I hear all opinions from redwood is ok for ground contact to only pressure-treated lumber can be used. As for weathersealing, some say the old redwood was great but the new redwood is no different from any other wood so seal it like any other wood and some say under no circumstances ever seal redwood.
So is redwood in 2019 any different than cedar, pine, etc.? Can I use it in ground contact? Should I leave it unsealed in northern Colorado weather?
I have never heard of new redwood. Is it genetically modified?
The redwood I am familiar with just gets purdier and purdier overtime. No need to baby it.
I haven’t used redwood because of the cost, it’s quite expensive in Canada relative to PT pr cedar.
I’ve never heard of any difference between newer or old redwood in regard to fence use. You do hear about new vs old for pine, but usually pertaining furniture making. Newer pine is a farmed product and made to grow rapidly. This results in bigger growth rings which makes the wood more prone to warping and cupping than “old growth” pine.
As far as fencing goes - my understanding is that you use it and finish it exactly like you’d use cedar since it’s very similar. Cedar can definitely be placed in contact with the soil, but I believe pressure treated is better for ground contact and will last longer. [As a possible option: When I built my cedar fence, I used PT 4x4’s as posts and then clad them in 1/2" cedar fence boards to “bulk them up” and give them a 6x6 look. They’ve held perfect for 20+ years.]
Similarly for finishing, do what you’d do with cedar. As harmonica says, it will grey / silver naturally. Some people like that look, some prefer the new-look reddish colour. I prefer the newer look so I use a some product every few years from Home Depot that renews the new-cedar look. You apply it and then hose it off.
I’d suggest that if you are going to put a finish on, you use a clear coat finish to keep the original red colour. If you’re thinking of using a tinted/translsucent/opaque stain, then what’s the point of using the redwood (unless you’re getting free redwood)? A non-clear stain will just hide the fact it’s redwood.
Lastly - unless you’re getting really low cost redwood, I’m not sure the overall advantage. I recently used the new style of “cedar-look” pressure treated wood for a dock. Way cheaper than cedar which is way cheaper than redwood. Everybody thinks I used cedar (although nobody thinks it’s redwood:))
All that said, I really wouldn’t listen to me, but I do suggest you post on this site:
They have a great woodworking forum with lots of knowledgable people and I’ve always received very good advice there.
There is a difference in the strength and durability of old growth redwood and new growth. That said, I’m not sure how easy it is to get old growth redwood at this point. I also wouldn’t waste it on a fence. Maybe you can get some recycled redwood if you really want it.
You should use the pressure-treated redwood for ground contact. Handling the fence like you would for cedar is good advice.
There have been a good amount of studies looking at the decay resistance between old and new growth cedar and redwood. The studies generally find that old growth wood can be up to 5 times more decay resistant. The studies also usually find a large amount of variability when it comes to amount of heartwood, genetics, site, speed of growth and density. None of them really provide solid conclusions.
Here is a pdf, the first few slides show what you’re looking for if you’re picking out the lumber. Basically no pith and no sapwood.