I’m building a set of outdoor stairs down a 14 foot drop over 60 feet. I’m going to use 6×6 as the front edge treads and then backfill.
This means the wood will be in contact with the ground. I am aware this will limit its lifetime. My question is whether PT will last significantly longer in this situation than hemlock?
The local sawmill has rough 6×6 hemlock for 550/1000 vs about 20 for a PT 8’. Unless the PT lasts way longer the 40% difference seems worth it?
Any other suggestions on outdoor stairs?
Best Answer
Pressure treated will last significantly longer. Hemlock performs about the same as Southern Pine and its above ground life is significantly less than treated pine’s in ground life. In ground, you can’t expect untreated wood to last more than 3-5 years.
In ground, I think you can reasonably expect pressure treated to last six times longer (even more if you treat with an additional product like copper naphthalate). Given that plus installation costs, pressure treated is clearly the choice.
As far as other options, I think concrete or blocks would be the only other cost effective options.
References
https://www.fs.fed.us/t-d/bridges/documents/tdbp/decayres.pdf https://bct.eco.umass.edu/publications/articles/wood-myths-facts-and-fictions-about-wood/