Install a Tilt-In Window in the Old Jambs

May we talk about your leaky, clanky, clunky double-hung windows? Windows are weak spots in many houses, especially the common double-hung variety—with sashes that slide vertically. Double-hungs that once were good have turned bad. Windows that started life with a quality disadvantage have only gotten worse.

Replacing windows can be a nightmare, if you have to replace the jambs—the frame around the window. More often, it's the moving parts, not the jambs, that have failed. If you've got good jambs, you can buy a kit to cure what ails your windows. You strip out the junk, install the kit, and renail or replace one small molding. Among many advantages: You don't touch the casing molding around the window, and you leave the storm window in place.

The Marvin Tilt-Pac kit I use in these directions had insulated glass, a “tilt-in” feature allowing easy cleaning, and aluminum cladding on the outside to resist weathering. I installed the window in two hours, even though this was my first experience with these windows, and I was taking the photos seen here. Replacing the entire window would have been far more expensive, and could have taken five times as long.

Step 1: Planning the Installation

First of all, are your jambs in good shape? Is there rot, which usually starts at the bottom? Are the side jambs reasonably vertical? Are the sill and head (top) jamb reasonably horizontal? (“Reasonably” is hard to quantify, but let's say within ¹⁄₄".)

If your jambs pass these tests, measure your windows. Each particular company may have its own instructions, but in general, you measure the width between the jambs, the height, and the sill angle. Marvin said to measure height on the inside, from the sill to the head (top) jamb. Use a sliding bevel to measure sill angle. Transfer the angle from the sliding bevel to paper, then measure the angle with a plastic square.

Measure carefully. Measure again. Measure until your measurements agree. Then place your order. When I used this foolishly redundant but foolproof technique, the kit fit perfectly.