Replacing Broken Window Glass

This article will show you how to replace broken window glass in a old wood single pane window. It does not cover metal or vinyl framed windows or double pane windows.

Step 1: Removing the Broken Glass
You can either remove the glass with the window sash in place, or remove the sash then removed the broken glass. Wear heavy gloves and use crisscross duct tape over the broken pane. Remove some of the old putty holding the glass in with a screwdriver, chisel, or putty knife. Remove the broken glass. If it needs to be broken up more, cover with an old towel, and break with a few taps of a hammer. Wrap the broken glass in cardboard, or newspaper and duct tape closed. This is to prevent cuts to your garbage collectors, or anyone else reaching in the garbage. Vacuum up small shards with a shop vac.


Here's one of my attic windows that had a broken pane. I removed the glass before bringing it to the workshop, but don't have photos of that. (Note: You can click on photos to enlarge them.)

Step 2: Work Surface, Tools, and Materials

I've got a good level spot to work here on my workbench, but you could also saw horses, or saw horses with plywood on top, and clamps to secure the frame.


Here are the tools and materials you will need:
1. New glass (cost for my piece: $12.00)
2. Glazier's points (cost for small box: $1.00)
3. Needle nose pliers
4. Screwdriver
5. Putty knife
6. Sanding block
7. Exterior grade caulk, or window putty (cost: $3.00–$4.00)
8. Caulk gun (cost: $4.5o and up), or just use a small tube of caulk (no gun needed)
9. Optional: heat gun, wire brush (not shown)

Step 3: Buying the Replacement Glass
You can get new glass by Googling "Glass and your Town, State", or go to a Home Improvement store, both will cut the glass for you. Measure the width and height of the replacement glass needed, and subtract 1/8" from both dimensions. This allows you to install the new glass without cracking it, and allows for glass expansion when hot. I took my whole window sash to my local glass shop and let them measure and cut the glass for me. If your not up for this project, you can leave the sash with them, or of course you can always call a glass repair shop to make a house call for the whole project. For large pieces of glass you may want to bring a blanket to wrap it in during transport, and you may need a helper.

Step 4: Removing the Glazier's Points

Look closely at the sash and you will see metal points that were holding the old glass in. These are called "glazier's points". Usually there are a few per side, and if you don't take them out before you put in your new glass, you will crack the new glass.


To remove the glazier's points, use needle nose pliers and pull straight out. You can either keep these to reuse, or use new and easier to install points (shown below).



Step 5: Preparing the Sash for New Glass

Next, use a putty knife, screwdriver, and utility knife to remove the old window glazing/putty. You want to remove as much of it as possible so that your new glass will fit without breaking. Try to make the surface (shown in photo above) smooth, as the glass needs to be well seated on that surface. You can use a heat gun to loosen up stubborn glazing, but be careful not to scorch the wood, or start a fire!


You can also use a wire brush or a sanding bock (shown above) to help remove old window glazing.

Step 6: Seating the Glass
Blow the dust and debris from the sash, and put down a thin layer of caulk on the surface the new glass will rest on (this step not shown). Gently insert the new glass. Do not let it drop into the sash.

Step 7: Installing Replacement Glazier's Points

You can reuse your old points, or for about a buck you can get a small box of new glazier's points that have "ears" that you can push on with a putty knife or screwdriver. The trick to inserting these without cracking the glass is to angle the points up slightly while pushing down slightly on the point with the screwdriver. If you push straight in or slightly down, you could hit wood fiber that might steer the point downwards, and thus crack the glass.



To get the points all the way in, it helps to push against a back stop like I have on my workbench, and it helps to wiggle the points left and right as you ease them into the sash. Place the points 4" from all corners and then a minimum of 8" apart on all sides.


You want the points to be inserted all the way, so they can be fully concealed with caulk. They should also make contact with the glass to hold it well in place. Gentle contact with the glass is all you need. Later, the caulk will hold the glass firmly in place.

Step 8: Applying a Bead of Window Caulk

Next apply a bead of caulk to the sash and window junction. It's better to use a bit too much caulk than too little. You'll remove the excess caulk later. Use any exterior grade window caulk. I'm using a silicone/acrylic mix which is cheaper than 100% silicone, but you could use 100% silicone too. Many "how to replace broken window glass" articles on the web use glazing compound/putty instead of caulk, but my expert glass guy at my local glass shop said, "those are the days of the past, we use caulk now".

If this is your first time using caulk, you'll also need a caulk gun. They range in price from $4.00 and up. You get what you pay for. I'd recommend getting a slightly higher grade for the do-it-yourselfer. Put the tube in the caulk gun and then cut the nozzle off with a utility knife at about 45 degrees. Then stick a long nail or wire down the nozzle opening to break the seal inside the tube.

Step 9: Smoothing out the Caulk

Use a putty knife, on an angle like this, from one corner to then next, in one smooth stroke. If the angle is too much, you'll hit and expose the glazier's points, if the angle is too little you'll see the caulk from the other side of the window.




Step 10: Removing Excess Caulk from the Sash and New Window Glass

Here's the finished window flipped over to show you how you will see the caulk on the other side (the inside view when installed) of the sash. When viewed straight on rather than at an angle (as shown in the photo above), you won't see the caulk.



Immediately after you spread out the caulk, you can use your putty knife to remove any excess caulk that got on the sash surface. Then let the caulk set over night, or until firm before removing the excess caulk from the glass.


I've waited for the caulk to set over night, and I'm now using a razor blade to remove the excess caulk from the glass. If you don't let it harden before you scape it off, you'll create a mess of your neatly caulked joint.

Step 11: Finishing Touches

You can paint the caulk and/or window if you like, using the caulk manufacturer's recommended wait time before painting. For this window I left it as is, as it's an old attic window which I plan on replacing in the new future. Clean off the new window pane with Windex and paper towel. Replace your window sash in the window frame and you are done!

Tips and Replacement Glass from
Interstate Glass & Mirror

Resources
RonHazelton.com: How to Replace Broken Window Glass
AceHardware.com: Replacing Broken Window Glass
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My Standard Disclaimer: This is what I did. This does not mean this is the best way, the right way, to building code, or even safe for your needs. So you are on your own with your project. I make no promises about the information presented here. I'm just a do-it-yourselfer, not a professional at all, sharing my story. So if something goes wrong with your project, you are on your own. Good luck, and have fun!

All content and photos, copyright 2009, Dover Projects
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