Installation Process

While Built up roofing systems can be installed in many different ways, we outline the essentials below. Built up roof installations start at the base with roof insulation to cover the roof decking. Mechanical fasteners are used to install these in place. The insulation works as a bottom layer of waterproof protection. Next, apply a layer of asphalt over this base sheet. Asphalt can be applied hot or using a cold-adhesive solution.

How Modified Bitumen roofs work

Bitumen roofing systems are made of five-layers of different materials as we stated above. As a membrane form, the rolls are installed directly onto the roof and sealed with an adhesive. Different sealing applications can be used, from heat welding, cold-adhesive and self-adhered. They can even be mechanically attached. Modified bitumen comes in two different membrane types, APP and SBS.

APP Membranes

APP stands for atactic polypropylene membrane, it consists of a blend of asphalt and plasticized polymers. When placed under high temperatures, it forms into an elastic material. App modified bitumen is installed with torch applications. Practical uses of APP membranes is that they are highly resistant to ultraviolet rays and are able to provide a cooler roof temperatures for buildings in hot climates.

SBS Membranes

SBS stands for styrene-butadiene-styrene. SBS membranes are made up from a combination of asphalt and polymerized rubber. This is what gives SBS membranes their elasticity and additional flexibility.

SBS is one of the best choices for buildings in hot climates, where the roof is able to expand and contract during hot to cold weather conditions. Additionally, SBS is perfect for high wind prone areas.

Differences Between the Two

The main differences between SBS vs. APP modified bitumen roof systems comes down to their material components. Plastic is included in APP bitumen, SBS bitumen has rubber. Out of the two roofing systems, SBS is more flexible. We do recommend that while both types of materials are great, to always hire and work with a trustworthy manufacturer and roofer in order to choose the best quality materials, quality and appropriate material for your roof.

Lastly, a major difference comes down to the application methods. For APP materials, the material is rolled out while heated up with a torch on the underside part, which melts this underside and turns it into a molten adhesive. This adhesive seals as it touches the roof area and dries. The process continues until the roof is fully covered.

For SBS roofs, the installation can be done as cold adhesives or peel and stick applications.

installation of sbs roofing materials on flat roof

Advantages of Modified Bitumen Roofs

  • Waterproof: Modified bitumen roofs are one of the best types of waterproof protection systems in today’s market. Of course, make sure that the installation is properly done, there are no issues present and make sure to add more layers in order to reinforce the material.
  • Energy-efficient: There are cool roofs and UV reflective materials available as additional features. These are great options for hot climate areas.
  • Tear-resistance: Another great benefit is the durability and strength of the material. Its tear-proof and can withstand all types of weather.
  • Efficient Installation and upkeep: Working with the best roofing contractor ensures that they are using the best materials and equipment available. They will also be more efficient in the installation and are typically done in a few days.
  • Seamless application: Depending on the type of application, MB systems are seamless for additional security.
  • Fire resistant: MB roofs are durable, so durable in fact, that they are resistant to fire, hail and wind damage.

Disadvantages of MB Roofs

  • Can be slow to install: Installations can take longer than other roof types, and slow other building projects.
  • Material absorbs heat: Due to the dark color of the material, its prone to absorb heat and not reflect it during the hot, summer months. This can cause the building to heat up, leading to higher electricity AC costs. The UV rays do not damage the roof, however.
  • Requires upkeep: Due to their flatness, standing water or puddles can begin to form with constant rain water. If not properly drained or cleared up, it can cause damage to the roof. Therefore, its recommended to inspect your roof after rain storms.
  • Costly: While the costs varies due to multiple different factors, the price of a new MB  installation is pricey for sure. Talk to your roofing contractor for payment plans if necessary.
  • May require additional costs later: We recommend a maintenance plan, as this can help with damages and costs down the road. However, a bitumen roof is an investment and damages can occur, resulting in additional expenses.

Additional Tips

Make sure that along with your yearly inspection to remove and clean any debris, leaves, twigs and dirt away from your roof. If the area is wet or moist, make sure to let it dry completely. You can now add a type of layer or coating in order to prevent pooling from occurring again. We recommend the 502 SEBS mastics roof coating, 670 silicone coating or 229 SBS rubber reinforced asphalt.

Make sure that other surrounding equipment are working as they should, to keep the integrity of the bitumen roof in good standing, You do not want any HVAC or gutter water leaks to accumulate water on top of your roof.

modified bitumen roof installation for APP membranes with fire torch

Repairs for Modified Bitumen Roofs

Similarly to other types of roofs, over time or perhaps after a particularly bad storm, built-up roofs receive damage. Sometimes they receive enough damage where repairs are needed. We list some of the most common types of damages for BUR roofs below.

  • Blisters: Small blisters are just that, they look like small, circular pop ups that appear on the roof. Using a knife, you can cut open the blister and allow that area to dry completely. If the damage area is deeper than that, then keep cutting until you arrive at a layer that is dry. Remove any of the damp materials, for example, the plies, and install brand new felt over the area. Next, apply new asphalt and cover it. Use liquid-applied coatings on top if necessary.
  • Open Joints: Sometimes, joints or seams start to separate and come apart. You want to add cement on this opening and make sure to press them together right after, to make sure the seams are closing in as the cement dries. If the damage is severe, then cut a large piece of felt and attach it over the open joint. Use nails to secure this felt down and cover these with roofing cement afterwards. To finish the repair, use the some gravel to spread over it.
  • Tears or Cracks: These are the easier fixes. First, clean the area, make sure there is no debris on top. Use asphalt cement and apply it over the damaged area, next use some roofing felt and install over it. Do leave 4 inches out on each side to make sure that the area is thoroughly covered. Continue this process a second time and finally, apply a coat of cement. Apply gravel if necessary on top.
  • Waves or uneven spots: If you can tell that the damage is superficial and aesthetics only, you can simply add another layer or number of layers on top of this area to level it accordingly.

Modified Bitumen FAQs

We have gathered some of the most frequently asked questions regarding this type of roof.

How long do Modified Bitumen last?

Modified bitumen on average last 20 years or more. This average time can be extended with a proper maintenance plan and yearly inspections.

How can modified bitumen roofs be applied?

There are several different types of applications that can be used, from regular welding, using a cold-process adhesive and self-adhesive membranes.

What is the main cause of roof damage?

Foot traffic is one of the main causes of damage for these types of roofs. We recommend not to use them if there is regular foot activity.

Can I repair my bitumen roof?

Yes, Modified bitumen roofs can be repaired! There is no need to do complete replacements, unless the damage is too severe. Repairs are typically done by cutting around the area of damage, removing the piece, checking to make sure there are no other issues and applying a bitumen patch. Lastly, you apply a sealant to secure it tightly.

When is the best time for my modified bitumen roof to be installed?

Modified bitumen can be installed all year long. For best results, we do recommend to work during times when the temperature is not too extreme or there is rain present. Do keep in mind that some materials are best installed in certain temperatures, for example, polyglass polar cap and base membranes require low temperatures for adequate installations.

Your Trusted Hoosier Commercial Roofers

Before getting started on your building’s new installation or commercial roof repair, make sure to schedule a consultation with the local roofing experts – Oscar Roofing.

Oscar Roofing has been helping homeowners with their residential and commercial home services since 2003. We focus on roofing, siding, gutters, painting and exterior and interior remodeling services.

modified bitumen roof installation for APP membranes with fire torch