Cordwood 2008: Lessons learned, tool reviews, etc.

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mtngun
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Cordwood 2008: Lessons learned, tool reviews, etc.

Postby mtngun » Sun Jul 27, 2008 11:21 pm

Miscellaneous notes on things I have learned and problems encountered.

-- the window frames made from 4" x 16" timbers are working great, as discussed on another thread. Just wish I'd used them from day one.

-- the grooved logs have proven their worth. The 2007 wall, built with grooved logs, has noticeably less air infiltration than the 2006 wall built with smooth logs. Oh, a few logs still shrink enough to require caulking, but they are the exception.

-- since I switched to grooved logs, there have been far more cracks in the mortar, even though the mortar is the same. I suspect that, with the smooth logs, the mortar could shrink (which it does as it dries) and pull away from the log without cracking, whereas the grooved log locks the mortar into place. Something has to give when the mortar shrinks.

The cracks are mostly a cosmetic problem, and probably could be eliminated by adding more sawdust to the mortar, or by using a papercrete mortar. However, those types of mortars are weaker, and more susceptible to water damage, and not recommended for a load bearing wall (if I had to do it over again, I'd use a timber frame and then I could get away with a weaker mortar).

-- speaking of mortar, here is my best recipe to date.

2 - 5 gallon pails special sand

3 - large coffee cans portland

1 - large coffee can type "S" lime

1 1/2 gallons wet sawdust (sawdust is screened with 1/4" hardware cloth). I am still experimenting with the quantity of sawdust. The sawdust acts as a retarder, giving you more time to work the mortar and supposedly reducing cracks.

Tile admix is added to the water -- I don't bother measuring it, just add enough to make the water milky. The admix makes the mortar stickier. It is not absolutely necessary, and it is expensive, but I had a hard time getting the mortar to stick to smooth logs unless I used the admix. Since I switched to grooved logs, the groove helps the mortar stick, so I could probably drop the admix now. If I had to do it over again, I might try concrete fortifier instead of tile admix.

The "special sand" is unwashed river gravel, which has both gravel and sand, not to mention a little dirt. I screen it with 1/4" hardware cloth. Then I add one shovelful of river sand in each pail of "special sand." The result is something that is thicker and stronger than a conventional sand mortar, yet still pliable and smooth like a mortar. I find the shovelful of sand necessary to make it smooth enough. Since your river gravel may be different than mine, my recipe may not work for you, but the point is that the addition of fine (less than 1/4") gravel is a good thing.

-- I use a teaspoon to smooth the mortar joints. Besides looking nice, it is easier to put a small bead of caulk on a smooth surface than on a rough surface. That comes in handy if a log shrinks enough to require caulking.

-- Here is my take on the three species of trees that I have to choose from.

Grand Fir (or White Fir, nearly impossible to tell them apart) is a "junk" tree, often left behind by loggers, so it is the easiest to obtain in my neighborhood. However, it shrinks a lot and checks like crazy. Not just big checks, but lots of little checks that are not practical to chink or caulk. It seldom splits well because it usually has a twisted grain and lots of knots. I used a lot of Grand Fir in the beginning, only because I didn't know any better.

Douglas Fir (the locals call it red fir, but the correct name is Douglas Fir). Splits easily, so I split it when the grain is straight. It does check, but not nearly as bad as Grand Fir. It is strongest of my three local species, so it gets the nod for window frames. It is the best firewood, too. Since the loggers and firewood cutters prefer Douglas Fir, I have a hard time finding dead Douglas Fir on public land, otherwise I would use more of it.

Ponderosa Pine (sometimes called Yellow Pine or Bull Pine) takes forever to dry out. It seems to soak up water like a sponge plus the thick bark tends to retain water. However, once it is dry, it is very stable, and doesn't shrink or check as much as the other local species. For this reason, Ponderosa has become my #1 choice for cordwooding. It typically has knots and a twisted grain, so I rarely split it.

Cedar. Cordwood experts often recommend cedar. It splits easily and it is naturally resistant to decay. Great, but cedar doesn't grow here.

-- Splitting. It is desirable to split cordwood, and especially to split it along the checks, to get rid of the checks. However, if you split a log that has a twisted grain, you end up with a crooked piece that doesn't fit in the wall nicely So I only split the straight grained logs.

-- Seasoning. I try to harvest dead logs that are already dry, but not so dead that they are rotten. Easier said than done. Even if the log is dry, I prefer to stack it and let it dry for another year. That's easier said than done, too.

-- DeBarking. Cordwood has to be debarked. If you are talking green logs, sometimes it is easy to peel the bark off green logs, especially during the rainy season when the bark is soaked with water. However, laws and deadlines limit me to dead trees, and the bark just doesn't "peel" off dead trees. I use a hatchet to debark after the logs have been cut to length. Debarking with a hatchet is slow and tiring. If I had to do it over again, I'd buy a Log Wizard, a debarking tool that attaches to a chain saw, and use the Wizard to debark the log before cutting to length. You are talking $300 - $400 bucks for the Wizard and a dedicated chainsaw, but it would be worth it in time saved.

-- Chainsaws. I started out with a reconditioned 16" Homelite that cost about $75, then later added a reconditioned 20" Poulan that cost about $125. The Homelite has required a few repairs, but it still runs great and the little saw is handy for cutting firewood and small logs. The Poulan has been used very hard, not just for cutting but also for milling, which it isn't meant to do. The Poulan ran fine for about the first year but it is starting to fall apart and lots of things are breaking. I can't complain, considering how little I paid and how much work it has done, but I would not buy another Poulan. If I had to do it over again, I'd spend the bucks for a "professional" quality saw, in the 60 - 70 cc range, with a 24" bar. The cheap saws are fine for occasional use, but if you are going to build a house with a chainsaw, you need a good saw.

-- Chainsaw sharpener. One of the best things I did was buy a cheap ($35) chinese electric chainsaw sharpener. It is just a flimsy plastic thing, that looks like a toy, but it actually works, and keeps the chain cutting like new.

-- Chainsaw mill. I did all the milling freehand. It works, but the rough logs required a lot of planing to smooth out. Just recently I acquired a $16 milling attachment, the kind that uses a 2 x 4 for a guide. I haven't used it yet, but suspect it can't help but be better than freehand. I'd love to have an "Alaskan" mill or something similar, but you are talking big bucks for that kind of setup.

-- Table saw. Yes, a table saw gets used a lot even for a cordwood house. Years ago I bought a Ryobi BT3000 for doing weekend projects. It is a great saw for the weekend hobbyist, but a little flimsy for heavy use. The fence is easily knocked out of whack, and the motor appears to be a proprietary design (meaning you won't be able to find a cheap generic replacement motor on ebay). The Ryobi is still running, surprisingly, but if I had to do it over again, I'd get a professional quality table saw, something solid, that uses a generic motor.

-- Cordless Drill. I'm still using the 18V Dewalt that I bought over 10 years ago. I literally use it every day, either in the shop or working on the house. The original batteries had to be replaced (Dewalt batteries are overpriced, but you can get generic substitutes on ebay), but otherwise the Dewalt is still going strong.

-- Circular Saw. I started out with a Dewalt but fried the motor. The Dewalt was replaced with Home Depot's cheapest Ryobi, about $20, and it actually works just fine. Eventually you will burn the motor out of any circular saw no matter how much you paid for it, so no point paying too much.

-- Concrete/Mortar mixer. A Horror Fright mixer, on sale, for not a lot of money, and it is still going strong. For mixing mortar, I removed the paddles, because they were constantly getting clogged up with mortar. Mortar is sticky enough that it does not need the paddles to spin it around. This mixer is designed for concrete, not mortar (a true mortar mixer has agitators), so it does take a long time to mix mortar, and you have to add the water very slowly, but it works if you accept that limitation.

-- Sawdust. In 2006, I got lucky and found a small mom and pop sawmill that let me have sawdust for free. In 2007, I got even luckier when my neighbor rented a portable bandmill to saw his timber into lumber. The bandmill produced a fine grained (1/8" or finer) dust that was ideal for cordwooding. In 2008, I have not been so lucky. I make a lot of sawdust while chainsawing and planing, but it is coarse and has to be screened with 1/4" hardware cloth, which is a lot of extra work. The finer sawdust is more desirable for insulation because it is freeflowing, so it is easier to get into the nooks and crannies. The fine dust is also more desirable for mortar because it is smoother.

-- Log protrusion. I like the cordwood to stand proud of the mortar. Standing proud gives it more texture and character, plus it makes it easy to caulk the log/mortar joint should the need arise. The downside is that standing proud catches rain and snow (and dust, on the inside). I started out with the logs protructing about 1/2" - 3/4", but have since switched to 1/8" - 1/4". The smaller protusion still serves to create texture and provide a ledge for caulking.

I'll try to post a few pictures as time allows.

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Re: Cordwood 2008: Lessons learned, tool reviews, etc.

Postby mtngun » Mon Aug 04, 2008 7:04 pm

Here is what it looked like today. Progress is slow, but at least there is progress.

I am experimenting with the amount of sawdust in the mortar, to reduce the cracking. I tried no sawdust -- it still cracked, and the batch set up quite a bit faster, which is not good when you are working alone. So now I am trying double the normal sawdust. It'll be a few days before the results are in.
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Re: Cordwood 2008: Lessons learned, tool reviews, etc.

Postby mtngun » Sun Aug 10, 2008 5:13 pm

Another day of cordwooding ....
Image

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Re: Cordwood 2008: Lessons learned, tool reviews, etc.

Postby mtngun » Tue Sep 09, 2008 10:55 am

Cordwood done. Hooray !!!!

Image

To follow up on the cracks in the mortar. Changing the amount of sawdust in the mix had no effect on the cracks, nor did changing the amount of lime. The cracks seem unavoidable when grooved logs are used.


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