Engineering and Construction

The heavy timber structure poses some special problems for the designer because the exposed framing and decking do not provide the concealed cavities that are present in light frame structures and other conventional building systems. Roof  thermal insulation cannot be hidden in spaces between ceiling joists  or roof rafters and, instead, must be placed on top of the roof deck. If the  roof is nearly flat, it can be insulated and roofed in the manner shown for  low-slope roofs in Chapter 16, or, if  the roof is steeply pitched, a nailing surface for the shingles or other roofing must be added on the outside of  the insulation. Electrical wiring for lighting fixtures that are mounted on the underside of the decking must  either run through exposed metal  conduits below the deck, which may  be visually unsatisfactory, or be channeled through the insulation above the deck. Ductwork for heating and  cooling must remain exposed. If  the walls and partitions are made of  masonry or stressed-skin panels, special arrangements are necessary for  installing wiring, plumbing, and me- chanical system components in the  walls as well (Figure 4.19).

Figure 4.19 When floors and roofs are heavy timber framed, lighting, communications wiring, ductwork, fi re sprinklers, and other services are exposed to view.