Frame and Panel Construction
How frame and panel construction handles wood movement: stiles, rails, grooves, floating panels, mortise and tenon, cope and stick, and where it fails.
Frame and panel construction solves a specific problem: a wide solid wood surface moves too much across its width to be held rigidly. A door, a cabinet side, or a chest lid made from a single wide board will expand and shrink with humidity, and if that board is captured in a fixed frame it will either split or push the frame apart. The frame and panel approach separates the two jobs. A rigid frame of stiles and rails carries the structure and the hinges, while a thinner panel floats inside a groove cut in the frame. The panel can move freely across its width without stressing the joinery.
The panel is not glued into the groove. That single rule is the difference between a door that survives seasonal swings and one that cracks down the middle after the first dry winter.
The frame: stiles, rails, and the joints that hold them
The vertical members are stiles; the horizontal members are rails. The frame needs joints that resist racking (the door trying to go out of square) and that hold the stiles and rails flat to each other. Four joints are common.
Haunched mortise and tenon. The strongest traditional choice for a frame that will be hinged or slammed. The tenon runs most of the way into the stile, and the haunch fills the groove at the top of the stile so the frame cannot twist there. Cut the mortise first, then the tenon to fit. A good fit is snug enough to need light hand pressure to assemble, with no side-to-side slop. See the haunched mortise and tenon guide for the sequence.
Cope and stick. A router bit set cuts the profile and the joint in one pass. The sticking bit shapes the inside edge of the frame; the coping bit cuts the end of the rail to match. The joint is a stub tenon, not a full mortise and tenon, so it suits cabinet doors and paneled casework more than heavy passage doors. The advantage is speed and repeatability; the disadvantage is that the stub tenon has less long-grain glue surface than a full tenon.
Bridle joint. An open mortise and tenon, cut at the end of the rail and the stile. It is easier to cut by hand than a blind mortise and tenon and shows its end grain on the top and bottom edges of the frame, which is fine for painted work or a design that accepts exposed joinery. Use it where the frame is light and the panel is thin.
Dowels. A row of dowels through the stile into the rail end. Fast with a jig, adequate for small cabinet doors, and weaker under racking than a tenon because the dowels are in end grain on one side. Not the choice for a door that will see heavy use.
Whichever joint is used, the frame members must be flat and the joints must pull the faces flush. A frame that is twisted at glue-up will twist the panel with it.
The panel: solid or plywood
A solid wood panel is the traditional choice and the one that needs the most care. It is usually raised: the edges are bevelled or stepped down to fit the groove, leaving a thicker field in the centre. The raised profile is cut with a router bit or a hand plane. The panel is finished on both faces before assembly, because a bare strip at the edge will show when the panel shrinks in dry weather.
A plywood panel barely moves across its width, because the cross-grain plies restrain each other. It can be glued into the groove without the cracking risk that a solid panel carries. Flat plywood panels suit painted cabinet backs and utilitarian doors; they do not give the raised-panel look.
A solid panel must be sized with room to expand. The exact clearance depends on panel width, species, and the season the door is assembled in. A panel cut in a humid summer will shrink in winter; a panel cut in a dry winter will swell in summer. The common approach is to leave a small gap at each edge of the groove and to pin the panel at the centre only, so it can move equally in both directions. Do not treat any single gap dimension as a rule; work from the expected movement for the species and the panel width. The wood movement guide gives the method.
Cutting the groove and fitting the panel
The groove is cut in the stiles and rails before the frame joints are cut, because the joint layout depends on where the groove runs. A groove centred on the frame thickness is standard; a groove set off-centre allows a thicker panel on one face. Either stop the groove in the stiles short of their ends, or run it out through the ends and haunch the tenon to fill the exposed slot at the end of the stile.
The panel is sized to fit the groove with clearance. Test the dry assembly: the panel should sit in the groove without forcing, and the frame should close fully. If the panel is tight, it will push the frame joints open when it swells. If it is loose, it will rattle; a small foam or rubber space ball in the groove holds it centred without gluing it.
Finish the panel before assembly, on both faces and the edges. A panel finished only on the show face takes up moisture unevenly and can cup, and on a stained door the bare strip that appears when the panel shrinks shows most.
Telling a good fit from a bad one
A good frame joint closes with hand pressure, shows no gap at the shoulder, and holds the frame flat on a bench. A bad joint either needs clamps to close (the tenon is too thick) or closes with a visible gap at the shoulder (the tenon is too thin or the shoulder is not square). A good panel fit allows the panel to move in the groove with light friction; a bad fit is either tight enough to bind or loose enough to rattle.
Check the dry assembly for square by measuring the diagonals. A frame that is out of square at glue-up will stay out of square, and the door will not hang correctly.
Where frame and panel fails
The classic failure is a solid panel glued into the groove. It happens because the glue-up feels more secure with the panel fixed, and because the panel can shift during clamping if it is not held. The result is a panel that cannot move, so it splits down the centre or pushes the frame joints apart when it swells. The fix is to glue the frame joints only, and to pin the panel at the centre of the top and bottom rails with a small nail or a space ball, leaving the rest free.
The second failure is a panel finished on one face only, which cups and shows a bare edge when it shrinks. The third is a frame joint that is too loose, which lets the door rack out of square under its own weight. All three come from the same habit: treating the panel as part of the structure rather than as a floating infill.
Comparison
| Option | Best for | Wrong choice when |
|---|---|---|
| Haunched mortise and tenon | Hinged doors, heavy frames, passage doors | The frame is small and light, and the extra cutting time is not justified |
| Cope and stick | Cabinet doors, repeated production, painted work | The door will be heavy or slammed, and the stub tenon is not enough |
| Bridle joint | Painted frames, exposed joinery, light panels | The frame will be seen in clear finish and the end grain is unwanted |
| Dowels | Small cabinet doors, quick assembly | The door is large or hinged and will see racking loads |
| Solid raised panel | Traditional doors, clear finish, visible panel | The panel is very wide and the movement cannot be accommodated |
| Flat plywood panel | Painted cabinet backs, utilitarian doors | A raised-panel look is required |
The mistake people most often make
Gluing a solid panel into the groove is the mistake, and it happens for a reason that is easy to understand. During a dry assembly the panel can slide in the groove, so it feels loose. Glue seems like the fix. It is not: the panel needs to slide, and the glue line turns a moving panel into a restrained one. The panel then either splits along the grain or, if the glue holds, pushes the frame joints apart. The correct approach is to leave the panel free in the groove, centre it with a space ball or a single pin at the middle of the top and bottom rails, and glue only the frame joints. The same reasoning applies to finishing: finish both faces so the panel takes up moisture evenly, and it will move without cupping.
Common questions
Should a solid wood panel be glued into the frame?
No. A solid panel must float in the groove so it can expand and shrink across its width. Glue only the frame joints. Pin the panel at the centre of the top and bottom rails, or use a space ball, so it stays centred without being restrained.
How much clearance should a panel have in the groove?
There is no single figure that works for every panel. The clearance depends on the panel width, the species, and the season the door is assembled in. Work from the expected movement for the species and width, and leave a small gap at each edge so the panel can move both ways.
Can plywood be used in frame and panel construction?
Yes. Plywood moves very little across its width because the cross-grain plies restrain each other, so it can be glued into the groove without the cracking risk a solid panel carries. It suits painted cabinet backs and flat panels, but it does not give a raised-panel look.
What is the difference between cope and stick and mortise and tenon?
Cope and stick uses a router bit set to cut the profile and a stub tenon in one pass, which is fast and repeatable. Mortise and tenon cuts a full tenon into a mortise, giving more long-grain glue surface and better resistance to racking. Cope and stick suits cabinet doors; mortise and tenon suits heavier hinged doors.
Why does a raised panel show a bare strip at the edge after a few months?
The panel was finished on the show face only, or not finished before assembly. As the panel shrinks in dry weather, the unfinished edge is exposed. Finish both faces and the edges before assembly so the panel takes up moisture evenly and the bare strip does not appear.
Read next
- Biscuit vs Domino Joinery: Alignment, Strength, and Fit Compare biscuit and Domino joinery: what each does, how to cut them, how to judge fit, and where they fail. Know which to choose for your project.
- Finger Joints and Box Joints: Cutting, Fit, and Failure Learn how to cut finger joints by hand and with a router or table saw, how to judge a good fit, and where box joints fail.
- Bridle Joint: Open Mortise and Tenon Guide How a bridle joint works, corner and T versions, cutting by hand or machine, judging fit, and where an open mortise and tenon fails.
- Adirondack Chair Plans: Choosing the Right Design Choosing Adirondack chair plans? Compare designs, wood, and joinery. Learn what to look for in a template and avoid common mistakes.
- Beginner Woodworking Projects: A First Project Path Choose your first woodworking project wisely. This guide outlines a three-project path, from simple to more complex, with tips on tools and common mistakes.