Replacing the sash on an Andersen double hung window is often the most cost-effective way to restore function and aesthetics without the expense of full window replacement. Whether your existing sashes are cracked, warped, or simply outdated, understanding the precise steps ensures a tight fit and smooth operation. This guide walks you through the entire process, from measurement to installation, demystifying what is typically a manageable DIY project.
Tools and Materials Required
Before beginning, gathering the right tools prevents mid-project frustration and guarantees a clean finish. You will need a precise measuring tape, a sturdy ladder, safety goggles, and work gloves to protect against old glass and sharp edges. A utility knife, pry bar, and wood chisel are essential for removing old glazing compound and freeing the sash from the frame. For installation, you will need a high-quality wood glue, exterior-grade caulk, and shims to level the new sash in the opening.
How to Measure for Replacement
Accurate measurements are the foundation of a successful replacement, as Andersen windows use specific dimensional standards. You should measure both the width and the height of the existing window frame from edge to edge at the top, middle, and bottom, recording the smallest internal dimension. Subtract 1/8 inch from both the width and the height of this measurement; this allows for easy insertion and proper alignment within the jamb. Note that the sash size is distinct from the frame size, and ordering based on the old sash dimensions ensures compatibility.
Removing the Old Sash
The removal process requires patience to avoid damaging the surrounding trim or jamb. Start by lifting the lower sash and sliding the tilt locks to the vertical position to release the upper sash. Carefully tilt the upper sash inward, lift it out of the frame, and set it aside in a safe place. To extract the lower sash, engage the tilt mechanism and gently pull the sash upward and out of the frame, supporting its weight to prevent sudden drops that could crack the glass.
Handling Hardware and Glazing
As you remove the sash, pay attention to the integrated hardware, including the balance springs and pulleys that enable smooth movement. These components are often held in place with clips or screws; document their orientation with a photo before disassembly. Use a utility knife to score the old glazing compound sealing the glass, then gently tap the glass outward to remove it. Exercise caution with aged glass, as it can be brittle, and wear gloves to protect from any shards or sharp edges.
Installing the New Sash
With the old sash cleared, prepare the new unit by inspecting the glazing beads and ensuring the tilt hardware is functional. Apply a thin, even bead of wood glue to the channels where the sash meets the jamb, then slide the new sash into place, aligning it with the previous configuration. Insert shims between the sash and the frame to maintain equal gaps and keep the unit plumb, securing it temporarily until the glue sets.
Securing Hardware and Testing Operation
Once the glue has cured, reinstall the balance springs, pulleys, and any locks, verifying that each component moves in sync with the sash. Slowly tilt the upper sash to re-engage the tilt mechanism, then test the full range of motion by opening and closing both sashes multiple times. The sash should lift smoothly without binding, and the locks should click firmly into place, indicating proper alignment and tension.
Finishing and Long-Term Maintenance
After confirming smooth operation, apply a generous bead of exterior caulk around the perimeter where the sash meets the frame to prevent air and water infiltration. Touch up any bare wood with a matching exterior-grade paint or stain, focusing on the ends where moisture can penetrate. Regularly check the condition of the glazing and the tilt locks, and lubricate the hardware annually to preserve the functionality and appearance of your Andersen double hung windows.
