Back in 2017, when I was wandering around the North Sea and Baltic (and other places) studying the Hanseatic League, I lucked into getting to watch some gentlemen replacing a thatch roof. The place was a few kilometers north of Husum, near the North Sea, and a weather system had started moving in. The supervisor had just finished getting things underway, and didn’t mind my small group standing at the edge of the property and watching. The homeowner asked what we were doing, I explained, and all was well.
As I said, weather was coming in. This gives you a sense of what they were setting up, and how deep the roof is.
Working around a modern window.
The roofs in the area tend to be thatch, which was/is traditional, or tile. Thatch lasts up to fifty or sixty years, although the supervisor said that forty was more common, because of the heavy weather. Thatch breathes and “keeps the houses healthy.” Tile roofs can be more durable, and require less upkeep most of the time, but they are heavy and can cause structural problems if someone slaps one onto a formerly-thatch house. The difficulty with thatch is the lack of thatchers, and getting the proper reeds and other materials. Originally, the thatchers used reeds and the like from local salt marshes. Today most of the materials used in Europe come from England and Scotland. I got the impression that the boss preferred local materials.
The little ladders have hooks to snag the thatch. The man is about to start folding the fringe over to make the roof peak water tight.
The raw materials. The bundles are tossed up to the guys on the roof.
As you can see, it looks like straw, but it’s really not. The narrow end goes upslope, so the water doesn’t get into the stems. Having seen first-hand how thick a real thatched roof is (two feet thick in some places), I understand why people don’t worry about leaks or rot. Fans of thatch say that they are warmer than the usual roof, don’t put as much stress on the walls, and let the house “breathe.” The lack of air-flow in modern, supper-efficient construction is a serious problem in some houses and buildings in Germany and other European countries. Thatch fans just smile. When done properly, a thatch roof is no more of less expensive than a standard roof, even up on the North Sea. Or so I was assured.
Cat Rotator's Quarterly 
That looks genuinely interesting, I would like to have been there to see that for myself.
Very interesting.
That is an awful lot of insulation. For all the “breathing”, they aren’t going to lose much heat through it.
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I built forts out of straw bales as a kid. They were awful handy in winter. Duck into one, seal it up, and it would get a darn sight warmer than the house in short order. (With no yelling about taking off boots!) Defrost a bit, then go back to playing.
Have you seen the houses they make by putting clay on hay bales now?
Thick, obviously, but….
I’ve seen a few, but the problem is that the county fire marshals do NOT like the idea of wires near hay, even with a protective layer between the wiring and the bale. I suspect too that once water gets into the hay, you’ve got a real mess to try and removed the wet stuff and replace it.
I think it’s more likely rodents.
Mice *love* packed straw.
And exercising their teeth in anything that might be edible. (Like, say, electric cables that resemble roots.)
Combine the two…
No doubt flooding would also be disaster. Just a slower one.
Seen the same type of roof at the reconstructed Louisborg, in Nova Scotia. Roof was thick and strong enough to accumulate a layer of soil, grass, and wildflowers. Warm inside, on a windy day.
Truly an art to get it right. And there IS a bit of weight when covered with rain/snow. First time I’ve seen pics of a roof being redone.
I’ve see claims that bugs tend to live in thatched roofs and fall on people in the houses (although in modern houses, there’d be ceilings in the way). Is that accurate?
I think it depends on climate. In the North Sea region? Probably not a large worry. In tropical environments? Yes, very much so.
That’s fascinating. It’s also beautiful. I think 40 years is longer than the rating for the asphalt shingles on top of my house.
I don’t think I’ve seen any documentaries on the process of thatching a roof, although I’m sure there is something if I start looking.
I’d think electrical conduit would be your friend when wiring either straw bale or cob houses.
From the limited reading I’ve done, rot is a problem in non arid climates. Wet hay tends to swell, even before rotting, which could crack the clay/plaster/stone shell quite badly.
I saw pictures of a modified style that looked like doubled post and beam, which is built first and roofed before the bales are slotted in place. It also provides structural support in snowy climes.
It’s probably a lot faster to build than cob houses, but I’d prefer a cob house myself. (In the US think of adobe as a type of cob.) They can last centuries, and I think thatch is the traditional roofing material for a cob house.
They’re gorgeous, and I wonder if the tule grasses found locally would work for such a roof. OTOH, I’d want to be at least a mile away from one during a lightning storm in our area. Preferably upwind. (We have our four seasons: Almost winter, Winter, Still winter, and Fire)
We don’t see too many flammable roofs in the rural areas. There might be some wood-shake or cedar shingle roofs in town, but no, not out here.
Maybe 20 years ago I noticed that prepainted steel siding, the kind used for industrial buildings, was relatively inexpensive and came with a 30-year warranty. I planned to our about-to-expire shingle roof with it. I happened to mention it to the insurance agent, who freaked out. No “tin” roof! They would cancel our insurance instanter! Reee!
His only conception of metal roofing was apparently galvanized corrugated sheet, and he wasn’t interested in any further information. We put a conventional roof on after finding other insurance companies have similar views.
Ten years after that, “metal roofing” was the premium-price option from roofers, and got you a discount from the insurance company. Looks like the exact same material I had originally planned to use…
[sigh]