Rigid Insulation

Numerous types of rigid insulation are now in use, and may be made from expanded polystyrene beads, rigid urethane laminate, low density fiberboard, or from fast-setting liquids poured on-site. They vary in thickness up to more than 2" (50.8 mm) and in length and width depending upon the manfacturer. All these types are efficient insulators and are usually of sufficient density to hold the weight of a normal roof covering without the need for lumber bridging.

Metal Deck

The covering of metal decks with shingles or shakes presents a rather unique problem. These decks are often used for economic reasons, but they generally require a finish roofing capable of shedding the weather. In addition, aesthetic considerations often require that the deck itself be covered with a material such as Western Red Cedar shingles or shakes to provide a pleasing finish. When a metal deck is to be covered, consideration should be given to the use and placing of vapor barriers. If insulation is placed on top of a metal deck, the entire roofing system must be taken into account. For example, wood members not be sandwiched between two vapor barriers. If this is unavoidable, the wood member should be preservative trated before installation. In some cases, the seams in a metal deck can be sealed to create an effective vapor barrier. Boards or a panel deck must be used as a nailing base for the shingles or shakes, supported by vertical lumber members fixed to the deck. This can be achieved in a number of ways:

1. On a corrugated deck, vertical lengths of lumber are fastened to the deck and horizontal boards or panels are applied across the vertical pieces. If insulation is required, it is best placed on top of the vertical members, held in place by the nails fastening the boards or panels to the members (Figure 26, Page 19).

2. On a sheet deck, or where the corrugations are very shallow, it may be necessary to use angle clips to attach the vertical members to the deck. The clips should be nailed to the lumber and bolted or screwed to the deck. Boards or panels are then applied as before. If there is a likelihood of excessive moisture buildup, as may be encountered in ice arenas, the cold weather roof principle can be employed, supplemented by a mechanically produced air flow if necessary.

Cold Weather Roof System Details

Western Red Cedar shingles and shakes are an excellent roofing material for cold weather areas that experience heavy snowfall and severe temperature extremes. A natural wood product, they offer the advantages of durability, superior wind resistance and good thermal and acoustical properties. As with any other roofing material, however, their best performance depends upon proper design, sound construction practice and correct installation.