Building with turf

Here in Scandinavia, the use of turf (otherwise known as sod) as a building material goes back a very long way indeed. As a covering material for roofs, it has several advantages: it can be found almost anywhere, it provides decent insulation, it looks pretty, and hey, you can let your goats out to graze on the roof! This last point has actually been standard practice in the maintenance of turf roofs in some areas.

Turf on its own is not a very good roofing material, since water goes through it readily. To keep the inhabitants of the house dry, the turf has to be combined with a water barrier. In most modern turf roofs, this is a rubber or plastic membrane. Traditionally, birch bark was used. Birch bark is waterproof and rot resistant, but doesn't handle UV light very well - much like plastic. The bark is needed to shed water, the turf is needed to provide insulation and protect the bark from light.

In some types of houses, turf has also been used in the walls. In the Sami goahti, the walls and the roof are the same thing, i.e. there are no actual vertical walls. In Icelandic turf houses, the walls are built from alternating layers of turf and stone.

Apparently, the Icelandic houses used to be routinely rebuilt every generation, so every 30-40 years, reusing the rocks and presumably as much of the wood as possible, but new turf strips. Here's a nice video about it.  

One weird thing: it seems the Icelandic ones did not use birch bark for a moisture barrier, possibly because of the generally tree-scarce landscape. The question is what they did use? Wood was precious, seems weird to expose it to moisture by leaving it in direct contact with soil. I can't seem to find any good info on that, except something that seems to imply (maybe?) that they used flat rocks... Weird. Does anyone know?

That is really cool.

I know in the USA there was a time period where people would build sod huts out on the prairie, simply because there wasn't a lot of stone or trees around.

I was pretty sure that turf was used relatively recently under thatch roofs in Scotland...digging around I found this video

At about 4:13 you can see him pushing the grass into the turf which then anchors the thatch. This must be much easier than having to construct a woven mesh of some sort to fix the thatch to - the turf with roots and all is like a fairly homogenous felt material.

Turf walls are something else too. Many of the summer shielings were turf walled huts. You can see the circular patches where they were built as green grassy places in the hills. From my previous thread on soil at shieling sites

shielings on Skye: green patches at right midground

from the Scotsman

they are constructed of branches of trees covered with sods;

A turf shieling at Ness, Isle of Lewis, in the late 1940s

source

According to Historic Environment Scotland, drystone was often used to coat the interior turf wall to stop animals damaging the surface, whether by rubbing or licking for salt.
However, drystone was later used on the outside to meet growing regulations from landowners, who could then claim their tenants were housed in ‘stone-built homes’.
Rules for tenants on Lewis Estate in 1879 insisted ‘the dwelling houses to be erected by the tenants ... shall be of stone and lime, or stone and clay, pinned and hurled with lime, or with stone on the outer face and turf and sod on the inside’.
However, according to HES, putting drystone on the exterior of the turf house held water, softened the surface and created erosion.

This quote from the above article I find intriguing:

Turf as a building material is enjoying revived interest in ­Scotland given its ability to waterproof and insulate properties

I wouldn't think of turf as waterproof! However, I know that dry soil can be difficult to wet, and I have also found when digging in my tree field that the soil under the grass is quite dry when the surface is slippery wet....

I've actually found the sods so robust I'm tempted to try this out!

Ooh, turf as a base for thatching? Cool! Never heard of that before, but it makes sense.

Waterproof? I guess it might depend on the type of soil. In much of Scandinavia we have mostly either sandy or peaty soil, so I would certainly not want to live in a house with our kind of turf as a sole roof covering. Maybe if there is a lot of clay or similar in there, that might make it decently water-resistant, and the fine roots of the grass might stop the clay from washing away? Also, in the Icelandic turf house video, he compacts the turf by pounding it with a club. That might help.

My husbands dear grandmother talked about living in a soddie as a child.  That is what they called them here in the US.  Houses made out of sod.

The pioneers built house out of what was available where the settle down.

Thanks for that anecdote Anne - that has led to another avenue of research. The North American soddy or soddie.
There is one in Western Canada standing since 1911!

Pictures and quotes from legionmagazine.com

The builder, James Addison, made it slightly different from the norm then, as he saw the durability issues that people were having with sod houses. His daughter was there when the house was built and explained:

“he found a slough where the grass was high and cut the sod three inches thick. Dad decided he would build the walls four feet thick at the bottom, seven feet high, then taper them to three [at the top],” said Gardiner. But the secret wasn’t just in making the walls larger. The technique was most important. “Every time he’d put a layer of sod on he’d [layer] it…so you didn’t have the cracks coming together,” she explained. And, critically, “he hollowed out the top of every layer.” When the sod dried it would crumble in on itself—toward the centre of gravity—and not fall away to the outside or inside of the wall.

the exterior walls were covered with growing vines for protection from the elements. “But the wind and rain gradually eroded it, so finally he put boards around,” she said. Later these were replaced with shingles, then asphalt and finally the current vinyl siding.

sod wall on the inside of the house

The main giveaway is the rather sloping siding covered walls - apparently forming really good insulation against the Canadian winter too!

sloping walls

One thing about sod that would make it good for waterproofing is that while it might be a porous material, it is alive and actively growing, so the grasses should be able to drink at least some of the water before it becomes a nuisance to the house.

I am very impressed at the idea of heating a space with only body heat! Iceland seems like a good place to learn from in using one’s wood efficiently, a skill useful in this time, when forests in general are in decline.

Maieshe Ljin wrote:One thing about sod that would make it good for waterproofing is that while it might be a porous material, it is alive and actively growing, so the grasses should be able to drink at least some of the water before it becomes a nuisance to the house.  

Depends on one's climate, I think. Might work okay in a prairie climate, where you don't tend to get too much rain at once (although the article Nancy found suggests that many Canadian prairie soddies leaked all the same) but in a rainier place I think the rain will often fall a lot faster than the grass roots can absorb it. Probably helps a bit, but we'll want birch bark under the turf once we get that far in building our cabin on the Norwegian coast...

I just saw this: