Red oak for outdoor structures?

[terrifictimbersllc]

Anyone make weather exposed timber frame type structures with red oak and have you applied any finishes to it?

Customer wants to make a pergola out of red oak timbers beams 3x6 to 8x8's  after he lets the wood dry for a year and then apply some kind of sealer.  Seems to me that  it won't be dry and if he applies a sealer the escaping moisture might just push the sealer back off.  

Occasionally I get the question of suitability of red oak for outdoor structures such as a pergola.  Have always said that RO is of moderate susceptibility to rot, that cedar, locust, even white oak are much better. If you want to use RO then regard your structure as having a 5-10 year life max.  The comeback is that they want to apply a sealer to the wood.  I say it is better to let it weather naturally and design joints which shed water and I don't know much about maintaining exposed RO with a sealer.  

[Lawg Dawg]

sure would like to here some ideas on this

[ljmathias]

I think there are really two questions here, one structural and the other visual.  Does weather change the strength of the wood?  Sure- the greying of the surface results from light plus oxygen degrading the wood, and as this process goes deeper, wood gets weaker.  At first (maybe for years and years) this occurs at and in the surface.  Rot is something else that involves "bugs" and warm, wet environment.  Dry wood doesn't rot, as far as I'm aware, but any moisture exposure can allow dormant fungus to regenerate, I believe, increasing the penetration and degree of rot.

Sealers work best by keeping out both light and water.  Since wood expands and contracts with temperature changes, the more flexible the sealer and the deeper the penetration, the better the protection.  Even with the best sealer, though, protection is only temporary meaning reapplication on a regular basis.  Done right, a good sealer will make the wood, any wood, last for a long time.  Most people hate to apply sealer, especially to intricate and high up structures which means that the sealer often quits working after a few years.  Then your strength, appearance and longevity depend only on what type of wood and how it was put together.

Lots of information on the forum and elsewhere on inherent weather and rot resistance of various kinds of wood and on designs that optimize various desirable properties.  No easy answer, really, so best of luck and show us pictures of what you make or see.   

Lj

[thecfarm]

Lawg Dagw,welcome to the forum. Do you own a saw?
I think the red oak would last at least 10 years, but I would not use it exposed to the weather. In 10 years I would expect it to be pretty easy to tear down and build another one.  Water will get trapped in most of the joints and stay kinda wet and cause it to rot. I know in the woods I have some red oak that have died and still standing. Still have the sap wood on it to protect it. Soon as I start to saw it up the sap wood is gone. But remove the sap wood and saw it into lumber is different.

[beenthere]

........... If you want to use RO then regard your structure as having a 5-10 year life max.  ............

That is a good estimate to pass out. Pergola's are about the worst exposure to the elements there is. IMO

[Lawg Dawg]

Yep, proud owner of a LT15, its small and manual but it gets the job done!

[Magicman]

Welcome Lawg Dawg, to the Forestry Forum.   

[terrifictimbersllc]

Got another possible customer looking to use pin oak for a pergola.  Experienced circle sawyer nearby agreed its similar to northern red oak in appearance.  Wants to set posts in the ground.   Told him better off finding some locust for that for sure. If he's intent on putting pin oak posts in the ground, is there anything he can treat them with?  What happens if one puts them in cement?

[Magicman]

What happens if one puts them in cement? 

They will rot.

[brendonv]

From my experience with working with my brother doing fencing is your better off with no cement with wood posts in the ground than using cement.

[Warren]

As stated above, locust or white oak would be better for the posts.  However, for the balance of the frame, practically speaking, a pergola is not a high stress, critical structure.  It's purpose is to provide shade...

As long as you are honest and up front that red oak is not the BEST option, and point out they will need to apply a coat of sealer/protector to it every few years, you have done your part.  If the customer understands the decidsion they are making, and the consequence of not treating it regularly, it is their issue if they choose not to do proper maintenance.

Just my $0.02...

Warren