Can I Replace My Own Windows?

Man in a blue shirt does window installation
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If you've received a high quote from a window company for installing replacement windows, you might be wondering if you can shave costs by doing it yourself. Or perhaps you've watched one of these companies in action on a neighbor's house and noted that it seems relatively simple to put in a window. There's no reason why you can't replace your own windows if you have the right tools and skills, but there are some important matters to consider before you decide to DIY it.

Replacement Window Types

There are two basic categories of replacement windows: full-frame and insert. Full-frame replacement windows are complete window units with a standard jamb frame and sill. These are the same as windows designed for new construction. Most have nailing fins on the front that allow the window to be nailed flat to the front of the house. The window unit slips into its opening from outside until the nailing fins are flush against the exterior wall sheathing (not the siding).

Insert replacement windows are pared-down window units that contain window sashes inside a small frame. They are designed to fit into your existing window jamb frame, and you install them from inside the house.

Inserts Are Easier to Install

With insert replacement windows, you don't have to remove or replace the existing interior or exterior window trim. With full-frame windows, you have to remove the trim on both sides of the window, and you usually have to customize it or replace it with new trim to fit around the new window. In addition, you have to deal with all of the exterior waterproofing, including installing new flashing above the window, and calking all of the window and trim joints.

So inserts are clearly easier to install, but that doesn't mean full-frame replacements are off the table. If you have some basic carpentry skills and know-how to install trim work, full-frame replacement is worth considering.

Full-Frame Offers More Options

When it comes to buying replacement windows, most manufacturers offer more models in the full-frame category than in the insert group. This is not surprising, given that full-frame replacements are just like standard new windows. The good news is that both types of replacement windows can be custom-ordered to fit almost any existing window opening, whether or not you're keeping the old window jamb frame.

Time Frame

Andersen windows estimates that a DIY installation of a full-frame replacement window takes four to six hours. If you have to alter the window opening or fuss with the exterior trim, count on a full day for each window, especially a large window. This time estimate does not include painting or staining new trim or drying time for the paint or caulk. By comparison, insert windows may take less than half the time of full replacements.

Make Sure Inserts Will Work

If your decision to replace your own windows is based on using insert replacements, be aware that not all window openings are suitable for inserts. For insert windows to perform as designed, the existing window frame must be close to perfectly square—the diagonal measurements can vary by no more than 1/8 inch.

The frame also must be solid and have no signs of rot or structural damage. If the existing frame has a sloping sill, you'll probably need some type of sill adapter to cover the gap between the insert frame and the exterior portion of the sill. Adapters are sold separately by window manufacturers.

Before settling on inserts, check with window manufacturers to make sure that their inserts will work for your project and to confirm all installation details for the windows you have your eye on.