Wood movement in hallway bench

[kwc]

Hello,

I'm building a hallway bench out of solid cherry but am uncertain how to deal with wood movement. A sketch of the bench is attached, with red lines denoting planned long grain orientation.

The carcase will consist of end-grain to end-grain joinery using tongue-and-groove, rabbet, and stopped dados that are glued together. Expansion of wood across the grain should happen in unison.

However, I'm not sure how to deal with the skirt around the base, and the rail along the permiter of the bench seat. At both ends of the bench, the long-grain of the skirt and rail would connect across the grain of the carcase. As a result, wood movement may present a risk of splitting the carcase or pulling apart the joints at the corners of the skirt or rail.

Any recommendations?

Thank you,
kwc

[steve-norrell]

Interesting questions!

You did't say how long the bench will be. Also, what kind of environment exists in the hallway and how much does it vary in temperature and humidity. Is the length long enough and does cherry expand and contract enough to be a problem?

I'll risk showing my inexperience and say that I would not have worried too much about differential expansion and contraction of the wood.

My only experience with this issue is a wooden floor made of TandG birch that seems to get a tiny bit wavy from time to time (although never enough to cause concern).

I look forward to learning more.

Regards, Steve

[kwc]

The bench will be 50" long, ~18 inches tall (base of skirt to top of rail), and ~16 inches deep. Therefore, cross-grain expansion would occur across the 16-inch depth. The reading I've done seems to point to the possibility that cherry will moderately expand and contract, as with most solid woods, as much as 1/8" or so across a 16-inch panel. I'm not sure if this is enough to be very concerned about but would like to play it "safe."

The house/hallway is air conditioned, but humidity levels vary as would be typical in Maryland (dry in winter, humid in summer). Ideally I'd like this piece to be around for a long time--I have aspirations of making it an "heirloom" for my kids. :-)

Regards,
kwc

[LarryG]

This specific problem is one reason I like to use hardwood plywood for projects like this -- although then you have to deal with the plywood edges, so I guess you're just trading one problem for another.

Two options, both variations on the same idea. The first is to glue the side aprons only at the very front corner of the side panel, and secure the other end with a screw, from the inside of the end panel, that passes thru an oversize or slotted hole in the end panel. (Use a washer under the screw head, to cover the gap caused by the oversized hole/slot.) The second is to join the two side aprons to the front aprons with biscuits, creating a U-shaped assembly. Glue the front apron on per usual (long grain to long grain) and secure the back ends of the short aprons with screws, per the above.

The second option is better because there's less chance of the miters opening up. With either, the screws are tightened just enough to hold the aprons to the side panels but not so tight as to prevent the side panel from expanding/contracting.

[Black wallnut]

Like Larry's method I have used sliding dovetails to mount the side aprons, only gluing at the front 3 or so inches. Glue the front and miters. Sliding dovetals must be sized carefully with the tail milled from end grain and glued and screwed to the carcase.

[drumpriest]

At the bottom, I would recommend using glue at the front of each side piece, that will keep the miters together, then use no glue at the back, and use a screw with an oversized hole to allow for movement. Pocket screws will allow for some, but you should probably use an even larger hole and pan head, that way the screw can move over time while holding the back tight against the cabinet.

[leehljp]

The only places that will present movement problems will be the side skirts, top and bottom where the grain is running front to back. Everyone gave great advice on overcoming this. Cherry does move with humidity changes even when finished with several coats on both sides of the wood. I learned that from a cherry breakfast table I made 30 years ago and still have and use.

[kwc]

All,

Thanks for the great ideas. I have a lot of good options to consider when I get to this stage in the construction of the bench.

One thing I should have clarified is that the front skirt is mirrored on the back side of the bench. That complicates things slightly, but I'm assuming I should still be able to fasten/glue the front skirt, screw or dovetail the side aprons, and leave the rear skirt "float" (glued/fastened to the side aprons) with just enough clearance to allow for expansion of the base.

Thanks again!
kwc

[steve-norrell]

See that!

Ask a question. LISTEN, READ, LEARN!

That's why I check in to this forum frequently.

Regards, Steve

[Russianwolf]

The third option is to make the Base, Carcas and Top three separate pieces and then use hardwar only to attach them together.

You could attach the carcass to the base the same way some people attach tabletops. Cut a kerf all the way around the inside of the base and use hardware that slips inside the kerf and is attached to the bottom of the carcass. Or it could just sit in place (in a rabbet like some of the modular bookcases they have running around).

[kwc]

Like Larry's method I have used sliding dovetails to mount the side aprons, only gluing at the front 3 or so inches. Glue the front and miters. Sliding dovetals must be sized carefully with the tail milled from end grain and glued and screwed to the carcase.

Black Wallnut,

Would I run into durability issues gluing an end-grain dovetail to the side of the bench seat? Likewise, would drilling into the end-grain present a problem? Or is there a proven technique that could work well to strengthen this bond (epoxies, etc.)?

Thank you,
kwc

[Black wallnut]

Gluing and screwing on a dovetail pin made of end grain should be plenty strong as long as you get a good glue joint. Drilling into end grain should not present much of a problem. Although I'm thinking you are worried that the wood might split. A good glue joint should keep the wood together.

Alternatively you could use an edge grain dovetail pin cut into several smaller peices and glue and scew them on individually, or one solid piece gleued and screwed at the front and screwed in several places along its length with slotted holes to allow for some movement.

IMHO the shorter and wider the dovetail pin the stronger it will be. So if you were to make your pin 5/16" high and 3/4" wide at the top and used a #6 wood screw it would be very strong. You could then either buy a 3/4" dovetail bit or cut the dovetail slot in several passes.