A roof that is nearly flat or just slightly pitched for water channeling is called a low-slope roof. No roof should be truly “flat”, though it may appear that way from the ground. Every roof should have an intentionally designed slight slope for drainage. Most often, low slope roofing is used in commercial buildings, although residential applications are common. Problems with low slope roofing are common and more difficult to diagnose because the leak area is usually not directly located where the leak is appearing inside the building. The roof should have no areas of standing water. Standing water on the roof is most often caused by sagging or rotted roof decking or improper drainage design.
Promar Exteriors is a highly trained and experienced Chicago area roofing contractor fixing and installing low slope commercial roofing for over 10 years. We’ve seen many interesting issues on many rooftops in Chicago and the Suburbs. Old buildings, new buildings, retro-fit you name it, we’ve seen it and fixed it with exceptional results. We have very strong relationships with the best commercial manufacturers and suppliers. Our stability and long history of fine work provides you with unparalleled quality and guarantees.
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Commercial Roofing Systems
Asphalt Roll Roofing: Used since the 1890′s, asphalt rolled roofing consists of one layer of asphalt-saturated organic or fiberglass base felts, applied over roof felt with nails and cold asphalt cement and usually covered with a roofing compound. Roll asphalt lasts about 10 years.
Single-ply membranes: The most common materials in single-ply roofs are thermoset, thermoplastic, and modified bitumen. These are generally less expensive to install, more durable, lighter in weight and more energy efficient than built up roofs. Single-ply materials can be attached chemically, mechanically, or held in place with a gravel or aggregate ballast. Single ply roofs last between 10 and 20 years depending on material used and service conditions. Single ply includes both light and dark colored materials, products that are highly reflective should be selected for heat island reduction and energy savings. Some products now are made with mold resistant polymers to maintain solar reflectance. Examples of single-ply products include:
- EPDM: A flexible elastomeric single ply roofing material.
- PVC: A synthetic thermoplastic polymer prepared from vinyl chloride. It is the most expensive of the three but known for long-term performance.
- TPO: A blend of polymers that may or may not contain desirable additives such as flame retardants or UV absorbers. It can last 30 years and is virtually maintenance free.
Built-up roofs: A built up roof(BUR) consists of the roof deck, vapor retarder, insulation, membrane and surfacing material. The roofing membrane is composed of two components- bitumens and felts. Bitumens provide the waterproofing agents and adhesive properties of the system. The roofing membrane is strengthened and stabilized by the felts. The roofing membrane is protected from the elements by a surfacing layer, either a cap sheet or gravel embedded in bitumen or coating material. BUR’s have a low albedo, so they must be finished with a reflective coating to achieve temperature reduction and realize energy savings. BUR’s require application of a new top layer every 10 years. Properly maintained, a BUR can last 10-30 years before it must be completely torn off and a new roof installed. While some components of a BUR system contain recycled materials, a BUR is generally not recyclable.
Metal Roofing: There are two basic classifications of metal roofing; structural and non-structural(architectural). Structural metal roofing attaches directly to the lathe boards and does not require any sort of solid support beneath it. Non-structural metal roofing will require a solid substrate beneath it, typically plywood, oriented strand board or a metal roof deck. Metal roof systems typically vary from 40-150lbs per 100 square feet, making them among the lowest weight roofing products available. This places fewer demands on a building’s structure, making metal roofing a great choice for retrofit projects. Low-slope structural metal roofing consists of interlocking panles (standing seam) that run vertically on the roof surface. These products may have a painted finish, mill finish or clear acrylic finish. Some products may require machine seaming during installation.
Most metal roofing manufacturers will have guarantees of 20 – 50yrs. However, most products have been designed so they can be refurbished onsite once the original finish reaches it’s useful limit. Metal roofing materials are 100% recyclable in the event they are ever removed. The long life and low maintenance, combined with the energy savings makes metal roofing a great value.
Cool Roof Coatings: Cool roof coatings are usually white liquids applied over an existing roof structure. They can be applied over a traditional roof to achieve energy savings, an extended lifespan, and protection from the weather and UV radiation. Since these coatings reduce the temperature of the substrate, they can extend the life of the material due to reduced thermal shock and reduced expansion and contraction of the roof structure. The roof coatings are able to retain solar reflectance over time and the new surface can last 10-20 years or more.