Wood Window Restoration
Today's “Blog” entry focuses on the nuts and bolts of the window restoration to the windows of the Eli Whitney Boardinghouse (1827). One of the things that make this project more than simply interesting is that the window on the Boardinghouse and their issues are the same issues that many of our readers face with their historic windows.
Cesar Lopez, the lead carpenter on the project, was gracious enough to allow me to interview him and talk about the window restoration process. Cesar has been with R.J. Aley for 5 years and has a background in carpentry. Cesar said that he's learned about 70% of how to do preservation through hands-on experience, with the other 30% through workshops and studying. As a matter of fact, when Cesar stopped by to talk to me, he was on his way to the Yale library to do some research on epoxy and router bits (epoxy is used to repair damaged wood, and router bits are used in carpentry, to carve the curves in muntins or trim).
Cesar told me the first things he does when he starts an historic window restoration project is to survey the condition of the glass and the wood to see how badly damaged they are. This site visit is generally followed up with some research. Cesar told me that there is a lot of written material on the construction techniques used in historic windows that can be researched by the building's style or the year of construction.
Even the positioning of the building tells Cesar something. The south and west sides of the building generally face the sun and suffer damage in the form of dried out putty along with faded and peeling paint. The horizontal surfaces, like the sills, usually take the brunt of the damage. The north and east sides, which get less sun, are usually damaged from moisture, particularly where it is trapped in the joints and causes rot.
Window restoration comprises a number of steps, including an evaluation of the window and surrounding area, some degree of interior and exterior paint removal, removal and repair of sash (including reglazing where necessary), repairs to the frame, weatherstripping and reinstallation of the sash, and repainting.
After careful evaluation, the next step is to remove the existing paint and putty. This can be accomplished through a number of techniques: steaming, scraping, sanding or applying chemicals.
One of the ten basic principles for sensitive rehabilitation, according to the Secretary of Interior's Standards for Rehabilitation, is “Clean façade [windows] using the gentlest methods possible. Avoid sandblasting and other damaging methods”. Steaming appears to be one of the gentlest methods and is the only method R.J. Aley uses for historic window repair.
Another reason for steaming the windows is to secure the debris for abatement. R.J. Aley's assumes that any and all paint or glass installed or applied before 1980 contains lead and the firm deals with them accordingly. The steamer keeps the lead paint in one place and easy to abate. The steamer heats the windows to a temperature of 212 degrees and after 1-2 hours per window in the steamer, the putty and paint are soft enough to slough off. The technique also saves 90-95% of the glass from breaking, which is a common occurrence with other techniques. The lead debris from the steamer is easy to dispose of safely according to abatement code.
Because historic windows vary greatly in size, the crew builds the steamers custom for each project onsite, according to the window size (although they do have ready-made steamers for projects with standard-sized windows). The steamers are made mostly of wood and use a portable steam generator to produce steam, which is then pumped into the chamber or box with the window. The one they used at the Boardinghouse was big enough for 2 sashes (of the same window) to be steamed at the same time.
After the paint and putty is removed, the windows are set out to dry and the workers jump to the next window. The windows must have 15% or lower of moisture still remaining before the workers can go on to the next steps, which are repair, priming and re-glazing.
The next “Blog” entry will discuss the final steps in the restoration of the windows and some very interesting facts about replacement windows!