The Forestry Forum

Building an outdoor gazebo in Florida using timber framing joints.  For the same price I have a choice of Cypress S4S KD or PT S4S KD.  Which would you go with and why?  ???

I know I'm paying a premium for S4S and especially for KD, but this is my first timber framing joint build and I don't have the time to dry the wood (or want to risk it warping during drying process).  Bottom line, I'm throwing money at insuring I don't run in to any unforeseen complexity due to wood quality, so it would not cost me more time or money if I screw up.  Not to say I can't or wont screw up anyways...  ::)

What spec is the pressure treated? It comes in various grades from borate only to wharf piles that are practically dripping chrome and copper... 

If the PT is treated to "Ground Durable" it should outlast the cypress. If it's a lighter treatment, the cypress probably wins, although that can vary, and faster growing "2nd growth" wood doesn't seem as durable as the older trees. 

Quote from: Ianab on December 14, 2022, 09:50:31 PM
What spec is the pressure treated? It comes in various grades from borate only to wharf piles that are practically dripping chrome and copper...

If the PT is treated to "Ground Durable" it should outlast the cypress. If it's a lighter treatment, the cypress probably wins, although that can vary, and faster growing "2nd growth" wood doesn't seem as durable as the older trees.

PT is Grade #1 SYP.  For 25% less could do Grade #2.  KD was a 50% premium.  That is all that was mentioned in the quote.
Cypress is from Southern Pine Lumber
PT is from Southern Pine Timber

The #1 is the quality of the wood, with One being the better stuff (least knots and defects etc). So that's good in that respect. 


What you need is the UC#. The USA uses different treatment grades to here on NZ, but from what I can see UC1 is treated, but only for interior (out of the weather) use. That's fine for house framing where it's not going to get wet. UC5 is rated for marine use, build your boat dock from it etc. You want UC3 or 4 for outdoor ground contact situations. A UC4 treated post is probably rated for 20 years in the ground, depending on "things", and that would beat cypress. 


Scroll down to the AWPA Categories section on this page. 
https://decksbye3.com/pressure-treated-grades-and-retention-levels-explained/