Louvers, in installations such as louvered doors or window shutters, are an attractive way to provide privacy and security while allowing for the free flow of air. Many people will buy louvered bi-fold doors for closets or position them as a screen for a dressing area.
What many woodworkers don't realize is just how easy it is to make louvers. The key is to use a jig with your router. A proper router jig will make it quite simple to align your louvers evenly.
While these directions demonstrate building a custom-sized window shutter, the same principle is easily adapted for any interior door or exterior wood shutter, using the same mortise and tenon joinery for the rails and stiles.
Equipment / Tools
- Miter saw or circular saw
- Table saw
- Tape Measure
- Plunge router with 1/4" spiral-cutting straight bit
- Router table and 1/8" radius roundover bit
- Power drill
- Large clamps
- 2 2x4 x 8' pine or hardwood
- Materials for rails and stiles for your particular application
- Woodworker's Glue
Cut the Rails, Stiles, and Slats
Each installation is different, so you'll need to know some principles before you can begin your layout with the particular measurements for your project.
Each slat in the louvers will cover one vertical inch of space. You should leave a 1/8" gap between the top and bottom slats and the corresponding rails. For instance, if you have approximately a 24" tall opening for the louvers, make the opening 24-1/4" and insert 24 angled slats at one-inch intervals. Additionally, each seat will be inserted into a 1/4" deep groove in the stiles, so the slats must be formed as 1/2" longer than the width of the opening.
Once you know the dimensions of the louvered piecen, you can determine the length and width of the rails and stiles. Use your best judgment as to how wide each of the rails and stiles should be ripped to maintain the integrity of the entire unit. As an example, in the case of the louvered window covering built here as a prototype, the opening is 30-5/8" tall by 23" wide. As such, the styles are 30-5/8" x 2-1/2", and the rails 20" (to accommodate a 1" long tenon on each end) x 2-11/16" wide. The rails and stiles resulted in an opening of 18" x 25-1/4". This means that thee needed 25 seats of 18-1/2" x 1/4" thickness were ripped out of a second 2x4.
Cut a few extra slats, as you'll likely want to cull a few that have some knots or other imperfections.
Round Over Each Slat's Long Edges
Set up your router in your router table with a 1/8" radius round-over bit equipped with a bearing tip. Adjust the depth so that the lower edge of the round over is flush with the top of the router table.
Then, place one salt flat on the router table (as shown in the picture) and ease the four long edges by pushing the seat along the bearing and down each of the long edges. Always move the stock from left to right, against the rotation of the bit. Any attempt to move the stock in the opposite direction may cause the bit to grab the stock and force it out of your hands.
After the four long edges on all of the slats have been rounded-over, sand all of the slats with a random orbital sander or 1/4-sheet sander. Use progressively finer grits of sandpaper to remove the sanding marks from the previous sanding. If you plan to paint your project, 300-grit final sanding should be sufficient to remove all sander marks and leave a smooth surface for painting. If you plan to stain your project, or if you want to ensure an optimum surface, consider a hand sanding with some 400-grit sandpaper for a very smooth finish.
Set the seats aside for the time being.
Cut the Mortises in the Stiles
Mortise and tenon joints will hold the frame together. You'll need to cut a mortise in each style for each of the tenons (to be cut on the ends of the rails in the next step).
When forming mortise and tenon joints, it is always easier to cut the mortises first then fit the tenons to the mortises rather than the other way around.
The easiest way to form mortises is with a dedicated mortise, which is essentially a drill press with a square chisel surrounding a drill bit. The drill bit in the center removes most of the stock, while the square chisel does the rest. This allows the operator to drill square holes, perfect for a mortise. Some drill press manufacturers offer optional mortise attachments with various sizes of square chisel bits.
However, if you don't have a mortise, there are some other ways to create an appropriate mortise. You could mark out the mortises and remove most of the material with a drill press or power drill, then clean up the mortise with a sharp chisel.
You could also use a straight bit on your router table in place of the drill bit, by easing the stock down onto the bit, moving along the fence, and then raising the stock back off of the bit. To make a wider mortise, simply move the fence a bit and take another pass. Then, clean up the mortise with a sharp chisel.
Your mortises should be about half the width of the stock. For this project, the stock is 1-1/2" wide, so the mortises are 3/4" thick, centered in the width of the stile. And since the edge of the tendon won't be seen in the bottom of the frame, the mortise can be cut back 1/2" from each end. On the 2-11/16" wide rails, there will be a 1-11/16" wide tenon, so the mortise will be started back 1/2" from the edge.
Cut the Tenons in the Rails
After the mortises have been cleanly cut, it's time to make the corresponding tenons. These tenons can be cut a number of ways: You could cut them by hand with a small hand saw, use a band saw, or cut them on a table saw with a tenoning jig. In this project, the tenons are cut on a radial-arm saw using a stacked dado blade set. (You could accomplish the same task with a table saw using the miter gauge.)
Set the depth of cut to match the width of the amount of material left behind when cutting the mortise. For this project, 3/8" will be cut off of each wide edge to leave behind a 3/4" thick tenon. If you're using stock thicker than 1-1/2", then you'll need to adjust the depth of cut.
After cutting the two flat sides of each tenon, adjust for a deeper cut. Then turn the stock on its side and make the remaining cuts of the tenons.
Always begin by cutting your tenons a bit larger than their finished size. Then try to dry-fit the tenons. If they don't fit, cut them down little by little, making any adjustments that you deem appropriate to ensure a perfect fit.
After all of the mortise and tenon joints have been cut and dry-fitted properly, disassemble the joints and mark the corresponding joints in discreet locations so you know how to re-assemble the frame in the final assembly. Then, sand all of the exposed sides of the rails and stiles.
Make a Louver Jig for Your Router
The key to making louvers is to ensure the grooves for the slots are properly spaced and parallel. A louver jig for your plunge router can be built out of scrap stock and will create a perfect groove every time.
- Take two long (at least 24") boards that are a bit thicker than the width of the style that you'll be routing. These don't have to be solid boards; you could use a couple of pieces of scrap 3/4" plywood and shim some other scrap stock beneath the two boards to raise them to the proper height. Make sure that the channel between the two long boards is clear.
- Position one piece of 1x2 in a 45-degree angle (using a layout square) a few inches to the right of center on the two parallel boards. Adjust the width of the parallel boards so that they match the thickness of the stile. Affix this 1x2 to the two long boards with screws.
- Position your router with a 1/4" radius straight-cutting bit on the two long boards, butted against the left side of the angled board you just attached. Position a second board parallel to the first angled board, on the other side of the router base. Attach with screws.
- Take a piece of scrap the same size as the style to be grooved. Mark a line across the width of the same edge of the board as the groove to be cut in style. Make a mark at the center of this line, then make a 45-degree mark (in the same direction that you positioned the router guides in the last step) through the intersection. Make a mark at 3/4" in each direction from a center point on this line.
Cut the Grooves for the Louvers
Position this board with the center mark directly under your router bit on the jig. Remove the router, and make a pencil mark on the jig that corresponds to the first 90-degree mark made on your test board. This will be the alignment mark for positioning your style when you cut the grooves (as shown in the image above).
Put the router back on the jig and move it forward to the point where the edge of the bit meets the far 3/4" mark on the diagonal. Find a short piece of scrap 1x2 and position it against the router base on the jig and screw it into place. This is a stop to keep you from routing too close to the edge of the stile.
Move the router toward you in the jig until you reach the other 3/4" mark on the diagonal line and attach another stop block against the router base for the bottom side of the jig. You should now have 1-1/2" of travel perfectly centered on the test style.
Set your router to make a 1/4" deep cut and clamp the jig and test style to your table. Route a test groove, remove the style, and dry-fit test the fit with one slat. Adjust the jig until you are happy with the fit.
Next, set up one style for cutting by making a perpendicular mark every one inch along the edge of the stile to be grooved. Start by making a mark at the halfway point of the length of the style. If you have an odd number of grooves to cut, make one mark on each side of the center every inch until you have the requisite number. If you need to cut an even number of grooves, you must make a mark 1/2" on each side of the centerline, then a mark every inch on each side until you reach the desired number of slats.
With all of the marks completed, clamp the style to the table and route the first groove. Then, remove the clamp, slide the style to the next mark, clamp, and route. Continue until all grooves have been routed.
Assemble the Louvers
Either build a second jig or disassemble the first jig so you can repeat the same instructions from the last two steps for the opposite 45-degree angle. Once you have a matched set of grooved stiles, dry-fit the slats in one of the styles as shown in the picture on this page.
Then, evenly brush a bit of glue into the mortises and the appropriate rail tenons, then slip the tenons into the mortises. Immediately wipe off any glue that squeezes out of the joints. Working quickly from one rail toward the other, place the individual slats into the proper grooves.
Complete the Louver Assembly
Once you have all of the louvers in their appropriate slots and the tenons securely into their mortises, clamp the styles together using some long clamps. Be sure to clean up any glue that squeezes out of the joints.
Check the unit for square by cross-measuring the assembly from diagonal to diagonal. If the cross-diagonal measurement across two corners matches the measurement across the other two corners, the unit is square.
Finish the Louvers
Either stain or paint the louvered assembly. You may find it easier to spray on your finish, as opposed to brushing it on, as this will ensure the finish gets into all of the grooves.
If you choose to paint the louvers, be sure to give it a couple of thorough coats of primer before adding a couple of coats of the final color. If staining the louvers, apply the stain with a brush, but you can spray on a few coats of polyurethane or lacquer as a final finish.