Why are the benefits of hewing the sides of logs?

[James Klash]

How come some log building styles have two hewn sides and others are completely round?

[Dana]

While I'm no expert I will jump in with my opinion   logs were originally squared to remove the sap wood which will rot quicker than heartwood. They were also squared so that siding could be installed over the exterior of the logs.

[D L Bahler]

Some also have 4 hewn sides, with courses tightly joined and fitted vertically.

The advantage of hewing is that you get a more refined surface -a step away from the primitive toward a more refined and 'modern' type of dwelling. With squared surfaces your walls are more useful on the inside, and to some look nicer on the outside. Also, a flat wall sheds water more efficiently than a series of arcs would.

I don't entirely believe the theory that squaring logs is done to remove sapwood and thus make logs more durable. Largely because this is a horribly inefficient way to remove sapwood, and often time square logs still retain a great deal of sapwood on exposed faces. I think it has more to do with the interplay of West and North Germanic building traditions with each other and with native Alpine traditions -West Germanic peoples (Low Countries, English, French, Swiss, South and Central Germans and half of the Austrians) invented timber framing as we know it in the European tradition, North Germanic and Alpine people were log builders -both originally with round logs. There is some evidence that the use of square timbers in log building arose out of a West Germanic influence -timber framers first squared logs in order to make their joinery better and allow for more complicated assemblies that weren't limited to the sizes of available logs. This practice was passed to log builders, who sought to, to some degree, replicate the refinement of the timber frame in their log houses.

Really, hewing in the context of log building is a step away from the natural form toward the more 'civilized' form, and in all likelihood that is the biggest reason for it.

Squaring your timbers also allows you to work in terms of systems and processes, by dimensioning the logs, you take away their uniqueness. This cuts down on the work of scribing and fitting. In the end, it is faster when building a large structure to square and fit logs with simple processes than it is to leave them round and carefully scribe them to each other.

For example, with square timbers I can cut my joints according to a certain size, using beveled entries to account for variations in thickness. The joints will be measured for height, meaning they still only fit in 1 place since the hewn logs vary in height, but since width is a constant (because the 45 degree angles allow for this) cutting this joint is a simple, repeatable process. I don't have to place the timber on the joint and scribe the two to each other, then move and cut. There is less moving of heavy timber.

In the Alpine tradition, we use what I will call a 'log rule' where the squared timbers that will make up a sinlge wall are all laid out on the ground, and all joints and opening marked on all at once. This is not possible of the logs are round, because they will not fit togetther the same once fitted. Round logs must be laid out and cut one at a time, square logs can be laid out all together.

[James Klash]

Thanks for the detailed answer!

[TW]

I work in the Scandinavian tradition with logs hewn on two sides and scribe fitted to each other top and bottom. The long groove protects the caulking better and makes the wall stiffer than the flat mating surfaces of the Alpine square log buildings. In the dry montain air of the Alps this would not matter but in our moist and windy costal climate it is an advantage to have the caulking well protected.

My oppinion is that hewn logs seem to last longer than round logs. They have fewer downward pointing cracks on the outside as most cracks will end up horizontal right in the middle of the flat face. Therefore there will be fewer water pockets which in time tend to become rot pockets. Hay barns and wood sheds and boat sheds and other simple building were often built from round logs but they do not seem to last as long as the hewn walls of better built buildings.

[mesquite buckeye]

You also end up with a lot of nice stove wood for cooking. I think we forget how much trees were the energy source as well as a building material. ;D 8) 8) 8)

[D L Bahler]

Thanks for the input TW, good stuff

I find that the mating surface of the Alpine style logs varies a lot. The oldest style is actually quite similar to the Scandinavian methods, using round logs with coped joints. But this changed over time in different ways depending on region.

I know some use caulking -moss or oakum in the old days- but in the Berner Oberland -the western range of Alpine Log- no caulking is used. Some very very old buildings may have just a flat mating surface, but most use a spline or tongue, or 2 or 3, along this joint to stop the moisture and air.

I do think hewn logs must be more durable. There are in the Alps some old round log structures dating back as far as maybe the 18th or early 19th c. There are squared log structures dating back to the 15oo's, and in one case I say a hewn log house built in the 1360's

As for the dry mountain air -well that depends on where you are. The 'Alps' which are high mountain pastures can be very dry, most of the water is snow runoff from up above. Down in the valleys, it can get very wet, especially around the lakes. Also don't forget that up high in the mountains, a cloud can get stuck above you and bring constant rain for weeks at a time.

The Alpine builders definitely built with moisture in mind, there chief solution was to give enormous roof overhangs -think like 8 feet. Also when they switched to square logs, they developed a system of ledges and profiling (no, the fancy profiling on Oberland houses is not only for looks) that encourage water to run off of the wood, rather than wick into the joints.

Their biggest insurance against water was to make the joints so perfectly fit as to be almost invisible. Sometimes it's actually quite hard to find the joints and old sun-darkened houses, what you think is the joint is actually splits

[D L Bahler]

I take that back about round logs, I have seen round logs as portions of houses dating back at least as far as the early 1600s, but they are almost always in poorer shape than the squared timbers on the same buildings (barn portion might be built of round or partially hewn logs, while the house part is built of well fitted timber)

[mesquite buckeye]

When you going to get your history of European timber framing book done? ;D ;D ;D 8) 8) 8) 8) 8) 8)

[James Klash]

it just seems that there must be a good reason, because there is a fair bit more labour if you hew all of your logs than just leave them round

[scouter Joe]

 A lot of it is aethitics or personal taste . A lot of the ladies think the flat surface is better for cleaning or hanging pictures . The checks are more centered and flat as has already been posted . An other reason is it is tipically used with dovetail buildings thereby removing the sapwood from the notch which leads to less shrinkage of the walls . Both styles ,round or flat will stand up very well if a proper roof design is used with enough overhang . scouter Joe