weathertight

Weathertight, or weather-tight, is a term used in architecture and construction to describe a building assembly, component, or object designed to resist the intrusion of weather elements such as rain, snow, wind-driven rain, and wind. A weathertight condition aims to keep the interior space dry and usable under typical service conditions while allowing moisture to dry to the exterior or interior as designed. It is not the same as waterproof; even weathertight assemblies may permit limited moisture under extreme conditions but are engineered to prevent infiltration during normal use.

In building envelopes, weathertightness is achieved through a combination of proper detailing, flashing, sealants, gaskets, weatherstripping, a continuous air and moisture barrier, and drainage planes. Key areas include roof-to-wall terminations, window and door openings, joints, penetrations, and connections to adjacent elements. Methods such as rain screens, drip edges, sill pans, and properly oriented flashing help shed water and manage condensation.

Testing and standards: weathertight performance is often verified by tests for air permeability and water penetration under applied pressure differences, and by field inspections. Compliance may be specified by building codes, product standards, or project specifications.

Maintenance matters: the effectiveness of a weathertight envelope depends on proper installation and ongoing maintenance of seals, flashing, and joints; deterioration can compromise performance and lead to moisture damage.

Weathertight design is common in modern construction, including residential, commercial, and institutional buildings, as well as in manufactured housing and portable structures where weather exposure is a primary concern.