Table with shelf - wood movement

[legenddc]

How do you account for wood movement in something like the Shaker End table with a shelf underneath?
 

I’m looking to build a coffee table soon like this but with traditional joinery. Don’t want the bottom to burst out. 

[Chestnut]

I don't run my lower shelves like that out past the legs. That's the biggest area where I don't know how wood movement is handled other than leaving a gap.

I just set the bottom shelves in an inch from the leg so there isn't a notch then it's as simple as attaching it like a breadboard to the lower rail

[legenddc]

That’s what I was thinking too. Do you attach the side aprons to the long aprons? Or double up the side aprons and just make sure to keep the shelf is short enough to not interfere with the legs?

[Mark J]

At the highschool wood shop, where I'm an aide, the students are building a similar style end table.  The shelf is plywood, and like Chestnut describes, the shelf width does not go beyond the inside margins of the legs.  The shelf sits in a dado/groove cut into the lower end rail.

On the other hand the school plans call for a 20" wide top of edge glued oak that is attached on all four sides with a dozen screws and no provision for movement. 

I raised the question, and while the instructor is open to change, this curriculum has worked for his predecessor for 25 years.  So below some width (and with stable humidity) you may be able to ignore wood movement. 

I don't know what that width is, but there are tables of wood movement in Understanding Wood and other sources.

[BillyJack]

..

 

[BillyJack]

The bottom shelf just needs to be able to float. It can be notch or extended past the legs..

[Wimayo]

On 12/10/2022 at 8:45 AM, BillyJack said:

The bottom shelf just needs to be able to float. It can be notch or extended past the legs..

I agree if the shelf is solid wood. You must mount the shelf to the stretchers in a similar manner as the top is fastened to the aprons. If the corners are to be notched as in the sample photo, there must gaps large enough to accommodate movement.

Another way to do it, if the legs are large enough to accommodate it, is to notch the legs on the expansion side extra deep to allow for the expected expansion. Make the shelf so that, when fully contracted, it just barely rests in the notch. Then when it fully expands, it moves into the extra space.

Another solution, as suggested above, is to make the shelf out of plywood or MDF (veneered).

[Chestnut]

2 hours ago, legenddc said:

That’s what I was thinking too. Do you attach the side aprons to the long aprons? Or double up the side aprons and just make sure to keep the shelf is short enough to not interfere with the legs?

I've just skipped the side aprons but I've done different designs. EG

[curlyoak]

One wide piece of oak with breadboard ends. Solves movement.