# Best Lumber for Trellis



## LaurieC (Mar 18, 2008)

Hello all,

I'm about to install a rather large trellis at a client's home. He has requested "S-dry" lumber be used (he read an article by the US Forestry Service about moisture content of lumber and the recommended uses). All of the lumber yards I've called will sale me kiln dried (they all say "s-dry" is in the kiln dried family), but tell me it's not worth the additional cost. Their argument is that once the dried lumber is installed outside it will change the moisture content, and within 3 yrs will look just like green lumber. The homeowners concern is that the green lumber will twist, check and crack. 

Any suggestions as to the best lumber to use, or personal experience with such would be greatly appreciated.


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## genecarp (Mar 16, 2008)

If the trellis must be all wood, around here the most available and my first choice would be Cedar. GMOD


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## tcleve4911 (Mar 26, 2006)

I think Redwood since it's native to your territory.


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## pinwheel (Dec 7, 2009)

My 2 choices have already been named, so I'll just echo them.


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## LaurieC (Mar 18, 2008)

Let me be a little more clear. He wants rough sawn Douglas Fir. My question is about moisture content. I can get the DF in kiln dried, but it's double the cost. Is it worth the cost to get the K-dried? My homeowner believes it will help with twisting, cracking and checking. What do you think about kiln dried, is it worth the extra cost? Lumber yard said it will make no difference after a few years.


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## TimelessQuality (Sep 23, 2007)

edit.... I's a slow typer


Rough sawn Cedar...


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## Ron Thompson (Feb 1, 2010)

Hello,

I built one for a high end builder that used to frame for in the Boise area, and we used green rough sawn DF. The logs had been cut for some time, but the mill did not have a kiln. The GC had his painter stain and seal them. I think that once kiln dried lumber is left out it will change the moisture content and you will see the lumber move. All the material we used was at least a full 2" x 4", these were for the lattice on top of the pergola. All other lumber was full dimension as well 4" x 6", 6" x 10" and 10" x 10"s. I did alot of the rough sawn stuff down there and it was all non kiln dried lumber. Hope this helps.


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## genecarp (Mar 16, 2008)

I would advice against using DF for an exterior application as you describe, he is creating a maintenance nightmare, GMOD


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## pinwheel (Dec 7, 2009)

The warping & twisting is going to happen with certain woods, whether they're kiln dried, or air dried when exposed to the elements over time. If you can get quarter sawn materials, you'll have a better time of them remaining straight.


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## BACKWOODS (Sep 10, 2007)

How about Cypress, I use it for exterior shutters all the time.


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## Dave R (Jan 20, 2008)

I've used kiln dried DF and it didn't twist ,crack or split, even after 2 years in the weather. Like you said, it is expensive but it looks good.


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## Gus Dering (Oct 14, 2008)

genecarp said:


> I would advice against using DF for an exterior application as you describe, he is creating a maintenance nightmare, GMOD


It doesn't rain very much in So Cal. But it does rain and it will present problems eventually.

One thing to keep in mind with df is the pitch pockets. Nothing worse than a nice bleeder right over the table.

KD will still have some but not as bad as green stock. The KD will be more stable than green too. You will have to decide if it is worth the money, or should I say the owner will after you educate them about the pros and cons.


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## jeffatsquan (Mar 16, 2009)

S-DRY Means surfaced dry

Rough-sawn means not surfaced, someone is confused


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## deckman22 (Oct 20, 2007)

Wood is going to do what wood wants to do when it's outside be kiln dried or air dried. IMO it's a waste of money to get the kd.


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## BuiltByMAC (Mar 11, 2006)

Metal caps over the beam/rafter tops will prolong the life, no matter the wood.Kicking it out a 1/4" off both sides will help prevent drip stains.
My opinions regarding your OP would be cedar or redwood as 'best' lumber and k-dried is not necessary for an outdoor setting.

Mac


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## custrel (Jun 30, 2009)

Ron Thompson said:


> Hello,
> 
> * I think that once kiln dried lumber is left out it will change the moisture content and you will see the lumber move.* All the material we used was at least a full 2" x 4", these were for the lattice on top of the pergola. All other lumber was full dimension as well 4" x 6", 6" x 10" and 10" x 10"s. I did alot of the rough sawn stuff down there and it was all non kiln dried lumber. Hope this helps.


Yes. Wood is hygroscopic so the higher the relative humidity, the more water the wood will retain.

Here's a link to a good book about the differences of kiln dried, air dried, green etc. 

Kiln dried wood is not 'more dimensionally stable' than air dried or green wood.

The suggestion (forgot the poster) to use quartersawn lumber is probably your best bet if you are worried about minimizing the movement of the lumber.

As for the species, we've got buildings with exposed DF in the northwest that have held up for over twenty years. Of course that is usually with old growth heartwood, I have no idea how resilient today's DF is.

But then I've read that today's cedar and redwood lumber are mostly sapwood as well so who knows how much better they really are.


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## KennMacMoragh (Sep 16, 2008)

I think it will make a difference, this article explains it pretty good http://www.globalwood.org/tech/tech_moisture.htm. Saying that the wood will absorb moisture anyway isn't really correct. Wood outside stabilizes at around 12% to 18%, the non-dry, or green lumber will be in the upper 20%. 

Around here, most everything outside is cedar. It will shrink and twist a lot after it is installed and dries, but that's something we account for in the design. You can minimize checks, splits, and bows by gluing and screwing your joints together, and giving the wood room to shrink. 

In California, I repaired a deck once that had douglas fir for the railing cap. I guess they figure since it doesn't rain much, no need to spend the money on redwood. But it did rot, which is why I was fixing it, so be sure to prime and paint everything good. I'd say if he wants S-Dry then go ahead and give it to him, but compare the prices for him first.


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## custrel (Jun 30, 2009)

KennMacMoragh said:


> I think it will make a difference, this article explains it pretty good http://www.globalwood.org/tech/tech_moisture.htm. Saying that the wood will absorb moisture anyway isn't really correct. Wood outside stabilizes at around 12% to 18%, t


The kiln dried wood WOULD absorb moisture since it would start off with a lower moisture content than the relative humidity outside.

That's why I think it's a waste of money to use kiln dried wood for an outdoor project.

Of course, depending on the part of California he's in, the relative humidity might be lower than 12%.


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## AustinDB (Sep 11, 2006)

I'll try to answer your question-if starting w/ drier lumber and sealing it very well, it should hold up, but the ends may eventually fail and allow the moisture in (metal caps may be used). Your best hedge against twisting will be to methodically pick through the lumber and choose what looks to be the best cuts of wood. 

As for the question of extra cost-I would consider it not to be advantageous but if the customer wants to make that decision, then so be it. In my area, if I'm after a non-stocked piece of lumber I have to order it by the pallet and possibly pay freight....that get's expensive!


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## KennMacMoragh (Sep 16, 2008)

custrel said:


> The kiln dried wood WOULD absorb moisture since it would start off with a lower moisture content than the relative humidity outside.
> 
> That's why I think it's a waste of money to use kiln dried wood for an outdoor project.
> 
> Of course, depending on the part of California he's in, the relative humidity might be lower than 12%.


Can't say I've done this, but if you walked around California with a moisture meter and poked some decks, then went to the lumber yard and poked some S-Dry lumber, I bet it would be pretty close to being the same. Enough to where absorption would be negligible. The article I posted says S-Dry has a moisture content of 19% or less, and moisture content outdoors will stabilize at 12% to 18%. If that's true, there wouldn't be any or very little absorption.


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## AustinDB (Sep 11, 2006)

question: let's say we had some lumber that was perfectly aclimated to the surriounding MC. we then build a trellis and the lumber is subjected to the weather without any sealing. 

Will the lumber remain stable because it was dried stable or will it have the propensity to move according to the grain patterns?


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## pinwheel (Dec 7, 2009)

72chevy4x4 said:


> question: let's say we had some lumber that was perfectly aclimated to the surriounding MC. we then build a trellis and the lumber is subjected to the weather without any sealing.
> 
> Will the lumber remain stable because it was dried stable or will it have the propensity to move according to the grain patterns?


Grain patterns will cause the wood to move. Wood is going to find a moisture balance for the conditions it's in. That's why I suggested quartersawn wood. helps eliminates the unstable flat grain.


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## custrel (Jun 30, 2009)

72chevy4x4 said:


> Will the lumber remain stable because it was dried stable or will it have the propensity to move according to the grain patterns?


Everything I read says the same thing: dimensional stability due to drying method - e.g. Kiln Dried - is a myth.

You can run into problems like case hardening, but it's the grain pattern that affects the lumber the most.

That's why quartersawn is the way to go. (like the poster above me said.)


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## cbfx3 (Aug 25, 2009)

I built a KILLER trellis out of ipe but that may be a bit more money than your client wants to spend.. the one we did was over 80' long and seems like it ended up in the 100k range materials and labor


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## naturalwood (Apr 18, 2009)

ok, first of all I am not trying to sell this wood. But check out thermally modified wood on goggle. it is very stable after that process and works very well for trellis's. but going to be expensive for the lumber. cedar is light so would be easier to build than D Fir. IPE is pretty heavy stuff might be afraid to walk underneath it unless pretty sold framing. Also have to factor in what is going to grow on trellis, one i have at home the branches have done a pretty major renovation job on their own,

Being southern california, don't you have some major requirements for decks as far as fire reg's. They may apply to trellis's also.

lorne


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## jlhaslip (Dec 31, 2009)

Nothing wrong with D Fir for this application. Cover it with a good product like Sikkens, and you will have no trouble with it.

Use it outside around here for everything.


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