What is a modified bitumen roof?

A modified bitumen roofing installation is five layers starting with an asphalt-based and is one of the top choices for a commercial structure with a flat or low-sloped roof. So, what is a modified bitumen roof made of?

Modified Bitumen roofing installation will have 5 layers, as we stated. This roof style of roof engineering originated in Europe in the 1960s and has been successful here in the U.S. since around the mid1970s. The framework that makes a Modified Bitumen Roofing installation consists of the following: 

• Insulation that provides the “R” value comes from a modified bitumen roofing installation. This provides temperature stability for the building. 
• Modified plies of asphalt alternating with the membrane-like atactic polypropylene, styrene butadiene styrene, or synthetic rubber.
• Modified Bitumen Membrane are factory-fabricated sheets of a membrane made with co-polymer and reinforced with fiberglass or polyester.
• A waterproof material and adhesive that is the bonding agent. The adhesive is applied either cold or hot with a welder. 
• The top surface is the weather-resistant layer that provides the UV protection.

How is modified bitumen roofing installed?

The steps for a modified bitumen roofing installation begin with the roof decking inspected and repairs made if needed. Then a rubberized asphalt is applied to the decking with two layers of rolled roofing felt next. The typical modified bitumen roofing installation will have  two layers of membrane minimum. Next, the base sheet is installed then the cap sheet. 

There are four ways that a modified bitumen roofing installation is performed: 

1. A hot tar applied 
2. A cold solvent based adhesive applied
3. An open flame to torch down that membrane by melts two sheets together
4. A peel and stick base and cap sheets that are self-adhered when the tape is removed.

When all is said and done and the modified bitumen roofing installation is complete, the asphalt combined with polymerized rubber, or a plastic has a fiberglass reinforcement. The ending results are a flexible but rugged and waterproof roofing membrane.

What does a modified bitumen roof look like?

The finished product with a modified bitumen roofing installation will be a roofing membrane consisting of multiple modified bitumen sheets, or a combination of roofing felts and multiple modified bitumen sheets. The rubber-modified asphalts, like SBS (styrene-butadiene-styrene) material is a granular surface. It is typically mopped on, torched on, or a cold adhesive applied. If the APP (atactic polypropylene), a -Plastic-modified asphalt is used, the final surface may be granular or smooth. 

Can modified bitumen roofing be repaired?

Absolutely, which is one of the reasons it is a popular choice in the Cincinnati area. The following are basics steps to repair a modified bitumen roofing installation: 

• Determine the damage and repair as needed. If the bitumen is wet and the decking or insulation are wet, replace those before making the repair. 

• Clean the membrane so the patch will adhere. It should be swept, removing any debris and dirt. DO NOT power wash, this will add moisture to the membrane.

• Deal with weathering damage and age of the coating as needed. This may require filling in gaps.

• Patch the roof membrane once the surface is completely dry. Using a liquid rubber coating, apply to the affected area and reinforce it with a polyester membrane, allowing a few inches all the way beyond the damaged area. With the fabric embedded into the mastic, use a paint brush to sweep the polyester membrane to remove any air pockets, blister, or wrinkles.  Last, apply a topcoat layer to seal the fabric and keep moisture out. 

Can you paint a modified bitumen roof?

If the top surface is smooth, yes. A granular, rough top finish shouldn’t need painting and wouldn’t take the paint in a smooth manner anyway. 

How do you maintain a modified bitumen roof?

A properly maintain modified bitumen roof installation will extend the service life of the roof. Modified bitumen roof are excellent for waterproofing protection, but the seasons can abuse the roof and the structural integrity of the building. 

 After a modified bitumen roofing installation, consistent maintenance is a must, including monthly visual inspection by your maintenance staff and a professional by a roofing contractor every 2 years. 

How long should a modified bitumen roof last?

With the recommended schedule of inspections and follow through with any repairs, a modified bitumen roofing installation should give you 20 years or more useful lifespan.