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#25303 - 01/24/11 09:37 AM Re: Infill and Half Timbering *
D L Bahler Offline

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Registered: 05/17/10
Posts: 946
Loc: Indiana
Wood will function better than clay in relation to temp and moisture swings, provided you accounted for that in the beginning.

The best thing to do is the allow the planking to do what it wants to. don't force it to do what you want it to, it will win. That's why you put the boards in channels, so they are free to move up and down and side to side if they want. And they do want to. That's also why you use narrow boards. I am thinking 1x4 for anything expected to support plastering, just to resist cracking.

One thing that you can easily do to prevent the ingress of moisture from the inside is to use an old technique, seal the cavity-side face of the inner planking with tar or some other sticky water proofer. But do not DO NOT use a vapor barrier as this will just hold the moisture against the wood, which is BAD.

The inner planking is no different than using boarding on an interior wall. The outer planking is essentially the same as plywood sheathing. The benefits of clay are not to be underestimated either.

The wood species used can just be common pine. Or it could be cedar. I would be afraid of using hardwood in most cases because of cost and stability.

If you are still scared of moisture travel, plaster the inside with clay. That will stop it right then and there.
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#25338 - 01/26/11 04:35 PM Re: Infill and Half Timbering
D L Bahler Offline

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Registered: 05/17/10
Posts: 946
Loc: Indiana
Again on the subject on moisture intrusion from the inside.

There is one technique that is by no means modern and has been used in various countries where a plank infill has been employed to stop drafts and moisture travel. In this case, the thick plank is instead replaced by two thinner planks and in between them a layer of some type of wrapping is placed, traditionally this has been paper or linen soaked in tar or blubber, but today we could use a modern house wrap or plastic for the same purpose. In my dual plank system, the inner 1-1/2 plank could be replaced by 2 3/4 planks with a barrier between them.

In The Swiss Bohlenwand, there are at times 2 layers of planks with the cavity filled with sand. This as a favored construction technique for old prisons as the sand would deaden any sound and also produce a dense, hard to break wall.
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#25627 - 02/23/11 11:22 PM Re: Infill and Half Timbering
D L Bahler Offline

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Registered: 05/17/10
Posts: 946
Loc: Indiana
I have been considering the moisture issue of this system some more, and am concerned. As of right now I intend to use the double plank wall system I have designed for my shop with a natural wood interior and plaster exterior, with exposed frame inside and out.

My biggest concern is that the posts will sweat where the boards are joined into them. This would give great occasion for both the boards and the frame to rot. The greatest concern I have is for interior, rather than exterior, moisture.

The following things I have decided:
1. Abandon the foam skim coat inside the cavity. In this case I think that this would just trap moisture and facilitate rot. The wall should be able to breathe to a certain degree.

2. The clay and plaster on the outside should be more than enough protection for the planks as far as keeping moisture out.

3. Before the outside is plastered, some sort of flexible seal strip should be put into the channel to protect this region should the plaster gap around the posts (which it certainly will) This could be a modern material, or an old-fashioned material like cordage soaked in tar (I doubt I can get whale or seal blubber for the purpose) This idea inspired by old ships, which had the gaps between the wooden planks sealed thusly.

Now what I need to do is figure out how to prevent moisture from condensing around the posts, and how to generally prevent rot in this region and on the wood as a whole.

The best solution I can come up with for the first problem is ventilation. The old Bohlenwand houses in many cases have the original planks that have stood there for in some cases over 400 years, often totally unfinished and unprotected -and generally made out of Swiss Pine, not German oak. The reason I think is that moisture had no real reason to gather there, it had plenty of opportunity to go elsewhere. On the old farmhouses the attics were wide open, because they were used to store the hay. plenty of ventilation there. The moist air could escape between the floorboards and up into the attic.

Now obviously a modern home needs to be a little bit tighter than all this, or at least the average homeowner would want it to be. But with a well and cleverly ventilated house I think the problem could largely be alleviated. But I think that if there was adequate ventilation in key areas such as along the walls, heat loss could be minimized while allowing moisture to escape. A well ventilated attic would be needed for this to work, I doubt an open ceiling with exposed trusses would be very good here.

For the second issue, there are two things I could think of that might help a great deal:
1. The wood on the inside of the cavity is thoroughly sealed with tar.
2. The wood on the inside of the cavity is thoroughly covered with plaster or a lime wash.

The first approach would seal off the wood from moisture, while still allowing it to breath.

The second approach may allow vapor through, but the plaster would make it very difficult for mold or fungus to grow and rot the wood.
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#26211 - 04/15/11 02:54 PM Re: Infill and Half Timbering
Housewright Offline
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Registered: 02/16/06
Posts: 332
Loc: Waldoboro, Maine
D L et al.;

Thanks for the eye candy (photos).

As I understand it bohlenwand translates simply as "plank wall", and the page from the book you posted shows both vertical and horizontal types of plank walls. Does bohlenwand have a specific meaning or is it a general term for different types of plank walls?

The Bohlenwand method of building with a single thickness of horizontal planks is also found in many parts of Europe, mostly Sweden, Jutland and part of Germany. I have an opinion that horizontal plank wall buildings are found in areas where Vikings settled. They are called a bulhus in Danish as one example, and are thought to have been brought to North America by the French known (with many variations) as "Pièce sur pièce". The oldest example I am aware of was found in excavations in Poland dating about 5,000 years ago but these used a V instead of a rectangular groove to capture the plank-ends.

This is an interesting idea to use two horizontal layers infilled with insulating material. Two thoughts I had looking at your drawing are to make the posts thick enough so you could leave small air spaces between the insulating and wall materials in the walls and to be sure the insulating material can be thick enough so condensation could not form inside the wall, but you have already addressed the moisture issues. Another thought for the non-traditional among us is that our forefathers used planks in grooves to avoid the high cost of nails. Now with cheap Chinese nails, the planks or boards could be nailed on rather than being fitted in grooves. Maybe the outside layer could be done using the "rainscreen" concept so the wall was ventilated.

I noticed at the last TTRAG conference that even the most experienced framers are still struggling with how to enclose a frame with our historically "modern" problem of heating, cooling, utilities, etc.

Now to be a smart a--, if you fill the walls with earth and use a sod roof is it an under-ground, timber-frame house?

Jim
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#26212 - 04/15/11 03:46 PM Re: Infill and Half Timbering
D L Bahler Offline

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Registered: 05/17/10
Posts: 946
Loc: Indiana
Jim,

Yes, it does mean 'plank wall'

The Bohlenwand is common in alpine and sub-alpine regions, and takes on a number of forms. The alpine method is generally to have horizontal boards.

From what I know of the Scandinavian practice, I think you are right. There was an old Viking age and early medieval technique that was very similar, only placing the planks vertically. There are many fine examples of this technique that have survived into the present day, the Norwegian Stave Churches. The Urnes Stave Church in particular, since it dates back to about 1050, or the very end of the Viking age. This technique is called Stavverk, or 'stave work'. It has a timber frame with planking caught in grooves cut into the sills, plates, and posts.

This technique is probably how the better houses and farms were built in forested areas populated by Norsemen, with the poorer houses having walls filled with waddle and daub.

----

as for nailing instead of grooves...

I had considered this idea, and came up with only 1 solution that seems suitable, which is the first nail a piece of wood to the posts, and the nail the planks to this piece of wood. I do not think it would work to nail the planks directly to the posts, as they would barely be supported that way.

This solution is not without its problems however. The extra wood takes up insulation space, and creates a few more seams for water to collect and cause damage.

In addition, the groove does more than just hold the planks in place. It also stops drafts, and hides movement. I would suspect that if the planks were nailed to the edges of the posts, expansion and contraction would cause the nails to pull out over time. With the grooves, the wood is all allowed to move up and down and side to side as much as it wants.

For most projects, there is no need for timbers exposed inside and out. The double plank wall is designed for this particular situation. Today in America frames are typically exposed only on the inside, in Europe in the past frames were often exposed only on the outside. It is also common to have frames completely covered inside and out (which is the simplest to enclose)

Personally I think having 8" of timber jutting into your living space is a bit silly. (oops, did I say that out loud?) and I much prefer the look of a barely exposed timber, which is either flush with the inside wall or sticks past at most 1". The bohlenwand is really the ideal method of accomplishing this, the planking could simply be a means of supporting drywall or plaster, or form an attractive wood interior wall.

If you don't want timbers exposed on the outside, then this system lends its self readily to numerous insulating techniques. Just have an inside plank wall, and enclose the outside wall in one of many methods.

and to your last comment, look at Icelandic turf houses, and you tell me!
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#26213 - 04/15/11 03:59 PM Re: Infill and Half Timbering
Housewright Offline
Member

Registered: 02/16/06
Posts: 332
Loc: Waldoboro, Maine
I was taking a look at the Handbuch der Architekture D L provided the address to earlier and thought I would quote the machine translation regarding the infill materials:

"As a filling agent use: hay, straw, woody parts, tan, straw, sawdust, wood wool, wood shavings, peat, soil, sand, ashes, charcoal, kieselguhr or diatomaceous earth, slag wool."

and the original text:
"Als Ausfüllungsmittel benutzt man: Heu, Stroh, Schäbe, Lohe, Häcksel, Sägespäne, Holzwolle, Hobelspäne, Torfstreu, Erde, Sand, Asche, Holzkohle, Kieselguhr oder Diatomeenerde, Schlackenwolle."

The book goes on to discuss the suitability of some of these materials. Great book!

Thanks;
Jim

p.s. I'll bet the Icelandic houses are cool and damp, but "way cool" in my opinion.
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The closer you look the more you see.
"Heavy timber framing is not a lost art" Fred Hodgson, 1909

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#26215 - 04/15/11 04:25 PM Re: Infill and Half Timbering
Housewright Offline
Member

Registered: 02/16/06
Posts: 332
Loc: Waldoboro, Maine
As for the use of horizontal plank infill in timber frames in NE Europe check out this site showing a reconstruction of a boat shed using the "bul-teknik" like i mentioned earlier (bulhus, translates as "bole house", bole as in the trunk of a tree from the original plank material of split tree trunks rather than planks). This Stavgard looks like an interesting place.

http://www.stavgardgotland.com/husen.htm

In Sweden the horizontal plank method is skiftesverk which translates as "shift work" possibly relating to the planks shifting or sliding into the grooves.

http://sv.wikipedia.org/wiki/Skiftesverk

Jim
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The closer you look the more you see.
"Heavy timber framing is not a lost art" Fred Hodgson, 1909

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#26216 - 04/15/11 04:41 PM Re: Infill and Half Timbering
D L Bahler Offline

Member

Registered: 05/17/10
Posts: 946
Loc: Indiana
In Switzerland, they also have what they call Fleckenwand, which can also be classed as bohlenwand in some ways (and sometimes is called that)

Fleckenwand might be the evolutionary step between a post frame and a log building. What it is is large timber corner's and posts now and then, with thick timbers as big as these posts stacked in between them, and grooved into them. From this, people develop the complex corner joints and abandon the posts altogether, and end up with Blockbau.

The Buhl of Danish and Bohl of German are probably from the same root word.

Before saws were plentiful, planks would indeed have been made by splitting out a tree trunk...

Bole, from Old Norse Bolr- tree trunk...
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#29806 - 11/20/12 07:28 PM Re: Infill and Half Timbering [Re: D L Bahler]
Hylandwoodcraft Offline
Member

Registered: 03/23/11
Posts: 141
Loc: Western NY
To revive an old thread... I am talking to an architect about building a half timbered house, possibly with SIP infill. The ply facings of the SIPS would be grooved into the beams, with a gasket material applied to the inside of the grooves to prevent excessive air infiltration. One of my considerations is wood species. I think cedar would be totally ideal, but not within budget. My local options that I was considering would be white pine or white oak. White oak would have rot resistance but high shrinkage. White pine the opposite. What does everyone think?

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#29808 - 11/21/12 04:09 PM Re: Infill and Half Timbering [Re: Hylandwoodcraft]
timberwrestler Offline
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Registered: 11/07/05
Posts: 271
Loc: Becket, MA
White oak for sure. Heartwood only. Look at all of Europe.
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