Typically, building paper is installed as soon as the sheathing is installed.
#Weather wall frame code#
Your local code may not require you to use felt or housewrap, but unless you live in an extremely arid climate - you need to use it. The truth is, whether water is propelled by wind, capillary attraction, gravity, or some combination of these forces, sooner or later it finds its way behind, around or through the siding.
Many carpenters make the mistake of thinking that siding – wood, brick, vinyl, stucco – is an impenetrable barrier against the elements. If there is no building paper, water will get wicked up into the wood sheathing where is often causes structural problems. It is perfectly clear that butt-joints, seams, holes, and siding overlaps are siphon points driven by air pressure, gravity and capillary suction. I’ve stripped problem walls immediately after heavy rain to monitor rain intrusion and establish moisture profiles. This pressure difference works to suck the water inward through any hole it finds. The area directly behind a wind-blown wall surface is at a lower pressure than its exterior face. It moves from areas of high pressure to areas of low pressure. As the wind’s speed and direction shifts, water moves up, down and sideways under the influence of air pressure. But the film of water sticks to all siding products. Non-porous materials like freshly painted wood, aluminum and vinyl don’t. Porous materials, like unfinished shingles, stained wood clapboards, and masonry veneers soak up water. During a storm, a thin film of water clings to windward surfaces. Most of us live in climates influenced by rain and wind. Another concern is that leaking air strips heat from homes and dollars from energy budgets. Leaking water rots wood, grows mold, corrodes steel and lowers insulating R-values. Also, we generally use water-sensitive materials for siding and structural elements. Water and air are driven through these leakage points by wind, gravity and capillary forces. There are a multitude of joints, laps, and connections making it discontinuous. Wood, brick, masonry, vinyl, and other sidings do not function as barriers to driving rain. So it is in this light that we should view a primary, but often overlooked, component in residential wall systems: weather-resisting wall wraps.
Siding, siding finishes, housewraps, insulation and wall frames must work together while achieving distinctive goals.
And this requires all components in a wall assembly to be compatible for the long haul. Walls function as a weather barrier, nail base for finish materials and an energy conserving boundary. The shell of a house serves as the first line of defense between the occupants and the outdoor environment. A second line of defense is a critical component in smart weather-protecting wall designs. Some information contained in it may be outdated. Please note: This older article by our former faculty member remains available on our site for archival purposes.
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