Most exterior wall cladding systems leak. Wind pressure and capillary action can drive rainwater through the many cracks, joints, and small gaps in a building's exterior. With typical residential siding systems, it is nearly impossible to seal all those holes. Even if a builder succeeds in sealing a majority of the holes, using caulk on the exterior of the wall is not a long-term solution; the caulk will need to be reapplied fairly often. A more practical way to protect building exteriors from rainwater relies on a drainage approach. With this approach, any water that leaks through the cladding will run into a water-resistant surface and safely drain down and out of the wall. The water-resistant surface could be house wrap or rigid foam that is securely taped or sealed at all seams. . House wrap should be lapped over any exterior wall flashings installed around window and door openings or where roofs intersect walls. Any holes through the wall, such as for water spigots, exhaust vent outlets, HVAC line sets, or wiring for outdoor light fixtures and receptacles, should be carefully sealed or gasketed.