How to Restore Sash Windows

Reading Time: 4 minutes

In this article, we will be giving tips for people who like to undertake DIY projects. However, when you read the steps below, you will see that it can be quite a tricky job, especially for beginners.

If so, you could also consider using a Sash window restoration company to get the job done neatly and quickly. It may even work out cheaper in the long run, as self-restoration can become a costly project if you are unsure of what you are doing.

Find a Knock Out panel

If a window is essentially in good shape but just needs weights re-hung, look for a knockout panel: a square score on the side of the frame that’s usually about 2 inches wide and 6 to 8 inches tall, just big enough to pass a weight through. These are usually only found in higher-end windows.

If one exists, however, it’s a convenient way to access the ropes and weights on a sash window without removing the trim. Determine if you have a knockout panel by looking for a horizontal line between the stop points. You may have to use a narrow tool to break through the scored lines if it has been painted, but rest assured that it was designed for this purpose.

With a multi-tool equipped with a wood-cutting blade, you can perhaps saw out a knockout panel in the absence of a knockout panel. You should remove any trim around the window if you need access to more than just the weights and ropes.

Remove trim stops and sashes

Hopefully, the trim and interior stops can be removed intact first. With a 5-in-1 painter’s tool, you can pry trim off the frame after cutting through any paint and caulk with a box cutter. Take care to ease nails out and remove screws if you discover any. Press gently on the trim to pry it from the wall.

Apply gentle force with a flat crowbar after you’ve cleared some space. Now you can remove the bottom sash. This component and all others should be marked so you can make sure you reassemble the window correctly. After reassembling the window, the parting stops should be removed. Obtain window trim from the local lumberyard to replace the damaged stops. The top sash should be removed last.

Determine the frame’s condition.

The frames in old houses are seldom square or snugly fitted due to years of shifting and settling. As moisture penetrates the frame’s lower joints, nails holding the joints together rust or wood rots, causing the side jambs to separate. It’s essential to have square frames for good window function. Therefore, use a square and a level to fix any twists, adding shims as needed to achieve a square frame, but being mindful not to place shims too close to the window-weight well. Lattice strips can be added where the shims won’t show if they aren’t enough. In the case of an expanded bottom, a board can often be hidden inside of the bottom frame.white flowers in shallow focus

Take care of the cleaning.

A 5-in-1 paintbrush can be used to remove debris, such as old glazing compounds, nails, and screws. In old houses, paint is often layered so thickly that it prevents windows from opening, so it needs to be sanded or scraped off at this point. Thin, good-looking paint is usually okay to leave alone.

Sandpaper can be used to cut through thick paint, and chemical strippers can soften paint so it can be scraped off. Sandpaper is best for areas with fine details, such as interior trims with delicate carvings or sashes with routed areas. If you must have a fine finish, you should use an orbital sander. Chemical strippers can also be used on those delicate parts. In addition to scraping the paint away, you can fill holes with putty or make repairs with wood epoxy once you have removed the paint.

Glass and glazing compounds should be replaced if damaged or missing.

A good condition original pane can remain intact. When replacing wavy glass, keep an eye out for discarded pieces since replica glass can be expensive. Don’t hesitate to take salvaged glass to a hardware store to have it cut to your exact dimensions if it’s not the exact size you need.

The glazing compound should be loaded into a caulk-style gun to secure the glass in the sash. Run a small bead along the channel to secure the glass without pins. To apply external glazing, run the gun along the edge of the wood where it meets the glass. Often, a neat, uniform line can be achieved if the wood edge and the tip of the container are both clean. Smooth out the imperfections with your finger. After it hardens overnight, you can trim any excess off with a razor blade the following day.

Staining or painting.

Painting or staining interior sash is an option. Standard oil-based stains are recommended for the latter, and you should test them on a piece of wood that is old or hidden to ensure the colour is right before applying it to the sash and trim. If you have trouble matching the stain, you can add a touch of paint with the same base as the stain to get the right colour. Polyurethane provides a final layer of protection after staining. Exterior sash faces should always be painted for the best weather protection. (If the sash and trim are painted, a topcoat is not required.)

Reassemble everything.

Usually, 16- or 18-gauge nails work best (1/2″ to 3/4″) and just long enough (1/2″ to 3/4″) to do the job without going through the weight. Trim nails can be longer. Sash windows are assembled in the opposite order they were disassembled. Weights are tied to the top sash first; then, the ropes are attached. Now you can check that everything works correctly by doing an initial check. Immediately after replacing the parting stops and bottom sash, you can replace the interior stops. The trim can then be attached.


Thank you for reading!