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Old-House Online » Old-House Tips, Restoration Stories, & More » Repairs & How To » Window Repair Tips from John Leeke

Window Repair Tips from John Leeke

Discover the ins and outs of old-house windows through the eyes of a pro who's spent decades repairing them. By the OHJ Editorial Staff | Photos by John Leeke

    Preservationist John Leeke re-glazes an old sash.

    Preservationist John Leeke re-glazes an old sash.

    As a preservationist for nearly five decades (and an OHJ contributor for 26 years!), John Leeke has encountered more than his share of old windows. In between repairing the windows on his own 1899 Victorian in Maine (“My wife is going to shoot me if I don’t get that window in the back bedroom fixed before the first warm breezes of summer,” he says), he shared with us some of the lessons he’s learned over the years.

    OHJ: How can you tell when window sash is too damaged to be rehabbed?

    John Leeke: I’ve repaired hundreds of sashes and assessed the condition of more than a thousand, and never seen a sash that could not be repaired. It usually boils down to an economic decision. Will it cost less to repair and rehabilitate a sash, or to replace it with one of equal quality? The hidden trick is that most replacement sash on the market won’t be as good quality as the old sash, and replacements that do match the quality are very costly. The cost of repair/rehab varies greatly with the experience and labor cost of the worker. A professional window specialist keeps track of time and materials costs and will accurately estimate the rehab costs. A do-it-yourselfer does not have to pay for labor. If you are just starting out with repairing your own windows, repair or refurbish at least ten sash to learn how and get up to speed before you decide a sash is too damaged to rehab. Often I can repair one completely rotted out sash joint, replace a fourth of the putty, and paint a sash for less than the cost of a replacement sash.

    OHJ: What kind of safety precautions should you take on a window-rehab project?

    JL: First, determine the safety risks. Lead-containing paint and putty release lead particles that can get into the human body and cause serious health problems. Chemical fumes from paint and epoxy also can lead to health problems. Dry-heat paint and putty removal methods can start building fires. Working in high places presents the danger of falling.

    Protect occupants and visitors by hanging simple signs with big letters and red “keep out” safety tape to discourage people and pets from entering work areas. Wear safety glasses or goggles to protect eyes from flying debris, and wear a hardhats and a respirator to keep dust out of your body. Have a spray bottle filled with water and roll of paper towels on hand for damp-spot-cleanup of lead-containing dust during work. Set up a wash-station at the exit of the work area so you can wash your hands and face before leaving work area.

    Use blue painter’s tape to seal the edges of doors and windows to prevent lead-containing dust from spreading outside the work area. Also protect the building by covering floors with 6-mil poly sheeting taped to the baseboards. After the project is finished, fold up and dispose of the poly sheeting, and remove any remaining debris with a HEPA vacuum, followed by a damp rag and mild detergent.

    Savo Hall, a historic structure on the prairies of South Dakota, is a perfect candidate for a window restoration workshop.

    Savo Hall, a historic structure on the prairies of South Dakota, is a perfect candidate for a window restoration workshop.

    OHJ: What are some of your favorite tools to use when restoring windows?

    JL: To release painted-shut sashes, I use a portable steamer and pull-type scraper. A specialized tool called the Window Zipper also is great for loosening painted joints. I use a combo of two 3″ stiff putty knifes and a thin pry bar to wedge out stops, beads and sash. I rely on a very stiff 1.5″ putty knife to tool putty, and a soft, thick paintbrush to dust off the glass with dry powder whiting. I prefer a 4″ beveled sash brush for painting after the window is repaired, and a HEPA hip-pack vacuum for spot scraping and cleanup.

    OHJ: What type of glazing putty do you recommend?

    JL: There are three types of glazing compound, and each has its place in good window work. Traditional linseed oil-type putties (like Sarco MultiGlaze Type M or Allback Linseed Oil Putty) are hard, “knife grade” putties. Modified oil-type glazing compounds (such as Glazol, Perm-E-Lastic, and DAP 33, although many window specialists are not fond of the latter) are either semi- or non-hardening. And acrylic glazing compounds can be either hardening (Aqua-Glaze) or elastomeric and flexible (Glaze-Ease 601). The most important thing is to look for a putty that serves your needs and gives long-term performance, but can be easily removed and renewed when it deteriorates. My current standard is the traditional linseed oil type, specifically Sarco Type M, but I sometimes use others for their special characteristics.

    OHJ: When you must splice new wood in to replace a rotted piece, what’s your preferred joinery method?

    JL: I use a half-lap joint and glue it in place with either an epoxy adhesive formulated for wood, or a foaming polyurethane type.

    OHJ: What can you do to prevent future decay on wooden window sash?

    JL: Keeping water out is the most important consideration. In addition to performing spot paint and putty maintenance to prevent water from getting in, you should also keep the gutters above the window cleaned out and working. Treat the bare wood surface with a paintable water-repellent preservative after you’ve finished all woodwork repairs and before priming and painting, and also inject a borate-type preservative to treat the inner volume of the wood.

    When painting sash, it's important to "paint to the line" to help protect the wood from moisture infiltration.

    When painting sash, it's important to "paint to the line" to help protect the wood from moisture infiltration.

    OHJ: What’s one window restoration lesson you’ve had to learn the hard way?

    When painting sash, you should always lap the paint past the edge of the putty over onto the glass about 1/16″ to seal the joint between the glass and the putty to keep water out. I once had to go back are repaint a whole house full of sashes because we missed this critical detail.

    OHJ: What’s the strangest problem you’ve ever encountered?

    To me, the strangest problem is how many old-house owners have been persuaded to throw away all their fine old windows and replace them with plastic counterparts that will last only 5 to 20 years. A well-built old window can be maintained and repaired to last for centuries and can also be upgraded to meet current energy-saving goals with simple, low-cost treatments like exterior storms, interior air panels, or even ordinary roller shades.

    However, I have renewed hope for both homeowners and windows. Homeowners are waking up and realizing they can maintain and repair their fine old windows. Even if you’re not a do-it-yourselfer, don’t worry—more and more savvy tradespeople are recognizing this new market for traditional window maintenance and repair services.

    Want more tips on fixing your old windows? Learn more about sash window repair.

    For more information, including detailed step-by-step instructions for many of the repairs mentioned here, check out John Leeke’s newly updated book, Save America’s Windows, available at

    Published in: Old-House Journal May/June 2009


    Catherine Brooks September 30, 2011 at 12:49 pm

    There are some down sides to using steam for paint and putty removal.
    1) Time: It takes several minutes to get the sufficient moisture into the wood to release the paint. The scraping time is not so long. But then you must let the wood dry out completely for at least a day before new paint is applied. Moisture in wood is the #1 cause of poor paint adhesion.
    2) Damage to wood: That much water causes the wood surface to soften and feather when it is scraped. To remove those fibers, one must scrape down deeper or sand off the roughness before painting.

    Low infrared heat of the Speedheater at 400 degrees releases the bottom layer of paint in 20-60 seconds, rejuvenates the old wood, requires only a few scraping strokes to get down to the solid, bare wood, and leaves the wood with the right moisture content to be ready to paint immediately. The heat is more than half the temperature of a heat gun, so it does not vaporize the lead usually in old paint and minimizes the risk of fire from misuse.

    Chris Carozza September 4, 2012 at 4:26 pm

    Do you know someone by the name of John Scheekinchier? If so, can you give me his #? I was told he can fix window cranks.

    Benito Conca January 8, 2013 at 1:38 pm

    John, I watched an episode on this old house recently featuring a woman in business restoring windows & steaming the paint &putty to remove it all,thenreputting and using a powder to clean the glass. I cant remember what was used,can you help me . Thanks Ben Conca

    Benito Conca January 8, 2013 at 3:04 pm

    John were can i purchase dry powder whiting? Ben

    Erik March 23, 2013 at 4:53 pm

    Ben, check out John’s website: for the answer to all you seek.

    John Leeke April 19, 2013 at 11:18 am

    The powder is called “whiting” and the method is called “Polishing the glass” to clean it. You can learn more about it (including suppliers and videos), over here at the discussion forum at my website:
    (scroll about a forth the way down and look for the section on “Polish the Glass”

    take care, work safe,


    Patrick Hey May 21, 2013 at 5:56 pm

    John, I am doing Historic window rehabilitation, the windows are from circa 1890s. There are metal parting glides on all the frames with tracks on the sash’s. I am having a hard time sourcing out these parting glides. Have you ever come across any of these?

    John Leeke June 3, 2013 at 12:08 pm

    Yes, try Blaine Window Hardware at:

    take care, work safe


    susan weir July 18, 2013 at 7:50 pm

    i have old sash windows with the springs in the sides…i took them apart to paint them and now they wont stay up by themselves…why???

    Dick Gross August 6, 2013 at 4:28 pm

    We have a 1912 Prairie School home designed by Purcell and Elmslie in Bismarck, ND. We have 3 double paned picture windows on the main floor, all of which lost their seal long ago. We have tried dozens of window repair/replacement places in our area and spent a lot of money. Shortly after new window panes have been put in and putty put on, humidity, dust and spiders creep in between the windows.

    How can we restore the seal without going to a presealed window that won’t look anything like the windows we have which have 2 inch or so oak spacers between them?

    John Leeke August 14, 2013 at 12:41 pm

    Susan, there is a little metal clip or bracket that is attached to the spring. You have to pull the clip or bracket to load the spring as the sash is installed. Sometimes it takes a special tool to do this.

    Dick, the dust and spiders are getting in there through a nook or cranny that was not sealed up when the new panes were put in, which tells you something about the skill of the workers. It is possible to install a desiccant (crystals of a special type of salt) between the two panes that will absorb the moisture. After some time the desiccant has absorbed all the moisture it can. Sometimes a “pocket” can be created above, beside or below the window to hold the desiccant so it can be replaced from time to time.

    Bill Laswell June 25, 2014 at 1:00 am

    We recently purchased and are restoring an old house in Texas near the coast. We love the old wood windows but they are in bad shape. I would like to restore them but we have strict codes that required high design pressures. The city is saying that our windows will have to meet these requirements. Is it possible to modify the windows to meet the city’s hurricane code and prove to the city that the code is indeed met? Any thoughts?

    Thanks, Bill

    Wanda Brimmer April 17, 2015 at 10:36 pm

    I live in the Nevada desert with 70 mph gusts of wind blowing sand. We have aluminum double pane windows that are worthless on the west side of our house. After a storm the window sills are covered with sand. Is it feasible to caulk the offending windows? All rooms have other windows that can be used for escape in a fire situation.

    Alex Giadone July 7, 2015 at 5:04 pm

    Hi John

    I have a bunch of exterior windows to re-glaze on my house and I have been trying to decide what time of glazing putty to use. Can you go into a little more detail on why you are using the Sarco type M right now? You mentioned other special characteristics. For me, the priority would be longevity and not so much the feasibility of removing it later. I’ve heard good things about the allback linseed oil putty.


    Tom V. July 24, 2015 at 3:46 pm

    Love the article, looks like I don’t have an excuse to not start my reno. Well, wish me luck!

    Maine Mendez March 22, 2016 at 2:34 pm

    You got very good repair tips for windows, i am suggesting these ideas to my friends.

    Lynn Samuelson April 27, 2016 at 1:36 pm

    I am concerned about solvent fumes lingering in my house. I heard a story where Volkem 116 polyurethane by Tremco was used to glaze windows and the fumes rendered the house inhabitable. What product works best with the least fumes and can be painted when cured?

    Lynn Samuelson April 27, 2016 at 1:56 pm

    I meant to say uninhabitable

    Kyle May 31, 2016 at 11:43 pm


    I can use some expert experience on a glazing situation as I have only window glazed once. I have an aluminum skylight installed in the 1960’s. I spot glazed the window with DAP 33 but I did not pretreat the remaining glazing with oil prior to glazing with the new DAP 33. I have to say that I spent a long time getting the glazing to look almost perfect, and it looks really really good up close. However there are some micro hair-line cracks in the areas nearest the old glazing that are hard to see. I ‘m guessing that these are from the old glazing drawing the new glazing oil out? Or maybe because it is so hot on the roof with a metal frame? is there a remedy to midigate or reverse these micro cracks? Brush linseed oil to revive? I have not yet painted or primed the glazing and it has been one day since I glazed, although it is hot in San Jose, California and it is on my roof. The window is a two foot by three foot skylight and my window frame outside lip is about one inch tall.

    Thank you!

    Stephanie Rose July 24, 2016 at 11:29 pm

    I learned from John about using whiting to remove putty residue but couldn’t find it. A makeup brush and baby powder from the dollar store worked great. I am going to try cornstarch to see if that might also.

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