Simply by virtue of their location, basement windows face unique hazards every day. A lawn mower spits a rock out the discharge chute; a croquet ball takes an unintended turn; weeds overgrow the sill, trapping moisture; a snowdrift forms against the window and stays for months. If you haven’t inspected your basement windows lately, take a look. Chances are, they need to be replaced.
Even if your basement windows haven’t sustained visible damage, replacing them may be a good idea. Older basement windows often contain only a single pane of ordinary window glass, so they are not energy efficient. And because foundation walls are prone to settling, gaps and cracks may develop around the windows, further decreasing efficiency and creating openings for insects and vermin. A window may also be compressed in a distorted opening so it can no longer be operated, preventing ventilation.
Home security is another good reason to replace a plain-glass basement window. Glass-block or acrylic-block units are more difficult to break, and would-be thieves can’t peer in through patterned blocks to see your new power miter saw or your big-screen TV.
Finally, you might want to replace tired-looking basement windows with newer models for cosmetic reasons. The project is relatively inexpensive, and the results are well worth the effort.
Choosing new windows
Window openings in foundation walls are standardized in newer homes, and in-stock basement windows are based on these dimensions. Most are 32 in. wide, and common heights are 15, 17, 19 and 23 in.
At typical building centers you’ll find in-stock basement windows with hopper-style sashes and side-by-side sliding sashes along with fixed-sash units fabricated from glass block. Like awning windows, hoppers are a type of casement window — the difference is that awning windows are hinged at the top (for better rain protection) and hopper windows are hinged on the bottom (for better basement ventilation). Awning-style and fixed-sash basement windows usually must be special-ordered.
The most inexpensive basement windows have vinyl frames and a single insulated-glass sash. You can buy them on sale for as little as $50. Windows with higher-efficiency glass are costlier. Glass-block windows are slightly more expensive too, especially if they offer features such as louvered vents, dryer vents, fancy textures or designer colors. Acrylic-block windows are fairly costly. The hopper style units shown here cost about $400 each.
Because basement window sizes are so varied, new basement windows for older homes are usually custom-made. This is not as extravagant as it may sound. Custom sizing adds very little to the cost of a window, and in most cases you can get delivery in two or three weeks. But if you’d rather work with stock windows, you can install jamb, header and sill extensions to reduce nonstandard rough openings to accept stock window sizes. Some window manufactures can provide extensions, stucco flanges and other accessories that aid the installation process.
Though reducing rough openings is a viable option, enlarging window openings in masonry foundation walls is a bad idea unless you are adding an egress window. In that case, consult your local building inspector first.
Preparing the opening
When former HANDY Managing Editor Kathy Childers needed to replace the old windows in the basement of her 1920s house, she chose acrylic-block window units. Framed with rigid vinyl, the hopper-style windows won’t shatter, and they are practically maintenance free.
Acrylic block weighs 70 percent less than glass block, which is too heavy to be used in an operating window. Because the block units were custom made to exact sizes by fabricators at Hy-Lite Products (see SOURCES), installing them was quick and easy — especially with the help of Kathy’s son Sam.
Measure the new windows to confirm that they will fit before you remove the old window units.
For this project, we removed and replaced the original wood window frames. To avoid damaging the masonry opening, cut the sill in half with a reciprocating saw or circular saw and remodeler’s blade. Pry out the sill parts with a flat pry bar. Once the sill is gone, the jambs and header are easier to remove. After removing the wood frame, inspect the condition of the masonry opening and make any necessary repairs to the concrete, block or mortar.
If you have space, use 2x8 (or wider) pressure-treated lumber to build the new window frame. If the openings are square and uniform, you can build a new wood frame in advance for each window, using dado-rabbet joints at the corners, and then prime and paint the frame and install the new window before you secure the frame in the masonry opening. However, in many cases you’ll find it easier to “stick-build” the frames as you go. Look for lumber that has a KDAT (kiln-dried after treatment) rating.
Because installing a 2x8 frame would have reduced the window openings too much, we used 1x8 pressure-treated pine. Attach the frame parts, starting with the sill, using construction adhesive and masonry nails driven with a powder-actuated tool. Even though the masonry openings on this house are not square, we cut the new frame parts to fit flush with the opening. A perfectly square frame would have resulted in gaps that would require stucco filler.
Caulk all joints of the window frame before installing the window unit. (We used 35-year paintable acrylic caulk.) If you can leave the opening exposed for a long enough time, prime and paint the frame; otherwise, install the window before painting.
Installing the window
According to the “by the book” method, you should install the new window by setting it into the framed opening and then shimming so that it’s level and plumb before fastening it in place.
In many situations (especially in newer homes) this will work well. But in some older homes, you’ll get more pleasing results by squaring the new window with the opening and the surrounding wall. Foundation walls have a tendency to shift, and installing a window that is perfectly level and plumb will only call attention to the fact that the wall is out of square.
Squaring the window with the opening is not advisable with all window types. But because basement windows are relatively small and simple, they can operate adequately even if they’re a couple of degrees out of level or plumb.
When possible, remove the sash from the window before installation. Replace and test the sash after the window frame is secured.
As a general rule, install the window as close to the exterior edge of the sill as possible, making sure to leave room for stops if you plan to install them. If you’re installing multiple windows, keep reveals and setbacks consistent.
How you fasten the window in place depends on the type of unit you choose. When installing a vinyl-clad unit, screw it to the frame jambs a couple of inches in from each corner on the sides of the unit. Do not drive screws through the base or top rails of the frame.
On double-wall window models, such as the windows shown here, you can conceal screwheads by drilling a
3/8-in. access hole through the inner wall of the frame. Drill a narrower guide hole for the screw shank through the outer wall. Our windows included plastic plugs to cover the 3/8-in. access holes.
Make sure the screws you choose to secure the window are not too long. Because our window frames have 3/4-in.-thick jambs with masonry on the other side, 1-in. screws were the longest we could use.
After driving the screws, test the window to make sure it’s operable. If the frame has racked so the sash won’t operate smoothly, loosen and tighten screws on opposing corners. Check the diagonal measurements and continue adjusting the screws until the frame is square. (The diagonals will be equal.)
Local codes in some wind-prone areas require 3/4 x 1/2-in. or larger jamb stops around the window frame. In addition to making the windows more resistant to high winds, the stops improve security by making the units more difficult to kick in. Check with your local building department to find out if jambs stops are required.
We weren’t required to install them, but we added 3/4 x 3/4-in. stops on both the interior and the exterior to conceal the gaps around the windows. Before installing the stops, we squirted minimal-expanding foam into the gaps between the window units and the frames. Once the foam cured, we applied caulk around the trim and then painted the wood to complete the installation.
Sources
Hy-Lite Products Inc. (acrylic-block windows)
800-827-3691