How to Install a Metal Window on New Construction

Position 1-inch-thick wood blocks on the bottom of the window opening to support the window. Position one block at each end of the window opening. Position a third block at the center of the window opening if the window has a mullion post. A mullion post is a vertical support beam that separates two or more panes of glass.

Attach masonry clips to the sides of the window if the clips were not installed at the factory. Windows that feature a wooden frame are typically secured to the framing members with casing nails while masonry clips are used to secure metal windows to the framing members. Align the clips' screw holes with the holes drilled into the sides of the window then install and tighten the clips' screws with a screwdriver. Make sure that the clips point toward the interior of the home.

Insert the window into the window opening and lower it onto the wood blocks.

Slide window shims between the sides of the window and the frame until the shims are snug and the window is level. Check the straightness of the window with a level. Add and remove shims as necessary.

Bend the masonry clips around the framing members and secure the clips to the members with screws.

Fill the gaps between the window and the framing members with loosely packed fiberglass insulation. Wear work gloves, while handling the insulation, to avoid fiberglass particles.

Trim away the excess shim material with a handsaw until the shims are flush with the framing members.