Building a Divided-Lite Storm Sash
Changing the setup of router bits is the key to quick window construction.
Synopsis: Although it’s easy to replace a storm window with a vinyl or aluminum unit, nothing’s better than the real thing, according to Canadian builder T.H. Richards, who presents his technique for building wooden divided-lite storm sashes. Richards uses a modified router-bit setup to shape the wooden pieces for the sash, then uses hardwood assembly blanks to put together the windows. He incorporates vent holes to allow condensation to escape. Richards’s technique also can be used for building glass-panel cabinet doors.
A storm window is the sacrificial lamb that takes the brunt of the weather (and errant baseballs) so that an operable window lasts longer. When an old storm sash is beyond repair, people often turn to aluminum triple-track storms or vinyl replacement windows. But to my eye, nothing looks better on a well-weathered house than traditional divided-lite storm sashes. Divided-lite windows also minimize damage from the aforementioned baseballs: The glass repair is smaller.
Building replacement sashes for traditional windows is easily within the scope of any decent carpenter with access to a good router table. Cope-and-stick bits designed for cabinet doors but reconfigured for windows do 80% of the work. Modern weatherstripping and sash hooks make for a tight-fitting sash that’s easy to remove and replace. This technique also works for building cabinet doors with divided lites.
Choose the wood and glass wisely
Ideally, the wood should be clear, vertical-grain lumber of the same species as the original window. Vertical-grain lumber is sawn perpendicular to the growth rings and is more stable than flat-sawn lumber, meaning it is less likely to cup or twist. Depending on the species native to your area, softwoods such as white pine, Douglas fir, ponderosa pine, red or white cedar, redwood, and cypress are all excellent choices.
Single-pane glass is usually standard for this type of window. According to my glazier, 1 ⁄8-in. glass is considered safe for panes with a maximum single dimension of less than 30 in. and a total area of less than 6 sq. ft.
Design is harder than building
I always say that it takes me a full day to design and build the first sash and 45 minutes to build each additional one. That may be a small exaggeration, but the design is more complicated than the actual cutting and gluing.
The storm sash I typically build has an interior framework of vertical and horizontal muntins dividing the window into six individual lites.
Once I decide on a basic layout of lites, I next choose the dimensions of the stock. Then I refine the layout into exact sizes of the various parts.
Original storm sashes are obviously the most authentic layout guide, but they’re not always available. Scouting the neighborhood for similar houses with original sashes is one way to get traditional dimensions; most owners of period houses are happy to let you measure the windows.
When assembling a large gang of sashes, each of which is made up of many different pieces, all parts need to be as uniform as possible. Small variations in muntin length or width can make assembly difficult or impossible.
I have my supplier plane all the stock to 7 ⁄8-in. thickness and joint one edge so that I have a straight edge to run against the tablesaw fence. With a sharp blade on my tablesaw, each cut is smooth enough to pass directly to the router without more machining.
Magazine extra: Watch a step-by-step video of Richards configuring his bits to make rabbet instead of dado cuts.
For more photos, drawings, and details, click the View PDF button below: