Why not Eastern Hemlock Tim?

[jtilsond]

I suspect you might say that hemlock has a lower resistance to rot or insect, but isn't that compensated for my extra roof overhang and modern chemical treatments?

Is there someother problem?

I know of a cabin not far from here that was built with black pine more than 150 years ago. It was chinked with mud with the bark still on the logs. It still stands probably due to proper foundation and roof overhang. It is now being used as a commercial store building and looks original. Its on Route 52 going toward Roaring Gap,NC. Black pine will rot in about 4 years exposed to the elements.

I'm curious.
John

[blue eyed devil]

It's subject to "wind shake" more than any other species I know of.Allan Mackie used it for a guest house he called "knottingham" in his OWNER BUILDER book.He said it was a good choice for workabilty and definetly better than western hemlock.BUT.....The logs he was using had alot of taper and full of knots.
Ive used it as lumber and found it bad, for splinters.

[Tim Bullock]

jtilsond, Eastern Hemlock actually is better for rot resistance than pine.........Shake is the problem...........especially in the larger trees..........There are some very rare stands that escape this phenomenea (sp)..........

[Patrick Jenkins]

OK Tim what is " Shake". I know what a Cedar shake is, Milk shake, Hand shake, and Dang it's cold kind of shake is. All I can see in my mind is a bunch of trees dancing, except for the rare stands. They are just tapping their roots. :rolleyes:

[Darin Alexander]

Wind shake is a separation of the growth rings caused by exessive wind.

Darin

[Tim Bullock]

Exactly.....not a desirable trait for building logs..........Anyone really interested could do a search and find out...........

[jtilsond]

I did know about the windshake problem but I was under the assumption that that would only affect sawn lumber. If the trunk is left intact I assumed that to would only be subject to normal checking.

It would certainly be good to see on of the highlandslogstructures.com buildings if the have one that is about five years old. I know they have been around for about that long.

[MikeS]

Eastern hemlock is also a very poor choice for load bearing members, like loft joists, purlins, rafters, or truss members. It does work fine for posts. Not sure how well it stands up against loading at load bearing notches, parallel to the grain.

In college, as a forestry student, I did a lot of research on eastern hemlock for a silviculture class, although that was MANY years ago. Still remember a few things from then.

[Darin Alexander]

I think we may need a correction here. I recently came across a discussion on "shake" and according to Dr. Gene Wengert "shake" is caused by a bacterial action. Another example that old myths die hard? This is the first place I have ever heard of this.

To see this discussion.
http://www.woodweb.com/forum_fdse_files/sawdry/250200.html

To see Dr. Gene's credentials.
http://www.woodweb.com/gene_wengert

Darin

[Ed Miller]

Shake can be triggered by many movements of a 'green' tree. Besides wind, there is a remarkably high rate of felling shake damage. This may be restricted to a small area in a timber when the tree being felled impacts an large object such as another downed tree, bending from branches contacting the ground followed by heavier mass, or in a larger area from a broad 'smacking' impact.

In freshly felled trees and sawn timber/lumber, detection is practically impossible. And yes, working with dried E. Hemlock WILL earn you your splinters! The long separations will also produce knife-like edges.

Last Saturday (8/9/03) I traveled to the Bat Cave area of NC to dovetail some 8X10 milled sticks of E. Hemlock. Didn't know I was going until 5:00PM Friday so my prep was hurried. Was told that 16 more notches (the owner still had some extras from earlier) would be needed to complete a sun room addition. I had notched this owner-built structure back in 2000. At that time, the logs had been freshly milled locally from timber that was cut at the site. The word HEAVY comes to mind! Weather forcast was for rain in the afternoon and early next week. Piece of cake!

With dovetailing jigs set up to the original documented settings, a cut-off jig for end trimming, chain saw-bars and chains and some extra coffee, I'll be making chips near first light. Filed a trip report with others stating I'd be back at noon.

Well, the 16 notch count grew to 40, the temp in the shade went to 95 F, the wood over the course of three years went from manageable to rock hard so I used up the extra chains! But the worst thing was that I ran out of coffee!!!!!! I got home at 11:00PM that night driving thru pockets of rain.

Dried Eastern Hemlock is very hard!!!!!! Also on both occasions of working on this project, I discovered that carpenter ants love this species (at least in the state of being green and in moist storage conditions). But I will say that I didn't detect much twisting and witnessed some of the tightest lateral wood-to-wood joinery I'd ever seen; It stayed where it was put. Also, be cautious of upward sloping shake/checks/cracks that can direct water into the wood.

The house had lots of 12"-14" dia carefully peeled whole log Hemlock posts inside and out (porch). It also had over a dozen rooms EACH WITH A DIFFERENT T&G HARDWOOD PANELING THAT WAS HARVESTED FROM THE SITE. The owner walked me thru his 'wood sample' home while conducted a test; I didn't fare well. I did suggest however that he cut a square piece of each species and within the square, cut out a uniquely shaped jigsaw piece. Mount the squares conveniently on their respective walls and give the puzzle pieces to visitors so they could conduct their own tour and test!

Please don't invite me to your site to cut Hemlock!

Ed

[dr.]

I ran across a board again this week and remembered this thread. This is black locust with shake. Judging from the off smell and black funk in the ring separation I'm guessing its bacterial.

My understanding is bacterial shake is soil borne, slow moving, and nearly guaranteed in stands that have done a time with livestock. Hoof damage to surface roots is a common place of entry. I don't think I would use shake even in a whole round, but sometimes you can cut above it. Sometimes the shake goes too far.

[blue eyed devil]

MikeS reply got me wondering what specie I should use for my roof structure.
Mike says eastern hemlock is a poor choice for load bearing members yet if you look at a beam strength chart.....it's given the same values as alot of other softwoods including.......
Almost all spruce species except Sitka.
Some Pines including...Lodgepole,eastern white
Alpine fir,Balsam fir
Tamarack
Bending-horizontal shear is 1222 PSI Wet -1438 PSI dry for all these species.
Norway pine is a bit stronger BTW.
I'm planning to use lodgepole for my roof .If I need a bigger diameter log in a certain location I can source some huge spruce.

[blue eyed devil]

Quote from Moose Mountain's website:

"We build with lodgepole pine or Western Red Cedar for our log walls,White spruce for our Roof System and Structural Beams and Douglas Fir for our Stair Treads."
My question:
Is White spruce logs actually stronger than lodgepole?

[Sirscribesalot]

eastern hemlock 4 years old

[Patrick Jenkins]

Sirsribesalot,
I love your place. If you built it you did a nice looking job. The decor is right up my alley.

[mfritch]

This is an interesting conversation. I think there is a little of all the conversations that apply. Like Mike Senty, I studied forestry years ago. I remember the conversations about shake, but not the one about the bacterial source. I think dr. is probably accurate that the bacteria weakens the wood and allows for shake. A good way to see how shake really happens is to take a deck of cards, pinch both ends of the deck really hard and try to bend the deck. It is very difficult to do, but if you pinch only one end har and allow the other end to flex, you will see that the cards are all the same length when straight, but as soon as you start to bend the deck the outer cards appear to receed relative the the cards on the inside of the curve. This happens because there is 'slippage' between the cards. This is exactly the same thing that happens in trees. Depending on the strength of the bond between the growth rings the tree will show evidence of shake. It is species dependant for sure because Western Hemlock is noted for it. It doesn't surprise me that the same might be true with the eastern variety also. The bacterial thing fits right in too with it happening close to the ground. Shake is also more common in larger diameter and old-growth trees because it's kind of like having a thicker deck of cards. Also, wind shake that typically occurs higher up the stem just below the crown of the tree when caused by wind. I'll bet that the bacterial kind shows up in the butt cuts more commonly.

[Susan]

Sirscibesalot,
That looks like Highland Log Structures work. I haven't had a chance to get down to Abingdon to see their work in person, but I have to say that they were super-nice on the phone! If they built your home, could you give me your impression of them? (private e-mail if you think that's better) I'd appreciate any input you might have, since they are on my list of possibles.

[Tim Bullock]

Susan, It likely is Winstons work.......FWIW, It takes just as long to scribe/cut a pine log as it does a Hemlock......Why save a few $$$$$$ and take a chance.......LOL. I know Winston quite well and I am not talking behind his back................

[Susan]

Tim,
FWIW, I'll be choosing EWP-not because of $$ OR shake OR whatever. Just because I like the way white pine looks. I wouldn't choose a producer unless they would use EWP. From what I understand, Highlands will do either species.

[Tim Bullock]

Susan, Highlands does do an adequate job of crafting log homes and their heart is certainly in it!!!! I charge a wee bit more simply because I do know a wee bit more.........<wink>

[Ed Miller]

Or in other words, the 'arrogant factor'!

Ed

[Ed Miller]

Wait a minute; I think I just experienced some wind shake!

[dr.]

I was wondering about the original question here. I live just over the mountain, the Wooley Adelgid is starting to show up here. So far I've heard about and noticed it in specimen plantings...one a giant 5 stemmed, any one of which was a tree, mature trees. We've had several years of drought stress, before this year. There will be a large number of trees "available" here shortly I suspect. Shake can usually be seen, so can be culled out of a purchase, these trees will succumb to another pest and might be fine :confused: . A local logger built his home from hemlock that he selected, several years ago, it looks nice.

Mark's card deck analogy is one I use substituting a magazine, but for another phenomenon...horizontal shear, a design property. One of the things you check when sizing a beam is that it won't fail in horizontal shear when loaded. I like the card idea here. Hold the deck between thumb and forefinger, push down in the center of the deck with the forefinger of the other hand. The stress (the finger) causes the fibers (the individual cards)of the beam (the deck) to delaminate and slide past one another...not what you want in a beam. The beam is sized to safely stay within established design values that the species can withstand. I think tabular design value for hemlock is around 70 psi in horizontal shear.

Another hemlock around these parts is a Carolina Hemlock. The Eastern's cone dries still upright petalled, somewhat closed, the Carolina throws its cone wide open and lays its petals way back.

[mfritch]

There are two types of beam failures. Dr., the failure that you mentioned is actually a mid span bending failure. A shear failure is one that happens at the end of the beam where the beam breaks across the grain due to lack of sufficient sectional area. You have to deal with calculations on both types of failure. Typically, if you get the correct sizing for handling the bending load and you don't overcut the end of the joist during joinery, you will also have a log that is big enough to handle the shear.

[dr.]

Mark,
The magnitude of vertical and horizontal shear are the same. To quote Parker/Ambrose "The vertical shear strength of wood is seldom of concern because the shear resistance of wood across the grain is much larger than it is parallel to the grain, where the horizontal shear forces develop. Try splitting the next load of firewood crossways, it'll become clear in a hurry :D .
Yup, vertical shear needs checking too in necked down joinery or in very short, heavily loaded beams.

Now at the risk of misinterpreting what you described, I would call that extreme fiberstress in bending, or bending failure...
since we're dealing with another phenomenon, eliminate horizontal shear, glue the cards together, hold the deck as before, stress as before. The extreme (bottom most) card will be torn apart first when the tensile load exceeds its strength.
Fb (fiberstress in bending) for #2 Eastern Hemlock is 1750 psi, western #2 850. And yes, usually a beam that passes in bending is usually of sufficient size for shear...vertical or horizontal ;)

I misspoke earlier, shear for eastern hemlock is 65 psi, western 75

[Ed Miller]

Ponder orienting the the 'most likely to delaminate deck layer' vertically if possible!

Other approaches to minimizing load-induced end shear might include housed notching (mearly to captivate the end profile of the whole beam in a shallow mortice), circumferential strapping, pinning or bolting, a knee brace triangle basically fastened only to the beam (to allow for settling movement in a wall pocket, but my choice would be a short decorative shoulder secured to the underside of the beam and included into an appropriate tight fitting wall mortise.

In the latter concept, the grain of the shoulder piece would likely be horizontally oriented to mimic wall log shrinkage. Of course, you could even use this mearly as a beam lamination and let it float against to outside of a flattened wall area. This could even be attached after construction with bolting. Real tacky if it looks like a repair!

If a check from whatever cause is simply not a structural problem, but happens to look like hell; Jack or clamp the pieces together (if they'll move) and mortice a dovetail 'bowtie' shape that straddles the check and install a wooden (or metal?) same-shape piece. Walla, in harmony with nature! At least it says, "Yes, I know it's there".

I forgot to mention earlier in this thread that there is no doubt in my mind that 'something', perhaps chemically related, is contributing to the weak growth ring bond of this (these) species. I was trying however to point out that physical trama to the 'card deck' can be visually recognized.

Something that does have me bothered is the alarming number of milled lineal footage packages sold as White Pine containing as much as 20% E. Hemlock! Freshly milled logs/beams of Hemlock will darken to a redish-brown in very quick fashion; Even noticable at the end of the first day. White Pine will eventually tone to a like darkness, but not until a month or two later. In a milled log wall featuring both species that has been erected quickly, you can practically detect the Hemlock logs in a drive-by! I'm not saying Hemlock is bad, but I am saying I don't like the 'mix'. I especially don't like to hear about the builder/home owner who bought E. White Pine and got this mix.

Ed

[Tim Bullock]

Further to this discussion would be cost........Hemlock is waaaaaaaaay cheaper here.......and from time to time there is some shakefree material but seldom. Not sure what happens over time with Hemlock in a full scribe with lots of shake...Might be interesting to see.........

[mfritch]

Significantly lower cost in any industry or product generally reflects lower value. The market has put the Hemlock there for a reason.