The only type of commercial roofing used on a low slope system is structural metal panel roofing in Montgomery County. The structural metal panel roof is ideal for low slope systems due to its hydrostatic characteristics, in other words, its water barrier characteristics. Structural metal panel roofing systems can also be used on high slope applications.
The design of structural metal panel roofing in Montgomery County is such that it resists the ingress of water at the seams and other joints in the system. A sealant is applied at the seams and joints or an anti-capillary action design is used for waterproofing purposes. The metal panel roofing system is quite strong which allows the panels to span supporting members without intermediate support.
The structural metal panel roofing in Montgomery County is comprised of the roof deck, the underlayment, vapor retarders, insulation and ventilation methods. The roof deck is installed over a substrate, one type of which is closely spaced decking which gives solid support for the metal roof panels and the other is made up of closely spaced purlins where the metal roof panels span the supports. The most common method is to use purlins as support rather than a full support deck.
Under the roofing in Montgomery County deck is the underlayment which is commonly referred to as “felt paper”. This is often avoided when the roof deck is installed on purlins but is highly recommended when the roof deck is installed over a full substrate. The felt paper performs two functions, it acts as a temporary roof or weather barrier during construction and it provides a secondary barrier if water should somehow make it through the roof deck.
The common felt, when used for metal roofing in Montgomery County is asphalt saturated or impregnated or non-perforated felt which is all organic. The felt comes in two standards referred to as types I and II. At one time the systems were known as Nos. 15 and 30 which reflected their weight in pounds per square foot. When the underlayment of felt is used the industry standard is one ply of Type II (No. 30) applied in an overlapped shingle fashion when the roof slope in excess of 18 degrees and two ply if the slope is less than 18 degrees. The felt is applied horizontally across the roof.
In northern climates where the temperature can fall below freezing an ice dam is called for. An ice dam starts at the edge of the eave and go up the roof slope a minimum of 2 feet and 3 feet if the slope is less than 18 degrees. The material for the ice dam is a self adhering polymer.
As condensation builds up on the underside of the structural metal panel roofing in Montgomery County the design should consider vapor retarders, insulation and ventilation issues.
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