Q–I’ve heard about a widespread problem concerning houses that are rotting out because of water that gets behind the exterior stucco finish. Can this happen with other building materials like brick, stone and the many different sidings? Doesn’t the building code address rot concerns? How can you prevent rot in wood framing? Is it expensive?
A–The rot problem you are referring to is real. It involves a synthetic stucco material called barrier exterior insulation and finishing system (EIFS).
In many instances, this exterior system was applied directly to the wood sheathing of houses. Water that infiltrated the synthetic stucco system got trapped against the wood sheathing and caused the wood to rot. Wood rot can happen in any house, but the barrier EIFS has a tendency to accelerate the process dramatically.
Many builders, remodelers and homeowners forget that exterior finish materials such as brick, stone, cement stucco, vinyl siding, wood siding, etc., are the primary, but not the only, moisture barrier. These materials stop most of the water from wind-driven rain, water-balloon fights and lawn sprinklers, but not all of it.
Water can leak through brick mortar. It can leak around the caulked edges of windows and doors. When this happens and there is no water barrier behind the exterior finish material, problems can begin.
Lumber used for wall studs and floor joists and plywood and oriented strand board used for wall, floor and roof sheathing can resist a certain amount of wet/dry cycles. This is why the lumber doesn’t rot during the construction process. It can readily dry. But drying times lengthen considerably when these materials are covered.
The longer the wood stays damp, the longer the fungi that cause wood rot can live. If you want to stop wood rot, you need to stop water from contacting wood sheathing and wood framing members.
The model building codes do address the issue of water membranes. But keep in mind that the model codes are a set of minimum standards. You can find tables in many of the codes that actually state that sheathing paper is not required behind aluminum, vinyl and various wood sidings, but is required behind other exterior treatments.
The code and I do not see eye to eye on this issue. Secondary protection from water can be achieved easily and inexpensively. I would always install a secondary water membrane.
Many years ago, carpenters used ordinary asphalt-saturated roofing felt paper to do this job. I have taken apart 80-year-old houses where the wood framing and sheathing were in perfect condition because the felt paper stopped water from contacting the wood. The asphalt-felt paper was applied in horizontal strips starting at the bottom of the house and continuing up the structure, overlapping several inches at each new course.
You can still use felt paper, but the modern air- and water-infiltration barriers might be better. Felt paper comes in 3-foot-wide rolls. A one-story house will require a minimum of three separate strips of felt that wrap around the entire house. The modern water and air barriers are available in rolls up to 10 feet wide, requiring only a single pass on a one-story home.
Protecting a house from water is cheap. An average single-story house can be covered with a modern water- and air-infiltration barrier for approximately $325, including labor and material. Covering the same house with traditional felt costs a little more, about $380.
These costs are a drop in the bucket compared to the cost to replace rotten wood sheathing or wood framing members if rot sets in. Make sure that your builder or remodeler uses some form of water membrane to cover the wood frame of your home or room addition before any finish materials are applied.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, OH 45236-0352. Questions will be answered only in the column.
For a list of modern air and water barriers and tips on installing these inexpensive products, send $3 and your name and address to Tim Carter. Ask for Builder Bulletin No. 306.
For a list of past Builder Bulletins and a wide variety of individual job bid sheets, send a business-size, stamped, self-addressed envelope to the same address.
Ask the Contractor can also be accessed via the Internet at bancodeprofissionais.com/go/askcon.
