If you have a broken, foggy, or damaged piece of glass in your aluminum window frame, then it does not necessarily mean that the whole window needs replacement. If the frame itself is straight and is in good condition, then replacing only the glass will take much less time and effort than installing a new window and will cost considerably less. In addition, if you are careful and prepared, you will be able to handle the replacement by yourself in one afternoon.
Below we will describe how you should measure, cut and install the new glass in the aluminum window.
When Does Glass-Only Replacement Make Sense?
Before starting, make sure that your frame is in good condition. Glass-only replacement is suitable if:
- Your frame is not bent, twisted, or heavily corroded
- The corners of your frame fit together tightly and no separation has appeared in its joints
- There is no damage to the frame except for cracks, chips, broken seals or fogging between the panes of glass.
If the frame is bent out of shape, has many dents, or the window is quite old and difficult to open or close, a complete window glass replacement would likely be a better option.
Materials Needed
Prepare everything you will need prior to starting the process to avoid having to stop midway through:
- Work gloves and protective goggles
- Tape measure (steel)
- Putty knife or plastic scraper
- Utility knife or razor scraper
- Flathead screwdriver and a Phillips screwdriver
- Rubber mallet
- Glass replacement kit, cut to match the window opening
- Glazing gasket, vinyl glazing compound, or glazing tape (depending on the type of frame)
- 100% silicone sealant
- Isopropyl alcohol and paper towels
- Setting blocks (small rubber or neoprene discs)
- Cardboard or a heavy blanket for safe disposal of the broken glass
Step 1: Ensure Safety
Sharp glass causes deep cuts. Use heavy duty gloves, long-sleeved shirts, and safety goggles throughout. In case the glass is cracked, secure it using wide packing or painter’s tape diagonally on the glass. This holds the pieces together and minimizes chances of fragments falling. Place a drop cloth or blanket under the window for protection. Keep kids and animals away from the workspace.
Step 2: Take Out the Window Sash (Where Possible)
Most aluminum windows, particularly sliders, can be lifted out of their frames. It is far safer and more convenient to work at a worktable compared to working in situ.
For sliding windows, lift the sash and position it in the upper channel while tilting it to one side. If you cannot remove the sash, you can still work in situ, but with more caution. Place the sash horizontally, with the glass side facing upward.
Step 3: Remove the Old Glass
There are three types of systems that keep the glass in aluminum windows, and you have to know which one you have:
Glazing bead (can be snap-in or screw-in): This is a thin aluminum strip installed inside the window, holding the glass in place. Carefully remove it using a putty knife, without bending the bead. Some beads can be fastened by small screws.
Vinyl glazing gasket: This U-shaped rubber or vinyl strip holds the glass against the frame. Find its end, remove it from there, and pull it out of the groove.
Silicone or glazing compound: Some old windows can be attached with silicone or putty. Make a cut all along the edge of the glass, using a utility knife.
When you have removed the retention system, lift the broken piece carefully from the window. If it is cracked, remove the pieces one by one and put them directly in a cardboard box. Wrap any large pieces of glass in newspapers or a blanket before throwing them away.
Step 4: Cleaning the Frame Channel
This step is frequently overlooked and ignored, although it plays an important role in establishing the seal on the replacement glass. Use a plastic or razor scraper to remove any old sealant, glazing tape, and other debris from the channel. Make sure you do not damage the aluminum during this process.
Use isopropyl alcohol to wipe down the channel and allow it to dry. Check the frame for any burrs, rust, or dents that may have formed. Lightly sand any oxidization.
Step 5: Measure for the Replacement Glass
Accurate measurement is the key step in the entire process. You should measure the slot in which the glass is located from the inner part of the channel on each side, and not the old glass itself, because it may have been incorrectly cut or is simply broken.
The width and height must be measured in three places each (upper, middle, lower, left, center, right), and you should take the smallest measurement. Subtract from each measurement roughly 1/8 inch in order to give some clearance for expansion and contraction, since aluminum expands differently from glass.
Additionally, you should measure the thickness of the old glass. The average thickness of a single residential window is 1/8 inch (single pane) or from 1/2 to 1 inch (insulated glass unit).
It is also necessary to indicate the kind of glass that is needed:
- Single-pane annealed – the classic and inexpensive choice
- Tempered – required in accordance with the rules in case of proximity to the door, in bathrooms, and in case of low windows; breaks into small blunt parts
- Double-pane insulated (IGU) – more efficient
- Low-E coated – protects from heat and ultraviolet radiation
The local glass company can trim the glass to the right dimensions, check the specifications and advise you on how thick the glass should be.
Step 6: Installation Preparation
Install the setting blocks at the base of the channel and position them about a quarter of the way in from each of the corners. This helps hold up the glass without it touching the aluminum, which avoids stress cracks and also allows drainage of water.
In cases where your frame has glazing tape, install the tape in the channel where the glass will go and make sure to press it into the channel.
Step 7: Installing the New Glass
With help if your glass is big, lower the glass into the frame by starting with the bottom edge on the setting blocks, tilting it into place. Ensure that it is sitting evenly with clearance on all sides. Do not force the glass in if it does not fit.
Step 8: Reinstall and Seal
Reinstall your retention system:
Glazing bead: Tap the glazing bead back into place using a rubber mallet; you may need to replace screws
Vinyl gasket: Using a tool, apply pressure to install a new vinyl gasket in the groove around the glass starting from one of the corners; use a new gasket since the old one is likely to have hardened
Silicone: Apply a continuous bead of silicone sealant around the interface of glass and frame and smooth it out using either a gloved finger or tooling spatula
Only use 100 percent silicone that is safe to use with glass and aluminum. Do not use acrylic caulk as it tends to crack or shrink. Follow the instructions provided by the manufacturer regarding curing time which should be approximately 24 hours.
Step 9: Reinstall and Cleanup
Reinstall the sash in the track and make sure that it opens and closes smoothly and without difficulty; remove any tape or plastic protection. Clean the glass with a glass cleaner and a microfiber cloth.
Common Mistakes to Avoid
- Measuring the old glass instead of the opening. Always measure the frame.
- Overlooking cleaning. Residual caulk hinders bonding.
- Ordering glass without any clearance. Shrunken glass breaks due to changing temperatures.
- Applying inappropriate caulk. Caulking is not designed for glazing.
- Forgetting about safety glass regulations. Certain areas demand that you use tempered glass legally.
When to Hire a Pro
Think about contacting a glazier if your window is big, located at an upper level, or is made from heavy insulated glass. Professionals also have proper equipment and ensure code requirements. Getting a quote is not costly in comparison with breaking the glass or getting injured.
Final Words
Glazing your window with an aluminum frame is a relatively easy task to perform if you plan carefully and think about safety. A properly glazed window will provide good view and energy efficiency for many years ahead.