Your Roof Cost-Cutting Measures Facilities managers don't need to read up on roof curbs to save still more money on the construction and usage ends of the bargain.
Wood can be a costly curb choice.
Many mechanical contractors will recommend wood timbers for roof-mounted condensing units, gas pipes and rooftop units. It's not a good option for these applications because any wood member eventually snakes or warps, especially when it's used as an expansion joint. Also, gas pipe installed on top of wood causes movement which scrapes away the roofing stones, digs into the insulation and lets water into the building. This treatment means the equipment won't tumble across the roof and smash on the ground below in a torrential rainstorm. However, if Hurricane Hugo blows through, all bets are off.