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University of Minnesota Extension

Sealing roofs, walls, windows and doors to keep water out

Residential home.

While we may complain a little about the comfort and energy costs of older homes, we also speak with reverence of their durability. There are a number of reasons why older homes have endured the test of time. One reason is the difference between the dimension lumber used to construct older homes and the growing number of composite materials used in newer frame construction. While some composite materials are more durable than traditional framing and sheathing materials, others are less durable and are not able to survive wetting and drying cycles as well as dimension lumber.

Drainage plane

Another factor that contributes to the durability of homes is their ability to resist Minnesota weather. On the exterior of homes, building materials that can't stand up to repeated exposure to water must be protected by another layer. This protective layer is often referred to as the drainage plane. It should cover the entire house from bottom to top and includes:

  • The foundation (footings and walls) drainage system.
  • Weather resistive barrier (housewrap or building paper).
  • Flashings and roofing components.

The outside surfaces of windows, doors and skylights are also part of the outer surface of a building and must be carefully integrated with drainage plane components. Starting at the foundation, every element of the drainage plane must be installed so it will direct water out and over the layer below it in the same fashion as the overlapping of shingles on a roof. If they are not overlapped properly, or reversed, water may be directed into the building and result in a failure.

Every element of the drainage plane must be installed so it will direct water out and over the layer below it.

What to do


Richard Stone, Extension educator

Reviewed in 2018

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