The sash on older double-hung and single-hung windows are notorious for becoming stuck and difficult to open. A stuck sash is far less of a problem on crank-out casement windows.
Sash typically become stuck either because the counterbalance mechanism breaks or because the sash is painted shut. It’s important to note that if you do have a stuck sash, you should resist the temptation to pound on it with a hammer or hit it with your hand. You’ll only damage the sash or hurt yourself.
The counterbalance mechanism is installed against the side jambs and attached to the sash. It’s spring-loaded and designed to offset the weight of the sash, making it easier to open and close and window. However, if the mechanism seizes up or snaps, it’ll be very difficult to budge the sash.
New counterbalances are available directly from the window manufacturer, as well as from window replacement parts companies found online. The proper way to install new counterbalances differs slightly from one window manufacturer to the next but, typically, you must remove the sash, pry out the old counterbalances, and fasten the new counterbalances to the side jambs. Then, attach the spring-loaded mechanism to the sash and reinstall the sash.
If the window is painted shut, take a sharp utility knife to slice through the paint seal along the interior stops. Then, cut through the paint along the sill and at the meeting rail where the two sash meet.
Once you’ve sliced through the paint-sealed joints, push a stiff-blade putty knife into the joints all around the perimeter of the sash. Then, try lifting the sash with two hands. Position each hand near the upper outer corners of the sash, not in the middle.
If the sash doesn’t open, don’t force it. Instead, cut through the paint seal alongside each of the interior window stops, then use a thin pry bar to carefully pry off the stops. Gently tug the sash loose. Reinstall the old stops, or cut and install new stops against the sash.
