How to Install a Window

Installing a window correctly takes a lot of careful attention. The exact procedure varies with the type of window being removed, how it is removed, and the type of replacement window.  With over 9 years experience and not ONE single water or moisture issue, we are confident we can provide the best service in town!

1. Measure

Measure the opening into which the retrofit window will be installed width, height, and depth. Size the replacement window slightly smaller than the opening, allowing clearances recommended by the manufacturer. Vinyl frames require more clearance than those made of wood, aluminum, fiberglass, and composite materials.

2. Removal of old window

Remove the old window. For wood vertical sliders (single- or double hung windows), remove stops, trim, sash cords, and pulleys. For finned windows, cut away siding to expose the fin so the entire unit can be removed, or cut back the frame as much as possible, leaving the old fins intact.

3. Preparation

Prepare the opening. Remove all obstructions, such as loose materials and old caulk. If the opening is severely out of square, fill it in, leveling the bottom sill and plumbing the sides, before installing the new window. Try the replacement window to make sure it fits properly before applying sealant.

4. Seals

Restore the integrity of the moisture barrier and drip cap. If fins were exposed, seal breaches in the building paper. If the existing metal frame was collapsed to remove it, seal the entire perimeter gap liberally with silicon sealant. Reinstall or seal any damaged flashing. For box frame retrofits, make sure a drip cap is in place to drain away water.

5. Precaulking

Precaulk the stops, mounting surface, or fins with elastomeric sealant. When installing box frames against existing stops, caulk the surface of the stops against which the window will be placed. For finned windows, install a liberal and continuous bead of caulk either on the fin or on the mounting surface around the entire perimeter.

6. Bottom support

Install proper bottom support. Metal, wood, and fiberglass frames can be supported with shims spaced per manufacturer's instructions. Vinyl windows need solid, level support across the entire bottom (the sill jamb).

7. Installation

Install the new window level, plumb, and square. Use a level to plumb the unit. To make sure it is square, (a) adjust until both diagonal measurements are the same or (b) open the slider just past the edge of the sash channel and adjust until the gap is even along its entire length. Anchor the window securely per manufacturer's instructions. Use only corrosion-resistant nails and screws. Predrilling fins and frames is recommended. Anchors must penetrate solid material such as structural framing. Countersink anchors installed through wooden jambs.

8. Insulation

Insulate gaps between the retrofit frame and the rough opening. Fill the cavity between the retrofit frame and the rough opening with foam backer rod or loosely packed insulation. Non-expanding foam is OK when installed carefully. Never use expanding foam. Weather seal the entire perimeter of the installation with elastomeric caulk. Butt joints and other gaps over 5/8 inch wide need backup material (such as foam backer rod). The seal must be continuous and should be tooled to fill gaps and to remove air pockets and excess material.

9. Trim

Install exterior and interior finishing trim, also called molding, and caulk It's a good idea to install prefinished weather protected trim using butt joints.