material for ceiling?

Hi permies!

I've been building a rocket stove mass heater, and all is going well. Soon it will be creating a lot of heat. The ceiling about 4 feet above the barrel top is reed over fiberglass batting insulation and 2x6s. Though I will shield the ceiling above the stove, I would like to put a ceiling in there that is fire proof, so that I don't have to concern myself with it. I just can't figure out a fire proof material that I would not mind having over head.

So far, I've considered salvaged sheet metal, but the heat would go right through, so that doesn't seem that great.

My other idea is to make a light weight mud clay plaster, and try to put it onto the expanded metal type lath available at the local building supply place.

Anybody got any experience or good ideas?

Many thanks

Thekla

Hi Thelka,

Your idea for a daub or earth plaster is excellent, and there are many formulas on the net, not need to reprint them here. You could find one the post it here and ask question if you had any. The metal would have worked fine, you just need to put a spacer between it and the reed ceiling. The reed, if attached well should act as a lath for you earth plaster. My concern is with the fiber glass insulation as that has some challenges to it in general, especially in ceilings.

Regards, jay

Hi Jay,

I wonder what the concerns are about fiberglass insulation in the ceiling. I know it's not "green", but are there hazards not widely known? It is already in place. The shed roof: 2x6 rafters supported by a beam on posts on the south side, cob wall on north side. On the rafters, OSB decking. Tarpaper over that, and galvanized metal over that-- that rippled stuff.

On the inside, fiberglass batts between the 4x6 rafters and then I think I stapled up paper feed sacks, then over that just tacked up, some reed fencing. The reed is just up there to protect me from the fiber glass, and to give me something to paint a light color. It bellies down a bit in some places, pretty insubstantial, but I like your idea of using it to put the plaster onto. I guess I should anchor some soundly, and do a test patch, to see for sure if it will hold.

Thanks

Thekla

Hi Thekla,

I just know that it isn't a green material, can out gases formaldehyde and is know to loose it's R factor the colder it gets outside. I was developed as a heat insulator, not a cold insulator and it also looses almost all in insulative qualities if it's ambient humidity rises above 60%, which very often is the case in domestic architecture. There are some things you can do, such as make sure you have a "breathing" vent behind you siding and the roof, (often called a cold roof method,) but other than that, there isn't much past replacement.

Remember, you will have to replace the gaskets under you screws that hold down the roof. If you get a chance in the future, replace the roof with standing seem roofing or some other traditional method. If your reed is attached securely, it should be fine.

Regards, jay

Integrating walls and especially ceilings is one thing that seems to be sometimes glossed over or just overlooked in green building plans so I'm going to attempt to revive this thread. If it doesn't work I'll start a new one. I think plaster can always do the job but a suitable substrate is needed and I'm sure to find out soon that it's a lot of work which isn't really a bad thing but I've been building my house for almost four years now. I am promoting what I am doing as a resource and money saving way for people to build a very energy efficient home and so far it's working but I'm concerned that many will be scared off because of the huge time commitment.

So, here's another similar ceiling material problem to be solved:

The ceiling between two levels of the house consists of five inch diameter round timber joists supporting corrugated galvanized steel (roof tin) covered by 2.5 inches of reinforced concrete.

This method has been used several times before by our architect and it's been reviewed by an engineer. While concrete may not be the greenest material there is, it's a great way to even out slightly wavy timbers and add a whole lot of thermal mass to the inside of the building. It also makes a very rigid floor (no bounce!) and allows for the possibility of in-floor hydronic heating. This is not the problem.

The problem is what to do under it. One could just leave the bottom of the tin exposed or the architect's go to solution is to put down a layer of hemp or cotton canvas before the tin. People in my area tend to be very conservative and since I'm trying to advocate this type of building I'd like to see a flat-(ish) solid surface between the nicely finished and stained floor joists.

Expanded steel lathe could be used but isn't ideal because of the cost and the desire to reduce the amount of steel used. I like the simplicity of the architect's canvas method and that led me to the idea of using a coir mat material and troweling or brushing in a thin consistency plaster. I did a small test and I'm happy with the result but the coir material used came from a garden center and was prohibitively expensive. I used a little bit of outdoor carpet glue to help stick the mat to the tin to prevent sagging between the joists.

Now I just need to find the right type of mat material for a price less than expanded steel lathe, preferably in a huge roll. There is stuff sold as "erosion control blanket" available in 12 by 150 foot rolls but I'm concerned it might be too thick and too loose/ fragile for this application.

Any ideas?

Please check my understanding of this: you are down stairs and you look up and see round parallel timbers, loooking between the timbers and up above them, you see a layer of tin, on top of the tin, there is concrete which is the floor of the story above?

and you are searching for options to put before the tin, so the metal is lost from view.

could you use burlap?

when they stucco houses they put up something that looks like chicken wire, would that work?

is the tin really tin, or is it just some flat sheet metal, possibly galvanized steel, or the stuff they make ducting and flashing out of? could you not just paint the underside of the metal before it gets applied?

Or are you thinking of adding a layer below the parallel round timbers that will hide them, applying plaster to that?

Last thought, how about using light clay (straw and clay)? If your wood above is round, and you get the material into the corner above and below, and put a temporary support under the material to hod it place while it dried, when you removed the support layer you might have a nice texture, a light weight material that would stay in place. Be aware I just made that up, and have no idea if it would work. It's definitely a "try it in your back yard" idea.

If you do make another thread, will you let us know where it is? I still have the ceiling in my greenhouse to deal with.

Thakns


thekla

Thekla

I'll put some pictures of my test area below. The tin without concrete over it since that part will be done later all at once. Since the ceiling of the downstairs is lower than the floor of the upstairs it needs to be done first unless I was going to cut material to go between the joists which the architect did not recommend having done it once himself.

The "tin" is corrugated galvanized steel roofing. It has been salvaged from an old building and seems to be thicker than most new roof steel which is good considering I'll have to walk on it while pouring the concrete floor.

It is very important to me that the ceiling looks relatively flat and smooth from below and the timbers are exposed. So burlap, like the architect's other usually methods are out.

A clay straw technique may work however the clay here is frozen solid and probably will be for weeks and after that it will be too wet to dig for some time. The other challenge with that that I can foresee is that it would have to be supported from below and it could easily be damaged by walking on the roof steel above it. It will be a minimum of two weeks from the time the ceiling goes on until the final floor is poured above it. That's the reason I'm thinking it would be best to lay out some sort of dry matting material that could be plastered later.
l

For anyone who's curious, the upstairs ceiling was done by pouring and troweling out a 3/4 to 1 inch layer of a special concrete mix onto expanded steel lathe over a layer of 6 mil plastic sheeting.

The black plastic is visible in some of the pictures above and it will eventually be removed leaving behind the rough texture of the concrete keyed in to the lathe. I will apply a thin coat of plaster that is compatible with the concrete to finish it.

The downstairs could probably be done in a similar way but since the concrete layer is much thicker I'm concerned about it sagging or accidently stepping in the wrong place during the pour. That happened in a few places up above leaving a some foot shaped dents pushing down from the ceiling Opps!

I'm trying to use something greener (but still manufactured, at least for this project) and less expensive than the expanded steel lathe too!

one more!

Thekla,

What's the scoop with the greenhouse ceiling?

Hi Scott,

I think I'm the one who started this thread. and I have not yet many any changes to the ceiling in my greenhouse. I'd take time to describe the situation, or find the quotes, but I am headed to permaculture voices, so will not be doing a lot on line for the next week.

Check out what I already wrote, and we can take up the discussion later in the month.

I am hoping to get the modifications done on the ceiling as well as the rebuild and relocation of the rocket mass heater in the greenhouse before next fall, but the higher priorities here are establishing pasture for the goats and the first year feasibility / pilot project on the herd share goat cheese CSA.

I really like the photos of your ceiling, and feel like there is something in there to help me with my green house thing, and the WOFATI inspired "barn" I see coming in the next couple of years.

Thekla

i'm a bit surprised that expanded steel lathe is sufficient reinforcing for the floor, i think our codes here would require welded wire and maybe rebar

i'm a bit surprised that expanded steel lathe is sufficient reinforcing for the floor, i think our codes here would require welded wire and maybe rebar

You're right. I'm not sure what's actually required here and our plans were not engineered but very similar designs by our architect have been. The floor slab will have welded wire in it above the lathe and corrugated steel. The ceiling that's already done with lathe doesn't have wire in it because it's only a ceiling, not a floor, and the concrete is only 3/4 inch thick.

I've picked up some rolls of erosion control blanket and started installing corrugated steel over it for the floor and it's working well, will get some pictures posted later today.

This seems to be working!

I found a place only about 35 miles from home that manufactures erosion control blanket from straw, aspen, and coir and was able to buy a few rolls directly. It's nice to finally be starting the floor!

Hi Scott,

I commend your creativity, though I do have questions about your approach and overall plan? (Note fyi it is "coir" matting)

Cement has such a huge carbon footprint, and is not environmentally sustainable, why did you chose to use so much OPC on an otherwise "natural build" project?

I like the coir matting for the ceiling, yet why use an OPC and not clay, lime, or similar natural plaster?

Did you have or do the engineering for the floor system, and what is the DL for the floor and projected LL? What is the combined project load?

What is the species and grade of the logs you use for your structural members?

Do you have a projected R factor rating for the walls?

Being from Minnesota, I would think that there would be more natural building methods you would chose first over cement block. What lead you to this choice?

Regards,

j

Hi Scott,

I'm glad you are moving forward. I like the coir mat stuff. Maybe I'll look for some around here.

I haven't touched my greenhouse ceiling project.

Hi Jay,

I just read all the way back to the beginning of the thread, to find out where we are, and I notice you said fiberglass batting was developed as heat insulator, not a cold insulator. Since heat and cold are relative to each other, I can make no sense of the idea that it works for one but not the other. Can you help me out with that?

Thanks

Thekla

Hi T. M.,

Sure, FI was developed for insulating refrigeration units during and after WWII (among other things.) In a vacuum between to metal sheets as found in a refrigerator unit in the middle of a desert with zero humidity and zero air circulation this material performs at its optimum. In other words a hot dry environment with not air movement. The fact that it loses R factor the colder it gets outside, higher humidity than 30 percent and/or that it does not respond well to any type of convective air flow, never seems to make it into the advertising by the major manufacture and primary patent holder, "Owen Corning." It is basically worthless (in real world application) as a common wall insulation. That was my only point.

Regards,

j

Thank you Jay C. White Cloud for your comments. I admire you for the depth of knowledge you bring to these forums.

I'll start with your easy questions first:

Do you have a projected R factor rating for the walls?

The North, East, and West walls have R 27.5 in the XPS on the outside of the block plus perlite in-fill inside the 12 inch block and whatever the block and a layer of stucco provide. The south wall is 2x6 with cellulose and a cedar siding rainscreen. This past winter was said to be the coldest here in about 35 years and I was amazed at how well the house held its temperature. It stayed around 45 F only firing the wood stove usually one day a week.

What is the species and grade of the logs you use for your structural members?

Not sure what you mean exactly by grade but the joists are 5 inch diameter or greater in the middle and straight, at least in one plane, within either 1 or 1/2 inch (it's been a few years). The trees are elm, ash, and hackberry.

Did you have or do the engineering for the floor system, and what is the DL for the floor and projected LL? What is the combined project load?

I think I stated this in a comment above, but this specific building design was not reviewed by an engineer but very similar designs by the architect were reviewed and approved. I've had some engineering training myself but since I haven't used it for a long time it would be cumbersome to try to check it out myself so I'm trusting the design I was given. I do know that the compressive strength of concrete combined with the tensile strength of round timbers will make a very strong assembly. At one point while raising the 2nd level bent the entire thing was suspended by two floor joists. Here's the architect's website with some design details: http://wholetrees.com/engineered-structures/products/column-beam-assemblies/

As for your questions about why concrete I've been thinking all afternoon of how to answer in less than several pages. First I'd like to say that I have nothing but respect for anyone who successfully builds using all natural materials, you'll have an end product far superior to mine. There are many reasons for my decisions. First of all, the salvaged but never used concrete block was purchased on an auction for $150! It took some sweat to move all 2500 pieces but it was well worth the time. I hired a couple guys for about 5 days total (for two consecutive summers) and had walls. If I hadn't found the block the project would have probably taken a very different direction.

Probably the biggest reason for using lots of concrete has to do with the dominant culture of the area I live in. If you've every listened to "A Prairie Home Companion" and heard Garrison Keeler talking about the conservative lutheran folks that's here! I'd love to just be off doing my own thing but I've learned that it's almost impossible to bring about change alone. As stupid as it may sound I don't want to freak out the locals by building out of "weird" stuff. I've been working very hard lately to build my reputation as a level-headed, pragmatic individual.

This is a very small town and its slowly dying. Lack of others to help out is another reason for more conventional materials. When my father was my age he had probably a dozen of other farmers around his same age that he could call to help out with projects. I know of only a few who are mostly 10-25 miles away and busy all time. We don't have many people around here with the right kind of knowledge and experience to work with lime plaster for example and I personally only have so much time to invest in the house project.

It's my dream to help bring some vitality (and people) back to this area and then go on to do that sort of thing professionally. Naturally, permaculture principles and self-reliance are a big part of the strategy. If everyone left here and it went back to prairie and oak savanna that would be awesome! I'd come back and visit leaving only footprints, but the problem is that won't happen as long as civilization chugs on because the land will still be used for agriculture. This is some of the most fertile black soil on the planet. If the towns and most of the remaining population here disappear there's a very good chance that farming practices aren't going to get much better for the land and much of the remaining bit of edge in the form of fence lines, farm groves, and riparian areas will become mostly barren for over half the year like the rest of the landscape. On the other hand if people do start to see opportunity here maybe enough like-minded individuals can get together and start to build a saner future.

Back to not freaking out the locals... So I'm trying to take things one step (okay, maybe a few) at a time. Right now with the insanely cold winter ending and after record high propane prices folks are pretty receptive to ideas for saving money like passive solar. I wanted the house to be just a little different to get noticed but not so far from the norm that the same type that won't buy organic raisins at the co-op when the regular are out even for the same price(!) won't ignore me like "the crazy person". And yes somehow we have a food co-op here!

Once they see the house is beautiful and I can heat it with 2 cords of wood then I can say "Oh, by the way you could build the same thing out of clay from the ground"

There aren't many rocks here, stone is a precious commodity. Ironically even straw is hard to find, especially organic. The closest organic farmers are about 25 miles away and usually don't have much extra. Because all the concrete my house has a huge thermal mass which was very good over the winter, now, this time of year I've stopped bragging about the temperature because we'll get a 70 F day and it'll be 50 inside.

Last reason; I like my wife and would like her to stay. She really wants me to get done soon and has been amazingly patient with me. I want to get done too since we believe mold in the old house is causing health issues for her and my youngest son. It's hard to see people you love suffer.

I hope I answered most of your questions, let know if I should elaborate on anything.

PS
Once we're in the new house I'm planning to knock the old one down to the foundation and rebuild a smaller structure using almost exclusively natural gathered materials.

Hello S.H.,

The wall design, in and of itself, disregarding other elements of consideration, sound excellent. I like that you have used a rain screen system on the wood wall portion and kept your mase to the inside of the structure...brilliant. When I read the word "salvaged" I need not read further...most excellent, and only other factors to then consider. Block can present as an excellent modality for many builders with limited time or skill set. In due course we are going to see more "sustainably made" block systems come online that will lend themselves even further toward better architecture from CEB, geopolymers, to lime and other systems...

When I got to your, "Garrison Keillor talking about the conservative lutheran folks," I split a seam laughing...I know exactly what you are talking about in that area, and have had some really interesting...well...discussions with folks and there concepts of architecture...some of my favorite are, "Timber frames...like a barn? Who would live in a barn?..." It is a most interesting normative culture. You are wise to come at this "side ways," around that lot, especially if you would like to help others. With your system (and the logic you described) you can augment over time more and more completely natural and traditional systems that they will slowly take to. Roald's crew is doing that a great deal themselves with the "whole tree" approach. I also feel for your isolation, sorry for that. It is part of the reason I do so much pro bono consulting work, as there are so many folks coming on line in exactly your position. As such, there is not much about what you are doing (under those conditions and time parameters) that I would change.

Grade speaks to the condition of the logs before they had been bolted and installed elm and hackberry both rapidly decay under some conditions after felling and can present as sound yet have structural voids around limb wounds and other defects unless efficiently graded. Ash is much more forgiving in this and in your described size ranges would be serviceable even with considerable defect. I am not sure if you just used one of Roald's design parameters or know him. He and his group are grand folks that we have crossed paths with several times. Following these parameters are a safe consideration if the wood was in good order, as a whole tree is often better than a milled one.

Scott, your post was excellent, and you more than answered all my questions. You have added a lot to this conversation and I do believe you should compile an outline of your project and post your own thread here so folks can follow along on your adventure. It would be most educational, enlightening and helpful. I also think other could learn from this conversation and what you are doing. I have made a contact file for you in my system, should you ever need a question answer please call or email. I would be more than glad to give whatever help I can. I am sure there are many of us here that will be thinking of you and standing behind you.

Regards,

j

Thanks Jay!

Validation from yourself and other permies contributors feels great! And reading through the various green building forums has been a wonderful source of inspiration and solutions for problems. I should try to make a list of all the tidbits I've read here that have led to real-life applications on my house.

I did work directly with Roald and whole trees, unfortunately they're about 200 miles away so most of it was over the phone. I was lucky enough to spend a few days there in the early spring before the house project really got started and learned a great deal from that experience and also later a workshop they taught.

Thekla,

Thanks for your comments too, sounds like you have a lot going on and I hope to see more posts about your various projects! I'm still trying to decide if I should get goats this year or not (or a different ruminant). Pigs will arrive in late May or early June!

If I start a posting on my house project does anyone know which forum it should go in? Green building, passive solar, or my projects forum (not sure exactly what that one's called without looking)

Hi S.H.,

Post in "My Projects," and then I will create links to the other germane locations for it. Thanks for doing this...your project will, I am sure, be a learning oprotunity for everone.

Regards,