How to Install Interior Window Trim for a Bay Window

What You'll Need
Miter saw
Pneumatic nail gun or hammer
Finish nails
Wood putty
Fine-grit sanding block
Plastic putty knife
Paint or stain
Tack cloth

Installing interior window trim is a project that is not overly difficult. At least until the interior window trim ceases to be straight. Trying to install interior window trim for a bay window is trickier than other trim. This is because the interior window trim for a bay window is based on angles, much like crown molding. You can finish off your bay window by installing interior window trim, and the following article will show you how.

Step 1 – Finding the Correct Angles

The hardest part of installing interior window trim on bay windows is the angles of the window. Most bay windows utilize a standard 45-degree angle, but this does not have to be the case. To find the correct angle, use a protractor. Place the protractor so that it is centered. The 0-degree hash mark should line up with the corner. From this mark to the end of the protractor is the degree of the angle. Do this for each angle on the bay window. They can all be the same but they can also be all different.

Step 2 – Cut the Molding

The miter saw is a great tool to use when cutting angles. Measure the length of each section, and then transfer those measurements to the back of the molding. Set the angle on the miter saw to 1/2 the angle you determined previously, as the other piece of trim will marry with the first to complete the angle. Slide the molding into the miter box, and line up the mark you made on the back to the line on the box. Select the type of angle cut you need. You will want an inside cut since the bay window is recessed. How this is done is determined by the saw. It could be a switch or blade position. Cut each piece of molding.

Step 3 – Install the Interior Window Trim

Place the first piece of trim and make sure the angle is orientated correctly. Set the second piece of molding in place, to make sure they line up correctly. Nail the first piece in place through the center of the molding, every few inches. Butt the second piece of molding against the first. Hold it in place as you affix it with nails. Continue in this manner, until all of the interior window trim is installed to the bay window.

Step 4 – Finishing

You want the interior window trim to look as nice as possible. Apply wood putty to the putty knife and spread a small amount of it over each of the nail holes. Feather the wood putty out as much as possible, so it is even with the wood. Wait for the wood putty to dry, and then sand it down with the sanding block. Wipe down the trim with a tack cloth. You can now paint or stain the interior window trim however you please.