How to Install New Construction Windows in an Old House

Windows dictate the style and livability of a home by controlling natural light and temperature. Replacing old windows with those incorporating modern manufacturing principles can seem daunting, but the difficulty of the task varies and has a lot to do with the material in which the windows were originally installed. Replacing windows in a stick-constructed-clapboard- or shingle-clad-style home often requires less time and energy than say those embedded in a brick or stone facade. Although standard window sizes have increased over time, many manufacturers have lines designed to fit the size and style of older homes, and most also manufacture custom windows to fit any need.

Things You'll Need

• Treated lumber for rough framing
• Silicone caulking
• Spray foam and fiberglass insulation
• Level, saw, crowbar, hammer and nails
• Exterior and interior building materials and finish trim

Instructions

1. Take a thorough inventory of all the windows in your home that need to be replaced. Note their location, size, operating style (crank or double hung) and window detail, such as mullions or panel lights. With this list, begin online and in-store research to define the style of replacement windows desired and cost of options. After the new windows arrive, proceed to demolition of the old windows and installation of the new.

2. Deconstruct the old window assembly by removing the interior and exterior trims and any old insulation. Remove the old window fasteners, and lift out the old window. Inspect the old rough framing for damage and plumb, remove the old framing if necessary and rough in a new frame according to the new window specifications. Attach the rough frame to the surrounding structure with nails or concrete screws.

3. Place the new window in the rough frame, checking for level and plumb before securing the window flange with a bead of silicone caulking and nails or via the method outlined in the window manufacturer's specifications.

4. Use spray foam insulation to fill all small openings and joints, and use pieces of fiberglass insulation to fill in all other gaps between the window and rough frame and between the rough frame and surrounding structures.

5. Patch and blend exterior facade materials and replace window trim consistent with the aesthetic elements of the home. For the interior, patch or replace any missing wall material such a drywall, plaster or paneling, and then replace the window trim and sill details.

Tips & Warnings

• Good measurements make for a well-fitting window, which is critical to its function, efficiency and long life. Take the width measurement by laying a measuring tape at the top right corner stretching it to the left, including the depth of the window inside the jam within 1/16 inch. Repeat this measurement at the midpoint and across the bottom. If these measurements differ, use the smallest of them and subtract 1/4 inch to arrive at the new window's width. To identify the height measurement, place your tape at the top right corner of the window, measuring down to the bottom right corner at the top point of the sill. Repeat at the vertical midpoint and again along the left vertical. If these numbers differ, use the smallest and subtract 3/16 inch to achieve the height of your new window. For determining the depth, use your tape to measure between the outside wood stop to the point inside where the inside sash rests against the inside stop--basically the channel where both sashes slide. The depth is often between 3 1/4 and 3 1/2 inches. Not all modern replacement windows have a 3-1/4-inch depth, and you will need to choose a window that fits snugly in the wood frame.