The shell of a house serves as the first line of defense between the occupants and the outdoor environment. Walls function as a weather barrier, nail base for finish materials and an energy conserving boundary. A sensible wall system is durable. And this requires all components in a wall assembly to be compatible for the long haul. Siding, siding finishes, housewraps, insulation and wall frames must work together while achieving distinctive goals. So it is in this light that we should view a primary, but often overlooked, component in residential wall systems: weather-resisting wall wraps.

Wood, brick, masonry, vinyl, and other sidings do not function as barriers to driving rain. Siding is porous. There are a multitude of joints, laps, and connections making it discontinuous. Water and air are driven through these leakage points by wind, gravity and capillary forces. Also, we generally use water-sensitive materials for siding and structural elements. Leaking water rots wood, grows mold, corrodes steel and lowers insulating R-values. Another concern is that leaking air strips heat from homes and dollars from energy budgets. So air-tight construction is desirable.

• capillary break
• WRB weather-resistive barrier, house wrap

1. Choosing between oriented strandboard and plywood
2. Common failures in wood structures
3. Decision making in the purchase of siding: a survey of architects, contractors, and homeowners in the U.S. Northeast
4. Decoding building codes
5. Details that keep walls watertight
6. The evolution of engineered wood I-joists