Wood Window Restoration
Glass and Glazing
Traditional wood windows have glass that is either 1/8” or 1/4” thick, held in place by metal glazing points and sealed on the sash exterior with linseed oil-based glazing putty. This time-honored method ensures a weather-resistant seal with superior endurance and repairs are made with identical products. When replacing glass, it’s important match original thickness and weight to preserve the sash integrity and function.
Clear double-strength glass is most commonly used, though “restoration” glass that mimics original “wavy” glass is also available. We also offer stained glass restoration and have local resources for a vast assortment of glass textures and colors to match the originals.
Operation and Hardware
The most common impediment to smooth operation is build-up. If sash are painted in the closed position they become paint-stuck, requiring to be cut free from the interior and/or exterior. Additional problems are caused by paint build-up between the sash and jamb which needs to be removed by scraping and sanding.
Sash ropes are the one component of the counterweight/pulley system that can wear but are designed to be replaced periodically. They are rated for strength according to sash weight, and are attached on one end to the side of the sash and on the other end to the counterweight inside the wall. Removable panels are built into jambs of most windows to allow access to these parts.
Misalignment between sash and jamb will prohibit good operation and leak air. This can be due to hinges that require adjustment or warpage of the sash itself that may require component replacement.
Weatherization
Heat loss is often cited as a reason to repair traditional windows. Most heat loss occurs from infiltration, air leaking in around the edges of the sash. The other factor is convective heat loss across the surface of the glass where warm air inside cools and drops down causing an air “current”. [architect’s note: windows are often blamed for broader thermal comfort issues, notably HVAC systems that need appropriate capacity and distribution.]
Infiltration can be eliminated by assuring proper meeting rail alignment and installing modern weatherstripping on all sides of operable sash. Weatherstripping requires sash removal, but is not visible once the window is re-assembled. Convective heat loss can be reduced with interior window treatments, like blinds or curtains, that interrupt the air current.
If further treatments for thermal efficiency are required, exterior storm window are recommended. These can be wood-frame or aluminum and can include interchangeable glass and screen panels for seasonal apaption.
Millwork & Finishing
The quality wood components of traditional windows can last almost indefinitely if the paint coat is properly maintained. Unlike modern wood-clad windows they can be repaired and modified in many ways.
Failed or missing paint on exterior wood surfaces lets moisture in, causing checking and open grain. Subsequent freeze thaw action in winter months creates larger voids and eventually leads to twisting, bowing, and wood rot. The first line defense is removal of loose paint, priming bare wood, and finish painting exterior wood surfaces.
Dutchman repairs are used to replace deteriorated portions of wood members with new wood, cut to size, doweled in place and sanding flush to adjoining surfaces. More extensive wood damage such as bowing and rotted joinery require replacement of the component (rail, stile, muntin) in its entirety.