Don’t Get Nailed by the Wrong Fastener

Metal fasteners are a common element to most historic windows; often applied to wood stops, stile and rail joints, and trim. Since the most common installation involves setting the nail and covering it with a wood or epoxy filler, most people don’t pay much attention to the quality of their fasteners. There is often a significant difference in the cost of a stainless steel nail and a conventional steel one, tempting many manufacturers and contractors to take the less expensive alternative. This can prove to be a major mistake in the long run.

When a fastener begins to corrode in a historic window, it will cause the finish and any applied fillers to fail. That accelerates the fastener corrosion and opens the window system up for wood rot. We have seen many installations across the country where the entire window system has deteriorated just due to the use of corrosive fasteners. The attached picture features what can happen after only five years to a window stop with a corroded fastener. In this case the corroded fastener initiated a chain reaction of failures, causing the entire lower rail of the window to rot.

Most people know you should use fasteners specifically designed for exterior applications. The most common of these are zinc plated and galvanized. Galvanized coatings are most often thicker than zinc so they have a more durable coating. Galvanized nails are available in several different types and grades of quality, depending upon the thickness of the coating and the coating process. You can get mechanically plated, hot galvanized, electroplated, and hot dipped. All of these have a zinc coating which is applied to a standard steel nail.

Unfortunately, we have had problems with using galvanized nails for the fabrication and installation of historic windows. During the process of setting the nail, the galvanized coating is compromised due to the force required to drive the nail and the friction with the substrate. The galvanized coating can also react with many of the wood preservatives commonly used. Since wood preservative is typically used on soft woods like pine or fir, this will cause premature corrosion of the fasteners. It is also believed that the acids and chemicals inherent in cedar and redwood can cause corrosion of the coatings on galvanized nails.

We recommend the exclusive use of stainless steel fasteners for any fastener that could be exposed to moisture over the life of the window system. Since it cannot be assumed that the owner of the window will properly maintain the window, it makes sense that all fasteners should be stainless. It is important to note that there are varying degrees of quality in stainless fasteners. Type 304 stainless steel nails contain 18 percent chromium and 8 percent nickel. These nails are highly resistant to corrosion in most environments, but will corrode in more intense conditions such as marine climates. Type 316 stainless contains molybdenum which makes it resistant to salt spray found in ocean climates. We recommend type 316 stainless steel fasteners. Upfront they are more expensive, but over the long term they are an excellent investment.

Challenges with Wood Window Restoration

It is very exciting to see the window industry begin to embrace the value of restoring historic wood windows rather than resort to replacement. This trend towards restoration is probably driven by the limited lifespan of replacement windows and the recognition that a 75+ year-old window system can be adapted to perform at the same energy efficiency levels as replacements.

Although wood window restoration isn’t rocket science, there are many factors that can undermine the success of your project. Re-View restores thousands of wood windows per year so we have confronted many of the common pitfalls of window restoration over the past 20 years. In this blog, I am going to address the challenges of using chemical strippers to remove paint finishes.

Use of Strippers

Re-View has found chemical strippers to be very effective at the removal of multiple layers of finishes on window components. We utilize dip tanks that contain close to 50 gallons of stripping chemicals since this is the most cost effective means to remove finishes on a large number of window units. Many preservationists are critical of chemical strippers because they claim they ruin the wood. Strippers don’t ruin wood. The improper neutralization of stripping compounds from the window is what ruins the subsequent application of finishes.

It is critically important to effectively neutralize all components that are exposed to strippers. If you use the dip tank method for removal of finishes on sash, it is very important to completely disassemble the sash stiles, rails, and muntins to neutralize the window components. We find that the restoration of the mortise and tenon joints is better facilitated by separating the parts as well. Re-View will test the pH levels of the window components to confirm that proper neutralization has been performed. You want to use pH paper to make sure the wood has reached a level of at least pH7. We often will have to perform multiple neutralization applications if caustic strippers are used since they often absorbed beneath the wood surface.

There are many strippers out on the market and they fall into three different categories: caustic, solvent, and biochemical. The neutralizing techniques you will use will depend upon what type of stripper you are using. Most caustic strippers can be neutralized with a solution of vinegar and water. Some caustic strippers such as Peel Away require a proprietary neutralizer. Solvent strippers can be neutralized with mineral spirits. Many biochemical strippers can be neutralized with water. I fully recommend that you read the directions supplied by the stripper manufacturer. Unfortunately you will have to wade through many pages of health precautions to find the neutralization techniques.

If you are working on windows that were finished prior to 1978, you might have to contend with abatement issues. Proper removal and disposal of lead-based paint is critical. Many people fail to recognize that a fully stripped window that once contained lead-based paint will still be impregnated with lead. If you sand the surface of the wood, you will release lead from the wood fibers. Re-View uses specially designed downdraft sanding tables and all Federal, State, and OSHA approved safety equipment for the sanders. Also beware of asbestos fibers in glazing compound. We find that 25% of our projects have asbestos in the glazing.