Question re mortise and tenon with wide rail

[Jay Aubuchon]

What is the best way to accommodate wood movement in a mortise and tenon joint with a wide rail?

I am making a garden gate from western red cedar. The material will be as close to 1 ½" thick as I can get, after flattening. I plan to join the rails and stiles with mortise and tenon joints and West System epoxy.

The rails will be about 8" wide, so I am a bit concerned about wood movement. The suggestion I have seen is to split the tenon into 2 shorter tenons, but still glue them both. Will that be good enough? Any other recommendations?

[Andrew Hughes]

I think your on the right track with splitting the tenon.
I don't like epoxy for Wrc it drys too hard for a soft wood.
I use gorilla glue and sometimes a draw bore joint.
Its helps to keep pressure on shoulder of the joint.
Lots of movement in outdoor woodworks.

[Eric Schmid]

You'll obviously want to start with dry lumber. Cedar tends to move quite a bit in service, but I have not had issues with joint failure when using dry lumber. Green is a different story. Segmenting your tenon will provide more surface area for glue/ epoxy. Sealing the gate will help reduce moisture gain and loss. Seal all exposed sides and ends once assembled.

I have used Tightbond 3, Gorilla glue and epoxy on gates. Lately mostly epoxy. The long open time is helpful on complex assemblies; panels set in dados.

Loose tenons will likely perform just as well, unless your gate is unusually wide.

[Jerry Miner]

I don't think splitting the tenon into two really helps, as it's the overall movement of the rail that matters, not the individual movement of the tenons. But 8" is not too excessive. You could probably just glue the middle 6" and be OK. But you might consider a "breadboard end" type of reatment of the M&T joint, with draw-bored pegs:


Gate Joint 3-25-16.jpg Or Gate Joint [3] 3-25-16.jpg



I also don't like putting a groove in the bottom rail of an outdoor gate, as it traps water. Instead, I like to either shape the bottom rail into the "tongue" portion of a tongue-and-groove joint with the panel, or add a "saddle" that does the same thing and sheds water:

Gate Joint [2] 3-25-16.jpg

[Mike Cutler]

Jay

How wide are the stiles? Their width may effect the type of joint you use.
Split the tenon into two narrower tenons. I'd probably use epoxy also, but it seems as of Andrew's response is built on a personal experience of using epoxy and cedar. Each tenon would be about 3 1/2"+ inches wide, depending on type. I would also use a full shoulder in a stepped mortise.
I would not rely on glue only. I would integrate some type of mechanical locking mechanism into that joint. Foxtail tenon, wedge tenon, draw bore, etc.

[Robert Engel]

+1 on the poster about pinning.
Use oblong holes in tenons allows for movement.
You don't even need glue if you use draw bore method.

[Jay Aubuchon]

Jay

How wide are the stiles? Their width may effect the type of joint you use.
Split the tenon into two narrower tenons. I'd probably use epoxy also, but it seems as of Andrew's response is built on a personal experience of using epoxy and cedar. Each tenon would be about 3 1/2"+ inches wide, depending on type. I would also use a full shoulder in a stepped mortise.
I would not rely on glue only. I would integrate some type of mechanical locking mechanism into that joint. Foxtail tenon, wedge tenon, draw bore, etc.

Mike, they are 5 1/4" wide.

[Jay Aubuchon]

Jerry, yep, the bottom rail will have a tongue on top, not a groove.

[pat warner]

Outdoor, life time wear/tear, kids swinging on the thing?
Then joint connector hardware.
The best of joinery/paint will not stand up to wind, rain & snow.
Joinery? Nearly anything to register; the hardware will compensate.