Want an advice about earth sheltered house

I'm going to build a house like this



Well, I hope at least somebody understood, how it would look like. Ui (The specific error message is: "u" is a silly English abbreviation; use "you" instead.) form tires, straw bale wall in front, some earth around tires, round wood above them (as roof), then isolation and more earth (~60cm/2') above isolation.
What can you say about such design, would it be good?
The main question is about isolation. How to make it to avoid condensation? I'm thinking about layer of polyethylen (PE) (should it be thermally clued?), then maybe some 10cm/4" of polystyrene (PS), and then maybe paper, saturated with asphalt on top. Everything of this is cheap and affordable.

But what about condensation on top of round woods? If you think it would happen, maybe you'd offer another way of building such roof.
Thank in advance

Hi Alen
I noticed your drawing and had some concerns,
First , What climate are you in? And are you going to have a heat source and ventilation?
Then if im correct you have 20' from side to side for your roof , and your laying the logs across the 20' opening , im guessing that your straw bails are your front wall and insulation, so , wheres the support?
These things concern me!
Your question about waterproofing , i believe could be solved with clay, but i would not have a flat roof and if the logs are from side to side. Then there is a channel in between each set of logs.( a possible water way) . If your timbers/logs where supported from front to back, and you had a lentil/load bearing wall in the front then you could elevate that roof line for internal drainage just in case!
Your ideas about poly , well there could be some abrasion , either by the logs or the dirt layer on top. Even clay may have some abrasive qualities. But clay will always heal with rain and be easy to add .
Im pretty tired so i hope i have communicated my thoughts .
I hope you find your way and build a nice safe shelter!
Best wishes

Thanks for the reply

Location is Northern Europe, generally there is 6 months cold here, several weeks of them very, 3-4 months not so cold, and 2-3 months relatively warm.
Okay, let's go further (second round)
I was thinking about support earlier, so here is another drawing.



Now there is cob wall in the middle, as support, round wood rows will be in two pieces, left and right. What do you think about such construction?
And there is This thing, don't know yet what it could be, to allow water go down into all directions.
Probably this cob wall needs a foundation? So there would be tires without foundation, then wall in the middle with it. First I was thinking about front wall - to lay 3 rows of tires, then straw wall above, with doors and windows, but it could be cob wall also, then again it would need better foundation, than several rows of tires, isn't it? So it would be like mixed construction, several walls with foundation, and several (those of tires) without
And by the way, how do you guys dealing with all those wood eating insects?

I am not convinced that cob is a structurally significant material. Most constructions you will see call for post-and-beam, which you can do with unmilled wood. If you are going to experiment, I strongly urge you to get someone who knows about structural engineering and/or construction, like an engineer or a contractor. Or have a look at WOFATI, earthships, and Mike Oehler's work. I would not use straw bales to support an uninsulated steel roof (well maybe just a sheet of corrugated), never mind the kind of WOFATI-style green roof you seem to be wanting.

Your specific site details will dictate a lot of the needs of your structure. I haven't done this yet, but I have on my to-research list the style of earth-bermed long houses that were used during the brief Viking settlement of L'Anse Aux Meadows. I have seen the terrain, and I don't know if they would have used timber or what for roofing, considering the lack of it in the immediate area.

I don't know what resources you have on-site, but if you aren't familiar with Rammed Earth, Pisée, or Compressed Earth Block, you may wish to take a gander. The first two have much in common with the needs of cement, and the third uses the same principals to make a standardised masonry unit that can be tested and that should, with proper attention paid to equipment and the earth mix, well out-perform the commercial standard. I believe this could be an adequate work-around for those green builders living and building in areas where adherence to building code is strictly enforced.

Please be careful. This is like the boomsquish stuff with rocketmass heaters; all we need are some enthusiastic do-it-yourselfers to do the wrong thing at the wrong time and crush themselves to set back public opinion of alternative and green building. Plus there's the whole dying thing, and it's not very good as an educational tool. Kinda final.

Good luck.

-CK

Cob can be load bearing but it needs to be the right thickness for the weight it will support. I'm sure there are places you can find out how thick of a wall to build for a desired load. I haven't build with cob before but I have done some research into it. I've read that cob is more structurally sound as monolithic structure, meaning when it's used on it's own with no wood or anything else in it. But you have to have room for the thickness of the walls. A cob wall could work inside if it's protected from any moisture from above, just make sure you do all the calculations you need to for whatever material you use to hold up an earth covered roof. earth is heavy.