Mailbox pressure treated lumber

Willemjm

Willem
Corporate Member
Anyone try building the box from wet PT lumber?

Bought some from Lowe’s, but think it may be a bad idea, will probably warp and twist like crazy.

Perhaps the ultimate design to manage wood movement?
 

Jeff

New User
Jeff
So what if it warps and twists? Not a game stopper but your mail may get wet and soggy!
We have a metal mailbox from Lowe's or HD that suffices.



Anyone try building the box from wet PT lumber?

Bought some from Lowe’s, but think it may be a bad idea, will probably warp and twist like crazy.

Perhaps the ultimate design to manage wood movement?
 

ste6168

Mike
Senior User
Last May, at my old house (now rental property), the mailbox looked awful and wanted to "spruce it up" on the cheap - Since I was moving. I built a mitered box that fit around the current post, out of some PT 1x lumber from Lowes. I drive by the property a couple days a week, and although nothing special, seems to be holding up just fine.

IMG_1239-1.jpegIMG_1241.jpegIMG_1244.jpeg

That said, at our new house, I just installed (last week) a full powder-coated steel post (not a sleeve) and heavy duty mailbox. Didn't want to have to mess with it again anytime soon! I know that doesn't expressly answer your question, but may be an option to consider.

IMG_4108.jpeg
 
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JimD

Jim
Senior User
I think it is great for the post but I wouldn't make the actual mailbox out of wood of any kind. If I was to use wood, however, I would use PT. But it will crack some as it dries out which might make it leak. I have some chairs made of PT on my dock that badly need repainted. But they work and are structurally fine. The wood was wet when I made them but fastened together nothing bad has happened. If I had let the wood dry better before I painted it the paint might have lasted longer. But they are probably 10 years old. I do not know how old my dock is but I think it's even older and there is no finish on it. But when I flipped the deck boards over earlier this year, they were in great shape on that side.

PT wood holds up. I am just not sure how well it would protect mail. I wouldn't worry too much about warping if it will be made into a structure.
 

Raymond

Raymond
Corporate Member
My mailbox is metal but the post and newspaper cubby are all PT 1x from Lowes. Going on 20 years in DEC and still holding up - despite the fact that it has been knocked over by the recycling trucks twice in that time.
 

Willemjm

Willem
Corporate Member
The reason I am building it, as this is real fast and easy, but more important I can make it look the way I want it, rather than a steel or plastic purchased box.

Plan is to use finished ply, then a barrier for moisture, then clad it with 3/4 PT lumber, almost using the latter as a siding.
 
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nn4jw

Jim
Senior User
Somewhere in the back of my mind I remembered that there are "rules" that mailbox construction must meet. https://www.usps.com/manage/mailboxes.htm.

Interesting though is that the USPS site doesn't actually elaborate on those rules other than to state the plans should be shown to your local postmaster. Might be worth some more research just to be sure that after going to all the trouble to build the mailbox some overzealous mail-person doesn't get a splinter and give you a bunch of trouble.
 

Willemjm

Willem
Corporate Member
Somewhere in the back of my mind I remembered that there are "rules" that mailbox construction must meet. https://www.usps.com/manage/mailboxes.htm.

Interesting though is that the USPS site doesn't actually elaborate on those rules other than to state the plans should be shown to your local postmaster. Might be worth some more research just to be sure that after going to all the trouble to build the mailbox some overzealous mail-person doesn't get a splinter and give you a bunch of trouble.
Thanks, good information.
 

Jak3

Jacob
Senior User
I made these two and the post back in September. One from Cypress one from Western Red Cedar and cedar post. Finish is Spar Urethane. They've held up really well. Ordered all the material from Shavers. One is dovetailed one is just nailed. I personally wouldn't use pressure treated, I hate that nasty stuff.




 

TENdriver

TENdriver
User
I made these two and the post back in September. One from Cypress one from Western Red Cedar and cedar post. Finish is Spar Urethane. They've held up really well. Ordered all the material from Shavers. One is dovetailed one is just nailed. I personally wouldn't use pressure treated, I hate that nasty stuff.





Jacob, Those turned out nice!
 

Bear Republic

Steve
Senior User
Willem,
I've done a few projects with the PT lumber. It will move like crazy as it dries. With our weather, depending on your design, the dried wood may be highly mobile also. You might also look into marine grade ply depending on what you want to do.
 

Roy G

Roy
Senior User
The PT wood available today is not as rot resistant as it used to be. The additives have changed and the wood is not as durable. I would think of using white oak since it is very water resistant and fairly easy to work with. YMMV.

Roy G
 

Gofor

Mark
Corporate Member
If you do use PT lumber for the box, I would suggest starting with 5/4 deck lumber to get the best quality stock, and I would let that dry stickered for a least a month. Also may need a little more drying after the first rough milling to dimension. I would use a quality exterior acrylic latex for the coating if you are not going for a natural grain look. Once dry, PT pine moves, etc the same as untreated SYP, just less susceptable to bugs.

Although cedar does make a good post material from a weathering stand-point, it doesn't stand up well to even slight impact from a bumper (My first post was cedar and was snapped off at ground level by a contractor working on a neighboring house after only about 4 years). The treated pine post (4x4) I replaced it with lasted 9 years before a visitor to my neighbor snapped it off.
 

Dee2

Gene
Corporate Member
The last mailbox I made, I had to go back and modify it for bat resistance. Maybe folks in NC play nicer.
 

bob vaughan

Bob Vaughan
Senior User
The chemicals used in pressure treated wood are supposed to make the wood more impervious to organic attack like termites. That treatment is useless against mechanical problems such as water saturation and freezing. When the water freezes it expands, pulping the cell walls. That's why a lot of end grain gets pulpy over the years. Maybe once the cells are pulpy they are more susceptible to organic attack like various rots. The best protection for wood outdoors is paint. There are lots of good acrylic paints out there now. Sealing end grain is very important to keep water out.

Wet wood shrinks so keep that in mind.
 

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