Word to the wise about mixing natural materials with conventional, particularly milk paints:
Even finish materials have functions. For home interiors, drywall is 'expecting' a coat of latex paint, to complete its function as the interior vapor barrier/vapor retarder.
We did most of our bathroom ceiling in gypsum instead of green board (an iffy choice), and did not initially install a vent fan (recommended).
Then, we used milk paint instead of latex on most of it.
Now that we are using the bathroom more for physical therapy/soaks and long showers, we have a major mold problem in the ceiling, that will be a pain in the butt to fix.
Options for improving it:
1- Toxic gick retreatment: Bleach to kill mold, then latex paint, to see if the original drywall would have been fine if we'd finished it 'properly.'
2- Conventional upgrade: Mask up, tear out the moldy drywall, replace with green board (a water-resistant and mold-resistant sheet material, similar to drywall or cement board), then paint with a vapor-retarder paint. (Could go to linseed oil instead of latex at this last step, if we want a more costly / more natural finish layer in our space with us.)
3- Old-school upgrade: Replace or treat and cover the moldy drywall with tile backer, and tile the bathroom with ceramic tile. Could try a lime grout instead of plastic goop, but would want to research that option thoroughly so we don't end up with mold again.
4- Casbah natural upgrade: Replace the moldy drywall with cement board, or lime plaster-and-lath (both water-resistant, and firm). Plaster with lime, finish with burnished lime 'tadelakt' made with local dolomite and type S lime, and natural soap.
(0) - do nothing.... mold is 'natural,' right?
Time & money: We have already purchased the vent fan, which was about $100, and the wiring and switches to install it. Awaiting a final decision about ceiling replacement to proceed with the whole project.
1) looks like about 1 day's work, 1 person. Maybe $50 in supplies.
2) looks like about 3 days' work for 2 people, maybe $500 in supplies?
3) Looks like about a week's work for 1-2 people, depending on skill, and maybe $2000 in supplies?
4) Looks like a week or two of work for 2 people, high skill level to accomplish crack-resistant and water-resistant detailing; maybe $1500 in supplies? (plaster & lath is more time & skill vs. cement board which is more conventional coatings)
Budgets are very approximate. Things usually take longer, and cost more, than you think.
Natural materials that will handle the levels of humidity produced by warm indoor showers, without growing mold, are a bit of a technical specialty.
Let alone how to handle flexing (which happens with heat, moisture, & building movement) without cracking, peeling, or delaminating.
When looking at returning to 'natural' finishes and materials, it's worth looking at the traditional lifestyles that accompanied them.
Most pre-industrial areas did not have anything like our warm showers. Bathing (if it was regularly practiced at all) might be by washcloth and rinse, or by sit bath, or by a full-immersion pool.
Some cultures (medieval Europe) believed bathing was unhealthy; possibly due to disease transmission in public baths. Some cultures (various native American, middle Eastern) believed in daily bathing, which might be anything from a dip in the river to a scented indoor wash. a "japanese bath" is a tiled area where you sit or squat to bath, pouring water over yourself with a dipper; variations on this method have been used in many areas including Moroccan village-style 'hammam', American pioneers with washtubs by the fire, and re-invented by campers and RVers wherever the main source of warm water does not come through a tap but through a fire or stovetop.
Separate buildings or areas for bathing were and are common in many parts of the world (sauna, sweat lodge, hammam, 'Turkish' baths, Roman hypocaust baths, mineral hot springs, etc.). In some cases, this separation was known to alleviate concerns about fire, steam, hot water, etc. which might be expensive or dangerous to handle for ordinary homes. A bath attendant and/or maintenance specialist could assist in making sure both bathers and building had their needs met.
For our purposes, to maintain a walk-in shower that allows a 6'6" Ernie to stretch his injured leg under warm running water, we will probably be fitting out most of the bathroom in mold-resistant materials, one way or another.
Because the bathroom has suspended floors over drainage, as an addition, we will also need to pay good attention to frost protection for the crawl space plumbing, repair/replacement access for when attention falls short, and detailing corners and joints so that any flexing of the wood-framed building does not crack brittle finishes, allowing water to enter the walls and condense against colder surfaces.
Similar issues arise in greenhouses, especially those connected to living spaces. And, to a somewhat lesser degree, in kitchens where cooking and washing produces a lot of steam.
The older and more experienced I get with buildings, and their building issues, the more I respect the skills and knowledge embodied in a traditional trades apprenticeship (3 to 7 years, in Europe), and the value of experts' time and attention.
Sure, you can spend less money at a time to alter things yourself, but you might cause permanent damage/degradation, and dramatically reduce the lifespan of the building.
According to "001 The Perfect Wall," the priorties for any shelter are:
1) Control water - Keep out rain and snow, control drainage and groundwater exposures
2) Control air - Keep wind out or allow cross-breeze, manage ventilation, separate indoor air from structure ventilation (wall, attic, crawl space). This step also implies controlling critters: mice, spiders, bats, etc.
3) Control vapors - they move water and other stuff into/through your walls; all walls need at least 1 way to dry out, preferably 2 ways.
4) Control thermal transfer. If you don't have all 3 of the above handled, insulation won't do much for you, and may become an attractive nuisance/trap for condensation, mold, & critters.
The roof and foundations are your primary tools for #1.
The walls, ceiling (sealing!), trim, and finishing materials can all be important for #2.
The finish materials, including plasters, paints, drywall and its finishing, contribute to #3. (Unfinished wood may warp or crack, causing it to be useless as a wind/vapor barrier; so finishes to wood are also functional at this stage)
Thermal materials generally means insulation (foams, fiber, board or batt, straw-clay, or blown materials such as cellulose or chaff); but the construction and thickness of walls, ceiling, roof, and foundations can also play a role in final results.
Any given building material has a function - for example 'siding' generally is a weather- and UV-resisting layer, with good ventilation, that goes over the rest of the wall. So swapping an oil-painted wood siding for vinyl can work out fine.
Plasters are generally a wind and vapor barrier; they require fairly dry conditions for good performance, and if plastering both sides of a wall, you want to be sure you know how any trapped vapors are going to escape. You also need a decent roof overhang to protect most types of exterior plaster, if it's the kind that can dry outwards it can also suffer from excessive weather trying to penetrate inwards. (If it's not the kind that allows water to dry outwards, a new, impermeable exterior plaster can cause major damp problems inside of cold-climate walls.)
So replacing siding with plaster might be asking for trouble, unless it's the perfect match where their different functions are not critical to building performance.
Roofing materials have specific types of slopes, weights, and support systems.
Replacing a lighter roof with heavier (slate, tile) or with something that holds onto snow and moisture more (living roof), you'd need to give some consideration to the roof and building structural/load bearing capacity.
Steepest to shallowest, I'd guess the order is something like thatch, wood shake/shingle, slate/tile, metal (wide range), asphalt shingle, membrane /living roofs.
There's a lot of overlap, but if you try to put thatch on a flat-roofed building you will have a non-functional mess, or you'd have to build a new, steeper roof over the old one.
There is at least one good thatching training program in the US, Deanne Bednar at Strawbale Studio in Michigan hosts workshops and internships where folks can learn a lot about these methods (and help keep invasive Phragmites reeds in check).
As my own house shows, there are significant gaps in my understanding and workmanship.
I'm not claiming to know better than anyone else - just learning from the pitfalls of my own former optimism.
Houses are expensive.
One other thing that people used to do differently, was to have more adults sharing a home. That would in theory also provide more hands, and/or more income, to share the burden of housekeeping, maintenance, and repairs for a given house.
Being the 'head of the household" was a position of added responsibility and status.
I find the cost of repairing/remodeling daunting in both time and materials, but it's hard to convince Ernie (or any of our other relatives who also feel the pinch) to combine households.
Culturally, that seems to imply some sort of social failure. "I'm not 20 anymore."
But by living alone through our most productive years, and only rooming together when we are very young or old - is our reluctance to live together a sort of social failure in itself?
Shared bath-houses had a lot of social functions, as well as the basic function of keeping people clean and healthy.
Food for thought, anyway.