I've been reading about non-wood based alternative roofing. The house my wife and I are designing will have a flat terrace roof for her to tend potted plants, hang the laundry to dry, picnic etc. It's something traditional to her part of the world, but we live in the American mid-west. So I'd need to build something strong enough to resist snow loads and allow foot traffic, potted plans up to about 100 lbs, etc.
I want to avoid pouring large monolithic concrete slabs. I'm accepting using portland cement, but want to use as little of it as possible, as much lime or gypsum, etc. I've looked at poured ICF form deck solutions that minimize the amount of concrete poured, but am not comfortable with all of the plastic foam and am looking to do something with as little dependence on petrochemicals as possible. In Europe and the UK they have small load bearing pre-tensioned tee-beams that you can use hollow terra-cotta tiles or cement blocks as infil, and pour a minimal slab over. But we don't have those types of flooring systems in America, and it still takes me to using a lot of concrete.
I live in Ohio, and I don't think its seismically active where I live. So I started reading about masonry jack arches and flat arches, or reinforced brick floor building slabs, which are used in India. Then the thought crossed my mind of using shallow Catalan or Mexican style bóvedas, lightweight masonry vaults. I've seen some older vaulted floors and roofs in turn of the 19th century American buildings, and I've read that timbrel type vaults can take immense loads.
This was a great video
Fertile Roots HQ Barrel Vault
I'm really just in an information gathering phase, I'm doing a lot of reading but I was wondering what sort of thoughts people here on Permies had on the technique, its practicality, and value.
Brick or terra cotta tile is fired, and has some embedded energy in them. But the material seems more sustainable in theory than large scale concrete work. I mean, clay's everywhere and needs less processing to be workable as masonry than the processing of lime and clay into cement. It's also extremely long lasting, terra cotta and brick can last centuries, thousands of years even if hard fired. If a building is built with an eye towards permanence this seems beautiful to me. These vaults don't need extensive rebar, if at all, and seem to be really strong and load bearing.
Seismic reliability does concern me a bit. I'm not in an active seismic zone but there are small faults in Ohio. Moreover the increase in fracking really worries me, I've heard of small earthquakes being linked to fracking. The fire protection of non-wood flooring and roofing appeals to me, and using shallow arches I could probably just fill in the cavities with a lightweight fill and insulation and floor on-top of taht/
Could someone tell me if I'm being nuts, or should look into other things?
This book is probably a good place to start: Essay on the Theory and History of Cohesive Construction Applied Especially to the Timbrel Vault written by Rafael Guastavino. I believe that all the structures he built are still in use today and NONE have suffered any deterioration, and they're all 100+ years old. I imagine you would be able to acquire all the knowledge you need to build such a structure from this book.
As far as finding someone that actually does this kind of work MIT did some structures but I think they were temporary. But finding any real 1st world applications is probably nil.
The most difficult part would be to get any jurisdiction to permit such a structure and would probably also involve finding an engineer who really knew this type of construction and could convince the powers that be to sign off on such a structure.
There is also the Auroville earth institute, they do courses in such work but they are located in India.
I also like traditional nubian vaults this youtube video is really educational even if you dont speak spanish
You said flat roofs are traditional to your wifes part of the world? How do they build them in her part of the world?
All that being said, you should probably build for your neck of the woods, or move to a part of the US where rain is minimum and a flat roof is suitable to the region. I have some land for sale if you wanna move to the desert!
WAIT! The majority of Guastavino's structures are in New York and Pennsylvania, I believe, so maybe it could work in Ohio. I think the trick would be something like with earthships where the roof is slightly tilted to the south so the winter sun melts the snow off the roof and doesnt allow much build up.
Thanks for posting the video too. I really like it as a learning tool more for what not to do,but the structures are beautiful. Planning goes a long way. It seemed like they just built the walls and then discovered vault building, then decided to put it on a structure that quit possibly could collapse, SCARY! Guastavino's vaults only rose 10% of the distance they spanned and used no form work, I think they would have had an easier time building had they used Guastavino's technique. Also Nubian vaults (true ones) transfer all thrust down to the walls, not outward, however the walls need to be a bit more substantial and you can only span about 10ft using adobe brick.
Just my two cents, have fun!
Stay where you are, work with what you have, do what you can
If you don't want to use framing members, especially if you're going with a masonry roof, you're gonna make it harder on yourself. But brick vaults are awesome.
Question how you are going to insulate your roof since you are opposed to having petrochemical in your house? Your system is going to interact as a whole. I buy discounted bunks of various rigid foam either used or grade 2. I guess it depends on your motives: footprint, indoor air quality, natural philosophy, cost... Im not interested in debating this, I'm just saying that these values need to be addressed with each builder and owner so that one can appropriately choose/build a durable, highly performing structural system.
I also prefer ferrocement roofs because I'm low on time, but have done bag dome, Adobe squinch, brick vault. Metal roofing, epdm and roof tiles all for the pizza toppings.
If you aren't much of a mason, how about Quonset sections? Or frame? Or ferrocement? Easier with permits, quicker, cheaper.
But if you mason your roof without a slab, keep it simple, keep your spans small. in Ohio, remember that you need good insulation and good roofing or decking on the top. In your climate foam on a masonry roof is a good insulation combination. Or for foam free: cellulose in framed roof for the win.
As far as mortars: pure gypsum and lime mortars, maybe a curtain wall or veneer; Structural cavity wall -- I'd pass; Brick vault--i'd go inside that building but I would not build or live in it.
Ferrocement is way quicker, cheaper, diy-able, and reinforced. It can easily be thickened to match compression if needed for second stories. If you need brick and you're asking advice on permies, hire out local mason that you can labor under, or grab a crew from the Mexico, the East, or Africa. it's not that DIY. (Doubtful that an engineer would stamp brick vaults for a DIYer.) If you do DIY, think simple catalan barrel vaults, one reusable formwork that repeats itself. Yes groin vaults are beautiful, but every diagonal groin rib adds up, every dome adds up, every compound cut brick adds up, as does every piece of complexity or sculpture, every nicho or wide span vault. With the busy pattern of brick, i think simple forms shine. (Groins can be framed and drywalled or ferrocement). If you keep it simple, you have a much higher chance of getting a roof overhead, and will have a place to display your Gaustavino / Gaudi coffee table books. Price your time and examine how deep your pockets are right now. Brick also looks good on walls or floors instead...I also like to avoid valleys no matter the roof construction...
Edit: forgot his name, but there may still be a mason for hire in yellow springs that could do you brick vaults.
Edit again: http://www.structure1.com you may want to contact their engineers, or a similar firm licenced in your state about hire.
Location: Pahrump NV
posted 2 years ago
Here is another good video that will probably lead to more discovery
Stay where you are, work with what you have, do what you can
Location: Cincinnati, Ohio
posted 2 years ago
Kris and Christopher both, thank you so much. It looks like Ferrocement may be what I need to look at for domes and vault portions.
Really interesting video, thanks !
I've read a lot about it, it seems strong, but I'm not sure how to calculate out how much mesh, rebar, and cement in a curved dome I'd need to get such and such a load. For example, if I want a terrace room or deck at 50 or 60 lbs per sq foot (normal stick residential floors are 40 by code) and I decide to do pre-cast shallow ferrocement vaults and fill in the valleys with sand or cement or something to make it flat, figuring out how much I'd need to support a given load.
Or for an actual domed roof, what sort of loads it should e engineered for using a rebar frame, mesh and ferrocement skin.
I have a lot of ferrocement reading to do.