Modern Solutions to Thatching

[D L Bahler]

I am working on the design of a project replicating some old techniques and methods from Europe centuries ago. When it comes to roof covering, I have 2 options: I can either deck the roof with wood shingles or else thatch it. In order to consider the scenario fairly, I need to find some possible solutions to problems presented to me.

Thatching poses 2 immediate problems, namely the difficulty in obtaining suitable straw locally and the risk of fire. Regarding the latter I can say, first the roof covering is to be no where directly exposed to living areas underneath, the building is double purpose barn and house, and wherever the straw underside is exposed there will already be much hay and straw present, and much if not all of the roof will be decked with boarding under the straw. So there is not a great risk of fire from within.

Also the structure will be in a wooded area, meaning the straw will not be able to fully dry out. The ridge is oriented north to south, full hip on one side and 3/4 on the other.

[beenthere]

Seems the modern solution to thatching is a shingle roof.  Fiberglass shingles or metal. 

But slate or clay tile may be more "timely" for your desire to present a prior time replication.

[D L Bahler]

None of these are acceptable.

The second available option is wood shingles, and on a roof of this size this is a daunting prospect.


Clay tile is a remote possibility, assuming all else fails. As this is a recreative project, asphalt is strictly forbidden, and steel is acceptable only as a temporary cover.

[Satamax]

And what about "lauzes"

https://www.google.fr/search?q=lauzes&safe=off&rlz=1T4SAVJ_enFR550FR551&source=lnms&tbm=isch&sa=X&ei=XGJ1Uq_6JeKv0QWKioA4&ved=0CAkQ_AUoAQ&biw=1216&bih=515

Thatching isn't mainly made of normal straw in France, but more from long reed stems. May be you can find some suitable reed where you are.

[bigshow]

steam bent shingles

[canopy]

Thatch usually requires a high pitch roof. There is some debate on minimum pitch, but 50 degrees or more should be adequate. Otherwise the water does not run off quickly enough and rots. Thatch should not be used if there is a chimney for a fireplace due to embers. As mentioned reeds make for very long lasting roofs that can last 70 years. In my area of Thailand grass is used and lasts only a few years.

[D L Bahler]

The allowable materials are minimum. This is a specific replication of a specific style at a specific period in time. Thus the reason for the very narrow range of choices.

To be clear, this is a replication of a Hochstudhaus as would have been built in the lowland region of the Swiss Canton of Bern (The Berner Mitteland) any time from the end of the 15th century until the style vanished from the canton about 200 to 300 years ago, supplanted by a more sophisticated style suited better to the construction of very large structures. This structure will hold a mixture of 16th and 17th century features (thus creating the illusion that the structure was built and then modified at a later date)

The footprint is irregular, but measures something in the order of 40x48. The roof is at a slope of 14.4/12, or about 50.2 degrees with very generous overhangs.

As stated, no living area is open to the roof, originally these would have had a large masonry stove/oven that doubled as cooking range and heating, the serpentine shape of the vent flue prevents sparks from reaching into the hay loft (the chimney opens into the loft, not through the roof, making a very smoky place. Meat was hung from the rafters.) and ensures gasses are cool enough so as not to risk sparking fires.

Typically wheat or barley straw -long stem Swiss varieties- were used (Strohdach), or if the farmer had the money a covering of wood shingles could be used. These roofs are enormous, and expensive to cover. Straw was cheap and easily had, so it was the covering of choice. It would be tied in bundles and hung from spars driven in the roof boards.

Design features match the specifications of a typical structure of this style, I am not worried about meeting thatching requirements, because I am replicating structures designed for straw roofing.

Canopy, I spent some time in Thailand years ago. A good friend of mine is karen -not a refugee but part of the Karen that are Thai citizens. I stayed in his home village (he lives in Chiangmai) with his family, and thought about how I would love to help them build better homes, but I knew they would not appreciate me telling them they did nothing right, so I said nothing. What surprised me, and I saw this also in the temples in Chiangmai, was the use of large leaves woven into the roof as a sort of thatch-like covering. These would not last in Indiana very well...

[D L Bahler]

As to thatching method. That is specifically what I am asking about. Suggestions like the use of reeds is what I am looking for. All straw in Indiana is short stem winter red wheat or similar grains, mechanically harvested (and often chopped) so stems are short, crushed, and broken. This I cannot use. So I have to find a source from elsewhere (I could harvest all the bogs over the next 3 years to gather enough reed...)

Interested also in alternative approaches. I understand shortcuts will not work, and examining this logistically, maybe it would be better to harvest a few good trees and spend my spare time (spare time, what?) making shingles...

[Satamax]

DL, splitting shingles is loong, but would look posh :D  You don't have kids who would split the shingles for you? :D  Or make a shingle splitter?

Regarding heating and the mass stove, if you want far less smoky (if you don't plan on smoking things) there's an emerging trend.   Rocket stoves or rocket mass heaters. which are extremely clean.

http://donkey32.proboards.com/
http://www.permies.com/forums/f-125/rocket-stoves

[D L Bahler]

Here are a few pictures, some showing thatched and some shingled, all similar buildings. Most of these would now have clay tile on them.



  

  

  

  

  

 

[canopy]

That's fascinating, thanks for all the details and photos.

[ziggy]

Deanne Bednar of Oxford, MI is a great thatch resource. She is one of the few folks actively teaching thatch in the US. I believe she uses phragmites (or "common reed"), harvested during the middle of winter. I hope to help out with the harvest this winter.

Look her up, and "Straw Bale Studio" or "Natural Cottage Project".

[D L Bahler]

Might look into that, thanks for the lead.

Right now we are considering more seriously the prospect of shingling this massive roof. Keep in mind that this roof is somewhere in the area of 100 square (or 10,000 square feet) by rough figures.

One such building, the shingled example shown in the pictures above, reportedly took some 257,000 shingles to cover. But these are small shingles which are only about 6 inches wide, 18 inches or so in length and side lapped, at least 4 layers thick vertically with only about 4 inches or even less exposure on each shingle (Schipfidach) So if I were to do a larger split shingles roof (schindeldach) then there were be far less shingles needed.

[canopy]

257,000 shingles, holy mackerel. Imagine the cost if they were a dollar each. Imagine the roof load if they weigh 1 pound each. If they were 4 times that it means a $1 million dollar roof weighing 1 million pounds! I suppose wind loading on such a large surface will up the timber sizes as well. Whatever the final numbers and materials are, that will be one impressive and unique roof. Looks really picturesque against the mountains.

[Satamax]

257,000 shingles, holy mackerel. Imagine the cost if they were a dollar each. Imagine the roof load if they weigh 1 pound each. If they were 4 times that it means a $1 million dollar roof weighing 1 million pounds! I suppose wind loading on such a large surface will up the timber sizes as well. Whatever the final numbers and materials are, that will be one impressive and unique roof. Looks really picturesque against the mountains.

Well, DL was saying only 4 inch showing.   4"x4" let say, that's 28555ft² seems a bit much Exept if the sides are covered with shingles too. Accounting for the loss. Etc. If it's split shingles like we used in France, they weight may be 50 grams a piece. And from the latest price i've had,  for split shingles, that would be in the range of 265000$ just in shingles.

DL, you're sure that's not 25700 shingles you need? at the "purreau" of 4 with 4 wide by 16 long, you'd cover 265m² 2855ft²

[D L Bahler]

See here:

http://ballenberg.ch/en/Map/2/Bernese_Midlands

and here (will open a pdf file):

http://www.digibern.ch/jahrbuch_oberaargau/jahrbuch_1982/JBOAG_1982_051_068_haus_von_madiswil.pdf

The last is in German, scroll down for pictures (or read if you know German)

Also see this to understand the small size and minimal exposure of these shingles:


 

[Satamax]

Hi DL Bahler.

I hadn't thought this was soo small in exposed surface of each shingle. I know what they do around col de mosses, with criss cross covered shingles, but they use a "pureau" of 1/3 split shingles, often rounded. Specialy on the walls.

[D L Bahler]

This is good:

 
Here you can see sclearly how it works with the side-lap type shingles