I am in the process of replacing my deck boards using pressure treated pine. I have a main section of my deck that has a roof over it. I plan to build a compass rose in this section. My question is can I use untreated pine for this part. I would be staining it and can stain both sides. Each piece of the rose will be joined together with biscuit joints, glue and pocket screws to keep the pieces together. They will be stained on the non-glue edges and sides before assembly. This part of the deck is about 5' off the ground and is except in driving rain or snow protected from moisture.
As long as you can keep it sealed, it will work fine and last for a long time. Even pressure treated started out life as regular, untreated pine and even though it's treated to resist bugs and rot, it can still deteriorate quickly if the conditions are just wrong.
The worst thing for exterior wood is exposed end grain that can remain in contact with moisture. Sealing that end grain, either with paint, stains or other coatings will make it last much, much longer. In theory, if you can maintain a waterproof coating the wood underneath will last forever. For your compass rose, make sure that all surfaces are sealed. With it mostly protected by a roof there is every chance that the non-treated but painted pine will last as long as the remainder of the deck.
Thank you for the response. I had mostly convinced myself that I could do this, but was looking for some confirmation of my reasoning. The only reason I considered untreated wood was the wider width in 1Xs that I could buy. I do have a table saw and considered half-sawing wider PT boards. Point to center on my rose is 6' so I was thinking I needed wider than the 1x6 PT boards to keep my angle from being too severe at the tip. I am re-bracing under the rose to provide adequate support. Does my thought process seem correct or should I take the time to half saw a 2x8 or 2x10 board?
Like i said above, as long as you seal all surfaces your wood should last a long time.
That said, your PT decking should either be 5/4 material (a true 1" thick) or 2x material (a true 1-1/2" thick). There are other material options to make the compass: Ipe, Redwood or Cedar are all naturally rot resistant and would open the door to some really dramatic finishes. Sure, they would cost a little more but for such a small amount of material it could be worth it.
Thank you very much. I appreciate your insight.
MusicMan, I'd love to see photos of the finished installation. I think your plans to add a lovely, cherished and historical design to an outdoor structure.
And, actually, you've given me some ideas for some new formal garden designs.