Restoring Old Windows

Pete Cone

October, 2009

This article documents some of the things I learned while restoring windows in my century-old home. There are more extensive articles on the subject on the Internet, and those can be referenced for more detail. This article will explain some of the things I learned to do (and not to do) while trying my own hand at it. Before starting your window project, read through the following information for the tools and supplies you’ll need and things to be aware of.

THE PROBLEM:

My windows are five feet wide by seven feet tall. This posed problems just in the sheer weight and size of the sashes and moving them around. The lower sashes all worked, although some had one or both of the sash cords (that connect to the weights) broken or missing. Without the sash weights, it is difficult or nearly impossible to open the window. The upper sashes were all stuck in their openings. Previous owners had painted the windows inside and out, and had gotten paint into the gaps between the sash and the jamb. It was like they were nailed shut. Additionally, they weren’t closed all the way to the top of the opening, so the two sashes did not meet in the middle. Since the windows did not seal tightly in the center, bugs and cold air could enter freely. Also, the sash locks would not function because they were caked with paint and did not line up in the center.

The glazing on the outside of the windows was in very bad shape. It was cracked, falling out, or missing in spots. The paint on the outside of the sashes was badly deteriorated. But the old windows with their craftsmanship and the wavy old glass were just too nice to part with. I decided to take the windows apart, remove all the old paint and finishes, restore any broken or missing parts, re-glaze and repaint the sashes, and provide weather stripping to seal out drafts. The restoration breaks down into a few not-too-complicated steps for each window. It’s easier to complete one window at a time and attack the project as time permits.

WARNING

When dealing with an older home with deteriorating paint, there is a good chance the paint has lead in it. You can either have the paint tested for lead to be sure, or make the assumption that lead is present. There are publications available on lead paint and how to handle it properly. Follow recommended procedures and remember that dust containing lead is your biggest enemy.

TOOLS and SUPPLIES

· Small pry bar (good for getting molding loose with minimal damage)

· Large pry bar

· Channel lock pliers

· Hammer

· 4p (four-penny) finish nails

· Nail set (for setting the finish nail heads below the surface)

· Paint scraper

· Heat gun

· 1-inch putty knife (get a good quality knife with a stiff blade)

· Glazing compound (I used DAP 33.)

· Glazing points

· Oil-based primer

· Latex paint

· New sash cord (get enough strength for the weights to be supported)

THE SOLUTION:

A. DISASSEMBLY

To get started, remove the inside stop molding that holds the inner (lower) sash in its channel. Use a putty knife or some similar thin blade to gently pry the molding away from the side of the opening. You may need to use a utility knife to first cut through the layers of paint that are also holding this molding in place. Work carefully along the length of the molding to pry it out from the side. The finish nails that hold it in place will be exposed as you pry the molding loose. The nails may come out with the molding, or tear through the wood and stay in the jamb. When you get the molding off, remove any nails that are still embedded in it by pulling them through from the inside. Large channel lock pliers work well for this. Do not try to pound them back through the molding. The heads of the nails will splinter the wood around the nails holes. You will then have to fill those holes later when reinstalling the molding. The nails still in the jamb can just be pried out. Discard all the nails and use new nails when you are ready to put everything back in place. The stop molding at the top of the window opening can be removed if it will make the job easier; it will not interfere with removing or replacing the window sashes.

Now remove the sash cords that are still intact and remove the lower sash. To do this, you will have to raise the sash slightly to clear the sill. Place a rag on the sill to rest the sash on. Pull one side clear of the opening so you can see its side. The sash cord will come through a pulley at the top of the jamb, extend down through a slot in the side of the sash, and have a knot in its end that fits in a hole in the side of the sash. Usually there will be a small nail that holds that knot it the hole so it can’t pull out. Holding the sash cord securely against the tension of the sash weight, remove the nail and gently pull the cord away from the sash. Do not let the sash weight drop. Make sure the sash is steady on its perch and carefully let the sash cord retract up into the pulley. If the weight does not come to rest at the bottom of the pocket it rides in, you may have to run another nail through the knot to keep the end from disappearing into the wall. Be sure to have your tools in easy reach so you won’t have to let go of the sash.

Repeat for the other sash cord. Once both weights are disconnected from the sash, you can remove the sash from the window opening. Place the sash in the area you have set up for working on the windows. One thing to keep in mind when moving and working on these old windows is that the glass will likely be chipped or cracked along its edges, and those small defects can cause the glass to break without warning if not handled properly. Keep the window sash vertical at all times, unless the glass has been removed. This is also true for the glass after it is removed from the sash.

Unless the upper sash is already able to move up and down freely, you won’t know if the sash cords are broken. The only thing holding up the full weight of that sash might be the paint that is locking it in place. Take a length of two-by-four or other sturdy prop and place it under the upper sash to support its weight. Then remove the rectangular stop molding (sometimes called a parting stop) that runs from the bottom of the jamb to the top, and lies in a groove between the two sashes. Again, use a utility knife to cut through any paint that is holding this piece in place. There will be small finish nails holding this molding in place also. Usually this molding is a standard size and easily replaceable, so not as much care needs to be taken in its removal. You will want to avoid damage to the sash and the jamb, however. I ended up destroying this molding to get everything else out without damage. Replacement stop molding was available at the local hardware store and was inexpensive.

Pry out the inner stop molding to free the upper sash starting at the bottom. Once it is out, you may need to pull on the sash to break loose the paint on the outside that is locking it into the opening. Once it is free, you will need to lower it slightly so it will clear the upper stop molding. Make sure your prop is still positioned under the upper sash in case it tries to drop suddenly. As with the lower sash, you must now disconnect the sash cords.

B. REPAIR

Remove the upper sash and relocate it to your work area. During the removal of the upper and lower sashes, take notice of any weather stripping that might be present. On my windows, I found two-piece zinc weather stripping on either side of the sashes. The two pieces were nailed into the sash and the jamb such that the interlocking pieces slid past each other as the sash moved in its channel. The upper strips were in fairly good shape since that sash hasn’t moved for decades. I was able to reinstall them when I put the upper sash back in the opening. The lower weather stripping had been badly smashed by previous attempts at replacing sash cords, so I was unable to save them. If you can salvage the original energy-saving elements of your old windows, they will still serve you well today.

Once both sashes are removed and safely stored elsewhere, it is time to replace sash cords. There are two upper and two lower cords. Replace missing or broken cords now. If in doubt as to the condition of a cord, replace it. You won’t want to get your windows all fixed up, just to have a rope break. Sash cord is available at most hardware stores. You might need to see how heavy your sash weights are to get the right strength cord. Or just get the heaviest cord available to be safe.

To replace a cord you need access to the weight. Toward the bottom of each sash channel (where the sash rides up and down) is a section that is cut away from the rest of the jamb. Remove the nails or screws used to hold this section in. The access panel can be pried carefully out of its pocket, exposing a cavity behind the sides of the jamb. There may be just one panel that gains access to both weights, or one for each sash. If a cord was broken, the weight should be resting in the bottom of the cavity.

Repair the sash cords for the upper sash first. Remove the weight from the cavity. Cut a length of sash cord with enough extra for the knots using the length of the old cord as a guide. If the old cord was missing, get the length from the pulley down to the top of the weight as it rests in the bottom of the cavity and use that length to cut your cord. Fish the cord through the pulley and down through the cavity until you can reach it through the access opening. Tie a knot at the upper end of the cord, and use a nail if necessary to prevent it from falling through the pulley opening and down the cavity. Tie the lower end of the cord through the hole in the weight with a strong knot. A square knot or a sheep shank will work well. Place the weight back in the cavity. When you pull the upper end of the cord through the pulley, the weight should move freely up and down in the cavity. Do this for both of the upper sash cords.

Using the same technique, now replace the cords for the lower sash weights. Once you have good sash cords for both sashes in place, you can begin the removal of the old paint and finish on the window jamb, if needed. Remember to follow the proper procedures for handling lead paint waste. I used a heat gun and scraper for removing the old paint from the window jamb. After removing the paint and old shellac finish from those areas, I sanded them smooth (wetting the surfaces to control dust). I used an oil-based primer on all the bare wood surfaces, followed by latex enamel paint. If your windows are stained and varnished instead of painted, you can re-stain and finish them. Mine had several coats of paint over the original finish, and the base wood was pine, so repainting them was the best option.

Assuming you are re-glazing the sashes, you will need to use the heat gun to soften the old glazing that remains. Do not let the heat gun apply too much heat directly on the glass or it can crack. I used a 10-inch drywall taping knife to shield the glass as I worked around the sash. Once the glazing is removed, remove the old glazing points (small metal tabs that hold the glass in the sash) with your putty knife. The glass will still be sticking to the inside of the sash, so gently break it loose so the glass can be lifted out. Remember to keep the glass vertical as you remove it. Set it down on a tarp or old rug for cleaning. Use a razor blade scraper to remove old paint and glazing from the glass. Work slowly and carefully to avoid breakage.

Now remove paint and any remaining glazing from the wooden sash. Inspect any seals still on the sash, and remove them if they need replacing. If you have limited space, start with the upper sash. It will be the first one that gets fit back into the jamb once it is refinished. Once the paint removal is complete, sand the roughness off the bare wood. Prime the entire sash, except the sides that will contact the jamb. Be sure to prime the pocket where the glass will rest. Allow the primer to dry completely.

To prepare for the glass to be placed back into the sash, you need a small bed of glazing for the glass to rest in. Remove a working amount from the can and knead it in your hands. This will mix and soften the glaze, making it much easier to work with. Then form a thin bead around the entire sash where the glass will contact the inside lip. Only about 1/16-inch thickness or less is required. This will form an inner seal, but you don’t want it to be thick. Once this is ready, being sure the sash is now propped up in a nearly vertical position, carefully set the glass on the bottom lip and lay it back into the sash. Gently press around the edge of the glass to compress the glazing and set the glass firmly into its bed. New glazier’s points should now be installed around the glass to hold it firmly in place. “Push points” work well because they have a lip you can push them in with using a putty knife.

Now add the triangular bed of glaze around the sash. This will require some practice to get smooth, uniform results. You should knead a ball of glazing compound about the size of a golf ball at a time, roll it into a rope about ¼-inch thick, and lay it in place against the glass. Using a clean putty knife held at a fairly flat angle, draw the knife along the entire length of the bead, one side at a time. Work slowly, and angle the putty knife blade so the inside edge of the glazing matches the height of the wooden sash on the other side of the glass. Try to get a good, smooth finish on the glazing in one pass. The more you go back and try to “tweak” the bead, generally the worse it looks. Don’t get discouraged at the first few attempts. If it’s looking bad, just remove the glaze while it’s still soft, and start over. It will get better with practice.

The finished glazing generally needs a few days to firm up enough to paint. An oil-based primer should be applied over the glazing to seal it from the weather. Once dry, the entire sash can be painted. Again, leave the sides that will contact the jamb unpainted to avoid too much sticking.

C. REASSEMBLY

When the upper sash is ready to go back into the opening, place your padding rags on the sill and rest the sash there. You might need some help in steadying the sash as you work. Next, grab the knot on the end of one of the sash cords and pull it down to the sash. You should be pulling against the weight during most of its travel. Push the knot into the hole in the side of the sash, and guide the cord into the slot. Tap a one-inch or so finish nail into the sash so it will prevent the knot from pulling out of the hole. Either nail through the cord, or just use the nail to “pinch” the cord against the sash so it can’t pull out. Repeat with the other cash cord. As you affix the cords to the sash, the weights will begin to support the weight of the sash. The sash at this point is basically ready to slip back into its channel in the jamb.

At this point, the issue of the weather stripping should be addressed. I reused the original zinc strips on the upper sash, and those were nailed in after the sash was in place. If you found no weather stripping on your sash, or it couldn’t be salvaged, you can try adding a plastic “V” weather strip to the outside surface the sash will ride against, and possibly another on the inside stop molding. The tightness of the fit will limit how much thickness you can add without the sash binding in the opening. The sash should have a firm feel to it once the stop molding is in place, but still move up and down without a lot of force.

The stop molding is installed against the upper sash next. It should be primed prior to installation, but painting can be done afterward. The upper half that contacts the sash will not need paint, but the lower half that will show will need to be painted. The one thing you will want to avoid is having two painted surfaces in contact between the sash and the side moldings and jamb. If you end up with two such painted surfaces in contact, just apply a thin coat of petroleum jelly to the edge of the jamb before sliding it into its channel and installing the stop molding. Over time, the two painted surfaces will bond to each other, and you’ll be back to having windows that don’t operate.

Next install the lower sash into the channel the same way, installing the sash cords and sliding it into its channel. Use weather stripping on the lower sash as required. Remember, this sash will be doing most of the sliding up and down, so make sure it moves easily. I used the self-stick “V” strips on the inside and outside of the lower sash, plus I added a 1/8-inch by one-inch felt strip to each side. This helped seal the sash, and eliminated the “rattling” around in the opening due to the loose side-to-side fit. The extra thickness of the “V” strips on both inside and outside of the sash is okay on the lower sash. The molding that holds this sash in its channel can be positioned to give the amount of tension against the sash that you want. Now nail the inside molding to the sides of the opening and pressing against the lower sash. Use appropriate finish nails, making sure the sash moves freely. Set the heads of the nails just below the surface of the wood with a nail set and fill the holes. The final paint finish can then be applied.

Replacing the hardware is the final step. I used orange paint stripper to remove the caked-on paint from the lock and other hardware to get the lock moving freely. You can install new or salvaged hardware, depending on your goals for the restoration. When done, both windows should be movable and able to be locked. The locking mechanism serves to pull the two sashes together tightly at the meeting rails, providing a better seal against drafts.

D. SPECIAL PROBLEMS

As you approach each window, you may be faced with unique situations that require different techniques. On the very first window I restored, the meeting rails did not line up after the sashes were back in place but before I nailed the inside molding. I noticed the upper sash was not closing evenly across the top of the opening. After some measuring of the diagonals of the window, I found that the window opening had “racked,” or was more of a parallelogram than a rectangle. It was too late to trim the upper sash without removing the stop molding, cords, etc., so I trimmed the bottom of the lower sash to let the meeting rails line up. Make sure your opening is square before reinstalling your upper sash. If it’s not, you will want to test fit your sashes in the opening while the glass is still removed so you can do any trimming you need to before the glazing and painting are done.

ENJOY!

When beginning your project, be as sure as you can that the window is okay mechanically before worrying about its esthetics. When you’re done, you will have an historic window in like-new condition. You can bore your friends and family with the details of what you went through to get there.