How much 'slack' in 6" * 22" solid wood panel

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

Attachment 421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

Yeah, 1/8th is plenty for such good wood and small space.

The length isn't going to change dimensions any appreciable amount.

According to the USDA FOrestry products you can expect seasonal moisture changes in the ranges shown on this map.Attachment 421106

Lee, is that map showing EMC indoors, or outdoors?

Quote:

---

Originally Posted by mark mcfarlane

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

Attachment 421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

---

On the time scale wood cares about, humidity barely changes in Houston. See here. You basically have a 4% RH change over the year. So, as long as your piece stays outside, given QS White Oak is a very stable wood to start with, you're going to see very little movement at all.

And even if you were in a place where here are 15% plus RH swings, with your materials and dimensions you'd be OKith the 1/8" for width. Length isn't going to change measurably at all.

I believe it is out doors, but here is a link that is definitely for outdoors

Quote:

---

Originally Posted by Lee Schierer

I believe it is out doors, but here is a link that is definitely for outdoors

---

Yep. I was assuming that when the OP wrote he was building "a small outdoor shelf," that it was permanently outdoors, under a roof. Obviously if it's indoors or moving back and forth, it's a completely different story.

Permanently outdoors, at least during my lifetime.

My theory on fitups like this is I fit the panel exactly to fit. I can normally use the molding cuts on the outside to get the dimensions. Then once it is done and verified I cut one blade width off on two sides. So about 1/8" off in both dimensions.
Bil lD

With the internal panel floating in the frame, regardless of humidity change, I would expect essentially no seasonal movement in the whole panel.

Thanks everyone for sharing your experience on this question.

Sorry I have been slow to respond. I've been really sick with some severe flu-like symptoms for a couple days. I actually pulled muscles in my back due to the most violent vomiting I have ever witnessed. Hopefully I'll be back in the shop in a couple days after I rehydrate and get some nourishment onboard.

Quote:

---

Originally Posted by mark mcfarlane

I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

Attachment 421095

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,

---

I finished milling all the wood and built the frame today. I put in my prototype panels with 1/8" of L-R play.

The sides are made from two panels, so at least for now (before finish is applied) the two panels slide independently so they can potentially leave a gap (or a crooked gap) in the middle as per the attached picture below. Not really what I want. What should I do? Order some 1/4" Space Balls and cut them in half ?

Attachment 421813

Thanks everyone for the help on this project. I ended up using 1/4" space balls from Woodcraft, and cut them in half so they were 1/8".

Here's the finished project. Turned out to be too nice to put outdoors, as originally planned :).


Attachment 423344Attachment 423345Attachment 423346