Promotional literature promises lifelong performance for pressure treated wood. The Forest Products Laboratory and other research groups have shown that treated wood stakes placed in the ground for more than 40 years remain rot-free. But young pressure-treated decks, many less than 10 years old, are being shoveled into landfills. A technical report in the Forest Products Journal (November-December 1998) indicated that the average pressure-treated deck only lasts 9 years. Why?

Pressure treating does make wood rot resistant. But --- it doesn’t make wood water resistant. Pressure treated wood still soaks and looses moisture. And as a result, the wood moves, cracks, twists, bends, cups and virtually tears itself apart. There is hope.

You can enjoy pressure treated decks for a very long time. All it takes is a little extra care during installation and a yearly dose of maintenance. Keep the wood stable by applying a coat of water repellent treatment onto all surfaces before installation. Securely fasten the deck boards with long corrosion-resistant screws. Brush-treat raw wood that is exposed when cutting and drilling. Retreat the tops of the boards with a good brushing of water repellent every year. The water repellent will keep the boards looking bright and will minimize the uptake of water. As a result the boards will have fewer cracks, splits, cups and twists.

New home builders can easily avoid paint failure problems by taking preventive measures during the construction phase of a house. By following several simple steps, homeowners can ensure a high-quality, long-lasting exterior finish. Fortunately, this process seldom involves a major additional expense.

Owners of homes with existing paint problems will benefit from understanding what causes their paint to fail. Once these causes have been identified, they can be addressed, and future problems can be eliminated.

The most common reason for exterior paint failure in houses built since the mid-1970 is energy efficient, airtight construction. It seems ironic that in solving one problem, the conservation of energy, another was created – peeling exterior paint. At the time these new, energy-efficient homes were designed and constructed, architects and contractors did not realize all of the consequences of these previously untested construction methods.

Recognizing that exterior paint problems have resulted from efforts to construct energy-efficient homes, many builders have experimented with inexpensive, frequently ineffective solutions to the problem. The most common procedure is to install a “vapor barrier” between the interior wall and the fully-packed insulation. While in theory this barrier should be effective, it can only function well if installed without seams and used in conjunction with constant interior dehumidification and/or “dilution techniques”. Dilution serves to introduce dry (cold) exterior air in an effort to moderate the level of interior humidity. We cannot help but note that these efforts involve a considerable use of energy and capital in themselves.

The vast majority of exterior paint failures on modern homes occur in the spring, near the end of the heating season. These failures invariably result from a high level of interior humidity forcing its way through the walls and coming into direct contact with the cold, unpainted interior surface of exterior siding, where it condenses. The resulting condensation soaks the wood. Failure may be uniform or limited to specific areas of the home (normally sunny side exhibits the most severe problem as the sun acts to “draw” the moisture against the exterior paint film). Please note that exterior paint failure may also be a symptom of a much more severe problem – the rotting of interior construction framework; a frequent occurrence in the presence of moisture, warmth and darkness. Modern homes are also much more likely to attract exterior moisture as the capillary action in the laps (edges of siding and clapboards) draws moisture into the house.

These problems associated with airtight construction are not encountered in older homes where the wall cavities are either empty or partially filled with insulation, thereby providing an air channel which allows interior humidity to escape. Admittedly, these older homes are sometimes drafty, and fuel consumption is greater, but they seldom, if ever, experience exterior paint failure.

The interior humidity problem and its impact upon exterior painted surfaces is further exacerbated by the broad range of moisture sources found in the modern American home. Clothes dryers, dishwasher, saunas, whirlpools, and frequent daily showers contribute to extremely high levels of interior moisture release. A family of four can easily release twenty gallons of water vapor into the interior of a home in a single day! While the human body is quick to recognize gradients of ambient temperature, we do not possess the natural ability to sense extreme levels of humidity. It is unhealthy to reside in a high-moisture environment and yet entirely possible for us to do so unknowingly until the paint begins to fall off the home rapidly.

The following recommendations have proven to be effective in correcting exterior paint failure.

PREVENTING THE PROBLEM – PRE-CONSTRUCTION PLANNING

* Deal only with reputable professionals who acknowledge that special planning is required in the design and construction of energy-efficient homes.
* Insist that seamless vapor barriers be properly installed before wallboard or plaster is applied. Effort should be made to avoid “leaks” such as those which occur around wall switches and baseboard plugs.
* Consider the use of less insulation that your wall can accept – use 3” insulation with 4” studs, 4”-5” with 6” studs. This will allow for an evaporation chamber. Your walls will retain a much greater “R” value with 4” of dry insulation than with 6” of wet insulation.
* Rather than nail your clapboard directly onto the sheathing of your new home, consider installing it onto vertical furring strips in order to provide an air space of at least 1/4” between the sheathing and the back of the clapboard. As an alternative, please consider the use of roll-type spacing material such as “Cedar Slicker” (http://www.benjaminobdyke.com/visitor/product/key/homeSlicker)
* Eliminate the possibility of a moist basement by providing good water drainage and sealing all exterior foundation walls.
* Install exhaust fans vented to the exterior in kitchen, bathrooms and laundry room. Clothes dryers and Jacuzzis must have exterior venting. Cover all standing water when not in use (hot tub/Jacuzzi).
* If possible, plan a well-vented crawl space and/or attic with at least one sq. foot of ventilation area for every 300 square feet. The same one sq. foot of ventilation should be provided for every 150 square feet or crawl space. Crawl space and attic insulation must be installed with the vapor barrier or foil side toward the living area.
* Specify that each piece of trim and siding to be used on the home’s exterior be primed on all “six” sides with alkyd (oil based) primer before being nailing in place. All cuts should be sealed by carpenters with one heavy, grain filling coat of primer/undercoat immediately before nailing. Many lumber yards and mills offer “factory priming”. If you use this service, please insist that alkyd (oil based) primers be used exclusively and confirm that they will not be over thinned – many of these pre-coating firms use very low quality waterborne primers whose sole attribute is quick drying. (Unless you are able to monitor activity closely at the mill, we recommend priming at the jobsite.)
* Please note that homes heated with a ducted hot-air system are much less likely to experience problems with humidity related paint failure.
* Prime the “top side” of all floor sheathing material used between the first floor and basement with an alkyd (oil based) primer.

POST-CONSTRUCTION SOLUTIONS

* Determine the location and degree of the problem. Keep in mind that exterior paint failure is not the problem, but merely the solution. A simple moisture meter will enable you or your contractor to measure the existing level of moisture within your siding. Where failure is particularly severe, we suggest that you arrange to have your home inspected by a structural engineer or other person capable of measuring levels of moisture in wall partitions. If these tests are conducted with the correct instruments, there will be little impact upon the appearance of your home. Ideally, testing should be conducted in late spring or early summer when moisture levels will still be near their peak. Paint application should not begin until after July 1st when the home has this type of moisture problem.
* Install exhaust fans vented to the exterior in your kitchen, bathrooms and laundry room. Ideally these devices will be tied into your lighting switches so that they activate automatically when these rooms are occupied. NEVER vent exhaust devices into an attic.
* Examine all crawl spaces and attics in order to bring them up to the ventilation specifications indicated for new construction.
* Attempt to eliminate any sources of moisture infiltration from the outside. A damp or leaky basement can frequently be corrected by installing new external drainage and/or ventilation devices.
* Prime all interior sides of all exterior walls with alkyd (oil based) primer. These alkyd primers will serve as “barrier coatings”, drastically reducing the passage of water vapor from your home into your walls.
* Install a dehumidifier or air conditioner in your living area. Although there is an expense involved in running this equipment, it will make your home environment healthier and drier, and may save you thousands of dollars in maintenance expenses.
* Use of a hygrometer to track indoor humidity levels is suggested. Humidity levels in the home should never be above 45%.
* Do not, however, bring unseasoned firewood into your house, not even in the cellar, as a cord of green wood can be expected to release more than 200 gallons of water!
* Maine Painting can install a wedge vent system. This system is recommended in the event that you are unable to obtain moisture levels below 15% by natural venting.
* Remove and replace exterior wood which has already begun to rot. Such wood can normally be detected with a pocket knife. Avoid future problems by encapsulating new wood as recommended in pre-construction steps.
* Do not allow snow or ice to maintain contact with exterior siding for extended periods.