Planning cob building for later addition

I'm reading books on cob building and am planning to build a small house. My plan is for a house with a rock stem wall foundation, an oval shape, and a simple gable roof with two sides. There will be one round center beam (tree trunk) spanning the building. The center beam will support dimensional lumber beams, on top of which there will be dimensional lumber boards. Large plastic laminate roofing pieces will cover the boards. I chose this type of roof because I am a novice builder and where I live roofs are commonly built like this. I currently live in an adobe house with this exact type of roof, and I think it's something that I can imitate myself on a smaller scale, designing the size and dimensions of the new cob building to coincide with the size of the straight trees on my property.

The way these types of roofs are built here, the center beam sticks out into the open air on the outside of the house, with the roof covering the beam. Since the beam ends are exposed, sometimes people put buckets on the ends as a way to try to further preserve them. Most of the year is dry, but it rains heavily for five months a year (around 1000 mm).

My plan is to build one small room (maximum 20 m2) with this style of roof and later add a series of other similarly-sized rooms, creating a chain of rooms linked together. I have plenty of space to build in this stretched-out style, and I want to keep the rooms one-story to allow for easier building. Building like this will also allow the building to have a long stretch of southern wall, helping to keep it warm.

(In this coldest months, it gets down to below 4 C at night and up to 20 C in the day (38 F to 68 F), with very strong sun due to the location and moderately-high elevation (2200 M).  I've lived in very cold adobe houses here that didn't get much sun due their proximity to trees, but a thermal mass style house, if positioned correctly, can be very comfortable due to the strong sun and relatively high daytime temperatures.)

With hired help to allow for faster cob mixing, I think I can reasonably expect to get one of these small 20 m2 rooms finished myself during a dry season. Then I can wait and continue building my little rooms in a row in the following dry seasons.

My questions is about how to connect these small rooms. My original idea was to have a series of these small rooms and then not even link them up at all, since the climate allows for this. My next idea was to link them up with covered walkways, or maybe cob hallways with their own independent roofs. Gutters are used here to collect rainwater, which helps immensely with the roof runoff during the rainy season.

Then I realized that these plans would necessitate building an extra wall. If I could link up the rooms in a smarter way, I'd only have to build 3 walls instead of 4 for the second room. What I'm having trouble visualizing is how the roofs would connect. My biggest question is: where would I place the tree trunk center beam in the second room? What would support it?

As I'm sure you can tell, I know very little about building and nothing about architecture. Would anyone be able to point me in the direction of some resources that might answer my questions?

Thanks for reading, Saludos

One question that might help suggest an answer is, is there a slope from side to side in the area you want to build these rooms? If you make the first one, then the next and the next a step up or down, you could make the roofs nest over or under their neighbors, and potentially allow a pocket in the first wall for the beam of the next to slide into.

Thanks for your reply. The building site has a slope that runs down towards the south south-west. The eventual long building would run more or less from east to west. So I don't think I'd be able to take advantage of that slope.

From what I gather, the second room/building is always going to have to have four complete walls, rather than three, and then the idea is to have its roof a little lower or higher than the roof of the first building?

The adobe building i live in has a loft on one side, over the kitchen, and so the couch and desk are in an area with a high roof, which I found I really don't like-- another reason I wanted to make one story rooms with fairly low roofs.

Also, I'm open to other roof styles. It just has to be something relatively easy to construct and also easy to attach gutters to, since the only source of water on the property is rainwater. A friend in the area made a reciprocal roof that's very impressive visually, but I'm not sure I want to deal with the complications it seems to present at the time of building.

I hope this photo can give a better idea of the type of roof I'm planning. My building would be similar but made of cob, and without the steel/concrete beams and posts, and also much lower.

My recommendation would be to build a rectangular building with a pulpit roof. Door(s) to the future addition would be just thinner wall that would be cut/knocked in the future. this way you eliminate the 4th wall in the addition.
I consider roofs to be most complicated part of the house and creating passages with gutters, etc will add complexity and complexity is less reliable than simplicity.
With rectangular building you would add rectangular foundation for the addition and the addition's roof would be lower (and well flashed). Or you could leave pockets at the ends of first building's rafters that would receive rafters from the addition. It would create a very strong roof - rafters would meet (even load distribution) and would be supported by the center wall instead of the ridge board. My house is built this way.

Thanks for the reply and the idea. A rectangular building is definitely a possibility. Sorry I'm not familiar with pulpit roofs, and my online searching isn't turning anything up. Does that style of roof not have a center beam?

I don't have any actual experience with any of this, so take it with a grain of salt. But my first thought is to delay the savings. You're going to build one of these single-room dwellings anyway. You'll learn a lot while doing that. When you're done, next dry season, build another -- but site it with a connective future in mind and maybe build them two feet taller than you're thinking of right now:


Maybe you'll like them unconnected. Maybe you'll want just a covered walkway, like you suggested, for a while because it's quick and easy to put up and controls mud during the rains:


Maybe you eventually connect them with a room but you go with a simpler design if the geometry works out. A tall wall and a short wall connecting the two buildings with a shed roof. Maybe it's a greenhouse instead of cob, or cob only on the north:


Or maybe you connect the two with the exact same construction style but you don't try to meet the roofs and beams, you just tuck the center building under, excavate a hole in the cob on each side for this beam to rest in (along the lines of Glenn's suggestion), but two feet down from the others:

I live in a relative warm climate year round.

If I were to add an addition to my home it would be attached, considering expense.

Not knowing the reason for not attaching this room, I would say that if I were to do it that way, I would not want the added expense of building a third structure.

Beltran,

Pulpit roof is just a half of a most popular gable roof. After re-reading your post I have realized that a pulpit roof with 1000 mm of rain would not be the best option.
I have quickly prepared a design, showing a pocket for the ridge beam extension and thinner wall (mustard color) that would be knocked down to create a door to the addition. I have also added brick cornice so entire roof structure can be encapsulated in masonry that with clay/cement/stone/steel roofing material would make a house not fearing wildfires and it would make the house look better.
I have assumed 40 cm thick wall, 200x200 mm ridge beam and top plates and 100x150 mm rafters with 500 mm spacing.
The version with concrete beam would not have the wooden lintels above the door openings.
If you need detailing of the wood joinery, or reinforcement/anchor placement I can help by adding them to this quick design.
Are you going to build from cob loaded by hand or with adobe/CEB blocks? If the latter is the case, you could leave some blocks out or loosely connected to the main wall, so when you add the addition you could remove them and replace with blocks being also part of the addition wall, so a good bond would be created..

Wow, this forum is great! Thanks for the drawings, designs, and ideas!

The adobe building that I posted in an earlier message has 50 cm thick walls, and I was planning on making the cob walls a similar thickness. The old adobe buildings in this area (near Patzcuaro, Michoacan) often have very thick walls, but the newer adobe buildings I've seen often have 30 cm thick walls, with no beams or posts of concrete and steel.

I don't understand why the center beams typically extend out beyond the building wall. When they installed the center beam in the house in the photo, I asked them why they didn't trim it down, and they told me that it was a preventative measure -- if the end began to rot in the future from the rain, you could always lop off the rotten part with a saw.  From what I've observed, the rain doesn't typically hit this part of the house. Usually, in a heavy rainstorm, the rain will hit only the first meter or so of exterior wall.

It never occurred to me that the center beam could be placed so that it only reaches the middle of the wall, leaving a space for a second beam to be placed later.

The only reason for the typical beam placement that I can think of is that this is a seismic zone, and maybe such a placement allows for more of a safety margin in an earthquake, but with very thick 50 cm walls, there'd still be plenty of coverage.

So the options for connecting the rooms without building a 4th wall on all additions are (?): 1) line up all center beams at the same height 2) make the second room's roof lower and punch a hole into the original wall, placing the second beam below the first beam (would this not be too much weight for the wall?)

The arguments in the Hand-Sculpted House have me itching for some round rooms, but situations like this make me understand a little better Lloyd Kahn's point of view. Most of the videos I've seen with really interestingly-shaped homes feature roof styles that I just don't think would work here in the strong sun and rain, and whatsmore I need to use them to collect water, like I mentioned.

Is a pulpit roof the same as a shed roof? I thought about using a shed roof, since I don't think it would require a center beam, and the wood stores here will sell be dimensional lumbar beams long enough to cover the width of the rooms, but I think such a roof would change the skylight situation, and, as I think you were alluding to, the southern side's upturned overhand might let too much rain hit that part of the wall.

I was planning to use cob mixed and placed by hand, unlike the adobe building I posted. I still don't understand exactly how one leaves exposed areas so that the future cob has a good grip, but I think that might come later in the book.

Cristobal, in your example designs, the east and west sides don't have a roof overhand. Is this necessary in order to allow the connection of the future addition? I worry that the lack of overhand might expose the roof to too much rain.

I'm still trying to figure out a lot of these building terms. The ones I learned down here don't seem to be the same.

I'm toying with the idea of having, eventually, when all is said and done, three connecting rectangular rooms that share walls, and then small oval or circular rooms that are connected by hallways.

Regarding encapsulating the ends (east and west) of the roof to aid with fire prevention -- this sounds great. I'm looking up the terms to try to understand better your idea. Tomorrow in the daylight I'll try to take some pictures of this adobe house's roof to compare.

Beltran,

1. The pocket at the end of beam can be bricked up. Remember to always leave a gap, at least 1 cm between the lumber and masonry so it will be ventilated.

2. Roof decking can extend to create overhang without the need of the ridge board to stick out. The one side that will never get addition can extend more.

3. Pulpit = shed roof would support the rafters without the ridge beam. It's much easier to set rafters this way. You read my mind well - shed roof would not have good rain protection at the top, until you built addition. Rafters could have the same pockets and wait for rafters from the addition.
The advantage of such solution is that such a house would be closer to square shape than elongated rectagle and it would be easier to heat and cool.

4. For seismic zone I strongly recommend to make thicker walls and at least top it with a concrete bond beam reinforced with a cage of four 12 mm bars with 10 mm stirrups  spaced not more than 40 cm. 30 cm unreinforced adobe is not much, asking for trouble. My walls are 60 cm exterior and 40 cm interior CEB, reinforced vertically every 80 cm on both sides of the wall and by all openings, and horizontally (ladder mesh every 3 courses = 30 cm).
The bond beam is 25 cm thick with fi 16 mm L shaped anchors, threaded, so the top plates and some rafters were bolted nicely.
Openings should be far from corners and rather small. If walls are longer than 5 m then they should be braced with perpendicular wall.

5. If you build a cornice it will look great, but you will still have exposed decking material of the large overhangs. I have continuos cornice and overhangs are 15-30 cm.
I'm quite obsessed with cornices - it's a dying art in the ocean of ugliness. I already utilized three different designs in various buildings and can share with you some details and pictures.

Christobel

https://www.aseakoelectricbikes.com.au/

Do you have an image of a cornice please?

A cornice is a thickened top edge of a wall extending outward. It can be quite ornate with fancy brickwork or (in wood) fancy millwork. Cornices were pretty universal in Victorian times but have died out in the past century.

John,

The house is not plastered on the outside yet, so cornices will really shine when it's done.
Cornices are integral part of masonry architecture and started in classical times. Made from stone then brick.
They completely encase wooden roof structure and gradually and gracefully extend the roof overhang. Every older building has/had cornice. Most people are not aware of it, but subconsciously sense the harmony between the wall and the roof.

I like the way the cornices look.

I'd never thought much about the possibility of earthquakes here before. I've talked to a lot of people here about building and it's not something that comes up much. I need to start asking around more, and possibility reconsider my entire plan. I didn't want to use concrete and steel in the structure mainly because of the cost and also the additional complication. Maybe it's time to look at round buildings again?

I've been told that my building site has a lot of rock underneath, and that during the big earthquake in 85, the buildings in this particular area were not much effected.

I love that cornice concept.
I lEarthquake danger is about how quickly the house collapses.
Concrete beams at the top hold the walls, bamboo or steel mesh with in walls holds it up a bit more.
Beams with overhang don't drop immeadiately.

Beltran,

If you make a heavy timber bond beam it will also help. All connections should be traditional joinery and then additionally bolted or pegged with large wood dowels.
If you make a concrete one, then you need a rebar bender, formwork and the way to pour the concrete, which without boom or at least inline pump is not easy, but still can be done by hiring a few guys with buckets for 20 minutes. I can help with details.

I've seen wooden bond beams here done in adobe houses. What kind of traditional joinery should be used to connect them? Are the wooden dowels used to join the wooden beams or are they used to connect the wooden beams to the cob or adobe wall? I'm reading about deadman (I forget the term) anchors, which are pieces of wood sunk into the cob wall and then attached to the rafters with something, in order to keep the roof flying away. Should the bond beam be well below the rafters or do the rafters connect directly to the bond beam.

I could definitely hire some guys to pour a concrete bond beam. I've seen them do it with a mixer, or by hand, buckets, and with armex (preformed cages -- I don't know if armex is a common term elsewhere) . I don't know about bending the rebar on site. I've never seen someone do that here but I'm sure there's someone.

For round buildings with wooden bond beams, does one need to use curved wood? It seems like the wood would be challenging to source and fit together. I've found one example online of a round cob house with a wooden bond beam, but the bond beam was formed by a collection of short pieces of wood. I'm probably missing something, but it seems to me like the short pieces of wood wouldn't serve for what the bond beam is designed for.

Thinking more about earthquakes, in the cob book, they mention adding long pieces of wire to a stone and mortar foundation, which I've never heard about being done here.

In theory, if lightning hit the ground nearby, couldn't it kill someone who was standing inside a cob house on an earthen or concrete floor? Would burying wire or armex in a circle around the house prevent that?

Joinery depends on the purpose. I have created joinery lock for horizontal top plates, that also got bolted to the bond beam, but they added additional horizontal connection so at least gaps would not form once the wood dried as I have used partially green wood for heavy timber roof structure. Forming curved bond beam from wood would be much more difficult than pouring curved concrete bond beam. Traditionally, for curved rafters a curved tree was used to have continuation of grain within the member. Short pieces would negate the concept of continuous beam.
The wooden bond beam should be anchored with L-shape steel dowels (threaded at the end) that would be set in cob first and then the beam would be bolted. Fi 16 mm would be a good size.
If you decided on concrete beam then you would also like to add dowels that would hold either a wooden top plate to which rafters would be attached or they would be used directly for attaching rafters.
In Europe, all new houses have bond beams and most of them are not in seismic zones. Bond beams reduce the chance of wall cracks if soil shifts from either imperfect compaction or uneven wall weight distribution.
I never heard about lightning killing someone in steel reinforced house and there are probably several hundred millions of such houses on the planet.

Beltran, where are you planning to build, it helps us with giving an opinion.

Thinking more about earthquakes, in the cob book, they mention adding long pieces of wire to a stone and mortar foundation, which I've never heard about being done here.

Give us the context please?
What is Armex?

I've found one example online of a round cob house with a wooden bond beam, but the bond beam was formed by a collection of short pieces of wood

The wood needs to be cut short to form a circle, but there may be additional fastening methods or system in use.
That is an important part that is missing in your comments.

Armex is a cage of metal used to make "castles" and concrete posts, among other things. When I have bought it, it has always measured 15 x 10 cm I believe. I forget how long they are. I'll attach a picture of some armex I have lying on the ground, and also the resulting "castle" for which it was used on a brick storage shed. I'm also attaching a picture of the same house from earlier, this time completed.

This is the passage from the Hand-Sculpted House that I was referring to,

"Once you have a good idea of what kind of rock you want for your foundation (see above, and chapter 10), go to fill sites, roadcuts, any kind of excavation. Carry a rockbar or a 4-foot piece of ½-inch steel pipe that you can probe the ground with. If there’s no surface rock, look for areas where the vegetation is poor or which dry out quickly in droughts. There may be good rock just below the surface.
For a foundation to stay in one piece if the ground moves, it needs tensile material incorporated. Look for old wire fencing, polypropylene fishnet or baler twine, and random lengths of wire and steel. You can bury this reinforcement in a cast concrete ringbeam beneath your stemwall, or set it into the mortar between courses of brick, stone, or urbanite (recycled concrete)."

I have an e-book copy so I don't know the page number, but it's in the section called Finding Other Building Materials. I didn't know that a stone foundation needed additional tensile strength.

I'm building near Patzcuaro, Michoacan, Mexico, on a hilly piece of land. The ground drains very well and there is a lot of (large) rock 2 or 3 meters down.

I know that a lot of small, round cob houses are built, and I'm just trying to understand how they made their bond beams. I can find a lot of in person examples of adobe houses but there are only 1 1/2 cob houses in this area.

PS Regarding lightning striking the nearby ground, I was wondering about cob/adobe buildings that do not contain steel. The majority of the adobe homes here are built like that, and from what I see online, most cob homes are small, round, and do not contain metal or concrete. I have read that people have died like that, since the electricity will travel through the ground, through the floor, and shock the house inhabitant.

With earthquakes, it may go in a following manner: nobody remembers the previous one, so nobody cares, building seems strong, then it hits and 20 thousand people die.
Round building will be more resistant, especially if it has thick walls. Rectangular with thick walls, small openings, bracing walls will fare better than a large building with thin wall and large windows. At minimum I would reinforce the foundation and add the bond beam, so the walls will be held together from both sides.
For round reinforced building, everything will be more difficult: bending rebars, formwork, timber, building roof and building addition. It will be also less functional.

I doubt that a cob house without steel is more dangerous near a lightning strike than if a person was standing in a field in that spot without a house. The interior would probably be dry and less conductive than a wet field. A steel reinforced house might be safer than an open field.

I imagine people were too poor to have bond bems.
I have worked in mud for 55 yeras and are familiar with its use by impoverished communities.
I would not wonder too much and just use 'modern' ideas if its easier or better.

In your case I would consider a concrete beam on a road house, and look at building a boom crane to lift buckets of concrete to the wall top.
boom cranes

There is an earlier almost medieval designs that have long booms, human powered cranes
and another

even a gantry would do well, or a simple block and tackle system.

Cristobal, regarding earthquakes, yeah, I think it's something like that. And people sometimes don't have a choice. People definitely remember the big earthquake in 85, because a lot of people died in Mexico City. From what I understand, building codes there were changed, and also a lot of people migrated out of the city, although I believe the population continued to rise. I'm going to ask around more about what happened here in 85, although it might not be that relevant. I found a paper in which they analyzed the type of ground in the nearby city of Patzcuaro, which doesn't apply to me directly, but there was some general information about the area. They mentioned in the paper that most houses are made of brick (with armex castles/castillos, I imagine) or adobe, and that the adobe houses are much more susceptible to failure during earthquakes. I've seen larger buildings built, like those used for stores etc., and the construction style seems much different, as they incorporate large metal beams.

I guess I had previously thought that adobe houses were resistant to earthquakes. The paper I found mentioned that the top of the famous Patzcuaro basilica church collapsed twice due to earthquakes in the 1800s. But I don't think the church collapsed, and I've always heard that the large adobe buildings are hundreds of years old. Maybe older adobe buildings, with much thicker walls (up to a meter, I believe), are more resistant to earthquakes? Maybe the foundations were very substantial? Maybe the old lime-based mortars helped compared to modern cement-based mortars? Or maybe they were worse?

So for natural building, am I correct in saying that adobe performs worse in an earthquake, cob second, and earthbag is the best?

I'm looking more into earthbag, and it sounds almost too good to be true. No need for a rock or concrete foundation? My thoughts, possibly wrong, so far on earthbag buildings: A round earthbag home would be stronger in an earthquake, but might make the roof more difficult, and would require a concrete bond beam? A rectangular earthbag structure would require buttresses. Would the buttresses need to be covered by the roof overhang to keep from getting wet, or is there some other way to protect them from the rain, or do they not need to be protected from rain? Maybe they are made of gravel bags, like the foundation? How resistant is a plastered earthbag wall to getting wet? One of the problems I see with houses here is that they have very long overhands, which often entirely block the sun from hitting the wall, resulting in a cold building. If the overhand needs to be long, maybe transparent plastic roofing panels could be used instead of the opaque ones.

Beltran, can you set out your questions in a easier to read format, it will make ut easier to read and asnwer.
IE new line per question.

One of the problems I see with houses here is that they have very long overhands, which often entirely block the sun from hitting the wall, resulting in a cold building.

I am guessing the overhand is for rain protection, since maintenance is required.
Older adobe buildings in Africa etc often have sticks jutting out for planks to be set on for annual maintenance.
EARTHQUAKE DETAILS
There has been a lot of design, investigation work in Columbia about adobe, I have details to hand.
Earthquake Damage Prevention in Adobe Dwellings - https://www.eird.org/eng/revista/no-16-2009/art22.html
- Harvard studies
- Australian studies on circular buildings https://aees.org.au/wp-content/uploads/2013/11/25-Jinwuth.pdf
- The good news peru-earquake-resistant-houses-made-from-adobe

The crane looks interesting.

I've seen big concrete roofs poured here with just buckets and a bunch of guys.

The whole point of what I'm doing is "wondering."

I'm not opposed to modern methods or old methods. I don't know much about building and am trying to learn.

As of a few years ago, Mexico was the 16th richest country in the world. If you look up current GDP rankings, they might be slightly different.

I'm still perplexed by the overhang / cold house dynamic.

Thanks for the links.

I'm still perplexed by the overhang / cold house dynamic.

Beltran, can you give me more info on the overhang cold building assessment?
Adobe tends to not store a lot of heat for retransmission inside, I believe?

It's an interesting topic. If buildings survived destructive earthquakes, they were surely thick-walled, low, well braced with other walls and maybe even had reinforcement that we do not know about. Cheap, peasants' houses built of thin walls with no consideration for tremors would fail and they do not exist any more.
Overhangs are double edged sword but at the same time this approach makes sense in warm places, because it's more difficult to cool a building than heat it, but in a place with scarce firewood availability, it may be equally hard. Stabillized adobe with a good plaster or regular masonry may have smaller overhangs.
It's always a matter of material cost and amount of labor. If you want to make it somewhat earthquake proof you have to make thick walls (a lot of labor) or use reinforced stronger material (more money).
Buttresses have their individual roofs, but they may be insufficient for an unstabillized cob adobe building.

Down here at this latitude, the sun is high in the sky. Long overhangs block the sun from hitting the wall and heating it directly. Without sun exposure, the buildings sometimes stay cold all day (sometimes 12 C during the daytime in winter).

Other adobe houses with shorter overhangs let the sun hit the walls. I live in an adobe house here and it's often around 20 C during the day in winter. The house can be chilly in the winter mornings. I think this is because the roof isn't insulated at all, and all windows are single pane.

I think that the sun-heated walls do continue to heat the house-- if I have the doors and windows open on a winter night, it'll be cold inside. If I close the house up, the temperature begins to rise, which I interpret as having to do with the walls heating the interior home air.

In an adobe house here, heating is not really needed. I have a Menonite-style woodstove where I live but I rarely use it. If the chilly mornings bothered me, I'd burn a load of pine at high temperature first thing in the morning and wouldn't run the stove again until the next day.

So overhangs can make the house cold. But they protect the walls.

Transparent roofing for the overhangs might solve this problem.

From what I understand, cob and adobe walls are resistant-enough to rain that in this climate a short overhang would be enough.

Since I am currently looking into earthbags, I am trying to understand if earthbag walls (plastered with cob and then lime) are less resistant to getting soaked in the rain. At the moment, it seems to me as if they are less resistant than adobe/cob.

Information on regional temperature variation and rainfall: https://weatherspark.com/y/4444/Average-Weather-in-P%C3%A1tzcuaro-Mexico-Year-Round#Figures-Summary

Cristobal, great point about the different types of adobe construction. I'll try to take some pictures of some old buildings and ruins around here.

Lime plastering is a good way of weather proofing cob walls.
That how they do it in England.

I love the way lime plastering looks. In the earthbag book I'm reading, they have a list of different coatings and their permeability rating. Lime plaster is permeable. So it lets the inner wall get wet? And also lets the inner wall dry out? Cement in the plastering mix protects the inner wall more and also hinders its drying? It's quite the dilemma. The more I think about it, the more complex it seems, with rain patterns influencing the decision.

Speaking of lime plastering, I'd like to spruce up this composting bathroom. It was built with materials that were lying around. The wood should be more protected from the rain.

I was thinking of cobbing over the wood and then plastering the cob with a lime mix. Does that make sense? Bottle caps could be used to get the cob to stick to the wood.

You may consider stabillized adobe (usually with 5-10% portland cement), it would greatly improve adobe's water resistance and with plastering you could have smaller overhangs. For inspiration please also read about the SIRE wall (rammed earth system) - moisture proof, insulating, seismic proof.

I would not cob over the wood in this case. It may not want to stick to relatively smooth planks without any "teeth". You could try to lime-wash the wood. It should work.

Thanks for the ideas.

Nailing metal bottle caps into the wood wouldn't help the cob stick? Or chicken wire nailed to the wood?

I will read about stabilized adobe and rammed earth for sure.

The plan is to practice on various small structures: dog house, shed, workshop, and then house. From my current perspective, the advantage of adobe in this area is that it's readily available to purchase: 50 x 30 x 10 cm adobes are available for around 1.2 USD a piece without transport. Someone could probably be convinced to make them some cement.

Lime plaster is permeable. So it lets the inner wall get wet? And also lets the inner wall dry out? Cement in the plastering mix protects the inner wall more and also hinders its drying? It's quite the dilemma.

An explanation;
- by being permiable it means misture can move in and out
- it does not mean it behaves like an open window
- the inner wall will not get 'wet' to touch.
- use of portland cement stops this and traps moisture inside the wall causing the material to expand and the wall will start breaking down.

As for the bathroom;
-  will that timber rot if left exposed?
- is thebathroomweather tight?

Thanks for the explanation about the permeability of lime plaster and cement plaster.

What I don't understand is: if the lime plaster keeps the inside of the wall from getting wet, why are overhangs so encouraged? I keep reading that they protect the wall from the rain.

As for the bathroom, I don't know if the wood will rot. That's how it looks after 2 years. The wood isn't treated with anything. It does get wet, but not super wet.

The bathroom has open windows with no glass, and the door usually remains open. I'm not sure if I understood the term weathertight correctly or not.