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windows, preservation, architectural history

Preserving Historic Windows

By The Craftsman on Nov 22, 2011

Whether your historic home is still in its infancy or whether your historic structure is hundreds of years old, preserving the original architecture and design elements are crucial to keeping your historic home historic. Keeping the siding, roofing materials and other architectural features in their original state can be tough, but well worth the effort. More often than not, outdated and damaged windows are replaced with newer more energy efficient models, destroying the original look and feel of the historic structure. But the fact of the matter is, older windows can easily be preserved and restored, often at a much cheaper cost than a total replacement, and all without ruining your historic homes historic appeal.


The first step towards preserving and restoring historic windows is evaluating the entire window to determine if they are indeed restorable. There are three main categories that a historic window can fall into during the evaluation:

  • Level One—routine maintenance
  • Level Two—structural restoration
  • Level Three—parts replacements

Level one window restoration and maintenance can easily be done by the homeowner. Level two and three repairs are a bit tougher and may require a professional to complete.

When evaluating older windows, it’s a good idea to create a window schedule for each window. This basic list will help you to determine and keep track of each window as they age. Noting the windows geographic location, how the paint, stain and glazing is holding up and what the condition the frame, sill, sash and hardware are in, are all important items that should be noted in your window maintenance schedule. Water damage, rot or other decay can be evaluated by pressing a sharp nail or awl into the wood to determine weak spots in the structure. Each window should also be opened and closed to exam the working condition of the window structure and hardware.

Level One: Maintenance

Historic windows need regular maintenance to keep them in good condition. While most window work is uncomplicated, it can be labor intensive. There are five basic maintenance techniques that you can use to get your historic windows looking like new again.

  1. Removing the old exterior and interior paints—great care must be taken when using any heating equipment to remove old paint. Older window panes are very sensitive to heating and cooling. Cover window panes with a piece of sheetrock to prevent breaking the glass when using a heat gun to remove old paint.
  2. Repairing the sash—always secure the sash cords in place with a thumbtack or tape before removing the sash to prevent the cords from falling into the weight pocket.
  3. Repairing the frame—rotten spots in wooden frames are easy to repair using wood putty or epoxy. Treat any wood with a fungicide first before making repairs.
  4. Weather stripping/reglazing—window panes should be removed and individually labeled when removing and replacing any deteriorating glazing to avoid mismatching panes when they are replaced.
  5. Repainting—most paints need a minimum of four hours to dry. Take advantage of long drying times by repairing sash cords and other hardware while the window is disassembled for painting. A piece of plywood cut to fit the frame can help keep out the weather while you work on the window.

Level Two: Structure

Reglazing windows is one way to prevent air leaks and protect the frame

Evaluating the structure of the window is sometimes necessary when wood damage is visible. This process typically involves a quick check with a sharp object. If the wood is spongy, decaying, wet or falling apart, then structural damage may be present in the window. There are three distinct methods for repairing a historic windows structure:

  • Smaller Repairs—repairing the structure is sometimes possible with an application of fungicide followed by repairing any damage with wood putty.
  • Larger Repairs—after a fungal treatment, an epoxy or resin is injected into the wood to make the structure stable again.
  • Heavy Damage— in worse case scenarios, parts of the sash or frame may need to be removed and replaced. When this process is required, always use the same materials when possible.

Level Three: Replacement

When damage is so severe that replacing parts are necessary, it can be a difficult undertaking that probably isn’t in the average homeowner’s skillset. With the help of a professional historic renovator and the right millwork, replacing muttons, sills or other window parts can be easy and painless. Hardware replicas can be purchased for a modest price as well. Sash replacement is a common occurrence with many replica pieces being replaced for a reasonable fee. When splicing new and old materials together, it’s always best to keep new wood materials as close as possible to the original. This will prevent the different wood species modular elasticity from damaging the entire window unit when weather and moisture content changes occur. Of course, you can always take a trip up to your local architectural salvage yard to look for a historic replacement which can be found for $20-$40 if you’re lucky enough to find the right size! Visit our previous post Salvage & Save for more info on local salvage yards in your area.

It’s always recommended to preserve and restore historic windows whenever possible. Repairing and preserving existing wooden windows is more practical than most homeowners realize, and unfortunately many historic windows are replaced because of the lack of awareness for techniques of evaluation, repair, and basic maintenance. By preserving and maintaining your historic windows, you greatly extend their lifespans and preserve the historic character of the building for future generations to enjoy for years to come.

To learn more about the history and mechanics of your windows read our post All About Historic Windows.


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