Storm Windows USA · Installation library
Installing Aluminum Exterior Low-E Storm Windows
Exterior storms attach outside the original window. Standard flanged frames and architectural frames with a central flange have different measuring rules. Identify your frame and mounting method before confirming the finished size.
Before you begin
Use the order-specific installation drawing supplied with your window. This guide explains the workflow; your selected mounting detail controls final dimensions, fasteners, sealants, and clearances. Handle glass with support and suitable protection. Preserve any required emergency access, and have damaged or difficult-to-reach openings reviewed by a qualified installer.
Have these ready
- Tape measure, level, and square
- Specified screws and screwdriver
- Compatible exterior window sealant
- Sill expander where specified
- Safe access equipment, gloves, and eye protection
- A helper for large or heavy glass assemblies
Step one
Measure for the mounting method
- Measure at the intended blind-stop or overlap mounting surface. Record multiple widths and both side heights to the nearest 1/8 inch.
- For double-hung models, record the upper meeting-rail position as well as the overall width and height.
- Tell us whether the numbers are opening dimensions or finished tip-to-tip frame dimensions. Mounting allowances differ by frame type.
- Record the sill slope and any irregular trim. Confirm the sill expander and final fabrication dimensions with the order drawing.
Installation, step by step
- 1
Inspect and prepare
Match each unit to the opening. Repair unsound wood or other unsuitable fastening surfaces. Fit any specified sill expander before positioning the unit. Use professional help where safe exterior access is difficult.
- 2
Dry-fit the assembly
Center the frame and verify that all attachment holes land on sound material. Check the meeting-rail alignment and sash movement before applying sealant.
- 3
Seal the head and jambs
For standard flanged exterior frames, apply compatible exterior sealant where the top and side flanges meet the surround. Do not seal across the sill or block the drainage path. Architectural central-flange units use their approved flange-to-stop detail.
- 4
Secure and square the frame
Start at the head and then secure the side attachment points. Keep the frame square and the operating gaps even. On standard flanged units, follow the supplied head-clearance instructions. Do not transfer that clearance to a different frame design.
- 5
Set the sill detail
Adjust the specified sill expander to the sill without twisting the frame. Keep weep slots open for ventilation and water drainage. Use the supplied retaining detail for the expander.
- 6
Test and maintain
Open and close every operable sash, check screen retention, and confirm the original window remains usable. Recheck drainage after painting, caulking, or seasonal cleaning.
The finished-installation check
- All fasteners land on sound attachment material.
- Sashes move freely and close fully.
- Screens and glass retainers are secure.
- Head and jamb seals are complete.
- Sill and weep openings remain unobstructed.
If something does not fit
Water remains at the sill
Inspect weep slots and the sill drainage path. Remove obstructions; do not add more caulk across the bottom.
The operating sash jams
Check frame squareness, even clearances, and fastener tension before adjusting hardware.
The original opening is irregular
Have the installation detail reviewed. A different flange position, expander, or custom frame may be needed.
Windows covered by this guide
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