Common Issues with Exterior Wall Cladding: Part 1- Water Penetration

This is the first in a 6-part series covering some of the issues that apply to all types of exterior wall surfaces. In this part, we will be discussing water penetration.

Most serious wall problems are related to water in one way or another. Rainwater may enter wall systems in several ways. It may be driven by wind or it may enter by gravity or by capillary action.

Water may also be a problem in wall systems if warm, moist air moving through the wall (from indoors in cold weather and from outdoors in warm weather) is cooled and deposits condensation inside the wall system. Smaller amounts of condensation may also form if moisture moves into the walls by vapor diffusion.

A major clue to detect water penetration hiding behind the walls is if the siding is deteriorating.  Unfortunately, in many cases (metal or vinyl siding or synthetic stucco) the siding looks fine while the sheathing and wall structure behind are deteriorating.

The ability of a wall system to dry often determines the amount of damage done to the cladding and the structure. Wall systems with siding with good drying potential, such as aluminum or vinyl, may be less likely to suffer damage than synthetic stucco, for example, which has poor drying potential.

At your home inspection, we examine the exterior wall surfaces and discern if they are in good repair. Then we try to determine how the water might get into the wall system and whether there are any areas where we should reasonably suspect concealed damage. We then move inside and focus on vulnerable areas that we noticed from the outside. In some cases, the water getting into the wall system will show up on interior finishes, allowing us to confirm our suspicions. However, damage to wall assemblies doesn’t always show up on the building interior, at least not in the early stages.


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