Replacing glass in a vintage door

It’s not a particularly difficult DIY job, but takes slow, careful work

Q I live in a 1935 row house. The original kitchen door has glass panes and one has a crack. How can the glass be replaced without breaking the trim and giving that section a different look than the other panes?

A Glass doors typically have pieces of wooden moulding, rather than glazing compound, to hold the glass in place. It’s fairly easy to remove the moulding, replace the glass and then reinstall the moulding. But it takes careful, slow work to prevent splitting the thin pieces of moulding or denting the surrounding sections of the door. If you would rather leave the job to a pro, some glass-repair companies take on small jobs like this.

If you want to tackle the job yourself, decide whether to work with the door in place or whether you need to be kinder to your back and knees by taking the door down and setting it on sawhorses or a sturdy table. There are Youtube videos on how to remove hinge pins so you can lift a door off, which is much simpler than removing hinge screws.

Spread tape, such as painter’s tape, on the back of the cracked glass. This will keep shards from scattering as you remove the glass. Spread a drop cloth if you have one, and wear goggles and thick gloves. If needed, tap on the glass with a hammer to break it into pieces that you can wiggle out. Loosen stubborn bits with a small pry bar or putty knife. Clean up the broken glass and vacuum thoroughly.

Put a fresh blade into a utility knife and score the paint where the moulding fits against the door. It’s easy to get off track if you press too hard, so make several passes, going deeper each time. Also score the mitre joints of the moulding. This keeps the paint from tearing and creating a ragged edge.

Slip a stiff putty knife or a painter’s five-in-one tool into the opening you sliced and gently begin to pry one of the moulding strips toward the centre of the opening. Begin a little way away from the mitred corner, not right at it. After you loosen one area, move the tool to another place on the same moulding strip and nudge it slightly toward the centre, too.

Once the strip is loose, you might find that it is still caught at the corners; moulding is often cut slightly long so the pieces spring into place at the mitres, ensuring a tight joint. To deal with this, use a second tool — ideally a thin pry bar designed for work on moulding, such as the Shark Grip eight-inch pry bar (US$16.50 at sharkcorp.com).

Position it against the moulding from the back, where the glass used to be. Push the moulding out toward you as you simultaneously use the putty knife or five-inone tool to nudge the moulding toward the centre of the pane space.

After you get the first moulding piece out, the others are easier to remove, because the corner pressure is already relieved. Number the pieces on the back to help you reinstall them in the same spots.

The rest of the process is straightforward.

Clean the opening, including removing any small nails that didn’t come out with the moulding. Measure the opening and go to a glass shop for a replacement piece ⅛-inch shorter and skinnier than the measurements, so you have a little wiggle room when you install the glass.

Set the replacement piece in the opening and reinstall the moulding. If the nails are still in place and straight, you might be able to press them in and seat them with a hammer and nail set. But it’s often easier to start fresh, using wire nails, which are thinner and shorter than regular nails.

The nails need to go in at an angle. To avoid breaking the glass while you hammer them in, pre-drill first. Locate these nails where there weren’t nails before; if the old nails pulled through the moulding, they would have widened the openings too much. Well-stocked hardware stores carry very thin bits; choose one no wider than the nails. Or chuck one of the nails, tip side out, into a drill and pre-drill with that. You might need to wrap the shaft with painter’s tape to get something thick enough to secure in the drill.

Once all the moulding is back in place, fill any gaps with painter’s caulk, then touch up the paint and you’re done.