16″ × 20″ mirror frame plans

Parts

Cut list

Kerf 1/8″ included. Every cut runs edge to edge.

Steps

• Tape measure
• Speed square
• Pencil
• Drill/driver
• Clamps
• Safety glasses
• Hearing protection
• Dust mask
• Circular saw or miter saw
• Hammer
• Miter saw
• Band clamp or four corner clamps
• Six or more clamps, 12″
• Sander, 120 and 180 grit

Underlined words have a short explanation: hover or tap them. All of them are on the glossary page.

1. 1Before you start

   Read every step once, start to finish, before you buy or cut anything. Each step names the parts it uses by letter; the parts list gives their sizes.

   Set up somewhere flat with good light. A pair of sawhorses with a sheet of plywood on top makes a fine work table.

   Wear safety glasses whenever a tool is running, hearing protection for saws, and a dust mask for sanding and for cutting treated wood or sheet goods. Tie back long hair and loose sleeves. Keep children and pets out of the work area.

   • Tip At the store, pick straight boards: hold each one up to your eye and look down its length. Skip boards that bow, twist or have big knots near the ends.
   • Tip Measure twice, cut once. Most mistakes are a misread tape, not a bad cut.

2. 2Cut and label the parts

   Cut every part on the cut list. Cut the longest parts first: if one goes wrong, it can still become a shorter part.

   To mark a cut, hook your tape on the end of the board, make a small V with its point exactly at the measurement, and draw a square line through the point with a speed square. Put an X on the waste side.

   Cut on the waste side of the line, so the blade's kerf (about 1/8″) comes out of the scrap, not your part.

   Write each part's letter in pencil on a face that won't show, and stack the parts by letter.

   Sand the faces before assembly while they're flat and easy to reach: 120 grit, then 180.

   ✓ Lay the parts out and count them against the parts list. Measure a few: if one is off by more than 1/16″, recut it now.

   STOP. Let the saw reach full speed before it touches the wood, keep both hands clear of the blade's path, and never reach under a board you're cutting. Support long boards on both sides of the cut so the blade doesn't pinch.

3. 3Glue up the frame moulding

   You are making your own mirror moulding: a 1×4 face strip (A) glued onto a 1×3 back strip (B), with their outside edges flush. The face strip is 1″ wider, so along the inside edge it leaves a step 1″ wide and 3/4″ deep. That step is the rabbet the mirror and backer drop into.

   Lay each face strip (A) good face down on a flat bench. Spread a thin layer of wood glue on one wide face of a back strip (B) and set it on the face strip with one long edge flush with the face strip's edge.

   Clamp every 6″, with a straight scrap board on top to spread the pressure. Clamps make glued parts slide, so run a fingertip along the flush edge after tightening and tap it back into line before the glue grabs (about 10 minutes).

   Leave it clamped at least an hour, overnight if you can, before you cut it.

   • Tip Spread a thin, even layer of glue on one face with a finger or scrap: enough that a little beads out when you clamp, not so much that it runs. Wipe the squeeze-out with a damp rag right away, or scrape it once it turns rubbery; dried glue blocks stain and finish.
   • Tip At the store, sight down each board's edge like a rifle barrel and skip any that bow or twist: a bent stick makes a frame that won't lie flat.

   ✓ Along the flush edge you can't feel a step. Along the other edge there is an even 1″ step the whole length.

4. 4Cut the four miters

   Set the miter saw to 45°. Lay the moulding flat with its rabbet down and toward you, so the outside edge is against the fence. Measured along the outside edge, every piece runs long point to long point.

   Cut two top and bottom pieces 21 1/8″ long and two sides 25 1/8″ long. Swing the saw to the other 45° for the second end of each piece.

   Cut each matching pair with the same stop block setting so they come out exactly equal. Equal pairs matter more than hitting the number: if two sides differ, a corner gaps however good the angles are.

   Leave about 3 1/2″ between pieces on the stick: each 45° end needs its own triangle of waste.

   • Tip Make two practice miters on scrap and hold them against a square. If the corner opens on the inside or outside, the saw is not quite at 45°: nudge it and try again. A tiny error doubles at every corner.
   • Tip Sneak up on length: cut a little long, check, then shave off 1/32″ at a time.

   ✓ Lay the four pieces in a rectangle on a flat table. All four corners close with no gap at the inside or the outside edge.

   STOP. Keep your hands 6″ from the blade and let it stop before you raise it. Hold short pieces with a clamp, not your fingers.

5. 5Glue the corners

   Dry-fit the frame in a band clamp (or four corner clamps) first, to rehearse, then take it apart.

   A miter face is end grain, which soaks up glue like a straw. Brush a thin coat on each miter face, wait two minutes, then add a second coat.

   Assemble the frame and tighten the band clamp until a little glue beads at every corner. Where one piece stands proud of its neighbour, tap it down with a mallet over a scrap block.

   Measure both diagonals; they should match within 1/16″. Wipe off the squeeze-out with a damp rag.

   After an hour, pin each corner with two 1″ brads, one from each side. Drill a 1/16″ pilot hole for each so the thin tips don't split.

   • Tip Glue alone holds a miter only weakly; the brads carry it. Leave the frame clamped for 24 hours before you sand or hang it.
   • Tip Measure both diagonals, corner to corner. If they match, the assembly is square. If not, push the long diagonal's corners toward each other until they do, then let the glue set.

   ✓ The diagonals match within 1/16″, the frame lies flat on the table without rocking, and every corner face is flush.

6. 6Sand and finish

   Sand every face and edge of the frame with 120 grit, then 180 grit, always moving along the grain (the lines in the wood). Sanding across the grain leaves scratches that the finish makes darker.

   Soften every sharp edge and corner with a few strokes of 180-grit paper on a block, so edges don't splinter or chip.

   Vacuum the dust, then wipe with a tack cloth or a barely damp rag and let it dry 10 minutes.

   Brush on a thin coat of water-based polyurethane along the grain. Thin coats dry clear; thick coats drip and stay sticky.

   When it's dry (about 2 hours; read the can), the surface feels a little rough because the water raised the grain. Sand very lightly with 220 grit just until smooth, wipe off the dust and brush on a second coat. Three coats on anything handled every day.

   Let the last coat dry overnight before you handle it much.

   • Tip Pine goes blotchy under stain. If you want colour, brush on a pre-stain conditioner first, or use a gel stain.
   • Tip Finish the back and underside too. Wood that is sealed on one side only can cup as the seasons change.
   • Tip Work in a warm, dry, well-ventilated room. Below about 50°F (10°C) most finishes dry slowly and cloudy.

   ✓ The surface feels smooth and even, with no drips on the edges and no dull, dry patches.

7. 7Fit the mirror and backer

   Order the mirror cut to 16″ × 20″, 1/4″ thick, with polished edges, from a glass shop. That is the rabbet opening (16 1/8″ × 20 1/8″) less 1/16″ all round, so the wood can swell without squeezing the glass. It weighs about 7 lb.

   Cut the plywood backer (C) to the same size. It protects the mirror's silvered back from scratches and stiffens the frame.

   Lay the frame face down on a blanket. Lower the mirror in, shiny side down, then the backer.

   Screw turn buttons to the back strips every 8″ or so, 9 in all, and swing each one over the backer. They hold the mirror firmly without glue, so it can come out again.

   • Tip Don't glue a mirror with ordinary construction adhesive: its solvents eat the silver backing and leave dark spots. If it must be glued, use mirror mastic only.

   ✓ Lift one corner of the frame an inch and set it down: nothing shifts or rattles inside, and the mirror shows no gaps at the lip.

   STOP. Wear gloves and safety glasses to handle mirror. Carry it on edge, never flat: held flat, a big mirror can crack under its own weight.

8. 8Add D-rings and hang it

   Screw a D-ring to the back of each side piece, 3″ down from the top, pointing straight up. Drill 1/16″ pilot holes first.

   Measure the distance between the rings. Nail two 30 lb picture hooks into the wall the same distance apart and level with each other: draw a level line first.

   Hang a ring on each hook. The framed mirror weighs about 20 lb, well under the hooks' 60 lb together.

   Stick bumper dots on the back of the bottom corners so it hangs flat.

   • Tip Measure ring to ring after they are screwed on, not from the plan: a 1/8″ difference tilts a wide mirror visibly.

   ✓ The mirror hangs level, flat to the wall, and both rings sit fully in their hooks.