How to Replace a Single Pane of Glass in a Metal Frame
The glass in your metal-framed window may be broken -- in which case replacing it is an urgent matter -- or it may be simply scratched or unclear. In any case, replacing it likely isn't as complicated as replacing glass in a wood window. Instead of dealing with old, petrified glazier's putty (and applying messy new putty), as on wood windows, glazing in metal windows often is sealed with a rubber gasket or metal or plastic strips that fit into grooves in the sash frame. Disassembling the frame may or may not be necessary to replace the glass. If you have to remove broken glass, be sure to take appropriate precautions.
Cordon off the area in which you're working, if the glass is broken, and obtain an empty paper bag for the glass. Put on leather gloves and safety goggles, and pull out as much of the glass as you can by hand. Deposit the broken glass into the paper bag. Use pliers to pry out smaller pieces. You may not be able to get all the glass, but remove as much as possible.
Remove the sash from the window frame, if possible; the method depends on the window type. Newer single- and double-hung sashes often come out by raising the sash, angling the bottom toward you and pulling it gently out of the frame. The movable sash on a slider window typically lifts up then tilts inward and away from the bottom frame track. With casement and fixed windows, it's probably best to leave the sash in place.
Remove the seal(s) and all remaining glass from the sash frame. If the glass is sealed with a rubber gasket, you'll probably have to disassemble the sash frame by removing the screws in two or more corners of the frame, with a Phillips screwdriver. If the glass is held in place with metal or vinyl strips, carefully pry out the strips with a thin, flat-blade screwdriver or putty knife. Try to keep the gasket or strips intact, as you'll need them for reference when shopping for replacement parts, or possibly reuse them if replacements are hard to find.
Measure the dimensions of the sash frame with a tape measure (this may require temporarily reassembling the frame). Take the measurements from the insides of the grooves. Subtract 1/8 inch from both the length and width measurements, and quote those numbers when purchasing the new glass. If the old glass is intact, you can simply measure the dimensions of the glass -- you don't need to subtract 1/8 inch. Purchase new gasket or seals when you get the glass, if available.
Install the new glass into the sash frame, using the gasket or seals, as applicable. Work carefully and methodically to ensure the glass is secure and properly sealed along all edges. Assemble the sash frame around the new glass and gasket, if you took apart the frame.
Reinstall the sash in the frame, as applicable, by reversing the procedure you used to take it out.
- If the old glass is cracked, it may be safer to break it before you remove it. To prevent shattering, cover both sides of the glass with masking tape, spacing the strips 2 inches apart, and tap the glass with a rubber mallet.