Architecturally Sound Metal Roof Installation Method
Classic Products Architectural metal roofing products are designed to shed water in an efficient manner, and also to accentuate the other architectural elements of the home. What sets architectural metal roofing products apart from structural products is that they are applied directly to the roof decking and therefore are often manufactured from thinner metals than structural metal roofing products. In essence, architectural products are designed to pass rooftop weight loads through to the roof decking beneath them rather than support weight loads and pass them through to the building’s structural members. Architectural metal roof systems allow for standard attic ventilation methods.
Conversely, common structural metal roofing products are installed without a solid decking beneath them. That is, they are generally used in applications where the metal roofing is installed over purlins, also known as lathe boards. The spacing of such purlins is a function of the structural strength of the metal roofing and can be determined through load tables supplied by the roofing manufacturer. Structural metal roofs, because they are designed as part of the “structure” of the building, are generally manufactured from thicker metals. Structural metal roofing is usually intended for applications such as industrial facilities, strip malls, barns, warehouses, storage units, and metal buildings. Rarely are structural metal roofing products used for residential applications.
Proper Ventilation | Best Practices
Because of the potential for direct contact between the backside of the roofing panels and warm, moist air inside the structure, special ventilation issues can exist with structural metal roof systems especially on smaller buildings. If a structural metal roof is ever installed on a home without decking, it is critical that the property owner and the contractor take ventilation and condensation control into consideration. When metal roofing is installed this way, there must be, at the minimum, a vapor barrier behind the ceilings, a lot of insulation, and strong attic ventilation. If these things do not exist and work in conjunction with one another, disappointing results will follow.