How to Install a Modified Bitumen Roof

  • 2 hours
  • Intermediate
  • 400-600
What You'll Need
Tape measure
Propane torch
Hook blade (check if your utility knife has this feature)
Spark ignitor
Chalk line
Roofing felt
Cap nails
Drip-end flashings
Protective clothing

You need a modified bitumen roof if your roof is flat or low-sloped. Modified bitumen roofing sheets are made from asphalt-based materials, making this building material resistant to cold. This prevents the roofing from becoming brittle during winter months.

The components of this type of building material allows modified bitumen roofing to be adjustable to different seasons, making it elastic and with a greater flow at high temperatures. It is advisable to put a membrane on the roof to prevent standing water and moisture from making the roof brittle.

Step 1 - Prepare the Roof

Clean the roof first. Get soapy water and a brush to scrub the dirt. Once you are done cleaning the roof, make sure the area is clean from standing water. If the texture of the roof is not smooth, you will need help in curing it. Cure this 30 days prior to assembly of the modified bitumen roof.

Before proceeding, make sure you have consulted a contractor or your architect about this step. You will need some extra help on this since you will use a propane torch. Use your tape measure and get the measurements of the area.

Step 2 - Apply the Roofing Felt

After clearing the roof from dirt and obstruction, it is time to put the roofing felt on the roof. Use cap nails and hammer them, attaching the nails on the felt and the concrete. Leave approximately 6 to 8 inches between nails. Then attach the drip end flashings 8 to 12 inches apart.

Step 3 - Prime the Roof

After attaching the felt to the roof, use a primer to prepare the roofing. There are different primers available for sealing the concrete roofs. Get a sheet of bitumen roofing and roll it out, allowing an extension beyond the perimeter of the roof. Make sure the roofing is flat and free from creases and bubbles. Cut the roofing, but still maintain the allowance you’ve set for it.

Step 4 - Heat the Roof

Rollback the roofing again and switch on your propane torch. Wear protective clothing prior to this procedure. If this is your first time using a propane torch, you may seek the assistance of an expert. Switch it on and wait until most of the flame is blue. Since you’ve rolled the roofing halfway, use the tip of the flame to heat up the rolled roofing. While heating, use your foot to slowly move the roofing until it reaches the edge. Go to the other side and follow the same procedure.

If you plan to put layers on this, make sure all areas are sealed and well-covered before you heat it up again. Put drip-flashings at the side, then apply primer.