How to Install a Bay Window

Get the reading nook you've always wanted with a picture-perfect bay window. After a bit of labor, you'll love the results!

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What is a home without a picturesque window to gaze out of. Whether it's used as a reading nook, a breakfast seat, or a picture display, a bay window looks lovely in any home. Make this dreamy feature yours this season by installing one yourself! Homeowners with previous handiwork experience can feel confident following the steps provided below. Beginners may want to enlist help from friends or professionals with basic construction knowledge. This task should take one to two days, so it's the perfect weekend project!

Bay Window Design Ideas

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Getting Started

The farther a bay window protrudes from the house, the more dramatic the effect and the more it opens a room. You can choose among units that protrude at 45-, 30-, or 10-degree angles; the latter is sometimes called a bow window. Individual windows may be fixed, double-hung, or casement.

A bay unit attaches like a standard flanged window but with some important differences. Some units also require support from above using cables that attach to framing members in the eaves or the wall above. Some require support from below using brackets or a knee wall. Some need both types of support. A smaller bow window may not need this type of support and can be installed much like a standard flanged window.

Plan how you will finish the top and bottom of the bay window. You may be able to purchase a ready-made roof or you may need to custom-build one. The bottom is usually easy to trim out, but you may choose to build a wall down to the ground. In these the roof and skirt are built on the ground and then installed.

What You Need

  • Tape measure
  • Drill
  • Hammer
  • Level
  • Stapler
  • Caulk gun
  • Screwdriver
  • Flat pry bar
  • Circular saw
  • Bay window
  • Exterior casing
  • 2x4s
  • Shims
  • Caulk
  • Roofing felt or building paper
  • Drip cap
  • Flashing
  • Plywood
  • Roofing
  • Finishing nails
  • Staples
  • Roofing nails
  • Interior trim
  • Casing nails
  • Insulation

Cable Support Arrangements

Read the instructions carefully and be sure to install the required cable support. In one arrangement the cables are attached to an overhanging eaves structure. Cable attached to a header or studs must be at an angle no flatter than 30 degrees. Whichever method you choose, plan how you will cover the cables with a roof or a short wall up to the eaves. Some units have cables preinstalled; with others you have to add the hardware for the cable yourself.

Step 1: Prep the Opening

Your opening should already be cut and framed. Flash the opening. The jambs of the window shown fasten directly to framing members. Some other bay windows have flanges; with such units you'll need to set the window in temporarily, shim it square, mark for cutting the siding to accommodate the casing, and cut the siding.

Step 2: Mark Fasteners and Drill

Following the manufacturer's instructions mark the fastener locations. Drill four or so holes in the unit to allow you to firmly fasten it in place for shimming and leveling.

Step 3: Temporarily Fit Window

Cut a pair of temporary supports. With a helper or two, raise the window into place and temporarily support it. Check for level and plumb all around and shim as needed. Drive screws at the top and sides to temporarily hold the window in place. Check that operable windows open smoothly.

Step 4: Construct Roof

Make a template or carefully measure so you can prefab the roof. It is much easier to finetune the angled cuts and install the pieces while working at ground level. Drill large holes for the support cables. Measure and cut the final sheathing pieces.

Step 5: Install Roof

Set the roof in place and mark where you'll cut the siding to allow for the flashing. Use a spacer to mark for adequate flashing space. If needed mark the siding for cutting, remove the window, and cut the siding.

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