Historic Window Repair and Rehabilitation
"[T]he repair…of existing windows is more practical than most people realize, …because [they] a lack…awareness of techniques for evaluation, repair, and weatherization."
Secretary of the Interior National Park Service Preservation Briefs 9 and 13
"I've…assessed the condition of more than a thousand [sashes], and never seen a sash that could not be repaired."
John Leeke (contractor), Historic Home Works
Any window that can be repaired should be repaired.
Secretary of the Interior Standards for Rehabilitation Guidelines for Windows
What to Do?
Are Your Windows Steel?
For repair and weatherization of historic steel windows, see the article on Historic Steel Windows Repair, Restoration, and Weatherization.
There is not a single and simple answer, because the repair depends...
- on what parts of the window are deteriorated and how badly, and also
- on what the goal is for the windows.
Repair goals can range from minimal to extensive. In fact, the less, the better!
- Preservation. Original windows are repaired only enough to prevent further deterioration. This minimum repair is sufficient to preserve original windows into the future. By preserving the windows, they are saved for eventual rehabilitation.
- Energy efficiency. Historic windows can be weather-tight and energy efficient. If this is the main goal for the windows, then minimum repair may be enough. For information about weatherizing historic windows, see our weatherization information page.
- Rehabilitation. The Secretary of Interior (SOI) Standards for Rehabilitation are used by the Detroit Historic District Commission. Original windows and materials are preserved as much as possible. Windows are repaired to the least extent possible to make them functional and to preserve them from deterioration. Limited replacement of damaged material is allowed. Rehabilitation of windows is explained in the SOI Guidelines for Rehabilitation.
- Restoration. This is the highest standard. Windows are entirely restored toward their original condition. Finishes are replaced. Hardware is repaired or replaced. Windows are newly reglazed. Ropes are replaced. All damaged wood or metal is repaired with the same kind of materials, if possible. Total restoration is more than is required or expected by the SOI Rehabilitation Standards that apply in Detroit historic districts.
Have a plan
The How to Do It section shows what things can be done, from minimal to restoration. Know what the goal is, then plan just the repair needed to get there. Don't overdo it.
Here are ten reasons to restore or repair wooden windows, from the city of Boston.
How to Do It?
Historic windows are simple devices that are constructed of separate simple pieces.
- Though it is rarely necessary to do so, historic windows can be disassembled.
- Pieces can be repaired or replaced, and then reassembled.
Many repairs of historic windows need only
- simple low-cost materials
- common skills
- knowledge about historic windows
Basic repairs are as simple for the Do-It-Yourself (DIY) owner and as for a contractor.
- Many homeowners can do it themselves, once they know what to do.
- Look at the simple things first. Doing them may be enough!
Work together with contractors! Save money!
- An owner can do the simpler and lower-cost things.
- A contractor can do the more complicated things.
The two courses of action, both covered in detail below
DIY Window Repair and Restoration
The main thing is knowing what to do and how.
Repairs to windows usually are not complicated.. A DIY owner can save money doing some or all of the repairs. For wood windows, many repairs require only simple skills and common tools. Working with metal windows may be more complicated, but with knowledge about them, the DIY owner can learn to do many repairs.
What do you need to know?
You need to know how to do what you need. What you need depends on the goal, the objectives, and the plan.
This web site can help with setting goals and making plans. While the site is thorough on how to repair extensive window damage, it also discusses how to decide how much repair is required
Do It Yourself
The following DIY information is divided into three sections:
- Guidebooks. Comprehensive information about repairing windows. They are a guide to complete restoration of windows. But, one can use only the portions that provide information about the particular work that is needed
- Restoration. Information and demonstrations on the complete rehabilitation and restoration of windows. Most owners will not want to do such extensive work on their windows, and usually it is not necessary. Rehabilitation encompasses, of course, information about particular repair or rehabilitation methods. Demonstrations may help with specific problems.
- Specific Repairs. Information and demonstrations on how to repair specific problems. The methods are the same as for complete restoration
Complete Reference Guidebooks for Window Repair and Weatherization.
The guidebooks have information on all aspects of repairing, rehabilitating, restoring, and weatherizing windows. If only a specific repair is needed, then consult the relevant section.
- Window Repair and Weatherization in Historic Homes You can download it free.
- John Leeke, Save America's Windows You have to order it.
- Terence Meany, Working Windows: A Guide to the Repair and Restoration of Wood Windows, 3rd edition. You have to order it. Look on Amazon or another web bookseller. Some folks have found this humorous as well as helpful.
- New York Landmarks Conservancy, Repairing Old and Historic Windows. You have to order it from the Conservancy.
- U.S. Secretary of the Interior, National Park Service, Technical Preservation Brief 9, The Repair of Historic Wooden Windows. You can download it free.
- U.S. Secretary of the Interior, National Park Service, Technical Preservation Brief 13, The Repair and Thermal Upgrading of Historic Steel Windows You can download it free.
- U.S. Secretary of the Interior, National Park Service, Standards for Rehabilitation and Guidelines for Rehabilitating Historic Windows. You can download it free.
Demonstrations of Complete Window Rehabilitation
The materials here demonstrate the steps in the rehabilitation process presented in the guidebooks. If only specific repairs are required, only the relevant sections of the presentations can be used. Also, consult the materials and demonstrations for specific repairs below
The Michigan Historic Preservation Network and the City of Kalamazoo produced these five videos to demonstrate the process of window rehabilitation. For specific repairs, rather than a full rehabilitation, view just the relevant video. However, knowing all of the steps in window rehabilitation may be helpful even for making limited repairs. More information on each individual step is in the sections below.
- Video 1: Disassemble double hung windows; See note below on parting stops.
- Video 2: Finish disassembling sash. Remove window weights. Remove glazing and window panes. Reset glass and reglaze.
- Video 3: Stripping paint with heat gun. Resetting and glazing glass panes.
- Video 4: Bronze weatherstripping. Replace weight cords. Reassemble window. Note: sash cord is a special cord available at hardware stores.
- Video 5: Reassemble window. Install hardware
Demonstrations of Specific Window Repairs
Most historic wood windows are either the traditional double-hung windows or casement windows. The latter are much simpler.
Each of these problems is covered in more detail in the collapsable boxes below.
Windows may not open for a variety of reasons, although the principal problem usually is paint.
Also, the first step in removing a window sash for repair is getting it loose. See videos on sash repair (below) or the steps in the rehabilitation videos (above).
If a casement sash is painted shut, the approach is the same as for double-hung windows. If paint build up on the edges of the sash is a problem, selectively sand, scrape, or strip away enough paint so that the sash operates smoothly. Oil the hinges as well.
Another common problem is that a casement sash is not sitting squarely in the window frame. The problem most likely is the hinges. Often, just tightening the hinge screws will pull the sash back into alignment with the frame. Beyond the simple fix, one (or both) of the hinges may need to be shimmed in order to align the sash. Putting a one- or two-layer thin cardboard shim behind one of the hinges will change how the sash sits in the window frame. This usually solves the problem.
If the screws no longer tighten in their holes, try longer screws. If that does not work, the screw holes need to be filled and re-drilled. Fixing loose hinges.
Plane the sash only as a last resort. Any wood that is cut away is gone forever. Only plane the edges of a window if the casement window frame was shifted out of square. But first, look into re-squaring the frame, if possible.
Other problems with casement windows, such as glazing and wood repair, are the same as for double-hung windows. Obviously there are no sash cords.
Replacing Window Sash Ropes
Sash cords are long-lived, but eventually they wear out. Replacement is straightforward, but it is not obvious how to do it! Here's how.
- Replacing Window Sash Cords Tutorial (VIDEO) This is a good overview of replacement.
- Removing Double Hung Sash These are good directions for removing a sash.
- How to Replace Window Sash Cords (VIDEO) Good demonstration.
- How to Insulate a Window with Sash Weights (VIDEO) This shows a very clever trick for insulating weight pulleys. In general, however, the main insulation technique shown here requires major disassembly of the interior window frame. It seems inadvisable to do this, unless the frame has been removed for another reason.
- How to Replace Sash Weights with Spring Balances (VIDEO) An alternative to replacing ropes is to install a spring loaded mechanism. While this video does not show it, spring balances also allow insulation to fill the weight pocket cavities alongside the windows.
This is part of the routine maintenance of windows. Also, prior to painting windows, the glazing around panes of glass should be replaced where missing or deteriorated.
- How to Repair Window Glazing (VIDEO) Excellent demonstration of the process.
- How to Glaze a Window Pane (VIDEO) Glazing can be done with the window sash in place. It is not necessary to remove the sash
- John Leeke, Window Sash Glazing (VIDEO) Demonstrates technique of glazing.
Baseballs or bad guys, it happens. Repair can be done with the window in place. It is not necessary to remove the window sash from the window frame. Since one step is reglazing the window pane, also see the information on glazing.
- Replacing Window Glass from Ace Hardware Complete step-by-step description of a good job.
- How to Replace Broken Window Glass (VIDEO) He also demonstrates glass cutting technique.
- This series of videos follows a homeowner replacing a broken pane of glass with the window in place.
- Broken Window Pane Replacement: Step #1: removing the broken glass.
- Broken Window Pane Replacement: Step #2: removing the old glazing.
- Broken Window Pane Replacement: Step #3: measuring and cutting glass.
- Broken Window Pane Replacement: Step #4: glazing. On this final step, also see the section on glazing repair.
- A glass dealer can cut a glass pane to exact size. Always cut glass 1/8" less than the dimension of the window sash opening. If you have glass, and you want to cut it to size, here's how. Cutting Glass This Old House Also see the Ron Hazelton VIDEO above for a demonstration of cutting glass.
Sills and Casing
Repairing deteriorated window sills and casing. These get the most exposure to weather and need the most routine maintenance or repair. The usual reason is that paint has not been maintained and has deteriorated, exposing the wood.
Repairing Rotted Sills and Casing
- How to Repair Dry Rot in a Window Sill: Excellent demonstration of epoxy repair techniques.
- Also see Epoxy Repairs (below)
Replacing Rotted Sills and Casing
- Window Sill Replacement Installation (VIDEO): Simple replacement of front of sill. Touches on good points
- Windowsill Repair (VIDEO): This is good, but gets into frame repair, and doesn't show steps well.
The repairs needed on deteriorated or damaged window sash can range from minor to major.
Minor Repairs. The usual repair needed is to the bottom sash rail, because of exposure to weather. The usual cause is that paint has not been maintained and has deteriorated, exposing the wood. In many cases, repairing deteriorated window sash is like repairing deteriorated sills and window casing.
- Repairing and Removing Paint and Glazing: Very good pictures on repairing rotten sash. Uses an uncommon paint removal method. Any paint removal method can be used instead.
Major Repairs. Sometimes the damage or deterioration of a sash is so extensive, that it will require substantial rebuilding. This may just require the same techniques as for minor repairs, just more of them. However, for major deterioration, some part(s) of the sash or window frame may need to be replaced in whole or in part. A beauty of old windows is they are made of many parts that can be disassembled, fixed, and reassembled. Old pieces can be rebuilt or replacement pieces milled.
Such major repairs may have to begin with removing all of the glass panes and stripping the paint to get at the wood.
For extensive repairs and rebuilding of windows, one of the complete reference guidebooks probably is the best resource.
The following web site is thorough on how to repair extensive window damage, and on how to decide how much repair is required: How to Repair Rotten Window Frames and Sashes
If a piece is so deteriorated that a replacement needs to be made, the best route may be to engage one of the specialized window contractors to make the new piece.
Major repairs also may require replacement of some piece of hardware. Try H&R Window Repair, Hazel Park, 248-544-8282. They have an inventory of parts
Epoxy can be used for many wood repairs, is straightforward to use, and is inexpensive compared to alternatives.
- Epoxy Article at John Leeke's HistoricHomeworks.com: Excellent instructions and good diagrams on methods of applying epoxy.
- Fixing decayed (rotted) wood using an epoxy penetrant and filler: Good information and pictures.
- Restoring Wood with Epoxy - Fine Homebuilding: Somewhat more advanced information about using epoxy.
- How to Fix Rotted Wood with Epoxy: Good VIDEO demonstration.
- Window Repair Videos - Kansas Historical Society. Another good VIDEO demonstration.
Stripping Paint and Finish
Since most old windows have been repainted many times, when repairs are underway, it may be an opportunity to remove the paint build up and clean up the windows. Getting rid of paint also may be necessary to see wood or metal damage. However, paint stripping and repainting makes window repair a much more extensive process. Also, it may not be necessary to get windows working and repaired.
While chemical paint and varnish removers and strippers are well known, they generally are not the easiest method for removing paint build up. Heat is less messy, faster, and more convenient. If the surface needs to be completely paint-free, then chemical strippers can complete the job.
Caution about Lead It is customary to warn that the paint in old houses usually has some lead-based paint layers at the bottom. Lead is poisonous and a health hazard. For that reason, it is advisable to take precautions to minimize lead fumes from heat and air-borne lead particles from scraping. Keep the area ventilated, wear dust masks, and vacuum up debris and dust. Some workers choose to wear respiratory masks.
- Appropriate Methods for Reducing Lead-Paint Hazards in Historic Housing: You can download it free
The heat method that is most strongly advocated is the heat gun. This looks like a hair dryer, but it is much more powerful. Some paint and hardware stores sell low-powered versions, but these are slower than industrial quality heat guns. A quality heat gun will soften paint quickly, and then just scrape it off. It is dry before it hits the floor: no mess, just sweep it up. There also are heat plates that work on large flat surfaces, but for windows with muntins and milled details, the heat gun usually works better.
- Paint Stripping Process (VIDEO): Shows the full process of using a heat gun for major paint removal, and chemicals to remove the final residue.
- How to Strip Paint using a Heat Gun (VIDEO)
- How to Use a Heat Gun (VIDEO)
- Heat guns work not only with high wattage, but with high volume air flow. The classic brand is the Master Appliance Heat Gun. Hobby tool makers and paint stores sell inexpensive heat gun models, which may have high wattage, but they will not have high air flow volume.
This section is under development. See above videos on reglazing
Who Can Help? Hiring Contractors
There are reliable contractors who specialize in the window repair and restoration. They know how to do it correctly.
Since many of the tasks are simple, general contractors, handymen, or house painters may be able to do them. However, employing non-specialized contractors for window repair can be risky.
There are two reasons.
- First, contractors sometime will say they can do something, when they cannot. Then they do the wrong thing or to do it badly. They want the business, of course.
- Second, contractors may advise you to do what they know how to do! And this may not be correct for you. If contractors do not know what the right thing is or how to do it, they often give contrary and bad advice.
Advice: You need to know what work you need and how it should be done!
Here's how: study the DIY information. Even if you cannot DIY, that is the information that you need to understand what work you need contractors to do, and how they should do it.
- With this knowledgeable, you can talk intelligently with contractors.
- You can detect which ones know what is the right thing to do and how to do it right.
- And you can avoid the contractors who do not.
Having a plan is very important here again. With a plan that prioritizes the work to be done, an owner can work with a contractor and get the most important work done first and within the budget. Also, if work must be spread out over time for financial reasons, the plan will help the owner and contractor set up the work in a series of affordable stages.
More about Parting Stops
The discussions of how to remove parting stops are incomplete.
If the upper sash has to be removed anyhow, then the parting stop can be removed easily. Once the upper sash will move, just lower the upper sash all the way to the window sill. Then the lip on the upper sash is at the window sill and is not block the parting stop. Start at the top, break any paint seal, and loosen the strip from its track. There may be nails. Work your way down. At the bottom, just lift the stop, intact, past the lip on the upper sash rail.
For windows with interlocking zinc weatherstripping in the sash channels, the zinc strips may set into fine grooves in the parting stop. Such parting stops are not so easy to replace at the lumber yard. The zinc strips have to come out as well in order to remove the lower sash, and to get at the sash weight pocket openings. Getting the strips back into the fine grooves will take some practice and trial and error.
If an upper sash does not have to be removed, then the parting stop has to come out as shown in the video demonstrations. However, while the videos seem rather cavalier about breaking the parting stop, there are good reasons not to break it
- Replacements may be slightly too small
- Parting stops with fine grooves for weatherstripping cannot be replaced, and it is difficult to cut the fine grooves into replacement stock.
If the parting stop cannot be wiggled out, then it may be necessary to cut it or break it carefully so that the lower part can be saved and fitted back into place. The ends of the lip on the lower sash rail also can be trimmed a bit, at an angle, to give more wiggle room to get the stop out. This may leave an open gap for air infiltration, however.
What is "epoxy"? Epoxy is a specialized product that is not generally found in hardware or home supply stores. Some suppliers only sell by mail order (or e-mail order.)
What is not "epoxy"? A similar product is a polyester, not an epoxy. See below. There are pros and cons to the polyester products. They are readily available at stores supplying auto body shops and some paint stores.
Where can one buy epoxy?
NOTE: The following is reproduced from the article by Tim O'Brien in Fine Homebuilding (Feb/Mar 1997, p. 65), listed in the Epoxy Repair section above.
There are too many manufacturers to include in this limited space, but here is a list of the epoxy makers I've had experience with.
5501 95th Ave., Dept. FH
Kenosba, Wis. 53144
Abatron is the oldest and largest maker of epoxies for wood repair. Available only by mail order, their products are easy to mix and tool, and they come in convenient, easy-to-use packaging. Starter kits are available in a variety of quantities. My only problems with Abatron are that their small-print instructions are not comprehensive enough for first time users and that their technical support is inconsistent.
7 Goodale Road
Newton, N.J. 07860
ConServ is a much smaller operation than Abatron, but their products come with good instructions (a 65-page application manual is available for $10). Technical support is good, and the company's owner, Brace Whipple, will talk you through the procedure. ConServ takes longer to cure but after curing stays more flexible than most epoxies. ConServ is available only by mail order but comes in less convenient packaging. The mixing procedures are also more involved.
Repair Care Systems USA
300 Oak Street #155
Pembroke, Mass. 02359
Repair Care is new to this country, but it has been in use for many years in the Netherlands. Instead of using consolidation, Repair Care requires that all damaged wood be removed before rebuilding.
West System Epoxy
Gougeon Brothers Inc.
P. O. Box 908
Bay City, Mich. 48707
West System is intended mainly for boat repair, but it's also marketed for repairing wood rot. It's available at marine supply centers nationwide and comes with an excellent technical manual. I'm told that Gougeon Brothers are renowned for their terrific technical support. West System also uses no consolidant, and the 5:1 mixing ratio can be complicated.
Smith and Co.
5100 Channel Ave.
Richmond, Calif. 94804
Smith is another marine epoxy. I bought some but haven't had a chance to try it yet. It's also marketed for wood repair.
Thompson-Minwax Co. Inc.
10 Mountainview Road, Suite A
Upper Saddle River, N. J.
The Minwax product is actually a polyester rather than an epoxy. It looks and acts much like auto-body Bondo and is available in hardware stores and home centers nationwide. However, their instructions are skimpy, and they offer no technical support.