Lumber and Siding - Help building with redwood lumber

Got a silly question here but I'm not sure of the answer.

Last spring I built a couple redwood planter boxes with a redwood bench that spanned between them. Very similar to the one in this pic.:
Redwood Planter Bench - Fruit From Washington Outdoor Furniture Catalog (http://www.fruitfromwashington.com/product/furniture/planterbench.html)

The redwood that I used was precut and sanded that I bought at Lowes. It was really light weight so I am assuming that it was dried.

Now, the vertical pieces that I placed on the box sides have swelled and pushed the end pieces out of square, so all of my miter joints now look really crappy.

I plan on disassembling them to repair them but I don't want to have the same thing happen again. The plans that I used said nothing about putting a space between the boards, but now I'm wondering if I should. I always thought that redwood will shrink over time. I built a redwood fence years ago and put the boards tight and now there are major spaces between them. I thought the same would happen with these.

Will these boards continue to swell?

Thanks...Randy

Miters used in an exterior application are difficult if not impossible to keep perfect and tight.
I would guess that the moisture content that the board are at should remain somewhat constant although I am not familiar with your climate.(A little bit jealous, but not familiar..lol)
If I were to venture a guess I would say fix them and they should stay reasonably stable from now on.

Yeah, I kind of expected a little bit of separation but these had gaping holes. It was quite obvious what was going on as the boards themselves were not square anymore.

I am going to trim them and reset everything back to squareness and then seal everything as much as I can with a good quality stain that I have. Hopefully that will fix it.

Thanks for the comment.

Randy

Randy: You will also find it beneficial to use a liner in the planter and allow weep holes. I have found this to keep the moisture from sitting on the redwood. Must be nice to be able to buy redwood in the first place. Non existent on the right coast.

Oh, didn't you visit our area once? If I remember correctly....anyway, MaryAnn's closed and moved over to North Carolina. What a bummer.

Randy,

You have used redwood for 2 projects that you have mentioned -- the planter boxes and the fence. What you used for the planter boxes was dried and it absorbed moisture and swelled. What you used for the fence was green. It lost moisture and shrunk. Two totally different applications, and 2 totally different results.

For the planter boxes you'll need to line them like Larry suggested to keep the moisture away from the wood. I'm going to also suggest that after you get the boxes rebuilt and lined, and before you put dirt in them, install SS cables (1/8" or 3/16") with one from end to end and a couple across to prevent the pressure from the dirt from moving the sides around. And rather than miter joints, I would use butt joints for exactly the reason that ArmchairDIY mentioned. A couple of pieces of 1X trim vertically at each corner will conceal the butt ends.

These boxes will not come into contact with the dirt. I built them to hold a plastic planter that drops inside so the only moisture that they see is rain and fog. Oh yeah, and the water that my wife splashes them with when she is watering. But, that's ok. That's what I built them for, and I knew when I did it that I should have protected them with some kind of water repellent, like I did with the fence. I was just in a hurry to get them done for a back yard social gathering at the time. Then I forgot about them and now I am paying the price.

I think my current plan will work. I have already partially disassembled the end pieces, trimmed them and then reattached them...this time with glue and nails. Now all I have to do is reinstall the trim pieces, sand and treat with the stain/water repellent. This stain I have works really well. I applied it to my fence about four years ago and the water still beads up on the boards when they get wet. I'm pretty confident that it will protect them adequately.

Lefty, I think your analysis about the fence wood being wet and the planter wood being dry is absolute. I had thought about that but wasn't sure, but it does make a lot of sense. Too bad I didn't think about it as I was building it.

Thanks guys.

Hey Chandler, you're right. I lived in Atlanta for several years and redwood was not to be had, but cedar was abundant. Now, here on the left coast, redwood is abundant, albeit very expensive, and cedar is not that readily available. I really like the look of redwood but it is definitely not a structural lumbar. Too soft.

Too bad about Mary Ann's. I will have to ask my parents if they know where it is now. They are always driving around those mountains in search of new places. I wouldn't be surprised if they haven't already found it again.

I was just out there again last August for my mom's 75th birthday. I was there a couple weeks but didn't have much chance to do any driving around this time as my Dad had me working on his place most of the time.

Randy,

Screws would probably work better than nails, and you could use dark red Trap Eaze which wouldn't show nearly as much as nails do.

Rain and fog there in the Bay Area will keep the wood rather moist most of the time, and your wife will continue splashing the water to keep it moist the rest of the time. Whatever really good sealer that you have on the fence will do about as well on the boxes. About the only difference would be if you are laying a piece flat around the top perimenter. That would be oriented like a deck board, and, like a deck board, the sealer simply won't last quite as long. But at least you don't have to contend with the sun tearing it apart like we do up here!!

Randy,

What you are up against is one of the principal constraints in furniture design. As the humidity changes, wood swells and shrinks. Wood is pretty stable in the direction of the grain (a board won't get much longer or shorter) but are unstable across the grain (boards will get wider and narrower).

Using liners, sealers, paint, etc. will only help a little bit. These will retard the rate at which wood absorbs or gives off water. However, they will not completely stop the problem and the wood will continue to swell and shrink as the seasons change.

The only way to avoid the problem is to use wood that has an even straight grain and to use joints that are designed with swelling/shrinkage in mind. For a planter box, joining the sides to each other with miter joints should work fine as long as you are attaching end grains to end grains. However, the bottom will be a problem since the grain will be running parallel to two of sides and perpendicular to the other two. The bottom will get wider or narrower and force the miter joints out of alignment. Any wooden drawer has this same problem. You can avoid the problem by cutting a dado (slot) on the inside of each of the sides, cutting the bottom a little undersized and letting the bottom "float" in the slot. This allows the bottom to shrink or swell without stressing the sides.

Redwood shrinks and swells more than most other woods. I recommend cutting the bottom about 1/4" undersized.

If you are using a rigid liner, it should be a little smaller than the planter. While the wood won't shrink or swell much parallel to the grain, it will move a little bit.

Hope this helps.

Cheers,
Don

Well, it's finished and I think it turned out pretty good. I used Gorilla glue on everything so hopefully it will hold together for several years. I am attaching a pic of the finished product. I wish I had taken a before pic but I didn't think of it. It looked really bad.

You can see the inside lip where the plastic planter box (square) drops in. It has a lip on it that just sits on the inside ledge.

Thanks to all for your input and advice.

Randy

http://file.walagata.com/w/fubar94/IMGP0018_0.JPG
http://file.walagata.com/w/fubar94/IMGP0020_0.JPG