A broken window isn’t pretty, but aesthetics may be the least important reason to replace it.
“In addition to heating or cooling loss, a broken window can cause problems to the wood sash as it lets moisture in,” says Emil Novak of Kranz Hardware Co. in Villa Park. “Eventually, you could see wood rot and other problems.”
Repairing a broken window is a fairly easy do-it-yourselfer project and costs only a few dollars. And while the procedure is fairly simple, there are safety concerns when dealing with sharp objects and working on a ladder.
As a result, most experts recommend removing the sash and repairing the glass pane on a workbench. “That’s the best way to tackle a broken window and the most efficient,” Novak says.
On the other hand, removing a window from the frame can be a lot of work, especially with older homes. Several pieces of wood trim may need to be removed, and ropes or chains that connect the sash to weights will have to be disconnected.
“For many people, it may be easier to repair the glass than to get the sash out, especially if the sash has not been removed in 50 years,” says Matthew Murphy, an estimator with Keller & Associates Inc., a North Side general contractor of residential remodeling.
“As a result, you have to be even more careful when repairing a window in place, especially when repairing glass on a second floor,” Murphy adds.
Because windows not removed from the frame need to be repaired from the outside, you’ll need a ladder of adequate length to reach the broken window.
It’s also recommended that you have a second set of hands available to fix a second-story window. That way, a helper indoors can dispose of the broken glass through the window, so you don’t have to carry it down the ladder. The helper can also hand you the new glass pane from indoors, so you don’t have to cart it up the ladder-a special concern on a windy day.
Also, if the window has double panes of glass-often known as “thermopane”-you probably should check with the manufacturer’s instruction for repair. Special glass may be required to mend the window.
Newer windows feature insulation values produced by trapping dead air between two (or sometimes three) panes of glass. Certain types of windows even feature a partial vacuum or insulating gas between the panes. Windows may also be covered with a low-emissivity (Low-E) coating, which helps prevent heat loss on the cold days and admits light but filters out heat gain.
– To start the repair, remove the broken shards of glass, using heavy-duty gloves to handle the pieces. Work from the top of the frame down so that any falling pieces won’t strike your arm. Also, wear safety goggles to protect your eyes against airborne pieces.
If the glass is cracked but not broken, score it with a glass cutter about an inch from the frame. Then affix several pieces of tape across the scored line and tap the glass gently to loosen it. The tape will prevent the glass from falling and shattering. Remove the scored panels and gently pull the remaining glass out of the sash.
– Then remove the putty that held the old pane in the frame’s molding. If the compound is pliable, use a rigid putty knife to scrape it out. If the putty is hardened, warm it first with a heat gun or hair dryer until it becomes flexible.
Next, locate the glazer’s points-small metal triangular objects used to hold the glass in the wood-that you’ll find embedded in the frame. Use a pair of long-nosed pliers to remove the points and make sure you get all of them. A halfway hidden point can crack the new piece of glass.
With some windows, the glass is held in place by a wooden bead instead of putty and glazing points. That wooden bead is held in place with screws. Remove the screws to loosen the bead and remove the broken glass.
– Next, thoroughly clean any debris-such as small pieces of glass-from the sash and the recess where the glass rested. Use the rigid putty knife or a chisel to clear out the debris. Go down to the bare wood in the recess but be careful not to gouge the sash.
“It’s important to thoroughly clean the sash because even the smallest piece of old glass can crack the new glass,” Murphy says.
– Once the sash is clean, use a small paint brush to apply a thin coat of linseed oil to the recess. The linseed oil will prevent the oil in the new glazing compound from drying out, keeping the putty flexible.
– Now is the time to accurately measure the window opening from inside the recess. Measure both height and width from several points-top, center and bottom. “Very few windows are perfectly rectangular or square,” Murphy says. “In fact, the window could be more than an eighth of an inch off from the top to the bottom. And the sash can bow out in the middle by as much as a quarter-inch.”
Then, cut a piece of glass to match the opening, using a scoring tool or glass cutter. Do this on a solid surface such as a workbench, and secure the glass in place while you cut it.
If you have no experience cutting glass, your best bet is to take the measurements to a local hardware store and have them cut the glass piece. Again, give the specific measurements.
Also buy plenty of glazing compound and glazer’s points, at a hardware store or home center. Putty is usually sold by the pound, and a pound will adequately cover about 12 linear feet. “A pound should be more than enough for a typical-sized window,” Novak says.
– Next, take a golf ball-sized piece of compound and knead it to an even consistency. Sticky putty should be first wrapped in newspaper to remove excess linseed oil. Compound that is too stiff can be softened by adding a little linseed oil.
Roll the putty into a rope about an eighth of an inch thick and push it into the recess for the glass. Then, take the piece of glass and press it gently into the bedding putty.
If your measurements were off and the glass is slightly larger than the opening, use a sharp razor blade to trim back the sash recess to accept the glass panel. “Don’t use a chisel to trim the sash because you’ll crack it,” says Murphy.
Then reinsert the glass, making sure it fits snugly in the opening.
– Next, install the glazer’s points into the recess to hold the glass panel in place.
Push points have small folds or tabs in them, making them easy to push into the wood. Flat points have no fold. Novak recommends the push points, especially for windows that are being repaired in the frame.
Place a point about every six inches or so. Drive them into the frame with a 3/4-inch to 1-inch chisel or a rigid blade putty knife. “You want something with a wide blade to distribute the weight evenly over the glazer’s point,” says Novak.
Hold the chisel so that it lies flat with the surface of the glass. “Gently push the glazer’s points into the wood,” says Novak. “Be careful not to put too much pressure on the chisel or it will slip and you can crack the glass.”
If the window has a wooden bead, replace it carefully. Don’t exert too much pressure on the bead or it can crack the glass.
– After the points are in place, roll more compound into a slightly thicker rope, about 3/8-inch in diameter. Press the compound over the glazer’s points, completely concealing them.
Then, take a flexible-blade putty knife and compress the compound so that the exposed surface is flat and pitches 45 degrees from the sash to the glass. Remove any excess compound from the glass or the sash.
Clean the putty oil off the glass with window cleaner or mineral spirits.
Allow the compound to dry for at least three weeks before painting it with an exterior paint. When you do paint, spread the paint so it barely touches the glass to form a weather seal.
“Overall, most of the work shouldn’t take more than a few hours,” Novak says. “And you’ll appreciate it once the cold weather sets in.”
