30 m2 dome build out of wood frame, cob and styrofoam as isolation?

Hi guys!

I'm Sune from Denmark! I recently bought a house, which are basically rotten and need to be taken down and scrapped.

But I've considered building a new house on approx 30 m2, which I'll be living in both winter and summer times! I'm thinking to make it out of a wooden frame with styrofoam as isolation, and then adding cob to the outer and inner layer in order to smooth it out.

I'm thinking the wooden structure would look like this (a lot bigger ofc), with styrofoam inside each the triangle:


I'm still unsure if I should add a roof to the structure, or if I should add some limestone to the outside, in order to avoid erosion since it's quite rainy here in Denmark. Any thoughts on that?

But I'm still very new to this way of building, so I'm quite unsure if my plans would work out? (I bought the house this monday, so I haven't spend to much time reading about building out of dirt, clay, sand etc. yet)

Hi Sune, I know that domes are a very attractive idea, but it turns out that there is a good reason that you don't see many ever actually built, and you really don't see any that are still standing after ten years. Lloyd Kahn was one of the people who helped make geodesic domes popular, but he later came to see many important reasons that they are not practical. Please read this essay he wrote about the pros and cons of geodesic domes.

Rebecca makes a very very good point she has probably saved you thousands of euros and years of heart ache .
Cob or wood yes , dome no ( unless the planet is really f@@@@@ we have an ice age and you get to live in a year round igloo.  )


David

Thank you very much for the replies! I'll read the article as soon os I get off work.

So you'll just recommend a normal square house?

I dont know about normal but domes are one of those things that look really cool but when you try and build one ..................
There are lots of other cool types of building out there . Triangular for instance can  work well  http://www.strawbalehouse.co.uk/  . Straw bail construction may be ? https://www.strawbale.com/
cob http://www.thiscobhouse.com/ even thatch https://www.flickr.com/photos/eileensanda/4058673506 There are lots of web sites out
there Google is your friend

.

My house is in something we call a garden union here in Denmark, which means that I need to follow some rules set by the union. One of them is max. 4 meters roof (from ground till top, not from wall to the top), and 3 meters walls + i need to have 2,5 meters to the bush that separates my lot from my neighbor.

I've seen the houses made out of straw & thatch, but it will take up to much space since the walls need to be quite thick, and that's why I came up with the styrofoam solution. (to make the walls thinner) + then i don't have to make additional foundation for it, since I already got the old foundation from the old building (~30 m2)

I only have something like 12,5 meters from neighbor 1's bush to neighbor 2's bush, which means the house will have a max. width on 7,5 meters measured from the other walls.

Ok but then you are talking about only a one story house really
Basically the same size as the one you bought. How about showing some pics of the house you bought and maybe the folks here can make some suggestions about saving it

Since your width dimension is so limited, a dome would be a poor way of using the available space in any case. It also would not let you use much of the existing foundation. If you really like the idea of a domed space, you can make a dome roof on squarish walls; but you would want to cover it with a water-shedding roof. But a maximum height of only 4 meters from ground would not allow more than a shallow roof slope no matter what, and not enough height for a dome on walls.

We could give lots of ideas for practical structures,  but first we need to know the conditions of your lot. What are the dimensions of the existing foundation, and what kind of foundation is it? What possible extension could you make to front or rear? Pictures would be a big help - often there is a factor that the OP didn't think to mention that changes what is possible or desirable.

What is your climate? I know Denmark is quite northerly, but surrounded by North Sea/Baltic Sea it could be more temperate.

Hi Sune! Welcome to permies.com, and welcome to dome building!

I have build two domes recently, small one as a proof of concept and more sizable as a greenhouse.
The concept of a dome is fascinating, but there were a few things I learned the hard way.

In my experience, domes are particularly prone to leaking, because they are all roof.
Top of the dome does not have steep enough slope, so snow will accumulate there.
Besides the wooden frame, there are hubs that connect the beams (I can see them in your picture,) and set of them can cost as much as the wood. My design is hubless (requires twice as many beams cut lengthwise at various angles, and lots of screws,) and I am not sure if I like it more than the one with the hubs.

Standard windows and doors will be difficult to fit, and will cause deviation from the hemisphere shape. (Dome in your picture does not appear to have doors or windows.)

Small house I am planning to build will not be a dome.  

Would a Hogan work?

You first mentioned 30 m sq, and then 7.5 m maximum width... even with walls 1 m thick, a 30 m sq interior space would be 5.5 m x 5.5 m inside, 7.5 x 7.5 outside. So it doesn't sound from this that you are severely limited. It would be good to hear more about your desires, and also more about your neighborhood and surroundings.

If the height of the roof above ground level is fixed, you could still go below ground level …
Possibly the "cellar floor" 1.5m below ground and the "ground floor" 1m above the ground. With a sloped roof with 3.5m height at one end and 4m at the other.

I have seen hexagonal houses out of straw and clay, that could be another option.

A hexagonal house with the flat sides towards the neighbours 1st and 2nd bush with 7.5m width in between:
Straw bales (35cm) with 5cm clay on each side: 7.5m - 2 · 45cm = 6.1m inner diameter.
=> r = 3.05m
=> A = 2 sqrt(3) · r² = 32.22 m² inner floor area.

Just make sure the roof is up and waterproof before adding the straw bales …

Thank you for all the replies, I really appreciate it! And sorry for now coming back earlier, I had some things to take care of. Girlfriends birthday yesterday, and my mother borrowed my car and was complaining that it would drive any further.. Turns out she filled gasoline on my diesel car - but it should be working again today, and I'll go to my house/lot in this afternoon and take some pictures and some measurements!

David Lvingston wrote: Ok but then you are talking about only a one story house really  
Basically the same size as the one you bought. How about showing some pics of the house you bought and maybe the folks here can make some suggestions about saving it  

Yes, it'll be a one story house, maybe with a small open loft room!  

Glenn Herbert wrote: Since your width dimension is so limited, a dome would be a poor way of using the available space in any case. It also would not let you use much of the existing foundation. If you really like the idea of a domed space, you can make a dome roof on squarish walls; but you would want to cover it with a water-shedding roof. But a maximum height of only 4 meters from ground would not allow more than a shallow roof slope no matter what, and not enough height for a dome on walls.

We could give lots of ideas for practical structures,  but first we need to know the conditions of your lot. What are the dimensions of the existing foundation, and what kind of foundation is it? What possible extension could you make to front or rear? Pictures would be a big help - often there is a factor that the OP didn't think to mention that changes what is possible or desirable.

What is your climate? I know Denmark is quite northerly, but surrounded by North Sea/Baltic Sea it could be more temperate.

Thank you for your reply, I'm more or less convinced to quit the dome idea. I'm going to the lot this later today, and I'll take some pictures and measure the lot + the foundation, and reply back.
We have temperate climate here in Denmark, with a lot of rain, wind (always windy) and often below 0 in the winter time. I'm not allowed to use a woodstove, fireplace or anything else that involves fire to heat up the house, so that's a factor I need to take into my calculations as well.

Seva Tokarev wrote: Hi Sune! Welcome to permies.com, and welcome to dome building!

I have build two domes recently, small one as a proof of concept and more sizable as a greenhouse.
The concept of a dome is fascinating, but there were a few things I learned the hard way.

In my experience, domes are particularly prone to leaking, because they are all roof.
Top of the dome does not have steep enough slope, so snow will accumulate there.
Besides the wooden frame, there are hubs that connect the beams (I can see them in your picture,) and set of them can cost as much as the wood. My design is hubless (requires twice as many beams cut lengthwise at various angles, and lots of screws,) and I am not sure if I like it more than the one with the hubs.

Standard windows and doors will be difficult to fit, and will cause deviation from the hemisphere shape. (Dome in your picture does not appear to have doors or windows.)

Small house I am planning to build will not be a dome

Really nice domes, and thank you for your feedback. Like I write above, you guys have convinced me not to build the dome

Miles Flansburg wrote: Would a Hogan work?

Is this a Hogan? If so, I think it will be quite expensive?

Glenn Herbert wrote:You first mentioned 30 m sq, and then 7.5 m maximum width... even with walls 1 m thick, a 30 m sq interior space would be 5.5 m x 5.5 m inside, 7.5 x 7.5 outside. So it doesn't sound from this that you are severely limited. It would be good to hear more about your desires, and also more about your neighborhood and surroundings.

I most honestly say, that I didn't do a lot of math on it. I was just thinking about how the current house on the lot is already at 2,5 meters from the bush, but it's quite narrow as well. I'll take some pictures etc. this afternoon/evening when I'm off work.

Sebastian Köln wrote:If the height of the roof above ground level is fixed, you could still go below ground level …
Possibly the "cellar floor" 1.5m below ground and the "ground floor" 1m above the ground. With a sloped roof with 3.5m height at one end and 4m at the other.

I have seen hexagonal houses out of straw and clay, that could be another option.

A hexagonal house with the flat sides towards the neighbours 1st and 2nd bush with 7.5m width in between:
Straw bales (35cm) with 5cm clay on each side: 7.5m - 2 · 45cm = 6.1m inner diameter.
=> r = 3.05m
=> A = 2 sqrt(3) · r² = 32.22 m² inner floor area.

Just make sure the roof is up and waterproof before adding the straw bales …

I was thinking about the same thing, regarding lowering the ground floor. But sadly it's not allowed, only if i'm building a small basement for food storage or something. (Which I already have in the current house actually)
Haxagonal sounds quite nice, and your calculations makes it even more appealing! Yes, i'll make the roof first, or maybe put up some kind of tarp while buliding the walls.

Yep thats a hogan. If you buy all the logs it could be expensive.
If you have trees available on your property that you can use it would only be the labor of cutting , pealing, stacking etc.

Miles Flansburg wrote:Yep thats a hogan. If you buy all the logs it could be expensive.
If you have trees available on your property that you can use it would only be the labor of cutting , pealing, stacking etc.

I only got 5 apple trees on my property, so that's not really possible!

I just made a new drawing showing how my house is placed right now, + some pictures. (forgive me for my lack of drawing skills!)

From all walls to the bush, there's between 2,5 & 3 meters.








So, I've considered reusing the frame from the existing house, depending on the condition of the wood. (The roof has been leaking, so it might be all rotten)

But I can see that the house had sunken 20 cm. in one end, so I need to fix that as well.

My parents had a dome home built.
I would love to have one myself. Theirs never leaked.
It was a pretty good size with a upper 2 bedrooms and one down below.
Theirs was insulated with the foam that you spray in and it expands.
Sure it is a round home. You learn to built round.  Things will fit and work.
They can withstand many different kinds of bad weather.
One, they are great for tornadoes.  They walk around them. I know because we were in it when one hit. You could hear a few shingles  go but that is all. The neighbor just south of us had a A frame. It did not fare well. It was picked up and moved off the foundation.
There was no damage to ours except a few missing shingles.
Yes you could hear it walk around the home because it was round. No flat walls to run into.
When we lived in Florida the year hurricane Andrew hit ( cat5 ), most all the houses were gone in one area EXCEPT a neighborhood of dome homes. They survived. And one also up in the panhandle did survive also in another storm. They never leaked.
I guess it depends on the builder and how good they are actually built.
The foam is a very good insulator. Our house had three doors, so the wind could come in any door and had very good airflow. We had AC but when the weather was nice, it was great.
The electric was very cheap for it.
I plan on making some smallish ones like your picture for greenhouses.  One will be a tropical one for tropical plants and a small waterfall for my favorite plants in Florida that I miss. A room just to sit and enjoy. Others will have different uses. Different type foods and maybe a aquaponic one.
Ours did not have a fireplace. But it did not get cold in the winter, even though it was very cold outside. The electric still was not high.
I like the shape of the dome. Very modern and very safe.
Most people are still used to square shoebox style houses.
Round is more natural as in nature.
Just my experience in domes...