How to Install a New Window on Aluminum Siding

Adding new windows in a home adds value, more light and can give fresh appeal to exterior elevations. Installing windows in aluminum siding is doable for an experienced do-it-yourselfer if the proper time is spent on preparation and the window span does not require new header beams or other major construction. If the new window is very large or the aluminum siding has been hung over concrete block instead of stick construction, calling in a professional is probably a better option.

Things You'll Need

• Circular saw with diamond blade
• New window assembly
• Treated lumber for window framing and wood shims
• Window flashing
• Level
• Hammer
• Drill
• Masking tape
• Screws
• Nails
• Spray foam insulation
• Fiberglass insulation

Instructions

Select Window Location

1. Mark off the location of the new window on the interior and exterior with masking tape. Consult manufacturer's specifications for the window to determine required rough framing measurements. Remove entire siding panels that cover the location for the new window and set aside.

2. Cut the opening with the circular saw beginning with the interior making as many passes as needed and repeating this process on the exterior. Carefully remove the outcut of framing and building material and discard.

3. Build out a four-sided rough lumber frame with nails according to the window manufacturer's specs. Place rough frame into the opening and check for level. If needed, use shims to level and nail the rough frame into the surrounding building material to secure.

4. Lay down metal window flashing on all four sides of the opening, and secure with nails. Set window in rough opening, check for level and use wood shims as needed. Nail through the window fin to the rough frame to secure.

5. Spray expanding foam insulation into all crevices, and place fiberglass insulation in all larger gaps between the opening and the rough frame and between the rough frame and the new window.

6. Cut and fit siding pieces with circular saw around new window in keeping with the hanging pattern on the rest of the elevation.

Tips & Warnings

• Use existing hanging hardware when you can and add nails as sparingly as possible.