Treehouses for grownups

November 22, 2009 7:56 PM

Whole Tree Architecture - if you'd like a house built by pioneering architect Roald Gundersen, your first step might be to hike in your nearby woods to choose some young, wind-bent, and diseased "Charlie Brown" trees. Small diameter round trees have 150% the strength of milled lumber and twice the strength of steel in tension. Besides structural and environmental advantages, whole trees make for some beautiful and naturally sculptured environments.

From the NY Times article:
"And when the trees are left whole, they sequester carbon. “For every ton of wood, a ton and a half of carbon dioxide is locked up,” he said, whereas producing a ton of steel releases two to five tons of carbon. So the more whole wood is used in place of steel, the less carbon is pumped into the air.

These passive solar structures also need very little or no supplemental heat.

Tom Spaulding, the executive director of Angelic Organics Learning Center, near Rockford, Ill., northwest of Chicago, knows about this because he commissioned Mr. Gundersen to build a 1,600-square-foot training center in 2003. He said: “In the middle of winter, on a 20-below day, we’re in shorts, with the windows and doors open. And we don’t burn a bit of petroleum."

posted by madamjujujive (35 comments total)

Very cool and attractive.

Beats the Hell out of the concrete box we live in at the moment.
posted by bwg at 8:02 PM on November 22, 2009

Nice post, as always, madamjjj.

"Take one baby, a toddler and a building site. Mix well with a generous helping of mud, combine with 6 weeks of solid welsh rain whilst living under canvas. Do this in candle light without a bathroom or electricity for three months. Chuck in living with your father for good measure. Top with an assortment of large slugs. The result a hand crafted home of beauty, warmth and health for about £3,000."

A Low Impact Woodland Home
posted by netbros at 8:28 PM on November 22, 2009 [3 favorites]

I love this. I did not notice it in (blush) skimming the article, but don't these trees have to be like kiln-dried or something to make them construction-ready?

I mean, I'd love to haul some trees from the woods and start using them, but isn't there a lot more to the process than just slapping some clear lacquer on top?
posted by rokusan at 8:28 PM on November 22, 2009

I would like to live in Rivendell please
posted by The Whelk at 8:40 PM on November 22, 2009 [5 favorites]

rokusan, Gundersen's site says:

So, instead of clear-cutting we pick and choose. When the tree has been chosen we peel the bark from it while it stands in the forest (allowing the waste products to go back to the forest floor. Then we leave the tree to cure standing for several months, during which time it will loose up to 50 percent of its weight in water, making it easier and safer for us to move it out of the forest when we are ready.

Not sure if there is anything else they do to preserve the trees, tho. In the Natural Homes article he says this:

"It’s sort of a ‘slow food’ process," Gundersen says. "But you’re not just building a house, you’re building a local economy. On a conventional house, about 50 percent of costs typically go to labor. On this house, the ratio was closer to 75 percent labor with 25 percent material costs. That’s an important aspect of natural building—it can be locally sourced from within the community."

His site also says they will be scheduling workshops for the spring.
posted by madamjujujive at 8:47 PM on November 22, 2009

Thanks MJJ, I missed that. I was scanning looking for mention of some sort of drying kiln. I didn't think that just leaving it to stand would be enough, considering how regular lumber is dried and treated for construction.
posted by rokusan at 9:07 PM on November 22, 2009

For every ton of wood, a ton and a half of carbon dioxide is locked up

Yeah, but that ton of wood has to be traveling at a significant fraction of c.
posted by b1tr0t at 9:18 PM on November 22, 2009 [2 favorites]

no, that still doesn't make any sense (unless you burned half a ton of CO2 to accelerate the tree).

Cool architecture, suspicious physics.
posted by b1tr0t at 9:21 PM on November 22, 2009 [1 favorite]

Rokusan, they did kiln-dry the lumber that was used for the cabinets, trim work and dimensional framing lumber.

I imagine the whole trees that were used would have been fine as well. Since they are letting them dry standing and whole, they don't have to worry as much about splitting or checking. The logs will continue to dry once they are installed, but they likely don't have far to go to reach equilibrium.
posted by davey_darling at 9:34 PM on November 22, 2009

Thank you madame JJJ.

In my mind I have been slowly building a picture of the house I want to live in someday; this looks like something I would like to add. Not a huge fan of some of the straw-bale houses I've seen, but this has beauty and personality and out here in Texas, we have scrub trees a plenty that might work for this. Certainly more appealing than clear cutting them all out and importing a lot of chemical treated pine to build with.
posted by emjaybee at 10:06 PM on November 22, 2009

Don't know if I missed this looking through the links, but, what's the cost for this sort of thing? It looks and sounds super cool, but it seems like it would only be within the reach of the rather rich.
posted by Saxon Kane at 10:26 PM on November 22, 2009

With regards to 1lb of tree = 1.5lb. CO2, consider that one "unit" of carbohydrate (CH2O) weighs about 30AMU, while the CO2 produced by burning that unit of carbohydrate weighs about 44AMU. So, yes, one pound of carbohydrate burns to make about 1.5 lb of Carbon Dioxide. The extra half pound comes from atmospheric oxygen.
posted by agentofselection at 10:34 PM on November 22, 2009

Oh, duh, and trees are made of cellulose, not carbohydrate, for which the CO2 : fixed carbon ratio is even higher.
posted by agentofselection at 10:36 PM on November 22, 2009

Assuming a tree is made entirely of cellulose (C₆O₅H₁₀), it is approximately 44.4% carbon by mass. CO₂, however, is only 27.3% carbon, so growing a ton of wood (created largely from CO₂ and H₂O) would lock away the carbon from 1.63 tons of carbon dioxide. Assume some losses from other elements making up the wood, and 1 ton of wood to -> 1.5 tons of CO₂ is a reasonable number.
posted by JiBB at 10:51 PM on November 22, 2009

Or, what agentofselection said.
posted by JiBB at 10:52 PM on November 22, 2009

Small diameter round trees have 150% the strength of milled lumber and twice the strength of steel in tension.

Anyone who knows about such things care to comment on this? I didn't see the source for it in the articles, and my googling doesn't show up any tensile strength claims for wood above around 160MPa, while typical structural steel is 250MPa with other steels having much, much higher values (1000MPa+).

(Which of course takes nothing away from the post, just curious).
posted by markr at 11:08 PM on November 22, 2009

Yeah, expect the general public to understand stoichiometry.

A tree sequesters no CO2. It does sequester carbon.
posted by b1tr0t at 11:10 PM on November 22, 2009

In the article it says "a whole, unmilled tree can support 50 percent more weight than the largest piece of lumber milled from the same tree." This seems to have been misquoted as "Small diameter round trees have 150% the weight of milled lumber."
posted by Patapsco Mike at 4:46 AM on November 23, 2009

It's not the size of the tree, it's how it grows. Seriously, a tree grown in the shade of old growth trees can be small and yet very old. This tree will be super dense. When there is a break in the canopy, this tree will shoot up using its super dense core for the strength to become a massive tree itself.
posted by Pollomacho at 4:58 AM on November 23, 2009

Patapsco Mike, the opening flash presentation on Gunderson's site says "Whole trees are 150% the strength of milled lumber." That being said, I can't defend the math or the physics of any of these claims.

emjaybee, re cost: this 3 bedroom 2,160 sq.ft. home in Wisconsin was built for $200,000 or about $100 per square foot for finished space, which the article says is well below the national average for a custom home (article was written in 2007).
posted by madamjujujive at 5:02 AM on November 23, 2009 [1 favorite]

If you're making a ladder, for example, you want to start with the straightest grain lumber you can fine and you want to prepare the billets you're going to make your rungs out of by splitting rather than sawing. What you're trying to avoid is grain running like this:////// so that it can't split along a growth ring and drop you on the ground. You do the same thing if you're making a bow.

I suspect some of the strength over the milled lumber comes from this.

The big issues with normal wood that causes us to kiln dry it are warping and checking, but if you're using the whole log, you're going to get a lot less of the former as the tensions will tend to balance and the checking won't matter as much.
posted by Kid Charlemagne at 5:08 AM on November 23, 2009

Beautiful stuff - thanks for posting this.
posted by jquinby at 6:31 AM on November 23, 2009

Small diameter round trees have 150% the strength of milled lumber and twice the strength of steel in tension.

Anyone who knows about such things care to comment on this? I didn't see the source for it in the articles, and my googling doesn't show up any tensile strength claims for wood above around 160MPa, while typical structural steel is 250MPa with other steels having much, much higher values (1000MPa+).

You didn't ask about this, but the first part is why small round trees are stronger than milled lumber. It has nothing to do with the smallness or even the roundness per se. It's the fact that a tree grows pre-stressed (as in "pre-stressed concrete").

When the wind blows, one side of the tree is compressed while the opposite side is put into tension. Trees are fine with tension, but wood doesn't take compression very well. So if you put the outer layers of the tree in tension to begin with, then when you compress one side it's just lower tension, not actual compression, if you see what I mean.

When you turn a tree into lumber, you negate all the pre-stress strength because you are either cutting it off or using it in a geometry where it isn't useful. Apparently olden times ship masts used to use a whole tree with as little as possible done to it so as to utilize the original strength undiminished.

As for the strength comparison with steel: They probably aren't talking about the raw tensile breaking strength numbers. There are many everyday terms and concepts that are used technically, even counter-intuitively, in materials science. It's possible they meant to use "toughness" or some other measure, none of which correlates particularly well with "tensile strength". The toughness of biological materials in comparison with man-made ones is legendary. Toughness is more a measure of how hard it is to propagate a crack through a material rather than pull it apart with brute force.

(All of this information is from reading J.E. Gordon's wonderfully informative, readable and amusing books on materials and structures.)
posted by DU at 6:36 AM on November 23, 2009 [1 favorite]

Apparently olden times ship masts used to use a whole tree with as little as possible done to it so as to utilize the original strength undiminished.

Spars, masts, and booms as well as huge timbers were a large part of the colonial American economy. In turn the forests of North America, both the hard wood for timbers and the evergreens for masts, turpentine, and pitch, were a huge contributor to the British naval might.

My father-in-law is an old-timer at the Forest Service. We'll probably be having this conversation on Thursday.
posted by Pollomacho at 6:51 AM on November 23, 2009

I think it would be really fine to build a house like this where you can either walk from room to room normally, or climb the tree branches to reach them. I loved this post - I think living in a house like that would be enormously calming and creative.

Plus, yeah, Rivendell.
posted by Lipstick Thespian at 7:01 AM on November 23, 2009

What the hell IS NOT X number of times stronger than steel?

I'm pretty sure my own nose hair is some number of times stronger than steel.
posted by autodidact at 7:46 AM on November 23, 2009

....So, wait. Does anyone else think this is counter-intuitive, in the sense that if you take the small trees....they won't ever get big? And if they're small....you need more of them, so you're effectively killing ten future trees?

Isn't that like eating a bunch of baby somethings rather than one big grown-up something? Isn't that worse?
posted by EmpressCallipygos at 8:20 AM on November 23, 2009

....So, wait. Does anyone else think this is counter-intuitive, in the sense that if you take the small trees....they won't ever get big? And if they're small....you need more of them, so you're effectively killing ten future trees?

They are selecting out some trees and leaving others to get bigger. Thinning, not clear cutting.
posted by Pollomacho at 8:24 AM on November 23, 2009

Empress: It depends on their age; small trees are small for a reason, either because they're young or because larger trees block their sunlight. Small scrub trees are also excellent wildfire fuel, and even barring any human intervention, might get burned up before they ever grow large.

Plus, replacing a small tree with another small tree takes far less time than replacing a large tree. Which is why losing an old-growth (large) forest is much more distressing and possibly damaging to the local ecosystem than losing a stand of saplings or small trees.

Given that we are going to use some kind of wood for building (because synthetic materials are even more waste-generating), I think the concept here is that small trees are much more renewable than large trees and less energy-wasting than lumber from farmed or harvested trees.
posted by emjaybee at 8:30 AM on November 23, 2009

I would so love to find a builder willing and able to do such gorgeous work. It's hard to find builders who can knowledgeably use Green building methods. For that matter, it can be hard to find a builder who's sober (ask me about my kitchen). Great post, Madame.
posted by theora55 at 8:35 AM on November 23, 2009

East Glacier Lodge, East Glacier, MT

Old Faithful Inn, Yellowstone National Park, WY
posted by Antidisestablishmentarianist at 9:29 AM on November 23, 2009 [1 favorite]

Kiln-drying is done to wood to speed up the drying process (and increase profits for sawmills), not because it is necessary before the wood is used. Wood will dry naturally; it just takes longer. The wood is generally more stable after air-drying than after kiln-drying.

Another reason that whole trees are stronger than dimensional lumber has to do with the grain. The strength of wood comes from it's fibers. Milling a tree into a rectangle and then cutting the rectangle into a curve ignores the grain, and makes the wood prone to split where force is applied perpendicular to the grain. When you choose a tree curved to match the intended use, the grain follows the curve and is much stronger. One reason viking ships were so successful is that the planks were split rather than sawn, so there was no grain runout.

My brother built a house using whole trees as structural (and architectural) elements. It's amazing.
posted by fogovonslack at 10:38 AM on November 23, 2009 [3 favorites]

fogovonslack, your brother is an artist. That house is very beautiful.
posted by theora55 at 10:47 AM on November 23, 2009

fogovonslack, your brother's house is awesome - thanks for sharing. Also love his stone archway, which sure looks mortarless - beautiful work!
posted by madamjujujive at 3:13 PM on November 23, 2009

Small diameter round trees have 150% the strength of milled lumber

My guess would be that this claim is per unit weight. The steel claims are all per unit weight, which I entirely believe. Steel is not that great compared to wood, pound for pound. I did some structural work in my house a couple years ago, and compared the options of using steel support beams and LVLs, which are engineered lumber beams -- basically really high quality thick plywood. The only advantage to steel is that you can use a steel beam that is physically smaller to support the same load as an LVL. But the smaller steel beam will be much heavier than the larger wood beam. In my case, it was worth working around the greater size of the LVL in order to be able to put it in place by hand with a couple of friends.

It also makes some sense to me that a 100 pound whole tree is 150% stronger (at least) than 100 pounds of milled lumber. Milled lumber is cut square, which in deflection, at least, would be weaker than a round tree shape.

The 150% number might also just be compared to what you could mill from that whole tree, in which case the extra strength would come mainly just from keeping (in the whole piece) wood you'd have milled away in the milled piece.
posted by rusty at 3:36 PM on November 23, 2009