How to Repair a Wooden Window Sash

Wood windows add a classic aesthetic to your home. Properly maintained, they can look great for years. You can paint them one color, and years down the line, repaint to match any changes to your home’s exterior and interior, giving you more flexibility than you would have with other materials, like vinyl.

But eventually, wood window sashes may become damaged or degrade, especially in older, historic homes. As a natural material exposed to the elements, over time your window sashes can chip and eventually rot, even with regular maintenance. Sash window repair involves attention to detail, but it is something you can manage on your own with patience and knowledge.

If you’re active in inspecting and keeping your window sashes looking good, it’s possible that all you’ll need is a few spot repairs to fix chips and splits in the wood. You can repair these surface issues with a sash repair kit. These sash window repairs will also keep out water and pests that can lead to more rot. 

If, however, you don’t check your wood window sashes for damage regularly, rot can set in, which will then require a full or partial wood window sash replacement.

Depending on the extent of your sash window repair, you may be able to get it done without removing the panes from the sash. If you’re only patching a small crack in the sash, you may be able to sand it, fill it in with epoxy, sand some more and paint.

If, however, the damage is more extensive, you may need to take the whole assembly apart to repair or replace window parts.

Below are the steps to replacing an old-style wood window sash, the kind that is typically seen in homes pre-1970s. While we understand you may want to stay true to your older home’s windows, it’s important to realize that they could be costing you money on your energy bills. Old windows, even ones well maintained or recently repaired, don’t feature the same energy efficiency and function as newer windows. 

If you want to save money on your energy bill and avoid the hassle of continuously repairing your window sashes, you should consider replacing the entire window. Companies like Fenster USA offer a wide variety of wooden windows, so you are sure to be able to find a new window in the same style as your old window. You’ll get all the beauty of your old style with all the benefits of modern window technology.

Step 1: Remove the Window Sash From the Frame

If you’re removing parts of the wooden window sash, you’ll need to take the sash out from the frame. To do so, unscrew the stops, which are the two blocks that keep the lower sash from sliding up too high, or parting beads, which hold the upper sash in place. Remove any cords or chains and tie them off to keep them from retracting if they’re weighted.

Step 2: Release the Glass

Glass panes in a wood window sash are held in place with glazing compound or putty. While durable, glazing compound will crack and split over time. To release the glass from the sash, you’ll need a heat gun and chisel. Gently heat the glazing compound with the heat gun and then scrape it off with the chisel, taking care not to scratch the glass.

Once the glazing compound has been removed, you can gently pry off the glass. If you’re working with more than one pane, make sure you label them so you know where they fit when you’re done with your repair.

Step 3: Re-Inspect the Sash

If you’ve gone to the trouble of taking the glass out of your sash, it’s a good idea to go ahead and do another thorough inspection of the whole sash. You’ll be able to identify any previously-hidden places where the wood may have started to rot or where old glue, weather stripping or hardware has also degraded. While this may be an extra step, it will save you from having to do even more repairs in the future.

Step 4: Repair Damaged Joints and Chips

Clean out the joints to remove any crumbling epoxy or rotting wood. Sand down any chipped areas. Prepare your fresh epoxy or wood filler according to the manufacturer’s specifications, and apply using a knife. Let it cure and sand down. 


Step 4: Take Apart the Sash and Build Replacement

If you need to replace some or all of the sash, carefully take apart the old sash. Keep the existing parts, as you’ll need them to mark where any hardware goes as you assemble the new wood window parts.

Window sash replacement kits can be purchased to make your window repair project simpler. They are pre-cut to the dimensions of your existing sash and can be built to match a number of models from older window manufacturers, so the joints and grooves will fit with your existing parts if you aren’t replacing the entire sash.

Assemble your wood window sash replacement. Make sure all your joints are flush and smooth so the panes will fit properly and the completed sash won’t catch on the tracks. Use the older sash parts you kept so you can measure and mark the location of any hardware like hinges and screw them in place.

Step 5: Prime the Sash

Priming is an important step. Sealing the wood will protect it for years and save you the work of having to do additional repairs before you really need to. Priming also means the wood won’t suck necessary oils out of the glazing compound, which could cause it to crack and fail prematurely.

Step 6: Bed the Glass

Use glazing compound to secure the glass back into place in the repaired sash. Don’t be afraid to be liberal with the compound; you’ll wind up cutting most it off, but you want to make sure it’s been fully and evenly applied to the sash rabbet. Gently press the glass in place to make sure the sash is filled, and then cut away the excess compound.

Step 7: Set the Points

Points are set into the reassembled sash to fully hold the panes in place. They can be applied with a gun or by hand. Depending on the size of your panes, you may need more than one on each side. Points should not be more than 10-12 inches apart.

Step 8: Tool the Putty

Apply another layer of putty on the sash and outside of the glass. Don’t worry too much about making it look clean at first; the goal is simply to apply an even layer all the way around the pane. Pack the putty into place with the edge of the knife. Apply a second layer, and use the knife blade to create a smooth and thin bevel all the way around. Let it cure fully before painting.

Step 9: Paint

Once your window repairs and replacement parts are fully cured, you can paint and stain as desired to match your home’s interior and exterior.

Step 10: Rehang the Sash

Before you rehang your repaired wood window, add weatherstripping or replace old weatherstripping. This protects your home and your window. Lubricate the tracks. Reattach cords or chains and slide the sash back into place. Replace stops and parting beads.

Ready to Start?

Repairing a wood window sash sounds complicated, but the actual step-by-step process is not overly complex. With the right wood window replacement parts and a little patience, you can repair your own windows and have them back in place in no time. 

Or, if you want to save yourself the hassle and get more energy efficient windows in the style you want, visit the Fenster website to explore our line of wood windows.


  • Dennis Didio
    Posted August 21, 2019 at 9:58 pm | Permalink

    I need a Caradco style C-2000 casement sash. I am just a homeowner and have no need for three. Would you consider making me just one?

    • Posted August 28, 2019 at 12:34 pm | Permalink

      Dennis, We understand your situation, but that doesn’t change the time and overhead it takes to set up our entire shop just to make one sash at a time. Over my nearly 20 years in window repair, I have inspected FEW homes that only had one bad window. Considering your model of window and presumed age of the home, I would be highly surprised you only have one that is bad. Perhaps further inspection might identify additional units that require attention. We would certainly be happy to put an order together for you that meets our minimum requirement. You can contact customer service at or 844-973-4462.

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