Roofing options

[rainyjim]

Safety from moisture and termites!

As I see it those would be the two main issues

[Jay Bondesen]

I don't have a good picture of what you mean by a layer of cement over burlap over framing. Cement is a rigid material and usually cracks unless cured in a controlled environment. It's almost always coated with something else to make it waterproof. Concrete can certainly be safe structurally, and termites won't eat it, but a specific mix and seamless application possibly with steel reinforcing would be difficult to do and probably too heavy for burlap to support. The spray foam I used was lightweight and easy to waterproof. There are folks who do concrete domes with inflatable structures and gunnite equipment, spraying the concrete on. They use the air-form and air pressure to support the concrete until it cures.

Jay

[Rob Tucker]

I don't see the value of involving burlap with concrete at all. Why mix any organic with inorganic? Sounds like the equivalent of a paper mache project in grade school.

[MarkP]

I have often wondered what the true properties of "papercrete" are, long term. The benefit of mixing in something that can rot eludes me.

[rainyjim]

Jay, look at the link I provided on the first page, it has pictures that illustrate what I am talking about - from someone elses similar project.

Rob, I'm a little surprised by your comments. I am not trying to say this is a superior method to your companies products I am just curious about the longevity and safety of such a structure. I can infer it wouls be completely unsafe from your comments but it's very unlike you to say something like your posts above - a snide remark? I'm genuinely curious about your input given your obvious experience, so, if you think it would be completely unsafe, and/or could comment on the longevity of such a structure I would love to know your thoughts in a more clear concise manner rather than wondering if you are seriously commenting on the questions I asked or not. No offense meant - request for clarity.

MarkP, I totally agree, and thats what I'm wondering also? How long do these sort of methods/products hold up?

[Jay Bondesen]

I went back and looked. My reasoning still applies that it wouldn't be my choice. Stucco and lath w/plaster are popular in many places but not so much here. I wouldn't expect it to be water proof. It wouldn't rot or feed the termites but certainly is a coarse enough surface for mold to inhabit. It's an interesting concept but as with most of the concrete designs is better in the desert.

Jay

[Rob Tucker]

Jim, I am quite fond of concrete for a lot of reasons. What's with the burlap though? Is it supposed to provide tensile strength? It won't. Since concrete in combination with any other material is a design issue it is not possible to offer a blanket statement on safety... depends on the configuration. Unreinforced concrete,especially for a roof, is a bad idea from a safety point of view.

So again, Why burlap? What does burlap do?? Does it do it well? WIll it last as long as the concrete?

[MarkP]

I know ferro-cement boats have been built that have lasted decades. I also know that steel reinforced concrete buildings have been built in coastal areas where the rebar is rusting and spalling the concrete. It seems that reinforced concrete can work if built properly and can fail if not built properly. I have been told by people who built ferro-cement boat hulls how important the quality of the work is to the finished product. The pictures smack of a make it up as you go attitude which coupled with embedding materials that can rot into the concrete seems to me to place this project at the "it's going to fail eventually" end of the spectrum.

I am often amazed how long the water droplets on the shower curtain hang around in Eden Roc. The concrete would stay moist, the bamboo and burlap would stay moist, and they would rot. The burlap seems to be a substitute for the final layer of steel mesh usually used in ferro-cement.

[rainyjim]

Thanks all for the input, answered exactly what i needed to know.

I only have interest in burlap because I saw other people using it AND it seems like it would be a cheap building material. Nothing else really...

It sounds like the better choice would be to go with a rebar structure and use the steel mesh as a medium to apply the concrete onto instead of burlap.

I was mainly hoping to utilize the ohia on my property while taking advantage of the termite/moisture resistant properties of the concrete. The burlap was a secondary idea spurred by some examples I've seen elsewhere.

This will probably be my route since you've convinced me organic + inorganic is not equal to safety ...

http://organicarchitecture.weebly.com/th...mplex.html

definitely more expensive since I can't procure a lot of the materials for free, but obviously seems a lot safer and will probably end up being cheaper than your standard stick frame house like hpm, argus, etc. keeping in mind I will be building it on a relatively small size like the unit in the link rather than a whopping 2-3k sq ft suburbia standard.

[Kaixin]

I think burlap is a great idea, i am staying with some people who are currently using some to put up their final layers of clay plaster walls inside of a house,

the burlap is a fiber wall, thats mostly its purpose, you need fiber in almost all sorts of plaster jobs to hold the plaster together and kind of fastens itself to the wall like a piece of tape. Its the same way they make casts for broken arms. You can add fiber to the mix, but if youre just making a thin layer as a coating or a roof in this matter, than burlap seems like a great option. Cement is still a pretty organic substance, its been used for centuries and they did not always have rebar back then, but with wood..especially ohias..not so good.

I have faced the issue of cement with ohia as i am currently working with them and because cement does not breathe and collects so much moisture, i think lime mortar or lime plaster could be a good option for what youre looking for. it will harden like cement, it draws moisture out, and is a natural insect deterrent. if you check it out online i think youll find a lot more info and even videos on it