DIY Wood Storm Windows

Wood storm windows are ideal for homes with older wood windows, since adding them can help provide a second barrier to make existing windows more energy-efficient. Exterior storm windows with a wooden frame can be bought and easily installed, but if you have a hard time locating some that fit your windows or you simply enjoy DIY projects, then you may decide to construct your own.

Note: Constructing interior storm windows will require a very different process.

Buying

Measure your existing windows before you go to make a purchase so you know they will fit. Take width measurements of your interior window frame in three places: the bottom, the top, and the middle. Then, use the smallest measurement to find what you need.

When purchasing wood storm windows note that they are offered in both single-pane or insulated double-pane glass panels. Double-pane windows have a low-E coating that allows hot air to stay outside in the summer and keeps heat inside in the winter.

Installing Bought Windows

Step 1 - Fix Up the Windowsill

Before you can install the storm window, you need to be sure your existing windowsill is in good shape. Scrape off any chipping or peeling paint first and then sand smooth the surface that’s left behind. Wipe the wood clean to rid it of any dust or debris, letting it dry before you continue.

A quick coat of exterior primer on the frame and trim should be next, followed by an exterior top coat. Be sure to let the primer and paint have plenty of dry time between coats for the best adhesion.

Finally, before you can move on to installing the window, you need to drill small holes in the exterior of the windowsill for drainage. This allows any moisture that accumulates between the existing window and the storm window to drain out safely.

Step 2 - Secure it in Place

Exterior storm windows will attach with essentially a metal flap that screws in to the window frame. Line your storm window up properly against the existing window and screw the top of the window into the frame. Then, close the bottom sash and screw in the sides of the window.

It’s also a good idea to add a little butyl caulking around where the flap meets the frame for added protection.

How to Make Wood Storm Windows

Step 1 - Measure Your Window Frame

Start by measuring the inside of your window frame, once again at the top, middle, and bottom. There are actually two different styles of casings you can do for storm windows and they will require different final dimensions depending on which you choose. An Eastern-style casing is one that actually hangs the window on the outside of the frame. As such, the storm window should be at least 1¼ inches wider than the window’s widest measurement and the height should be about 5/8 inch taller than the window, but no less than half an inch. A Western-style casing tucks the storm window inside the existing frame, so you’ll need your dimensions to be up to ¼ inch less than the window’s smallest measurements to allow for foam weather stripping. The ¼ inch space should be taken from the total height and width, but it will end up appearing as 1/8 inch on all sides.

Step 2 - Choose Your Wood

You will need to pick something that is appropriate for outdoor applications, regardless of whether you plan to varnish or paint it. Pine is a good, inexpensive choice, but cedar or redwood can be more durable. Whichever you choose, you will need your pieces to be 1x2 inches in order to make your frame.

Step 3 - Cut the Pieces

Cut your 1x2 pieces down to the lengths you need for the height and width of the frame. Then, using a miter block, cut 45-degree angles on the ends of the wood. The outer end of the angled cut should be equal to the required length of the piece so your total frame’s dimensions stay the same. Cutting with a miter block creates a clean-looking corner joint for the frame of the wood storm window.

Step 4 - Make a Groove for the Glass

Using a router, cut a slot on the inside of the frame pieces for the storm pane, whether you’re using glass or plexiglass. It is actually the air between the interior and the storm window that is more important than the glass itself, so either material is suitable.

The insert can be as think as you’d like, but a 1/16 inch groove should be suitable for a standard thickness. Make sure the dimensions of your glass equal the interior size of the frame plus the depth of your slots.

Step 5 - Assemble the Window

Place the slotted frame around the glass by fitting the glass into the slots. Reinforce the corners with wood glue.

Spread the glue on the joints and clamp the window together while the glue dries. Be sure to scrape off any excess that squeezes out from between the joints.

Once the glue is dry, finish securing the frame together by inserting wood screws at the corners with an electric drill.

Step 6 - Add Caulking

Seal the glass to the window frame by adding a thin bead of clear silicone caulk. Add the caulking on both sides of the frame for a good seal.

Step 7 - Add Foam Weather Stripping

To ensure that the edges of your storm window are sealed, you will want to apply some adhesive-back foam weather stripping to the frame.

Step 8 - Attach the Window

If you’ve made a window to fit a Western-style casing, all that’s left to do is press the wood storm window frame into the house window opening. The foam weather stripping will tightly hold the wood storm window in place, and you can make the seal airtight with a bead of caulk around the outside of the window.

If you’ve made a window for an Eastern-style casing, follow the directions above for attaching the window to the frame, using either a flap or hangers.