Home's Outside Wall Material Has Little Effect on Moisture

"The choice of an exterior wall covering--siding or stucco--should be governed by aesthetic considerations, not moisture ones. Make sure that the architect specifies a first-quality vapor barrier to prevent moisture problems. This is easier said than done; even the architects aren't sure about proper vapor barriers."

"Wood siding has an edge--because of its porosity--over stucco if there is a concern about moisture and mildew, but it requires more maintenance than stucco. Make sure that proper ventilation is provided, in the form of roof and/or gable-end vents or attic fans. Bathroom ventilation is especially important."

"Vinyl vapor barriers are often recommended, but they are difficult to apply properly; one or two holes in the vinyl can defeat the purpose of the barrier. Felt paper as a vapor barrier under wood siding and a similar product under stucco is suggested as an alternative approach."

When choosing between wood siding and stucco for coastal construction, aesthetic considerations should drive the decision rather than moisture concerns. A first-quality vapor barrier is critical for preventing moisture problems, with felt paper recommended under both wood siding and stucco. Wood siding offers better moisture resistance due to its porosity but requires more maintenance than stucco. Proper ventilation through roof vents, gable-end vents, or attic fans is essential, with special attention to bathroom exhaust fans. Liquid foil vapor barrier coatings may be ideal for high-moisture coastal areas. Vinyl vapor barriers, though commonly recommended, are difficult to apply properly and can be defeated by minor imperfections.

Read at Los Angeles Times