Trim Out a Curved Bay Window
Finish carpenter Joseph Laskey shows how to measure, cut, and fit a mix of straight and curved parts to complete this unique interior trim project.
Synopsis: Finish carpenter Joseph Laskey describes a project in which he trimmed out a series of casement windows in a round bump-out to surround a soaking tub. The bay includes all the elements of a conventional multiunit cased window, but the parts must be cut and fit individually to match the curve. Laskey describes each part of the process, from cutting and fitting the stool segments to adding extension jambs and casing before fitting the mull covers and curved apron.
I’m a finish-carpentry subcontractor for Bayview Builders, a custom home builder in Annapolis, Maryland. This affluent suburb of Washington, D.C., provides plenty of interesting carpentry projects for me to work on. Recently I had to trim out a series of casement windows in a round bump-out for a luxury master bath.
The windows, which surround a soaking tub, were trimmed with mitered casing and a traditional stool and apron.
A project like this requires patience, attention to detail, and a good millwork supplier. Here we used a mix of materials, some radiused, some square. A custom millwork shop provided the laminated mahogany apron and head casing with the correct radius, but I had to fit and install them. For the stool, we started with square poplar stock, and I rough-cut the curve for these pieces on my bandsaw. To guide that work, I created a template, which I marked with the location of each extension jamb and decorative bead that surrounds the windows.
In the end, it took a little over three days to finish the job. It was a fun project and I think the finished space is among my favorite in the house.
Start with the stool
The stool segments, made from 5/4 by 8-in. poplar, are the first component to cut and fit. Each stool segment has one straight side and one curved side. The straight side butts against the casement window frame and the curved side matches the 6-ft. radius of the bay window. The oversize blanks are field-trimmed before the individual segments are joined together and fastened to the framing.
Make a template. A 3⁄4-in.-thick MDF stool template, used for all five windows, shows the location of casing, mull cover, and decorative bead. A centerpoint on each window is aligned with a centerpoint on the template and, later, each stool blank, ensuring a fair curve.
Trim the horns. The poplar blanks have oversize horns that need to be trimmed. I align the center marks on the stool and the window to mark the horn length. The two end horns, which receive casing, are longer than the interior horns, which meet in the center of the mull.
Scribe the horns. I use an AccuScribe to trace the horns so they match the wall’s curve, but a compass would work as well.
Joseph Laskey is a finish carpenter in Crownsville, Md. Top Photo: Julie Carlisle. Drawing: John Hartman. Photos by Patrick McCombe, except where noted.
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From Fine Homebuilding #294