bench back glue up attachment

[Don Jeansonne]

I am planning to make a 4 ft seating bench with a solid back of glued up boards. The bench back would be about 48"w x 36"h.
My question is for attaching the back to the sides or end panels. I was going to dado the back into the end panels and glue and/or screw to secure. Will attaching securely cause a movement problem? How to you attach allowing for expansion / contracion and still provide the ridgidity needed?

Also, can I use 12" boards glued up for the panels or is narrower boards necessary?

[Lee Schierer]

One way would be to change the dado to a dovetail slot and dovetail the ends of the back panel. The dovetail joint will be stronger than screws. You can place one screw at the bottom edge of the panel to keep it from coming back out and let the panel float in the grooves.

Be aware taht screws into end grain are not going to hold as well as screws into the side of the grain.

[Jamie Buxton]

If you make one big 36"-tall panel, (so the grain direction is horizontal), and attempt to fasten it firmly to an end panel whose grain direction is up-down, you're asking for expansion troubles. The common solution is frame-and-panel. In the simplest form, there's a rail (ie, horizontal) at the top of the back and a rail at the bottom of the back. They're fastened firmly to end panels -- mortise and tenon is common. The resulting hole is filled with your glued-up solid lumber panel. It is captured all around in dados. It is not glued in. It floats, captured in those dados. It can expand and contract without blowing anything apart. Of course, you do all sorts of decorative versions of this. You could have a style (ie, vertical) in the middle of the back, or maybe ones at each side.

[Don Jeansonne]

If you make one big 36"-tall panel, (so the grain direction is horizontal), and attempt to fasten it firmly to an end panel whose grain direction is up-down, you're asking for expansion troubles. The common solution is frame-and-panel. In the simplest form, there's a rail (ie, horizontal) at the top of the back and a rail at the bottom of the back. They're fastened firmly to end panels -- mortise and tenon is common. The resulting hole is filled with your glued-up solid lumber panel. It is captured all around in dados. It is not glued in. It floats, captured in those dados. It can expand and contract without blowing anything apart. Of course, you do all sorts of decorative versions of this. You could have a style (ie, vertical) in the middle of the back, or maybe ones at each side.

I talked to a cabinet shop that makes church pews and they said that gluing and screwing the ends would not be a problem. After I did an old pew that was apart and tey had it glued and screwed at an angle and this was done many years ago with no signs of damage.
I am still confused as to why this worked.

[Jamie Buxton]

Is the back panel in your proposed design really 36" tall? Or is the furniture 36" tall, but the back panel itself is more like 15" tall?

[Don Jeansonne]

Is the back panel in your proposed design really 36" tall? Or is the furniture 36" tall, but the back panel itself is more like 15" tall?

Yes -- the overall height is 36" but the actual back panel is more or less 24".