Tiny house build in Hokkaido

Hey folks⛰🌞⛰

After much thought and deliberation we have decided to build a new tiny house. The old house that we are presently in has too much foundation damage and lack of insulation to warrant any further renovation.

I’m thinking of building a small one story, open floor, on grade structure, on grade, with no basement of any kind. Presently considering options for construction using as much reclaimed, recycled, and natural onsite materials as possible.

At present, the building is planned to be 4m 5.5m internal space. I’m considering building a stick frame, with all the posts set on cement footers, which are pored from bellow frostline and extend well above grade, maybe 50cm. All the load baring posts will be set in this way. Then the space between each of the footers will be infilled with some sort of steam wall. Most likely, salvaged cinder blocks, earth bags or tiers. This stem wall will be insulated with pumic, perlite, or some other form of natural insulation (hopefully).

The steam wall will be wide enough to accommodate a double studded frame work which I’m thinking will be roughly 30cm wide. Plan to do Light Straw Clay (LSC) infill starting from the top of the stem wall up to where the wall meet the ceiling. I understand that LSC requires time for drying prior to surface finishing, however I am thinking of build the framework of a RMH, that we can use during build to help promote a quicker drying time.

I have been playing with different ideas as to the construction of the building, but nothing is set in stone. Will need to have the building relatively completed by late October, early November, so that we can live in it through the cold of winter.

Do not need “finished” floors and interior wall. Not looking to put in a bathroom or shower, full kitchen etc. All of that can come later. Basic electricity if we are lucky.

Looking for advice on:

1. Steam wall ideas with insulation
2. On grade subfloor insulation ideas
3. Thoughts and advice on foundation and drainage
4.  Natural insulation ideas for ceiling
5. Should we build in a basic square format? Are there other formats that could make sense? (Hexagon, Octagon etc)
6. How high above grade should the steam wall be before the LSC infill begins (Living in snow country in Hokkaido Japan with moderate snow fall)
7. What needs to go on top of the steam wall before starting the LSC infill
8. How much overhang should we have on the roof

This is our first building so I would like input, of any kind, regarding technical and logistical guidance.  How should we approach this project? What should we be focusing on? What should we watch out for? etc.

We will likely have access to a small backhoe during the construction. Also our neighbor, who is an old contractor, will likely be helping us with the details of the foundation, steam wall and erecting the frame work. He’s 81 years old, and understands traditional Japanese building and modern concrete foundation construction. He does not, however, know anything about western natural building technics. But if I explain to him, what we are thinking, he is willing to give on site support and advice.

Here are a few sketches and images of what we are thinking to get things rolling.

Thanks in advance, Peter & Mimi✌️

P.S.- Please let me know if there is any further information necessary for a basic project brief.

Oooo, I hope you post as much information, pictures, and drawings as you did with you RMH project! That was a treat! Good luck with the build. I am sure there will be a lot of great input from knowledgeable people on here!

Hi Peter;
This is awesome for you guys!  A new house all yours, fully insulated OH MY !!!  
A new build RMH, maybe your first batch box...
There is nothing more satisfying than constructing your own home from the ground up!
You will sleep very warm next winter.

Sadly, I am not an accomplished builder so I won't have much helpful advice on your build, but I am anxious to watch it commence!

I like the look of the "round house" in your photo's.  
I do think the traditional square house would be a faster easier build.  Your contractor friend might feel more comfortable with a traditional design as well.
My only suggestion is to extend the roof eve as far as possible. Drainage, snow buildup, simply storing things. All my buildings I look at and think gosh, if it only hung out another foot...

Lets hope you get to operate the mini  trak hoe during construction... they are quite fun!
Just don't sink in the mud....

Bravo Peter & Co. for deciding to build your own home!

When building in the manner that you are, where nothing is finalized until the moment it is being put into place, you have so many options for building materials and techniques that it turns into a labour of love rather than sticking with a rigid plan that can't morph into what it really needs to be. So thank you for encouraging that by setting such a great example!

I agree with Thomas in that operating the hoe is so much fun! Quite jerky at first, but you'll get the hang of it. Also agree with large eave overhangs as well. I made 4' overhangs on a pole barn I constructed which we now use for our wood storage and have never regretted it. Snow and rain coming off the roof barely even touches the base of the the posts which really helps to keep the structure protected. Also great for blocking out the sun during the summer months when its arc is high but lets it in when the winter comes and its arc is low.

With that, I would highly recommend reading The Hand Sculpted House by Ianto Evans if you haven't already. In chapter 4, he gives a great rundown on so many things before a house is even begun to be built that a modern builder may not even consider. He talks a lot about getting to know the land and elements that are present in the proposed location year round are important to utilise them so your house becomes more self sufficient in its energy needs rather than energy inputs to keep it habitable.
Later in the book, Michael Smith covers a lot of details about a lot of the questions you have asked.

Personally, I think square or rectangular buildings are designed that way mainly due to the manufacturing of materials that mostly force you to build that way rather than the way you may find more pleasing, like curves and oddities that are pleasing to the eye. Its been said that air flow in a curved house tends to flow better and not stagnate in corners as much.

I really look forward to your build and will help out whenever I can even if it is from the other side of the planet!

Oh yeah.....and don't forget about the doggie doors too!

Thanks folks for the support!

So much to think about and planning to do. Let’s hope the weather works in our favor. Noted on the roof overhangs for sure.
Will try to find a way to read more of the book if I can, but tough to get a hard copy here in these times and don’t have the download capabilities to handle the soft copy with my smart phone. (No wifi)

For now we are collecting as many of the materials we think we need. One of the farmers near by just tore down his old barn, so we have managed to salvage a lot of blocks from there. Spending days chipping off old mortar to give the blocks a second life. Thinking of laying drainage with a footer and then two rows of three stack blocks with some sort of insulation for the stem wall.

I’m sure plans will change and we will adjust as the project progresses. Will do our best to keep the content clear and full of fun.

Happy building and dreaming.

Mimi, Peter and Chimichanga

🐕👩🏻👨🏻‍🦱🐕

Those old chunks of mortar will make a great addition to either your drainage ditch or as thermal mass also. A nice score so close to home.

How are those smaller straw blocks working out for you?

Gerry Parent wrote:Those old chunks of mortar will make a great addition to either your drainage ditch or as thermal mass also. A nice score so close to home.

How are those smaller straw blocks working out for you?

We’re gonna have a bunch of chunks.

The small blocks are working really well and teaching me a lot.

I’ll post on the other thread more of my thoughts and findings...

✌️Peter✌️

This is me thinking through the process right now. Few drawings and a quick wall mock up to give a clear idea what we’re hoping to accomplish.

Please let me know if this makes sense and, in fact, it will be structurally sound.

Thanks in advance, Pete✌️

So your deciding to do blocks as infill with your light straw clay rather than tack forms onto your studs and infill between those and leap frog upwards?
I've read its important to also make 'keys' along the centre of each stud to keep the lsc from just falling out of the studs.

From your drawing, it appears that the cement posts that hold up the wooden posts travel all the way through the thickness of the wall. In your mock up, these same posts only travel half way. The latter would be better as the first technique will create a thermal bridge and transport the cold and moisture right through it.

Are you going with a rubble trench under the foundation? If your soil is the same here as it was at your house, there may be a lot of clay that will hold water and needs to be dealt with.

Hey Gerry!

Yeah, after looking at my last post I can see how some of the images could be misleading. That was just to show my real time thought process, from drawing to mock up. The live mock up is much more the design I’m thinking of using. The block is just there, as a placeholder, to identify where the light straw clay infill will sit with respect to the other materials in the wall fabrication.

I will keep updating and would appreciate any and all comments and tips moving forward.

Thanks again for all your help.

Cheers, Pete

Think about getting a brick bolster to clean bricks with.
Its used in Australia for splitting clay fired bricks.
I also find a tomahawk very good as well.


They come 75mm to about 115mm wide

John C Daley wrote:Think about getting a brick bolster to clean bricks with.
Its used in Australia for splitting clay fired bricks.
I also find a tomahawk very good as well.


They come 75mm to about 115mm wide

That brick bolster chisel looks great. I’ve got and old chisel for now. Maybe check if they have at the home center next time we are in the city.

Thanks, Peter ✌️

So the backhoe didn’t end up planning out in time so I decided to start digging the foundation by hand. Solo gig in heavy clay soil with a shovel and a pick. Not really a recipe for a good time, but doing my best to stay positive.

Only did the first run of one of the walls. Set to 80cm wide and roughly 50cm deep. Double block wall will be 40cm wide (15cm wide blocks x 2 + 10cm insulation gap between). With this in mind we’ll be doing an 80cm wide footer at the base of the foundation which will be 10cm thick. There will be 20cm of drainage gravel under the footer.

Do we need to use geotextile to wrap the drainage gravel or is it fine as is tamped in place? Our neighbor says we don’t need and it is proving hard to get at any price and amounts we can afford.

Also, after digging I found a soft spot in the bottom of the trench. It feels like really wet clay and it sucks your foot in when you step on it. Here are some images of what the clay looks like. Was thinking of digging as deep as I can in the soft spot and filled with large rocks and gravel. Then more tamped gravel, before laying a footer.

Also any advice on insulating the block stem wall. Was thinking of infilling the voids in the outside course of blocks with perlite. As well as infilling the 10cm space between the two lines of blocks with perlite. I can also potentially get volcanic sand/ash from the mountain near by. Would that be useful as insulation in any way?

I’m new to using batter boards and string line, but doing my best to keep things straight. I’ll have my neighbor take a look at what we are doing before digging the rest of the trenches. I’ve added 40cm extensions on each of the trenches so that we will have space to set up boards and run lines when we are ready to lay blocks.

Have removed the piers from the plan. We will just run 2 course of 3 stack block and start to frame on top of that as that was what was suggested by the old man, Mr Yoshida.

Thanks in advance, Peter & Mimi🌞

Hi Peter;   Bummer your backhoe couldn't make it to help.
I have a suggestion as a substitute for a pick.
A small hand held gas powered rototiller.. I have seen an entire foundation trench easily made with one. Their tines are usually 8-10" or so.
They will quickly dig down the depth of the tines. Simply shovel the dirt out and till some more.
You end up with a rather nice foundation trench without the mess made by a digging machine.

Now it may be your soil is so tough it won't dig but if it does.... lots less work for Peter.... sounds good right.... it also would be dug in way less time.

A great start Peter.  
It looks as if your soil doesn't have very many larger rocks in it so the tiller idea may work just great. If it does work out, it could potentially save you quite a bit of money if your renting the backhoe - always a reason for things that can direct you in a way that you may not have considered but turns out to be just as good or better :)

By the sounds of it, your neighbour (old man Mr Yoshida) is quite knowledgeable. Always great to have a local who can tell you about the conditions and what techniques work best for the area. That said, the fabric sounds like its not necessary to keep any fine sand and gravel from filing the voids in your rubble trench. Perhaps though, old bed sheets or something could be used to keep the initial fines from falling through until things are all packed and stable. Works great for an earthen floor. I usually use newspaper for this but both have worked great for me.

Not sure about the volcanic sand/ash, but stabilized perlite would work great. Pumice rock would also work good if you can find some. I've seen it in the classifieds as a free giveaway occasionally, and while your looking, there may be able to salvage some rigid insulation boards as well.

You guys are awesome!

Thanks so much for the ideas. The tiller sounds like a good one. I’ll have to ask around. Someone in the area might have one we can barrow for a few days.

Have 6 sheets of 90cm x 180cm sound insulation panels, used in the tunnels of the Japanese bullet train. That gave me the idea of cutting them in half and using them in conjunction with perlite to insulate the void in between the two cinder blocks in our stem wall build.

I’ve been told there is a place in the mountains, about 45 minutes from here, with all the free pumice you want. Mr. Yoshida knows where it is. Just have to figure out the logistics of getting it and if it’s worth doing considering cost of gasoline and transportation.

Also any ideas for roofing insulation would be much appreciated. Would love to do straw blocks or something eco like that, but time my be a factor.

You may find that 'old wood chisel', may be laminated steel and of fantastic quality.
It would be a waste to use it to clean bricks if it is.
I used to sell them.

Peter, for your ceiling you might want to make SIP modules. Try a frame about 600x600x50 mm and pack it with your clay straw mix. Once these are dry, just screw or nail them into place and plaster the inside surface. Go thicker if you need more insulation, or blow some wool into the cavity.

[EDIT] You will want some reinforcement in these. I did some using slender bamboo. Drilled the timber frame and poked the bamboo through the straw after it was packed and before the forms were pulled away.

John C Daley wrote:You may find that 'old wood chisel', may be laminated steel and of fantastic quality.
It would be a waste to use it to clean bricks if it is.
I used to sell them.

I know what you mean, but I’ve got a rusty old one and nothing else that fits the bill right now. Blocks are cleaned and stacked and ready to layup. So the chisel gets a rest for now.

Peter

Phil Stevens wrote:Peter, for your ceiling you might want to make SIP modules. Try a frame about 600x600x50 mm and pack it with your clay straw mix. Once these are dry, just screw or nail them into place and plaster the inside surface. Go thicker if you need more insulation, or blow some wool into the cavity.

Hey Phil!

Sounds like an interesting idea.
At 50mm thick that would give much in the way of insulation though would it?

Peter

It's a balancing act between ease of installing and insulating quality. 50 mm won't get you a whole lot but they're light and easy to put up as a ceiling. Depending on how airy your straw mixture is, I bet you could easily do 100 mm thickness without making them hard to lift and secure. I think you would still want wool on top of that given your cold winters.

I'm planning a sleepout/studio conversion of part of my garage and this is what I plan to do for the ceiling. Since the climate here is a lot more moderate than yours I will go with 50 mm and toss some wool into the attic cavity. We have over 30 million sheep here and wool insulation is being promoted heavily as a green alternative to fiberglass.

Another option for roof insulation is shredded newspaper (Cellulose) which is made from recycled paper that’s treated for fire resistance.

Gerry Parent wrote:Another option for roof insulation is shredded newspaper (Cellulose) which is made from recycled paper that’s treated for fire resistance.

Saw that!

Will inquire more if that is available here in Japan and if it fits in to our budget. Have a feeling this project is going to cost a bit of money so we’ll be pushing pennies around.

Thanks for all the tips everyone...

Peter✌️

Now we’re cooking with gas...😉

Actually, cooking with Diesel Peter..... :)     EDIT- Thomas pointed out to me that some diggers do run on gas so my apologies.

I see the backhoe came with its own professional operator too. Perhaps once she's finished with your digging, you can convince her to stay on as a hired hand?

Looks like Mr Yoshida has taken a fondness for your project. I'm sure you are teaching him with your 'weird' project just as much as he is teaching you what a lifetime has taught him.

With out him right now I would be lost in space...🛸🤷🏻‍♂️🛸

I had to drive the backhoe on the road to the site. It only goes about two miles an hour so it took an hour and a half to get it here, but should be well worth it.

Your right about the diesel.

Keep cookin...😉

Peter

We’ve got the start of a foundation. Rain has let up so will continue to shape the trench and get ready to infill with gravel and then the footer.

Will keep you posted.

Cheers, Peter🙏🏼

Looking good Peter & Co!

With the rain you've been getting, does it pool in the trench or percolate very quickly? Are you planning on any sort of drainage tube to be placed in the trench to carry water away from the foundation?
If its high clay, the soil itself could be sloped to a low spot and trenched away downhill too. Perhaps you've already considered this, just checking to make sure you get full use out or your rental before it goes away.  

Gerry Parent wrote:Looking good Peter & Co!

With the rain you've been getting, does it pool in the trench or percolate very quickly? Are you planning on any sort of drainage tube to be placed in the trench to carry water away from the foundation?
If its high clay, the soil itself could be sloped to a low spot and trenched away downhill too. Perhaps you've already considered this, just checking to make sure you get full use out or your rental before it goes away.  

Hey Gerry!

Really appreciate all the comments. Was debating about a pipe but for now I just sloped the base of the trench towards the back of the house on the south east side by 15 to 20 cm. Dug out all the soft spots and filled with urbanite and other shrapnel. Packed that down as much as possible. Plan to lay another heavy level of overnight for about 10 to 15 cm. On top of that drainage gravel. From there we will set up form boards to pour a footer. Wasn’t planning to use this amount of concrete, but the salvage concrete cinderblocks I feel make up for what we are ending up using in the footer and will give us a good solid foundation. Yoshida san said this is way more than is necessary for the site location, but I’d rather take a little bit extra time and be safe rather than sorry on the backend.

The site is relatively level and butts up against a gentle slope down to a service road. If we feel we need more drainage in The future, we can always dig out a trench from the back corner of the foundation to the road.

Here’s where were at today.

Heading out to potentially get some free double pane windows from a local who says he has some in the garage about an hour away.

We’ll see if that pans out.


Over and out!

Peter & Crew✌️🌞✌️

Overnight = urbanite🗿

Windows!🤸🏽🌞🤸🏽

🌞Quick questions🌞

Wasn’t really keen on using this stuff, but Gerry got me thinking.

Modern day Japanese tatami mats usually are polystyrene insulation boards covered with a traditional woven fiber skin. People throw these things out all the time and replace them with new ones. If I start searching around I’m pretty sure I could find a bunch. Was thinking two things.

A. Stack multiple layers of them over a packed gravel sub floor in different directions so that all of the seams are overlapped by the next layer. No thermal bridging. Sounds groovy?

B. Do the same thing in the ceiling cavity under the roof. Ideas on construction?

Won’t have a clear “R value” rating from random stuff I salvage from the dump etc, but if we use two layers in a tiny house and we pay attention to sealing details should be enough? Average January low temps are around -7°C. Very rarely goes to much below that. (Once or twice a season maybe -10°C to -15°C)

May couple the floor insulation idea with an additional layer of perlite depending on material costs. Definitely keep the stuff away from the RMH subfloor.

This is becoming a bit more fun every minute ...

Peter🛸

Peter; I would say you hit the free insulation jackpot!
Those look perfect!
And besides with your new tiny house, with already planned better insulated than your old home, and your RMH running... you will be sleeping with a window cracked!
Your island is beautiful... except maybe for those snakes you say are all over!

EDIT)  Got to watch that Gerry... dang guy makes you think about stuff all the time!

Hey Peter,    Recycling those matts under the floor as insulation sounds like a great idea. Not sure of the density of them, so several layers may produce a bounce to the floor which could be a good thing or a bad thing. I know when I added some perlite to my shop earthen floor, it did give a bit of a softness to the floor which was nice, just took forever to dry. Really nice feature to have if your walking on it barefoot. No comparison to cold, hard cement floors.
R-value is somewhere usually around 3-4 per inch.
Insulating the ceiling sounds great too. If the covering on them is to your liking, then it serves as a finished product. Or, I guess you could recover them with a different type of fabric too.  
Will be a lot of cutting of course to get enough of them together to get enough ceiling R value but if they are free and your labour is cheap :) then may be well worth it.

Thanks for that!

I’ll see what we can find and keep you posted. Try to make a house out of garbage.

One man gathers what another man spills...GD

Peter and Co.✊🏾🗿✊🏾

Peter,  I just added you also to the upcycling forum as well seeing your build is turning into a house of castaways.

Cool! I’ll check it out for sure.

Thanks, Pete🤸🏽

Another possible solution, that I have become quite excited about lately, is rice hulls and lime. Rice hulls, hydrated lime, and water are mixed together and installed as an insulating system similar to straw-clay. Advantages: better insulation than straw-clay, extremely mold-resistant, can be installed in wet weather, very easy to mix and install. Disadvantages: higher embodied energy for the lime production; requires permanent lath to hold the hulls in place since they are much more crumbly than straw-clay; only appropriate where rice is grown. Rice hulls are light and easy to transport (especially if you can buy them bagged); the weight would be much less than an equivalent volume of straw.

Here are the ratios I use for rice hulls and lime (“ricecrete”):

1 part dry hydrated lime
equal part by volume of water
equal part by weight of rice hulls

For example, here in California I can purchase both lime and rice hulls in 50-lb bags. I put one bag of lime into the mixer with an equal measure by volume of water - about 10 gallons. I let that mix for a few minutes then add one bag of rice hulls. The resulting mix fills about 6 to 7 cubic feet of space, so that will give you a sense of how much material you need. You don’t need to tamp or compress while installing the mix. Just pour it into the cavity and move it around a little to make sure there are no big voids.

The ricecrete mixture is far too light and crumbly to accept plaster directly. Rather than install ricecrete in moveable shuttering as I would for straw-clay, I hold it in place with permanent lath, installed prior to the infill. For lath I have used split bamboo, thin wooden slats, and also reed mat which is readily availble in hardware stores here. I don’t know whether mesh would be stiff enough on its own to do the job - it probably depends on the distance between your framing members. With the lath in place, there is no need to compress the ricecrete as it goes into the wall. This is advantageous because less compaction means more air in the wall, which means better insulation - and also less materials cost, less weight, less mixing, etc. I would not add any kind of fiber to the ricecrete because it would make it harder to mix, harder to install, and less likely to fill narrow cavities completely. Do be careful as you are filling to move the ricecrete by hand underneath electrical boxes or any other horizontal obstacle inside the wall cavity. You can lath one side of your wall completely and then on the side you plan to fill from. Don’t do more than 50cm vertically at a time so that you can reach the bottom and make sure that the cavity is completely filled.

Hey John,

This sounds extremely interesting. There’s a organic farmer not far from me. I was talking to him last fall. He uses the rice hulls in his green houses for bedding. He was saying that he buys the rice hulls from some where near by for about $5 a ton. That would make your idea a potential option in my book. I’ve been making a lot of my own lime putty from seashells since last summer. Have about six 20 gallon buckets stored up. It’s homemade so it’s less than perfect. Would have to process out some of the leftover shell bits I’m sure, but I have them slaking under an inch of water or so. This would be stronger than bagged builder lime for sure as it hasn’t been sitting in powdered form getting exposed to air. Would probably have to make a lot more as well.

I’ll start to have a think and a play around. Like the advantages you brought up and the fact that we wouldn’t have to wait two months for the walls to dry seems like a good alternative to LSC.

I’m still open to ideas for sure. Could we use this ricecrete mix to infill the gap between the cinder block stem wall? All the blocks will be above grade on a concrete footer. Two rows of blocks, three blocks tall, with a 10cm gap between the two courses of blocks.  

Thanks again for the ideas and inspiration.

Cheers Peter🧱🌞🧱

Interesting read...

https://theconstructor.org/concrete/rice-husk-ash-concrete-construction/15725/