Advice on a RMH build in Hokkaido Japan

Fox,  Gonna try posting in this manner if this works better for you :)..... You mentioned: "I would definitely not recommend a full ceramic fibre board construction for the feed chamber."  I agree too. The one that was being recommended was Matt Walkers CFB core which includes a fire brick feed tube.

Later you mentioned: "My new stove has some non standard design features, one thing that I have found a big improvement was building in small step from the feed box to the fire tunnel. In other words I made the bottom of the feed chamber 3/4” lower than the tunnel, I find this little step, stops the wood from falling into the fire tunnel and stalling the fire." I remember the original designs for the core included an ash pit at the base of the feed tube. I had not thought of the lip helping to keep the wood from sliding into the tunnel though. Thanks for the tip!

Peter,   "Thing that is hunting the back of my mind is punching a hole in the roof and the whole chimney thing for sure."  That can be a little daunting for the first time! It feels counter-intuitive to make a hole in the very thing that keeps the rest of the house dry. Perhaps some googling may pull up some videos to show how this is done for your specific roof or if it looks too complex for you to handle, to call in a local installer or carpenter friend. One thing I can say though, its recommended to put the chimney in first and work backwards as its much easier (and forgiving) to position the pipe in your bench/bell than it is to line up between the rafters and roof peak.

These numbers are not exacting but offer a starting point to work with. Not sure about temps each has to withstand.
1. Insulation under the fire brick floor pad?  2" of perlite/clay slip would suffice
2. Insulation around the feed tube?  Nothing definite that I know of but I would say at least 1-2" of perlite/clay slip or rock wool.
3. Insulation around heat riser?  1" Ceramic Fiber Board/Blanket or 2" perlite/clay slip

Love your progress photos. I can see your pups are really helping you stay focused .....and loved!

Thanks Gerry.

Didn’t realize there was a second page on this thread until now. Noted on all points. Will keep posting as we progress. Doing what we can to keep the water away from the house as the drainage set up here is less than ideal. Rained a bit yesterday and some water came in and settled in the right front corner of the room as I expected. This is the area I’m most concerned about moving forward as it’s the only spot where the perimeter of the room is exposed to an exterior wall. And dug a drainage channel that leads away from the house as a temporary solution. Could make quick work of it with a back hoe and a bit of regrading of the driveway, but not likely to happen until spring. Let me know if anything I’m doing looks suspect or kooky.

Thanks again for your time, Peter

Are you turning that ditch into a French drain?

Graham Chiu wrote:Are you turning that ditch into a French drain?

Just planning to fill with gravel for now.

Then put a gravel filled plastic box above grade, where the heaviest water falls, with a PVC pipe running out into the driveway for a quick fix.
Something like I have set up in the photos attached. Not the prettiest, but just to keep the water out for now.

Any thoughts? Peter

I can't see the images but if you don't put the french drain in, your gravel will become infiltrated with clay and render your drain eventually useless.  The gravel needs to be covered with non-woven geotextile fabric to stop the infiltration of clay, and then covered with turf but not clay.

Graham Chiu wrote:I can't see the images but if you don't put the french drain in, your gravel will become infiltrated with clay and render your drain eventually useless.  The gravel needs to be covered with non-woven geotextile fabric to stop the infiltration of clay, and then covered with turf but not clay.

Thanks for that Graham.

Think I'll leave it without gravel for the time being. See how it goes with rain and then make a decision when I have a better idea of just how much water accumulates in the area.

Cheers, Peter

So we are working away on the foundation part of the project still.

Planning on putting in the perlite earth bag insulation on top of the tamped drainage gravel layer, when it arrives.
In the meantime I was thinking about this area of the foundation in the room that is directly exposed to the outside. There were just a few rocks stuck in the clay soil original. (See attached photo)I was going to put them back with a bit of plastic board and be done with it, but then I thought while I have clear access to the area I should do it right to avoid issues in the future.

Would it make sense to dig the area between to two concrete foundation piers out? Make the space deeper than the area I have dug out in the room, then back fill with a bit of drainage gravel. On top of that build a concrete mortared stem wall that spans the distance between the two piers. Essentially, making a single mass of stone that sits above and below grade. (See attached drawing)

Is this a good idea?

If not, are there any better options that I have yet to discover?

Any and all advice on this would be much appreciated.

Thanks in advance, Peter

Peter,  I'm assuming that most of the water that's getting under the building is coming from the roof? At the risk of sounding obvious "DUH!" I notice that you don't have rain gutters to direct the water away from the building. Any objections to installing them or am I missing something?  

Admittedly I'm in a city in China right now but I'm not seeing any rain gutters or down pipes.  Rain just falls to the streets and is drained from there.

Hey guys,

Thanks for the input.

Yeah. That seems like it would be a good idea. However, when I ask the locals why none of the buildings here in Hokkaido have rain gutters and down spouts I'm told that the heavy winter snows tear them all off the buildings. Also faced with the awkward way that the two roofs meet. The roof of the entrance portion of the house sits under the roof of the main building.

Have a feeling that some of the things I'm told by the locals regarding building and design here are based on the mentality of "that's how we've always done it, so thats how it has to be done." Want to be able to make that decision based on my personal experience and observations. Really want to see a full season of rain and snow here for myself and then make a plan on how to retrofit the roof. For the time being, just want to avoid any damage to the inside until the spring.

I must add that there was no water build up on grade under the floor when we pulled it up the other day and no extreme mold or wet rot in or around the foundation in the room we are building our RMH. Looks like we are going to get heavy rains for the next two days. Think this will be a good chance to see how much water actually enters the area and how long it takes too dry. Was really wondering if my idea for the short steam wall, between the concrete piers, was good or not. I have access to the space now and would be relatively easy to do if worth doing.  

Any advice would be much appreciated.

Thanks, Peter

Peter,    I can see a french drain working the way Graham described (extending it all along the roof drip line and then a channel exiting away from the building) but I'm having trouble understanding the purpose of the stem wall. To partially enclose the area where your building or to keep rain from getting in? Maybe you said it but its not sinking in..... :)
Also, the reasoning behind the no gutter issue is the same here when there is a metal roof involved - shingled roofs are no problem as they hold the snow in place. One way around this is to put up snow guards:



                    ...................OR.........................

Thanks for all the ideas and image reference.

You guys are right in your approach to the issue of water for sure. The main problem I would be facing with rain gutters at this point is that the roof construction style. (See attached image for clarification) As you can probably see, it’s pretty basic old wood construction and feel that in the present state the edge of the roof would not be able to handle rain gutters. On top of that I feel I need to focus on the RMH build and can’t afford the time or money to dive into a rain gutter project until next year at the earliest.

On another note, we have finished the gravel layer, tamped and fairly level. Have perlite and earth bags. Will start that soon.

I have cleaned out all of the dirt, dust and cobwebs between the post and beams on the perimeter of the room. Cutting wood panels now to cover all the gaps along the edge of the room so that none of the cob or other building materials will spill out. Will send photos of that part of the build later so you can see what I’m doing. Going to char all the new boards I install to help prevent rot and water damage (Shou Sugi Ban or Yaki Sugi) https://en.wikipedia.org/wiki/Yakisugi I’ve been using this technic a lot on all the wood I’m using around the house.

I also had a closer look at all the foundation beams in the room, as I know that this will be one of the last times I will have access to the area for any fore seeable future. Most are in good shape. The one furthest from the door is showing bit of mold and wear.

I made a decision to char this beam in location to help prevent any further damage. I know this is probably an extremely dangerous thing to do, but felt that it was necessary. I would not recommend this to others, however here are some images of what it looks like now. (see attached images) I used a small torch and worked in a very confined area, one bit at a time and had water close at hand. Think that the char has probably killed the mold spores and seems to be a stronger surface than before. I only did the two exposed faces and avoided burning hard into any joinery as I was afraid that it might create ambers that I could not see or control.

I also plan to apply a natural wood preservative that is used here in traditional Japanese wood frame construction call mokusakusu（木酢酢）, directly translated as “wood vinegar”  Looks like it’s scientific name is Pyroligneous acid. It’s been traditionally used here to waterproof wood foundation posts and other timber that is exposed to wet conditions. I will let you know how it goes.

Found a local guy named Taka. Was introduced to him the other day and we got to talking about RMH. He made a fire brick one last year and used it through the winter. He says that he had some issues with his bench and is in the processes of redesigning. When I told him about our bell bench project he said he would be more than happy to help with the build and that he is excited to meet someone who is interested in RMHs, as there are very few locals that understand the concepts and very little information in Japanese on the topic.

He is going to help with the chimney supplies and installation as well. He says we can find a good deal of parts in Sapporo. We will go there early next week. I’ll keep you posted on lead if anyone else reading is having difficulty finding materials in Hokkaido.

Thanks again for all your input.  Will keep posting. Cheers, Peter

Hey folks.

Just opened the perlite bag and found this powder inside. Much finer than what I was expecting. Is this stuff too fine for me to use or will this work for floor insulation in the earth bags and as a mix with clay to insulate the RMH core?

Please let me know. Thanks Peter

I would say that the coarse perlite has a higher air porosity than the powder, meaning it can probably insulate better. Only a guess though as I have never used it.

Hi again Peter,

Has anyone mentioned yet, (1) your scaffold platforms are made to support weight above the sheet metal, on top of the framework. Best to use them right side up. Your plan to sit them upside down will put earthen weight on the sheet metal in a way that is opposite of the way it is meant to fight gravity. It might press the sheet down into the smoke chamber. I guess the first symptom might be cracks, in frequently used bench spots. (2) Also, one of the totally awesome drawings shows maybe too little clay on top of the metal, to prevent cracking of your finish layer. Thickening that layer of clay would need your scaffold platforms lower, because that is a doorway threshold you want level with the next room.

Hope this helps, maybe preventing some future redo.  You are working so fast, hope this comes in time to consider. Maybe it is lucky to have rain issues, so there is time for indoor head scratching :)

Peter Sedgwick wrote:Doing what we can to keep the water away from the house as the drainage set up here is less than ideal.

Sometimes commonly-correct advice from far away doesn't recognize your particular situation.  I see your entire area is likely top graded in clay. So the top grade of your yard on some side of the house drains water across the surface, to the lower grades. If that is true, any ditch you dig would fill with water. To have a so-called french drain, it needs to end "at daylight", that is some place where the pipe opens to a place for water to fall out of the pipe to a down-hill spot. Sometimes people dig deep wells for such a spot. But depending on the hillside you may live on, such a clay-lined well might completely fill, and so be unhelpful. If your entire area is top-graded with clay, digging ditches asks surface water to collect, not drain.  It is likely your old house is not rotting underneath because the builders recognized the geography well. Sorry to say, this would suggest removing the gravel and filling with tamped clay might be part of the solution. Sounds like a lot of work, so I hope I am wrong.

Thanks for all the insight and advice.

Regarding the grade of the house. I have included a few photos of the front driveway and parking area to give you a better idea of the space. If I can get the water just past the left side of our parked car it will be moving down hill. For the immediate future I think I’m going to use my makeshift plastic box of gravel and pipe idea. This will only be a temporary solution, but will work. Fat flexible corrugated drain pipe about 8m long that I can move around. Box of gravel will be above grade so no chance of being clogged with clay and silt. This will buy me time and allow us to focus on the RMH build we need to finish.

The room at present looks like this. (See attached images) Tamped gravel is level under the carpet. The carpet is there just because it was the same old carpet that was in the room before. It fits exactly to size. May put a plastic sheet on top of the carpet before laying perlite insulation.

The perlite that we have states that it is used for construction/insulation. It is a powder so may not have the same air/insulation capacity as larger perlite beads, but is intended for insulation use, not soil amendment. It was arrived in these large paper bags. Tried transferring to earth bags, but the powder comes out a bit through the holes in the weave. Also seems like it might be difficult to tamp in the bags by it self.

Would it make sense to do a 85% to 15% Perlite Powder to Clay mix and then put that in the bags?

Effectively creating a quasi earth bag fire brick block layer as a base.
Point: Still below grade here.

Is this a good idea?

If so how thick should I make this layer?

Tamped road base will go on top of the perlite layer.

The area under the fire box will get an additional base slab of perlite and clay fire mix for insulation.

As you can see I filled the gap between the two piers with concrete and urbanite to just above grade. The bottom of the hole is filled with gravel earth bags to act as a drainage point for small amounts of water. Had an open bag of cement mix laying around and figured it couldn’t hurt.

As you started, the site is clay heavy, however after inspection the water will drain within a few hours. (See photo of hole)

I understand your logic on the scaffolding, however I have weight tested them both right side up and upside down. There is a bit of play in the sheet metal either way. When I press on a drum can laying on its side it flexes about the same amount as the scaffolding. Matt Walker uses half barrels in his stratification bench builds without issue, so as long as all the welded joins are taped with high temperature tape and there is a sufficient amount of cob incasing the unit I feel it should work. Am I overlooking something here? Please correct me if my logic is flawed in anyway.

I would love to keep the edge of the bench flush with the door sill, but if it needs to come up above this high for logistical and safety reasons I am more than willing to compromise. Aesthetics and convenience play a secondary role for me now.

This project is an experiment and a learning  experience for us. We are likely to build other buildings on the property in the future. I want to use this project as a means of gaining an understanding of the build process and the local site specific variables, so that we can improve our technics and approach moving forward.

Would love your thoughts regarding my approach and above questions.

Thanks always for your time. Peter

So I had a bit of a rethink on how I could successfully use the perlite powder that came in the mail and I cam up with this idea.

Needs: Insulated sublayer several centimeters below grade.

Materials I have to work with:
1. Perlite Powder used for commercial building/insulation good to 1200°C/2192°F (as stated on the Japanese manufactures website)
2. Buckets of Natural Lime Putty Slaked 2 months ago
3. Tones of Biochar/Charcoal
4. None Biodegradable Earth Bags

Because the Perlite is in a powder form it is difficult to work with and flys all over the place.

I original thought to mix with a bit is clay and then fill the earth bags, but now I'm thinking that it might be better to mix with charcoal and a bit of quick lime paste.
Just enough moisture to keep the mix together. Then fill the earth bags and tamp them like tiles on top of the drainage grave.

Then fill all of the spaces between the bags with the same mix and tamp that level.

Top with 10cm/4in of road base and tamp that as well.

Questions:

1. Does this sound like a via-able solution for a sub grade floor insulation layer using the materials I have on hand?
2. Should I avoid tamping this layer too much as it may reduce the insulation value of the mix inside the bags?

Points: This perlite&charcoal insulation layer will not be in direct contact with the fire box of the RMH or the bell chamber of the bench. Fire box will have it's own additional base pad of perlite and clay on top of the tamped road base layer. Fire box will be made with refractory ceramic fiber board, good too at least 1300°C, in a 6" J-tube style core based on Matt Walker's plans.

Let me know if this sounds reasonable and if anything needs clarification.

Thanks, Peter

Peter Sedgwick wrote:Questions:
1. Does this sound like a via-able solution for a sub grade floor insulation layer using the materials I have on hand?
2. Should I avoid tamping this layer too much as it may reduce the insulation value of the mix inside the bags?

1. Can't say I've heard of that mix before but it doesn't sound like it wouldn't work either. One thing for sure though is that you want to only add enough of the binder ingredients to hold or keep the perlite from going through the bag to keep the insulation value as high as possible. Maybe do a test brick and see how it performs before committing?....or can you put it into a non porous bag first before it goes into the earthen bag? Seems to be the easiest and most insulative.....
2. Because this perlite insulation layer is load bearing, you certainly don't want it to shift/settle over time so I would think to tamp it quite firmly. Think of it like sand...you can tamp all you want but you will still have air pockets in between all the little grains.

It is said that perlite by itself can have an R-value of up to R-3/inch thickness but is relative since the R value of the perlite is unknown with the addition of the binders.  Not sure how cold it gets there or what local codes state as a thickness but this might give you a starting point.

Edit- Is your carpet also acting as a vapour barrier? If not, then vapour barrier goes below the insulation layer.

Peter Sedgwick wrote:Regarding the grade of the house. I have included a few photos of the front driveway and parking area to give you a better idea of the space. If I can get the water just past the left side of our parked car it will be moving down hill.

Glad to see the area slopes down across the driveway, for a future drain.  Does the area slope up in the opposite direction, to the back of the house? That could be a source of water, not just the roof.  

I really like your project and appreciate all the details you are considering.

Peter Sedgwick wrote:I understand your logic on the scaffolding, however I have weight tested them both right side up and upside down.

Ah good. Glad it looks good to you.  The reason I asked:  Right side up, when the sheet flexes, it is supported by the scaffold frame.  Upside down, when the sheet flexes, it puts pressure in the direction of pushing the welds apart.  half-barrel sheet-metal is strengthened by being shaped in an arch, so that's a bit different.  Maybe there is still time to lower the whole thing, or the flue so the top layer can be a bit thicker, without getting in the way of your threshold?  Others know more than me about how thick that top layer should be. I do know flexing would cause it to crack, and thicker earth is less likely to flex.

Gerry wrote: Because this perlite insulation layer is load bearing, you certainly don't want it to shift/settle over time so I would think to tamp it quite firmly.

That sounds right Gerry. Perlite isn't very sensitive to pressure, but it is very water absorbent, so the drainage is definitely important.

Peter, How about mixing the perlite with the clay you have? Clay soil is great for rammed-earth construction, and some people mix perlite in their earthen floors. For your insulation layer, maybe mixing with enough of your clay soil to make it tamp-able?  The lime idea could work too.  Perlite insulative plasters and gypsum are a thing.  From an Asian manufacturer, I read that powder perlite is heavier than course perlite when mixed with cement, so some light-weight concrete recipes combine both powder and course perlite together to make it stronger.  Mixing clay soil with dry perlite powder might require water, like mixing cement, just to keep it from flying away. Or maybe a cement mixer alone would be enough to contain it.

All of that is conjecture on my part. I've worked with cement plenty, and have read lots about light-weight concretes, but have never tried earthen floors.

Antigone Gordon wrote:

Peter Sedgwick wrote:I understand your logic on the scaffolding, however I have weight tested them both right side up and upside down.

Ah good. Glad it looks good to you.  The reason I asked:  Right side up, when the sheet flexes, it is supported by the scaffold frame.  Upside down, when the sheet flexes, it puts pressure in the direction of pushing the welds apart.  half-barrel sheet-metal is strengthened by being shaped in an arch, so that's a bit different.  Maybe there is still time to lower the whole thing, or the flue so the top layer can be a bit thicker, without getting in the way of your threshold?  Others know more than me about how thick that top layer should be. I do know flexing would cause it to crack, and thicker earth is less likely to flex.

Point taken on the curved half-barrel. Worth reconsidering. As far as I have read minimum thickness on the bench should be a least 12cm or so (4.5 in) It says in the book, but I just lent it to the guy in town who made a RMH last year. Will check again later. Was also thinking that it could make sense to add some perlite to the cob mix on top of the bench as a means of micro managing the temperature of the surface. If it's too hot add more perlite. Is that a reasonable idea?

Thanks again Gordon!

Peter

Antigone Gordon wrote:

Peter Sedgwick wrote:Regarding the grade of the house. I have included a few photos of the front driveway and parking area to give you a better idea of the space. If I can get the water just past the left side of our parked car it will be moving down hill.

Glad to see the area slopes down across the driveway, for a future drain.  Does the area slope up in the opposite direction, to the back of the house? That could be a source of water, not just the roof.  

I really like your project and appreciate all the details you are considering.

This is an other great question. Yes the house sits just bellow a step down with a mountain behind that. Drainage in the back is not fantastic but have managed to improve it drastically by hand digging a ditch that runs down to the old rice fields. Photo of the snow build up behind the house last spring. Lees then good to say the least. Will send more photos of the present situation later for sure. Give you a better idea of what we are dealing with.

Peter

I decided it was best to jump into this next layer of insulation. Innovation comes through experimentation I figured, and as long as we have a roof over our head and a source of heat we are bound to make it through the winter.

After reading your comments, Gerry, I felt that the earth bags really didn’t serve any purpose in the situation below grade. Best to keep the layer continuous with out any gaps. The binder didn’t seem to make sense either, so I put some of the perlite powder and some charcoal in a bucket and added a bit of water just to keep the dust down. That seemed to look alright so I mixed up larger batches in a big plastic tub and laid it out on the floor. Did a half a tub at a time with about 10 liters of charcoal at a time, sometimes less sometimes more. Left the big chunks of charcoal  in as I figured they would hold air. First batch was a bit charcoal heavy. Next batch was a bit too soggy.

Basically started to mix the water in so that it felt like damp beach sand. When I laid the mix out and pressed on it a bit it reminded me of the dark green floral foam stuff they use at the flower shop. That seemed like insulation to me. . . Will lay the remainder out tomorrow and tamp. Probably wont have the suggested 15cm of insulation with the perlite I have so likely to top it of with a bit more charcoal and then tamp that.

Willing to add  clay into the mix if you think it would help.


Making headway with the CFB and looks like we can get it at a reasonable price through the manufacture here. Should be able to start piecing the fire box together next week. Matt Walker has been extremely helpful and his plans for the J-tube core design are extremely easy to follow. http://walkerstoves.com/super-hot-ceramic-fiber-cores.html



Thanks again for all your insight and will keep you posted as the project continues to develop… Peter

Hey guys,

The perlite powder and charcoal layer by itself did not tamp down very well, so I took all the materials and mixed them with a bit of clay rich soil from the property and made earth bags out of them. Started to lay all of them out in a block formation to create an insulation layer for the sub floor. This seems much more stable and more consistent to build on. Some photos attached of our process. Made a lot more charcoal and added that to the mix. Will see how that goes.

Also was able to source a fair amount of chimney supplies yesterday in Sapporo, including the split fire bricks needed to line the feed tube on the ceramic fiber board core and larger grain perlite in big bags. Prices for this stuff was reasonable a the home center. Planing to start the install on the insulated chimney pipe middle of next week.

Taka, the local Japanese guy,  has been very helpful with sourcing and also showed us the RMH he built last year. He is using only movable fire bricks for his feed tube. He says it is not super efficient, but still uses less than half the wood compared to a conventional wood burning stove. He plans to make modifications to his chimney after helping us.

Regarding your question about codes, Gerry, we live in the middle of no where, so codes don’t really apply in this situation. Pretty much hillbilly rules…

Will keep posting.

Cheers, Peter

Peter Sedgwick wrote: Yes the house sits just bellow a step down with a mountain behind that.

Wow, That's exactly what traditional fengshui traditions call ideal! Got weather and invader protection on your back, and a clear path to water in front :) Sorry to see the snow piling against the back wall, that explains the water damage on the sheathing. That ridge you stand on must direct some water around the house, to the old rice fields you mention. So that seems like the thing to pay attention to with digging out under the RMH room. I've got a gut feeling you might wish that wasn't dug out, because it is a low spot at the base of the mountain, a pooling spot.

And the typhoon happening right now!!!  Oh my I just thought of that news I heard last night. Hope you are all safe.  I'll stop talking about construction while your heads are down under that deluge! Stay safe. The house is not as important as your wellbeing. .

. . . Ah, you just posted a couple minutes ago, and no flood in your pictures :).

Antigone Gordon wrote:

Peter Sedgwick wrote: Yes the house sits just bellow a step down with a mountain behind that.

Wow, That's exactly what traditional fengshui traditions call ideal! Got weather and invader protection on your back, and a clear path to water in front :) Sorry to see the snow piling against the back wall, that explains the water damage on the sheathing. That ridge you stand on must direct some water around the house, to the old rice fields you mention. So that seems like the thing to pay attention to with digging out under the RMH room. I've got a gut feeling you might wish that wasn't dug out, because it is a low spot at the base of the mountain, a pooling spot.

And the typhoon happening right now!!!  Oh my I just thought of that news I heard last night. Hope you are all safe.  I'll stop talking about construction while your heads are down under that deluge! Stay safe. The house is not as important as your wellbeing. .

. . . Ah, you just posted a couple minutes ago, and no flood in your pictures :).

We're in Hokkaido so well away from the Typhoons and most of the earthquakes that happen in this country. Thats one of the main reasons we chose this location. Little to no chance of catastrophic natural disasters and tons of space to do stuff. Consume less, create more.

Thanks for the concern Gordon.

Cheers, Peter

Update:

We have finished the earth bag insulation layer and tamped that. Also done a few inches of tamped road base, but am now back to grade. Need to install a perimeter block wall for the outer edge of the left side of the room which will act as one side of the supporting structure for our bell bench. I do not have as thick of a road base layer as I was hoping, but as we are back to grade I feel I have to lay the wall in order to insure any more layers above grade don’t spread.

Question:

Should I lay lime mortar on the ground before laying blocks to help stabilize the blocks and crate a more monolithic structure for our metal scaffolding top to rest on?

I am planning to insulate the inside of each block cavity with a mix of lime and perlite. The inside of the outer block wall will then be coated with a mix of perlite and cob. The floor of the cavity will also have the same perlite mix. The inside of the other wall will only have cob as we want the heat to transfer into the room.  Insulating the areas of the chamber that we don’t want the heat to escape from and creating thermal mass in the areas where we want heat to collect and travel.

Hope this makes sense.

Plan to start this layup in the morning. Let me know if I’m off with my approach.

Thanks, Peter

Wow, That's exactly what traditional fengshui traditions call ideal!

Glad to know we're in a good fengshui way...:)

Hi Peter,   It certainly wouldn't hurt to put a layer of mortar below the bricks if you feel that your roadbase is not thick enough to support the scaffolding. Extending the 'mortar' (technically mortar is a smooth consistency but should actually contain small rocks for strength for this application) beyond the footprint of the blocks would also help to distribute the weight over a larger area. Don't want any settling over time that could have easily been prevented!
The pictures were very helpful. Keep up the good work... both of you!

Gerry Parent wrote:Hi Peter,   It certainly wouldn't hurt to put a layer of mortar below the bricks if you feel that your roadbase is not thick enough to support the scaffolding. Extending the 'mortar' (technically mortar is a smooth consistency but should actually contain small rocks for strength for this application) beyond the footprint of the blocks would also help to distribute the weight over a larger area. Don't want any settling over time that could have easily been prevented!
The pictures were very helpful. Keep up the good work... both of you!

Thanks Gerry,

In that case I’ll lay down a layer of limecrete. 2” or so should be enough?  Also thinking of adding cut up scrap fiberglass fibers to the limecrete layer for added strength. That makes sense? Create an L-shaped perimeter of one set of blocks with a limecrete footing along the outside edge of where the bench will go.  From there I can infill a bit more road base and tamp even though we’ above grade.  This might bring the whole project a bit higher than the bottom sill of the sliding doors, but  I believe we should prioritize structural integrity over aesthetics and convenience in this situation now.  It’s 8 AM here now, I will start the process soon. Please let me know if I missing anything or there’s anything else I should consider before starting.

Thanks once again for all your advice and insight.

MIMI, the gang and I really appreciate all your effort.

Cheers, Peter

I better look at the front yard...:)

Peter Sedgwick wrote:In that case I’ll lay down a layer of limecrete. 2” or so should be enough?  Also thinking of adding cut up scrap fiberglass fibers to the limecrete layer for added strength. That makes sense? Create an L-shaped perimeter of one set of blocks with a limecrete footing along the outside edge of where the bench will go.  From there I can infill a bit more road base and tamp even though we’ above grade.

Just as in cob, fibers would help out with strength. Even more so since your wanting to keep the thickness down to a minimum. Makes perfect sense.
Not sure though about drying times and how they will affect your building schedule. As you may know lime takes much longer to set properly than cement (especially if you don't want cracks) and if the weather is cold even longer drying times. I have read that a limecrete slab strengthened with fibers is generally safe to walk on after about a week but will continue to strengthen over the following months. Another route could even substitute cement patio bricks or urbanite chunks instead?
PS... Nice front yard to wake up in the morning to!!

Roger that Gerry!

Building schedule really depends on the weather. It looks like it’s going to be sunny for the next week so we can get a lot done. I’ll keep considering options for laying up the blocks.  For right now here’s a rough layout of what the room might look like. (+or- the dog) Don’t need to walk on the lime slab any time soon so could give it time to cure. Again, limecrete would only act as a footing for the blocks to sit in.  Other option could be to pour formed concrete slab for under blocks to increase speed and drying time. Just feel the lime would provide more room to play if there was shifting in the future under the blocks.  Plan to use urbanite on far side of the barrel and other walls in conjunction with earth bags and more road base in fill.

Seem reasonable?

Peter

PS it’s a beautiful place to live...🌞

Quite reasonable Peter....
BTW,  love your feed tube!

Gerry Parent wrote:Quite reasonable Peter....
BTW,  love your feed tube!

Refectory plastic yellow box, good to 1 billion degrees...⛄️🔥⛄️

Hey Peter,   I ran across some pictures today that I had saved a while back and thought of your build. Here's the link: RMH

Gerry Parent wrote:Hey Peter,   I ran across some pictures today that I had saved a while back and thought of your build. Here's the link: RMH

Hey Gerry thanks so much.

Pictures are awesome.

Here is how I did the footing for the block wall. Pad of fire cement with rebar throughout. Blocks are embedded about 1/4 of the way up. Also filled all the blocks with charcoal for insulation. Will cover later with perlite and cob on inner face of outside wall and floor.

Worked on the scaffolding bench top. Found some galvanized post pipe for free at the neighbors farm, so planning to use that to reinforce the top. Concerned about air drag inside the bell chamber so still thinning it will work better upside down. Planning to fasten all the pipe to the scaffolding with bolts. This means more holes in the steel.

Could this be an issue?
Everything will be embedded in a lot of earth. At least 5”/12cm on top and all around. I read different things regarding this topic and I’m not sure what to follow.

Also laid out the room again with scaffolding and drum can. This should give a rough idea of the floor plan.

With the drum can as close as I can get it to the scaffolding the clearance on the right side of the drum can from the wall in 14in/35.5cm. Thats 4” shy of the recommended clearance distance from combustibles.

Any thoughts on this?

Starting the chimney part soon.
CFB will be here in two days.

Will keep working away.

Keep you posted. Cheers, Peter

Peter Sedgwick wrote:...Concerned about air drag inside the bell chamber so still thinning it will work better upside down.

Not too much concern with air drag in the bell. Lingering time to allow stratification to occur is important to pull as much heat out of the exhaust (to a point of not killing your draft). Internal Surface Area (ISA) is important which is why some people have used pillars or irregularities on the inside of the bell to increase the ISA. The bell sizing on the Bell sizing webpage remember is based on a batch box. J tube will need to be smaller as they don't put out as much heat. Not exactly sure how much smaller off the cuff. Matt might be able to help you out on this.

Planning to fasten all the pipe to the scaffolding with bolts. This means more holes in the steel. Could this be an issue? Everything will be embedded in a lot of earth. At least 5”/12cm on top and all around. I read different things regarding this topic and I’m not sure what to follow. Could this be an issue?

Everybody has a different panic button - With some its escaping gasses killing them in the night. Not downgrading escaping gas as an issue but depending on where you sit, will influence how much precaution you take, hence the variance in opinions. For me, I would seal all joints with an inch or so with straw rich cob, let that dry and then put your mass cob over top of that. This creates somewhat of a double seal. A good carbon monoxide detector could also be on your list if you feel the need.

With the drum can as close as I can get it to the scaffolding the clearance on the right side of the drum can from the wall in 14in/35.5cm. Thats 4” shy of the recommended clearance distance from combustibles. Any thoughts on this?

I remember you saying something like your in the boonies so only hillbilly codes (your own) to follow.  To be safe though, you may want to put a heat shield which could be as simple as a piece of sheet metal with a 1" air gap behind it.  Hard to write these kind of things in a book meant for the general public :0