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  • I think we need to address what seems to be a hole in the GVCS - constructing a good roof. Shelter is one of the big requirements we have to cover, and living in the pacific northwest, I am painfully aware of the importance and costs associated with a roof. Compressed earth blocks cover, to a decent extent, building walls. Floors are somewhat covered by the dimensional saw mill, compressed earth blocks, and concrete. However, what isn't taken into account yet is the most expensive and difficult part of a house - the roof.

    I think figuring out a good roofing solution should be one of the primary focal points for the first wave - getting the basics of housing/food/water/power up and running, as discussed in the GVCS bootstrapping thread.

    A good example of this need is the Factor E Farm workshop itself. To make a workshop to stage the development of the GVCS, they were able to make part of the structure out of compressed earth block columns. However, the vast majority of the cost of the structure was in building the roof. They had to use off-the-shelf metal roofing, which was paid for through donations: donations for roofing materials, building the roof.

    As you can see, building a roof was one of the first roadblocks, and was solved through just buying one.
    Perhaps we can brainstorm and come up with some good solutions. I've already started some sections and given some background requirements on the wiki. One option I find very intriguing myself is ferrocement. You can see it being discussed in the comments of the building the roof blog entry for the farm. I made a thread about the need for an open source metal lath making machine with roofing as one of its applications.

    I've started a wiki entry for the roof here: As we come up with ideas we can add them.
  • 40 Comments sorted by
  • My vote is for Steel trusses with concrete or clay shingles.
  • This is a great discussion to have! Thanks for getting it started Jason! We could start with listing some of the main types of existing technology, calculate the costs of each off the shelf, calculate the cost of the means of producing them, and rate them for how they measure up to the OSE specifications. Then we can see which would be good to use off the shelf for now, which would be effective with open sourcing the means of producing the materials, and which would be best as a long term goal to move toward.

    It looks like the sawmill was supposed to account for roofing, but it looks like a large project that wasn't finished and hasn't had a lot of work on it for a while. I wonder if a band saw mill with an open sourced automatic sharpener would be as effective/low cost as the proposed dimensional sawmill? We would have to look at the work flows and the associated cost of components for each work flow then compare them to what the cost/time would be of open sourcing the most expensive components.

    There's also sheet metal over other support materials (wood trusses) for roofing, which
    the GVCS set would seem to account for with the metal rolling and sawmill. Not much on it yet though, it
    should probably be considered for a later stage since sheet metal is
    currently kind of cheap compared to the infrastructure required to
    produce it.

    So it looks like the GVCS has some roof basics, but are they the best method compared to the OSE specs? The current materials seem to be low enough cost to buy off the shelf for now, as the workshop project seems to demonstrate, so the machines to produce the materials could be more of a later stage priority.

    Ferrocement looks attractive from a construction and durability standpoint. The only problem I've heard of is that it takes a lot of energy to make cement, and it's only as cheap as it is because of low cost oil/NG/etc. Metal is a somewhat similar situation though. Still if it's the cheapest thing off the shelf then it will work for initial structures until OSE spec technology can be made. Can it be made with lower cost/non-metal frameworks or is the metal strength essential? What would the off the shelf costs be compared to the off the shelf metal+wood costs in the workshop example? Are those bulk buys possible and how much area would need to be covered for it to be economical? If the off the shelf cost is lower then all OSE buildings should be using it until lower cost technology/designs are made.

    There are also the CEB vault roofs. It looks like more research and prototyping still needs to be done for them though to see if they can work with the Liberator's bricks or some other way of producing them.,_Vaults,_and_Domes

    We should also consider how insulation works for each roof type, and how much labor is involved with each type.
  • The real options for long lasting, sustainable roofs are either earthen/geopolymer domes/vaults or concrete roofs systems (ferrocement, LFC, etc).

    Metal roof and/or wooden supports are not long term solutions.  Ferrocement/LFC can economically compete with metal roofing, and I have built several FC roofs at $1/sf or less, including labor.

    Cement contributes 1 ton of CO2 per ton of cement. Consider that this is considerably less than the CO2 contribution by metal roofing.  It would be easy to offset a roof by planting some trees. LFC has the advantage of using even less cement than FC, so the CO2 contribution would be even lower.

    CEB/earthen/geopolymer roofs have the advantage of being carbon neutral or even carbon negative as is the case with geopolymers. These are the oldest roof systems in the world, and outlast wooden and/or metal roofing by a factor of 10 or even 100.
  • The reciprocal roof is an interesting design, with strong walls and reasonable supplied you have a good frame.  Then you just throw over a pond liner and some dirt.
  • I'd be very interested in details of how you were able to build such a low-cost roof, VelaCreations. Or anyone for that matter, if you've got ideas for me I need them. I'm facing a very real problem here that I'm dealing with immediately - like today. I've got a 40 ft iso intermodal shipping container that's got a roof which needs to be replaced. I've taken a section down already, and will likely take the rest down very soon.

    I need to build a roof a little less than 8 ft wide and a little less than 40 ft long. The sides it attaches to has 1/4" (I think) rivet holes ever 2 - 3 inches or so. I'd ideally like to make it a flat roof I can walk on. Right now I'm thinking of using a 2x6 every 16 inches, with plywood on top of that, bolted to the rivet holes (I'm dreading the cost of all the nuts, bolts, and washers. Lowes charges like 10 cents....for a washer). On top of that I really don't know what would be the best way to seal it. I'm thinking 2 layers of metal lath LFC with tar or roof sealant on the outside, though that is awfully expensive. If anyone has any good designs, I can 'prototype' them here.

    *Cost - as low as possible, below $500, not including labor
    *Time - immediate, within a week or so
    *Labor - I've got people who can help me, but there can't be any super intricate stuff like a reciprocal roof
    *Design - desired to be a flat roof to be able to support weight on top of it (thats why so many 2x6s currently). Could be a non-flat, non-load bearing design if the other design is not feasible.
  • ferrocement.  would be my first choice.   A simple vault built up by hand by slapping concrete over plastic supported by chicken wire.

    tile is also a choice.

    But if you're going that cheap its going to be tricky.  You might try the old tin roof with widely spaced supports - won't be load bearing but it'll keep the rain off, remarkably cheap.

    I'm still trying to figure out, though, what about your ISO shipping container has a roof that can be 'taken down'.  I would have sworn the ISO containers I've been around have welded steel roofs... rivets?  Things that can be taken down?  Curious....

  • Its one built in 1978. Walls and roof are made out of fiberglassed plywood.  It leaked and the previous owner tried to fix it by putting a rubber mat over the leak and putting tar around the mat. This caused moisture to accumulate under the mat and thoroughly rotted out those areas.

    Could you elaborate on your plastic/chickenwire vault idea? Not sure I can quite picture it.

    Also, another requirement is that its got to have a relatively good seal with decent air tight/insulation properties, because I want to make (temporary) bedrooms inside. I can probably go above $500, but that was my initial estimate with my construction method - 30 8 ft 2x6s at $3/board + 10 sheets of plywood at $12/board + 32 sheets of metal lath at $7/sheet = $434. When you add in the cement, sand, nuts and bolts, and roof sealant, its closer to probably $550 or perhaps $600, factoring in a 10% sales tax. Maybe even a little more.
  • Okay, this is what its basically based on: HERE


    See here how the wire grid (not quite chicken wire in this case, but you get the idea) is put into an arch and held up by the boards into position.

    A sheet of plastic is placed over that, and the concrete is applied in a thin layer on it - not so heavy that the wire and the boards can't hold it up.  You apply concrete like so:


    Something like that, then you can lay rebar over it, and lay up more concrete over that so you have a thin shell ferrocement vault.  I'd probably throw a pond liner over that for waterproofing, and 6-8 inches of soil on top of that and plant some grass.  No more heat from the sun penetrating the roof. This is a good thing.

    Now, I'd be perfectly happy to put it on top of a steel ISO shipping container... you can stack those things, loaded, fifteen high.  But a fiberglassed plywood shipping container?  You're going to want to make sure of two very important things: 

    - it can support a few tons of concrete
    - its rigid enough to keep the vault sides from expanding

    You could counter the lateral force with a couple of ferrocement buttresses (flying or not) spaced along the sides, and/or putting in a flat-and-tied bond-beam (6"x3"?) all the way around the top of the container with a few crossovers.  (typical concrete form made of 2x4s here, with four rebars spaced inside)

    That'd put a volume on the bond beam (with three mid-span crossovers) of about 1.2 cubic yards and if you made the vault all of 2" thick (thats quite thick, this isn't supposed to be a bomb shelter!  But better too much than too little.) it'd take an additional three cubic yards, making the weight of the roof alone as much as 7 tons (2 bond + 5 roof) all by itself.  That is not an unmanageable weight, of course, but its STILL... heavy.  Don't drop that on my foot!  (You could also put in some footings and vertical cement columns to take the weight load off the container curtain walls, though of course that will cost more)

    And thats alot of concreting that will probably run you $500 off the truck (though this method is better done by hand)

    But on the other hand, I doubt a conventional burns-easily roof as you described is going to be particularly cheaper.

  • While shipping containers are designed to stack high, they're designed to take all that weight on the 8 corners only. Laterally they're actually quite weak, and their roofs are generally strong enough for a grown man to walk on, but not much more than that. For the one I have, there is only 5/8" plywood with a thin layer of fiberglass over it for the walls and ceiling. The only other structural thing is some small metal spanning pieces every 3 ft on the ceiling, but other than that there is no additional support except for the steel edges and corners. In fact, looking at the wall from the outside, you can see it bowed out a few inches in places.

    Also, the location of the container is not going to be permanent, so I need to make sure whatever I'm building isn't too massive and fixed to the ground. I don't think a (heavy) vault roof would be a good fit for this application.

    Anyway, here are some pictures:
  • Dome's are the way to is a technique that I learned about years ago...that just seemed like a easy but solid idea

    I just saw this house recently...that I thought was beautiful, functional, creative, easy to maintain...check it out...let me know what you guys think ?

    I'm not a architect by any means...but the two ideas are compelling.

  • The first one is the monolithic dome technique. It's supposed to be a super strong and thermally efficient structure. It's construction method is a little bit complicated though. Basically you pretty much have to buy the mold from the company that specializes in making them (unless you think you could make one yourself). In terms of cost, I don't think it is lower than traditional methods. In fact I think it's somewhat higher. However, what you get out of it is not a structure that will stand for 30 years, but one that will stand perhaps 300 years.
  • @ Jason,  consider the "Cascaje" technique for your roofing: It is like ferrocement, but with less cement....
  • If you are just trying to put a roof onto a shipping container, then this is all rather too complex.  I think you would do well with just some 2x4s one way, then some plywood over it, then a rubber pond liner, then some sandy-loam, then plant onions and garlic.
  • @Jason well, I have to vote for @ARGHaynes idea - support some dirt and plant a garden.  The pond liner will do an awesome job of keeping the water out and the soil will keep the heat out.  Comfort is a good thing.
  • i think its funny how a roof is like a shield. like how it blocks sun, rain and air. a regular roof just absorbs the sun turns it into heat and sheds the water into gutters. the biggest drawback to growing stuff on the roof is wheight. but it does turn the shielding functions into productive ones. its kinda interesting how like a green house can protect from the air but uses the sun. its interesting how we wouldnt want to live in a green house but a plant would. how we have to design environments differently for different things. like all the different cages at the zoo. just to make things happy.

  • here is an idea for a lightweight living/green roof: green roofs
  • That pond liner looks like really cool stuff. Perhaps it could be used in place of a tarp to make the roof Vela linked to last for a long time. The pond liner I saw on amazon had a 25 year warranty. However one person claimed that the part that wasn't under water completely cracked after a few freeze/thaw cycles. Anyone know if the stuff tends to crack if frozen (the EPDM stuff, I would assume the PVC kind isn't as high of quality)? If its really rubber, I'd assume it would be pretty resilient to cracking.

    The other question I have is, how do you join the seems? Obviously for a 40' flat roof, there'd be at least one seem. If you overlap by perhaps 1 ft that would help, but what type of bonding could you do to chemically join the sheets together?
  • Here's a super cool video of the stuff being used to make cover a flat roof (epdm = pond liner, same stuff):

    It seems like the 45 mil epdm pond liner available online for between $0.55 to $0.65 per sq ft, shipped. For example, here or here. You can also get stuff  specifically for roofing, which I've seen as 60 mils for $1.05/sq ft + shipping.

    Of course EPDM probably isn't something we could make ourselves (or is it?), but I'm all down for pragmatic solutions. Anything to get the job done. We could have some EPDM roofing designs in our repertoire of roofing solutions.
  • pond liners seems to be the new hot thing :D

    how much is that ruffles potato chip metal roofing stuff per sq ft?
    it would be nice if we had a ball park cost for each type of roof.

    my only worry about the epdm is that we dont have any way of making it if we wanted to. like how much would the shipping to africa be. if we design a house with parts that have to be shipped across the world then we're getting in trouble.

    have we thought about ceb arches? or how about even underground? it would be a lot more labor. potentially less dollars though?

    how could you protect the bricks from water? are we stuck with pond liners again? ha :)
  • Part of localization means using what is local, epdm is local to where I live.  The question at present is not about every possible roof solution, but about Jason's roof solution.  I covered my chicken coop with a metal roof and remember it being more expensive than I anticipated, plus there is no insulation properties with plain tin.
  • you can't make EPDM, but you also can't make the high quality steels and metals we are using in a lot of these projects.  Start with off the shelf parts, then migrate towards a DIY design.
  • Making the cement would also be a challenge, for that matter. Although it is much more readily available.
  • Plastic film is fantasticaly usefull on a farm: Greenhouses (transparent one), water reservoairs, roofs, shading, plastic mulching, silage.... And I think that it is already covered in the GVCS,  with the Bioplastic extrusion machine: (

    For the Jason roof, I also vote for some plastic membrane. I have experience with greenhouses, and the 150 micra plastic film we use has a very good durability, under the full sun!  With some kind of UV and mechanical protection, I  think  it will last forever.
  • Here's something that could be done at FeF: ferrocement vaulted channels.  It is a very elegant roofing solution for modular housing.  See the attached for more info.
    Ferrocement_channels.pdf 2M
  • @VelaVreations - What about taking these channels and modifying their shape so they can be placed in an arc?  Ideally they would then hold themselves up without support beams below.  Even if the arc was rather shallow, it would shed water better and take some weight off the beams.

    The Dawg
  • they are arcs already, and they can sit right on the walls.  The support beams go on the ends, perpendicular to the channels, like the top of a wall.

    But, you could easily modify these shapes to fit anything, just adjust your form.  I think it would match up very nice with CEB modular housing.

    Now, combine this concept with a laminated ferro cement technique, and you could have roof channels that are 1" or less thick, lightweight, easily produced, and extremely inexpensive.
  • A couple of updates:

    I've got the roof totally removed from the container, and am finishing up removing the rivets. Some areas are pretty rusted, so I'm going to have to sand them down.

    I think I've identified the roofing materials I need. I've already ordered a 20'x20' 45 mil (or is it 40 mil?) sheet of epdm pond liner for about $200, shipped. I'm going to have to cut it in half to make a 10'x40' piece. For the joint in the middle, I'm going to have to do a couple of things. First, I need to get some seam tape/butyl tape, probably 6" wide, and about 8' long. I'm going to need primer to scrub on both sides of the pond liner. I then apply the tape over the primer.

    For sealing the edges, hopefully with the sanded down metal + pressure, it will create a gasket effect. To top it off, I'll use butyl sealant caulk, which should be compatible with the epdm rubber and give an excellent seal. Previously there was a bit of tar used to seal the rivet heads, I'll have to make sure that is completely gone since rubber and asphalt are "incompatible materials".

    Since I'll have about a foot extra in each dimension, I was thinking about taking the excess and bonding it to the main roof and letting it hang over the rivets and metal over the edge of the container. Anyone got an opinion on this? I think I can use the primer + butyl caulk to join the two, because I don't want to spend that much money on sealing tape. I think sealing tape is just rubber with butyl on the back of it anyway? Does anyone know?
  • The tape sounds tolerable, I do suggest a raised seam - fasten the bottom edge of one piece to a handspan from the edge of the bottom side of the other, then fold the extra length over and fasten it to the back of the shorter.  This can be supported by some boards or bricks or something to keep it upright, and the pattern should make it even less likely to have a leak.

    Do we need a picture?  :)

  • Here are the two most common joint types I've seen (primer not shown, but its between the tape and the membrane in all cases). I was going to go with Type 2 because I want to have a "gasket effect" between the plywood and metal, and a seem 3 layers high provides more of a gap than a seem 2 layers high.


    As for taking the extra and going over the side of the shipping container, the second pic shows what I was thinking.

    epdm joints.PNG 6K
    cut-away view.PNG 12K
  • @Jason
    On the "$50 underground home" videos the guy says that flat roofs or roofs with flat parts where water can sit, will always end up leaking eventually. Have you planned to make sure that your roof is going to shed the water effectively from all areas? This principle should also probably be researched and documented on the wiki page for roofs if it is a valid concern.
  • I'm not an expert, but I have worked with a few and have personally done about a dozen roofs of various kinds including shingles, and a couple of kinds of metal.

    Here's my opinion:  I agree with OmniPhoenix, or his source, flat roofs are bad news.  They will leak eventually, they have to be built more sturdily for snow, water, and detritus loads, and they allow less room for insulation etc.

    I've never owned one that didn't leak, and this very day I'm converting one from flat to pitched, getting started right after I finish my coffee.

    Second, the diagram you show is backwards from conventional roofing wisdom.  Conventionally you always want any layer to lie under the next one in the direction of water flow.  In this case, you'd have:  Plywood, then either the epdm or metal, then the other one, then the membrane on top. 

    Let's see if an ascii drawing will work here...

     \  roof membrane
       \  metal edge
           \  epdm
           (rotate about 45-60 degrees left for more realistic flat roof slope...)
         Each succeeding layer goes under the one above it... 
         Imagine the water trying to run back up hill between the layers, not impossible (capillary action, wind) but less likely than the reverse.
      Now, having said that, in some ways this forum is all about breaking with conventional wisdom, so maybe you have your reasons, furthermore, I also know very well that sometimes the rest of the world doesn't allow ideal solutions.
      If you have reasons to go with this, great, but let us know how it works out.  Whether you're right or wrong, or somewhere in the middle, we'll learn something.
  • Let me give everyone an update since I last posted. I've got the first section of 2x6s up. I went with 2x6s at 16 inch centers. The area being spanned by them is 83". I also changed the way I'm doing the joints, etc. Let me give a few illustrations.



    I think the idea of putting some dirt on top and planting stuff is a pretty good one. We'll see if I do it or not. I think it should be strong enough though.

    As far as making it so water doesn't pool...that is a good point John. I appreciate your feedback. I think I'm going to put drywall shims under the center of the span to give the whole thing a slight convex shape. That should eliminate pooling (though I am using pond liner...if anything could handle pooling I think this material would :P).

    Also, I'm going with the Type I joint above, not the Type 2. The 6" wide tape is much more expensive than the 3" wide tape.

    For the 2x6 structure, aside from being stronger and just better in a
    number of ways than the previous way I was doing it, I also don't have
    to buy the nuts and bolts ($40 in hardware) or the butyl caulking
    sealant ($20).
    front view.PNG 10K
    top view.PNG 12K
  • for plants, plant succulants (cactus, agave, yucca) and any native perennials.  This will avoid the need for irrigation.

    You need a drainage layer under the soil.  You can use 2" of gravel, or you can use 2" of 20% sand, 80% chopped, dry leaves or chopped straw.  On top of that, do 4" of 30% compost, 30% chopped leaves, 30% sand/local soil mix.  This will be considerably less weight than just 6" of topsoil, and allows for water to run off (reducing the weight).  The runoff from this roof would be really good for a garden, so consider catching it (it will come off like a compost tea).

    I would slope it at least 6" for decent runoff.  You don't want a pool of water up there.  6" of topsoil + water could weigh 80lbs a square foot, which could be 22,000 lbs on this roof.  Are you sure this structure will hold 10 tons?

    Allow for drainage/runoff, reduce the weight of the soil, and increase the chances that it will work.
  • Calculations for 6" of water over the roof (dimensions 39' x 7') shown here yield 4 tons.
    The same calculations for soil at 100 lb/cubic foot here yield 6.4 tons.

    Yes, I do think it could hold that much. Assuming 10 tons, that would be about 666 lbs load on each spanning 2x6 (assume 700 lbs worse case). This is absolute worse case, and doesn't count the double think 2x6s every 8', and it also doesn't count the reinforcement by plywood on top.

    Also check out this calculator:

    Anyway, I've already changed my plan a bit. It won't be just an even 6" of soil. More details to follow.
    spanning load.png 72K
  • yeah, do try and add a drainage layer at the very least, and a rise of 6" would help a lot.  With those 2 things (and a lightweight soil like I describe) would make sure you are never even close to failure loads.
  • Well if there's going to be an open source robotic arm, and if the Liberator can be modified to press roof tiles, then the arm can be programmed to lay the tiles.

    Here's an example
  • Making comments to the entire thread as I read through it...

    I agree, a roof is perhaps the most critical problem. You can make strawbale walls, earthblock walls, you can get by with a dirt floor, but without a roof things aren't much use. From some of my own readings on exactly this problem and trying to come up with my own solutions:
    - Light steel framing is strong, lighter than wood for the strength, and apparently cheaper. One downside is thermal conductivity in colder climates, another may be fire risks... wood survives better than thin steel at a certain heat level, the outside charrs. This isn't a veto trait, just something to consider. Superinsulation strategies (ie paying particular attention to the connection points, since heat gain/loss flows in 3 dimensions, and in such a roof would be flowing through the steel roof members... so you insulate the roof members at every attachment point to minimize this) may help mitigate this.
    - Ferrocement NOT necessarily a great idea if you ever have any risk of earthquake. (and even parts of the country that don't have earthquakes are starting to have them due to natural gas/oil extraction fracking going on, so this is of concern in places where even it hasn't been for centuries) Big heavy roofs falling on you tend to = death in every third world country, especially if the engineering sophstication may be below state of the art. You need very careful engineering, a good reason to have a heavy roof (protection or underground housing may be good reasons however) or maybe the use of ferrocement to be more like a sealant, mortar, or way to tie together individual blocks so individual blocks cant fall out or be knocked out of an arch/dome making it collapse being over lighter weight materials. It's also damn heavy so youre talking a nontrivial way to raise the roof unless it's built in place somehow.
    - Corrugated steel sheets is used for roofs all over the third world due to cheapness, durability, and such, the bigger question is how to support to and how to highly insulate it. It's ugly but one of my personal favorites for cheapness, and can cover over things like strawbales.
    - Wood OR homemade light steel trusses are doable, but design software would be needed. I'd like to saw my own dimensional lumber, and make my own roof truss... but it's not very efficient without design software, either overbuilt, weak in general, or not strong in all directions it needs to be for instance.
    - Domes and arches are my personal favorite. The use of slightly arched earthblocks could be one way to do it, you could make arches and domes out of strawbales too - some others have tried, with varying results. It's an idea I personally like.
    - Remember it's not just cheap materials, you also have to build it possibly by yourself. Already stated but one thing favoring any lighter roof over a heavy one. Heavy ones require tools that can be pricey as well killing the money saved.
    - Dont forget the insulation. Roof insulation is among the most important in the whole house since heat is lost that way in the winter. Strawbales is one way to do it if you can support their weight well, another idea would be ricehulls which can freefill available space to any thickness desired and are considered a waste product/free or very cheap.
    - Dont forget thermal gain in the summer. Heat gained through the roof adds tremendously to either AC load or simple uncomfortableness if it's an uncooled or just vented house. Reflective or white roofs are better, anything dark like conventional shingles might hit 180 degrees in summer from solar gain and transfer much of that into the house. In some environments with a wide delta like the desert (where during day it's too hot for comfort but at night it's too cold) this can be used to advantage if you have a thickness of thermal mass so that the sun beating on the roof all day takes about 12 hours to "go through" and then radiates down during nighttime, this also stabilizes temperature in general. This can be one reason to justify a heavy roof. Earthblocks provide this 'time lag' thermal transfer just fine btw.
    - The amount of work it takes DOES matter. Free that takes hundreds of hours vs very inexpensive but automated and taking almost no time... it's been said that earth friendly housing is often a project for either the idle rich or the idle poor. The working poor don't have enough hours in the day to say make shingles one at a time by crushing cans and such, although i'll admit such shingles are clever.

    So I guess we have four main areas to consider, just to restate:
    - Framing. Whether wood, metal, or somehow not needing a framing (monolith concrete slabs perhaps/thick enough or of a design that is self supporting) you still need design software to make the trusses efficiently. This seems to be a critical problem to me if you don't want to buy a commercial truss or roofing system. Eventually some type of bioplastic may be usable if it could be made fire resistant enough.
    - Insulation. Fiberglass is toxic like asbestos to the lungs/having fibers the same size. It is lightweight but not recommended for that matter. Reclaimed styrofoam IS often available secondhand for very affordable prices if you know where to look, it's also more efficient per inch, it's what I will probably use if I can get it. Strawbales are a bit heavy but cheap for the insulation value, they just have to be covered with something and supported with strong framing of some sort. Loose straw with borax to give it fire resistance is an option for less or thicker than strawbales are. A Truss CAD is still needed or premade scalable designs in several sizes. Natural fibers are an option - shredded denim for instance, though I don't know of a way to buy that bulk and make your own natural insulations that way/not sure where one gets such a thing. Ricehulls. Use of unsafe improvised insulations like say styrofoam packing peanuts is probably NOT recommended due to fire hazards. (could borax fix this like it does with straw?) Thermal mass in the roof (primarily earth, possibly cement, rock, or deliberate water tanks or something) can have benefits but by definition adds weight.
    - Covering. Whether shingles, rolled steel, or a waterproof plaster, it should also resist things like hail. Someone mentioned cement shingles, i'd fear them cracking on hail if they are thin enough to be light and cheap.
    - The Building Process. What tools are required to put it up, how much work, etc.

    Now commenting on others posts:

    I'm not sure why wood/metal roofs are "not long term solutions", metal maybe lasts 25-30 years before rusting bad which is probably long enough for most people. There are wood houses older than the united states. It's possible that certain treatments, polymer layers added inexpensively, or reprocessing of the metal when it gets really rusty at some point could make it usable much longer term.

    The $1/sq ft cement roof is interesting and seems light for concrete but but it's uninsulated, which isn't as much use to anyone outside seasonably warm climates like on their house or something... the entire cost of the entire roofing system, all inclusive, including modifications to the house under it and the tools to put it up needs to be taken into account.

    I'm not anti-cement just pointing out some problems... For "cement" style roofs consider light weight aggregates like pumicecrete is an option to have it insulated and everything, then it has to be thicker to have enough insulation thickness however. It will still weigh many tons. I still would be nervous in an earthquake unless it is very very solidly built, and even then. I remember reading a site talking of low cost nontoxic housing and being depressed when I found out that even low cost pumicecrete would cost tens of thousands of dollars. Stabilized earth is what i'd probably go with if I had to and i'd think beforehand what insulation I wanted to use and how to support the weight.

    Flat roofs arent good but a 'shed' roof (like a flat roof just at an angle) is probably the cheapest and simplest roof style if you dont mind one side being higher than the other. It's simpler than anything with a peak. If not an arch or a dome i'd want to use a shed roof for cost reasons.

    Green roofs + + + especially on any limited landspace, it makes sense to use all the land you can for something useful. Houses take up alot of space on a smaller lot or subacreage location. My own preference is for an underground house basically under a greenhouse personally for best use of space.

    Poured earth (especially if stabilized, i'd think you can do that?) might be an interesting way to make organic forms and nonangular shapes which might open up new possibilities at a low cost... I remember seeing some neat nonangular designs intended for cement, that I thought would be neat if you could do them lower cost with pumicecrete or lowest cost with something earth based. If you could build it out of bricks or at least sections somehow that could ease the building process as well.

    When thinking of wood, also include bamboo as an option...

    The "CO2 output of cement" construction should be irrelevant and i'm surprised it's even the discussion, carbon dioxide is not deadly toxic waste, demands to reduce it is a globalist scam to tax all human activity while ignoring real problems. Pollution potential of methods is a concern, carbon dioxide is not a pollutant, it's what plants breathe and they pump it into greenhouses to make plants healthier.

    Energy input IS a concern, concrete is very energy intensive. It might be okay when "subsidized" with cheap oil energy inputs for low cost housing, but in terms of long term sustainability without cheap energy it is not sustainable.

    Solutions that work now (ie what is more or less subsidized energy used to make cement, I mean you cant make it yourself for cheap) are not the same as options which are best "ultimately", and the solutions in different environments will be different. Therefore multiple solutions are going to be expected and needed, the solution for the desert is different than one in northern canada. But lets just figure out solutions that work now and worry about ultimate long term perfect sustainability later...

  • a couple of points:

    Ferrocement is not the normal concrete roof solution.  It is very suitable for earthquakes, being highly reinforced and dramatically lighter than normal reinforced concrete. They are usually made in place by creating a form work out of the reinforcement. Domes and arches made from ferrocement are substantially more efficient in terms of materials and durability than bricks.  They also require a lot less time and skill to construct.

    Wood has a short lifespan as a construction material compared to earth and/or concrete materials.  It should be used for ornamental stuff primarily, and structural things sparingly. While there are some wooden homes that are a few hundred years old, they require a lot of maintenance for service like that, and non can compete with the lifespan of earthern materials that are measured in millenia.

    $1/sf concrete roofing doesn't include the cost of insulation, but on just structural needs, no other material can compete on cost (aside from earthen materials).  Metal is around $1.50 - $2/sf without insulation.

    Energy is not a major concern for concrete systems, mainly because of their long lifespans.  Also, consider the vast majority of concrete buildings were constructed BEFORE  the era of cheap energy (Greeks, Romans, Africans, Mayans, Egyptians, etc).  Cement CAN be made at home for cheap, as it has been done for thousands of years. Geopolymers are the way forward for sustainable concrete systems.

    Solutions should definitely consider local climates and situations, always. For the majority of the world, earthern and cementious building materials have been the sustainable and durable choice for generations.

  • Did the "ideal $1 a square foot" roof ever get invented and used on here? Just curious, because it's been a few years, and roofs haven't gotten cheaper.

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