All Paint professionals agree that the key to any successful painting project lies in Preparation! Preparation! Preparation!
The Exterior of Your Historic House: A Basic Paint Recipe
What are the three most important aspects of any painting project? You guessed it — preparation, preparation, preparation! Proper preparation is particularly important when dealing with older buildings possessing many layers of brittle oil-based paint. When you think of it, the actual process of applying paint is a relatively easy task, requiring only a fraction of the total time to complete the project. I liken topcoat paint application to that of a baker spreading the creamy frosting on a multi-layer deep chocolate cake. Certainly the baker wouldn’t attempt the final frosting without all the layers being properly prepared and set in place. In order for it all to come out right, a whole lot of work has to happen prior to that final important step!
One of the hardest things to accept in painting a building is that this thin coating, in spite of its expense, is only a temporary shield, one put on to protect the wood from the elements (and of course to beautify the structure!). In fact, the Forest Product Laboratory (FPL), a test branch of the USDA Forest Service, says that one can expect a conventional two-coat paint application, if done properly, to last only up to 10 years! A sloppy preparation and poor application mean even more frequent trips to the paint store. By using some of the following tips, owners of historical houses can achieve greater longevity of this ever-important protective membrane.
Consider Your Building’s Weather Envelope and Correct the Defects
Before letting loose with all that elbow grease, it is definitely best to assess what you’re up against! Inspect the existing paint job (on the entire building!) looking for peeling or crazed paint, and consider any general carpentry repair needs. Most importantly, check for potential water infiltration points. The FPL indicates in one of its publications that moisture is the most frequent cause of paint failure. Leaking roofs, dysfunctional gutters, and poorly fitting or deteriorated carpentry elements all allow moisture to enter a building. It is also good to review tree canopy and vegetation around the structure, cutting back where needed to allow for good air circulation. Look for and eliminate any soil/wood contact that could allow moisture to be brought up by capillary action into the structure. Finally, investigate interior moisture penetration by way of unvented dryers, faulty bathroom fans, and other moisture-generating interior features.
After your building analysis is complete, address any carpentry repair needs you have found. Set nail heads, replace deteriorated trim or clapboards, use wood or epoxy fillers to correct larger holes or cracks, address roof leaks, and adjust gutters, etc. These defects all represent possible points of entry for water or moisture; if not resolved before painting, they can affect the performance and overall look of the final paint job.
Preparation! Preparation! Preparation!
Next, scrape all loose paint thoroughly with a variety of paint scrapers; then proceed to a comprehensive sanding of all old paint and bare wood surfaces. (This is the most critical part of the whole project and is often the phase most likely to be skipped over!) Sand with an electric palm sander, using a rough aluminum oxide sandpaper. (Be sure when sanding and scraping to use personal protective equipment, like masks and gloves, etc.) A side note: The National Park Service, a government preservation agency, strongly suggests that the surface of historical buildings be prepared for painting by the most gentle means possible. So forgo the harsh grinders and abrasive sandblasters that could easily do permanent damage to old wooden clapboards and trim. Feather old paint edges carefully, and gently scarify exposed wood thoroughly. Sand paintless areas to a bright stable wood, so that any subsequent coatings will have an excellent surface to bond to. In areas that the electric sander can’t reach, sand by hand, being sure not to miss any of the “nooks and crannies.” Buildings with a lot of architectural detail by way of elaborate trims and moldings will require the use of shaped scrapers, heat guns, or even chemical paint strippers to remove layers of paint that have accrued over the years.
Sometimes paint buildup is so great on an old house that complete removal of all paint coatings is necessary. For this type of project it might be best to engage the services of a company that specializes in exterior paint removal. This is expensive, potentially hazardous, and — from a historical preservation standpoint — should be done only when absolutely necessary. In its preservation brief on paint problems, the National Park Service suggests a cautionary approach to paint removal, emphasizing that with the exception of cleaning, scraping, and sanding as part of routine maintenance, removing paint from historic buildings should be avoided unless absolute necessary. Total paint removal obliterates evidence of historical paintings, their sequence and architectural context. If it is necessary that paint be completely removed, at least leave a small swatch of the original layers of paint somewhere for future architectural historians to gander at some 200 years from now!
After all the sanding and repairs are completed, it is time to bathe! (The house, that is, although by now, you may need a thorough washing too!) Wash the wooden surface with a stiff brush, combining cleaners like TSP substitute and household detergent with water. Be sure to rinse thoroughly after scrubbing, but be careful not to force water into the building through any cracks or crevices. (A pressurized power washer is not recommended for this task, as operator error could be a real problem, allowing water to penetrate into wall cavities.) If mold and mildew are present, add a bleach product to the washing solution. If not killed, these microscopic fungi could continue to proliferate, eventually discoloring the new paint coating.
Time To Pre-Prime
The FPL recommends that a paintable water repellant/preservative be applied to any bare wood before priming. This will help seal off and prevent moisture from penetrating the wood, thus decreasing any shrinking and swelling. Using a water repellant lessens stress on the paint film and extends its service life. I put in my material specifications a modified version of the above with a specialty product that dries quicker and is made with an alkyd resin and other proprietary ingredients. This product is exceptional and has been tested over the last decade or longer on a multitude of historical buildings. It is useful in other applications, therefore, particularly when trying to stabilize heavy layers of old paint that have become hard and brittle.
Putting the Primer On
Before priming an entire building, spot prime all nail heads to reduce future ferrous oxidation and bleed-through. Next on the agenda is a thorough priming with a quality alkyd primer. (I usually recommend an alkyd as opposed to a latex primer, because the modified oil product appears to be more penetrating, providing a stabilized base for the acrylic latex topcoats to adhere to.) It is also important to ensure that all primers and paints be of the same manufacturer, to ensure compatibility. A primer coat that is uniform and of proper thickness will distribute the swelling stresses that develop in wood, thus preventing premature topcoat failure. It is important, too, that the top coat follow the primer relatively quickly. If left exposed to the elements for too long, the primer can produce a soap-like compound that presents some topcoat adhesion problems.
After the primer has dried, caulk all siding and trim voids that could be penetrated by water. A high quality paintable acrylic latex or siliconized acrylic caulking is preferred. If any voids are excessive, use a closed-cell backer rod to build out a bond-breaking base and then apply the caulk. In any case, caulk only where necessary and be sure to apply a bead that is substantial enough to take the stresses of the wood’s expansion and contraction. Wipe any excess caulking off all surrounding surfaces.
With all the hard work done, it’s time for the frosting! Once the primer is dry, use a high quality acrylic latex paint, applying only when weather conditions are right. Apply two coats, allowing the first coat to dry before applying the second. Schedule the sequence of work so you’re not in extended periods of sunlight. Nor do you want to be painting in rain or mist. Make sure air temperatures are neither too low nor too high (and read the manufacturer’s recommendations). One last note on choosing paint: The debate over oil verses latex is about over, with the VOC regulations and greatly improved formulas giving acrylic latex paint the definite edge on exterior painting projects. If applied properly, acrylics are more flexible and breathable, retaining their sheen even better than the oil. I have been specifying acrylic latex for most applications for more than a decade with great success!
The above suggestions represent just the highlights of techniques and tips developed over many years of working with consultants and craftsmen in the paint field. Each historical building needing paint has its own set of problems and unique challenges, and sometimes it’s a good idea to engage the services of a building consultant. Hire someone who can provide real professional guidance, particularly if you’re planning on using an outside contractor to do the actual work. Whenever using a contractor, it is best to provide, in advance, detailed specifications of the work to be done; never leave it up to the contractor to decide what should be done to your prized historical possession! (Of course, that’s a whole other story—understanding how to select and work with outside contractors!)
One final reminder: all paint professionals agree that the key to any successful project lies in its preparation. Returning again to the concept of that chocolate frosted layer cake, you have to begin with a recipe and the necessary ingredients, invest in a large mixing bowl, select an appropriate spatula (Let’s see; I think the one with the wooden handle works best in terms of quality control—that is, taste testing!) and build that firm foundation before applying the delicious frosting! Ah … preparation, preparation, preparation!
Brad King is the Director of Landscape, Maintenance and Construction at Old Sturbridge Village, where he has worked for more than 20 years. The museum includes more than 40 historical structures on more than 200 acres of re-created 1830’s New England countryside.