Last time, I wrote about making a rustic barn door, this week I will show a matching mirror frame. Since we used rough-sawn cedar for the barn door, it is only fitting that we use the same for the mirror, hence the title, “Make a matching mirror frame.” I must keep consistent with these things. So, for the mirror frame, I decided on a 1x4 size plank of cedar. Now, depending on the size of the mirror and the look you are trying to achieve, you can leave the 1x4 the size it comes or choose to narrow the plank the width you desire. In any size mirror, I wouldn’t rip the board any narrower than 2½ inches wide.
In this case, we decided to leave the 1x4 the width it was originally made, 3½ inches. Determine the width and height of the frame to be and decide if you want to make a square butt joint or a mitered joint. Since it is supposed to be a rustic design, a square butt joint is preferred, the mitered joint adds a modern touch. The next decision is do you want the two vertical sides to run full length, top to bottom, or have the top and bottom to run full width across. Depending on whether you want to see the end grain intercept the edge grain or not. If the top and bottom runs full width, you will see the end grains whereas if the two vertical sides run full height, you can’t see the end grains.
Once you make that decision, you need to decide how wide and how tall the frame should be. Many times this decision is made for you if you are working between existing fixtures. For the height, this would be the existing countertop height and the wall-mounted light fixture. For the width it might be side walls, tall linen cabinets, towel bars, etc. If there are two sinks, the decision will be, “Do I want two separate mirrors or one larger mirror”?
These thoughts dictate the design layout, many times this is the toughest part of the job. If you have an eye for design, its simple, if you do not, it can be a daunting task. For this example, I will make the decision for you and say we are going to run the two vertical sides the full length of the frame. To make the actual joint, I will use Kreg pocket hole screws. I made my frame 36 inches high, so I cut the two side pieces 36 inches. I wanted the width to be 30, so I subtracted 7 inches from the two horizontal pieces, making them 23 inches long. With the four pieces of cedar cut to length, I sanded the rough surface just enough to remove the splinters but not so much as to remove the rough textured surface.
The next step is to drill the pockets. If you don’t have a Kreg tool but you are a do-it-yourselfer, it is not an expensive tool. You will drill the ends of the two horizontal pieces, using the jig. Kreg screws and 1¼-inch will be used to hold the parts together. The Kreg clamping vise grips, will keep the two surfaces flush with each other as you secure the ends with screws. Add a thin application of glue to the ends of the horizontal boards before clamping them together. The glue dries very quickly. Make sure to use a good quality wood glue, such as Tite Bond or equivalent.
After the frame is secured together, turn it over on its back and route the rabbet for the mirror to recess into. Go ahead and finish the mirror frame with the stain or paint finish you prefer, I chose the same aging stain that I used on the barn door. Cut the new mirror to size or use the old mirror and cut it down to fit or have a glass company cut the mirror for you, if you are uncomfortable cutting glass. Silicone the mirror into the frame. Control the amount of silicone applied so you don’t create a mess with excess silicone.
There are several ways to create mounting brackets to a mirror, you can route out a groove with a keyhole bit or install metal picture hanging brackets on the two vertical side pieces or the typical cable hangers. Whichever method you decide upon, install them before setting the glass. One last method is to use finish head screws and screw the mirror frame to the wall if you prefer, especially if you can disguise the screw heads.
Source : https://www.aikenstandard.com/lifestyle/how-do-i-make-a-matching-mirror-frame/article_f6b3d392-15f4-11e8-9f66-67517a649e74.html