Exterior untreated lumber... resistant to warping and rot (within reason)

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Forum topic by marcVT posted 08-14-2017 05:28 PM 4107 views 0 times favorited 19 replies Add to Favorites Watch
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10 posts in 1201 days

08-14-2017 05:28 PM

Topic tags/keywords: warping rot exterior wood

Hello all. I am doing a large car port (30×30) for a customer and they do not want copper treated lumber. The structure will not be touching the ground. Steel footings in concrete keep it up 12 inches off the ground. The vertical posts and rafters (glued composite beams made from 4×4 or 2×4 or 1×4 depending on type of wood selected. Glued with Weldwood Plastic Resin Glue. These beams are large and will be pre-drilled and permanently clamped with galvanized 1/2” threaded rod, large 3” diameter washers and nuts…. Resin glue in between. The beam construction is a topic in itself I know:).

So they want real wood. Treated by me before construction. Probably Sikkens or other. A recommendation on that is always appreciated to. I’ve had good luck with Sikkens on marine decking. Nothing lasts forever in the sun, rain and salt though.

My question… I want to use a wood that will not warp too much over time as it dries (from being green) and absorbs and loses moisture seasonally. Also if it naturally is rot resistant that is important. I’m in Vermont and cant get Redwood, Cedar etc. I have heard White Oak has a nice straight grain and is decent for rot resistance. The white oak I can get is green though. Will I regret using green white oak? I can get it cheap. (It’s not quarter-sawed)

Any recommendations on wood type selection? I do not need hardwood. I know southern cypress is good for grain and rot but that stuff is not around much here. Please correct me if I’m wrong. Maybe kiln dried pine with a decent preservative coating afterwards is my best choice?

Any advice is greatly appreciated. I’m asking a lot on my first post… Was happy to find this forum. It is terrific!

19 replies so far

View MrRon's profile


5954 posts in 4159 days

#1 posted 08-14-2017 06:52 PM

I’m sure any local lumber yard in Vermont can special order any wood you want; it will just cost you. Cypress would be my first choice. Down here in the deep muggy south, cypress is the go to wood for outdoor projects.

View gargey's profile


1013 posts in 1691 days

#2 posted 08-14-2017 06:57 PM

I’d go with the oak, unless the customer has a huge budget.

View magaoitin's profile


249 posts in 1865 days

#3 posted 08-14-2017 07:50 PM

There are a number of treatments other than copper based that we use all the time in Washington, and we have a lot of exposed wood timber structures that weather our rainy conditions. Most of the stuff my company does is all Doug Fir with clear sealers, and I have not heard of any warping on any of our work in the last 25 years. But all of our lumber is kiln dried prior to sealing. I think you would be end up being disappointed starting with a green oak

Boise Cascade has a en exterior rated Glulam beam that we use quite a bit, that is a kiln dried fir that is treated with their clear sealer and used exterior/marine grade adhesives, and maybe it would be worth it to buy premanufactured beams instead of laying-up your own.

Check our Permapost Hi-Clear II. It isn’t a copper based sealer, but uses IPBC’s for the mold and antifungal. It is an above ground sealer only, so it might work in your application with any species.

-- Jeff ~ Tacoma Wa.

View bold1's profile


345 posts in 2763 days

#4 posted 08-14-2017 08:34 PM

Can you get Hemlock? Little warpage when drying and if the old folk could not get Cedar or Chestnut their next choice was usually Hemlock for shingles.

View Kirk650's profile


680 posts in 1664 days

#5 posted 08-14-2017 10:02 PM

If you go with oak, be sure it’s white oak and not red oak.

View cabmaker's profile


1745 posts in 3724 days

#6 posted 08-14-2017 10:21 PM

douglas Fir

View marcVT's profile


10 posts in 1201 days

#7 posted 08-15-2017 11:27 AM

Thanks for the input. I think the Douglas Fir is a west coast monster. You guys in the west have a nice selection. I’ve got a brother in British Columbia on the water. They fall a tree in the water and tow it to the local mill and get a zillion board feet from 1 tree. Not so lucky in Vermont. Beautiful hardwood… just like weeds compared to the west. I love this forum. I started reading ‘understanding wood’ by Bruce Hoadley last night. Someone on a post had suggested it. It is an amazing book. I’m not a huge reader but I’m reading this one. Another lumberjock posted that its smart to seal the end grains with Anchor-seal when using green lumber. This forces the wood to dry uniformly instead of lose moisture like nuts out the ends where it is cut, causing unusual warping, splitting. This is novice info to you folks I’m sure but priceless info to me. I will check out the Permapost Hi-Clear II. Vermont has very environmental conscience people like Washington state. I grew up building sea walls from used creosote railroad ties:) Those things are outlawed now on the waterfront in Nova Scotia where I’m from. Funny how things that prevent pests from killing wood usually kills us humans also. I will post again and hope to contribute to this forum. I might go for the white oak with its good grain. It will make the customer happy and it’s a treat to work with. My beams will all be drilled on drill press and bolted tight. I’ll load some pictures in time. I can get hemlock (like bold1 suggested) dirt cheap and have a feeling it will cooperate more than the oak. That might be the smart choice. Cost is a constraint unfortunately. Rough sawed hemlock is ~80 cents a board foot. White oak ~$1.50. This is at mills around Vermont and upstate NY. Thanks again.

View ScottM's profile


752 posts in 3062 days

#8 posted 08-15-2017 12:42 PM

Ahhh, creosote. The good old days. That stuff lasts a lifetime. Burned your skin like hell!!!

View marcVT's profile


10 posts in 1201 days

#9 posted 08-15-2017 01:03 PM

Can’t wait to build my own portable horizontal bandsaw and make my own lumber. Probably not worth the investment considering the plane work and good planers are not cheap…...but all that sawdust!!! I’ve seen some that use a big cc husky/stihl on an aluminum ladder track but I like the bandsaw. Sorry way off topic. I’ll cease:)

View marcVT's profile


10 posts in 1201 days

#10 posted 08-16-2017 02:44 PM

As a follow up. I spoke with a local mill. They recommend Hemlock if using green lumber like bold1 suggested.
It’s cheap too! They can get Douglas Fir and Cedar but 5x the cost. I’ll post some pictures when I get this thing underway. Thanks

View CharlesNeil's profile


2501 posts in 4786 days

#11 posted 08-16-2017 03:38 PM

+ 1 on the hemlock.. have done work in VT .. and there are tons of cabins and houses and everything covered in hemlock and it last untreated for years

View josephf's profile


217 posts in 3012 days

#12 posted 08-30-2017 04:45 AM

why plastic resin glue ? just asking . Pretty much use Tb 111 for everything now .Water proof . I have read research and it performs very well . cleans up easy also . i forget why i stopped using plastic resin glue .
west coast guy myself and it seems we do have whole different wood selection .
as for sealer i do not like any of the plastic coating type products due to flaking and looking sloppy in few years . tend towards hard oils or just oils and then a sealer . some of the european products cost a lot but I get far better results with alot less effort .

View tomsteve's profile


1090 posts in 2135 days

#13 posted 08-30-2017 12:22 PM

a quick google search for me shows a few lumber suppliers in vermont that have cedar.

think i saw a sawmill or 2,too

white oak will shrink Radially 5.6%, tangentially 10.5%, per Bruce Hoadleys’ book Understanding Wood.
if you put a finish on it right away, youll be wasting a lot of money- especially if you use sikkens products- which IMO are great products.
IMO, stay away from using green lumber. take the time and find a supplier for kiln dried lumber.

i hope youve had an engineer ok these beams and construction methods
and the local building dept,too.

View CharlesA's profile


3458 posts in 2713 days

#14 posted 08-30-2017 02:17 PM

Is there any reason to use green other than cost and availability? I don’t know a lot about green lumber, but it seems like it brings in a whole host of complications.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View josephf's profile


217 posts in 3012 days

#15 posted 08-30-2017 02:33 PM

the shrinkage is murder .your post maynot stay straight and generally crack . beams will do the same plus get narrower .
I do not understand the question here . do you have all your lumber .are you unsure of using laminated material . was this only about the sealer needed

showing 1 through 15 of 19 replies

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