrane will need to be trimmed in order to fit properly. Measure the roof dimensions, and trim the membrane to these dimensions. After the membrane has been cut, lay it out on the roof. Maneuver it around until it fits correctly. Inspect the membrane to make sure you didn’t cut it short or too long. Make adjustments as needed. You can use small pieces of the membrane to take care of bare areas.

Step 3 – Attaching the Membrane

Open the adhesive, and stir it for several minutes. Make sure it is mixed well before trying to use it. Choose a section to start in, and lift the membrane off of the roof. Use the paintbrush to paint the roof or plywood with the adhesive, and then paint the back of the flat roof membrane. This creates the best bond possible. Do not use a lot of adhesive along the edges. Press the membrane down and continue until one section is finished. Use the roller brush over the section to remove any air bubbles. Repeat until all of the membrane has been attached.

Step 4 – Finishing Up

Clean the seams of the membrane with soapy water as you previouslycleaned the roof. Along the seams, apply the seam tape. Let the roof cure for several hours prior to doing anything on top of the membrane.