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Waterproofing fibercrete?  RSS feed

 
Kevin EarthSoul
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What are the best methods for waterproofing a fibercrete exterior, such as a dome construction?

I'm guessing that an industrial chemical will be the best performing.

What are some natural alternatives? What are their strengths and weaknesses?
 
Christopher Steen
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Hey Kevin,
If you're asking about Papercrete, or maybe other hull, husk or Hurd based cretes that could mold, remember that breathability is important so that the material can dry out. Interior humidity can generate a lot of moisture, even if 100% of ground moisture was kept out and your dome roof was 100% waterproof. Metal roofing with a vent would be best in my opinion, out else a durable breathable lime plaster with periodic maintenance washes to seal any cracks.
If you're asking about synthetic fibers on a ferro roof, I've used and been pleased with antihydro and gaco, as far as chemical products are concerned.
-earthbag Chris
 
Jay C. White Cloud
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Hi Kevin, et al,

In the general "flavor" of it...Chris's post really needs to be headed...

Before I go into some detail seconding some of Chris's poignant observations...remember...this is a permaculture forum...in as such...many of these "concept" approaches to architecture are "very experimental," unproven in the long term duration, and far from being either in the vernacular or natural disposition (ethos?) that is at the heart and soul of permaculture (as defined by many...not all.) When a form of architecture must rely on "technologies" to work...or more challenging...supporting and relying heavily on "large industry" such as petrochemical, and others...it fails at being either sustainable or part of the "permaculture mindset."

Chris Steen wrote:If you're asking about Papercrete, or maybe other hull, husk or Hurd based cretes that could mold, remember that breathability is important so that the material can dry out.


Whatever system you choose...a "cold roof," and "rain screen" system seldom (if ever?) fails to provide additional protection for the durability of the architecture. This is not always necessary in "mass wall" designs, yet still can be part of them in some applications. These two elements when working in concert with one another augments the drying and drawing effect that so many "air tight" structures are troubled with. In my experience, "draft proof" over "airtight." Incorporate and employ as many permeable elements as possible in all building diaphragms, minus perhaps the roof area...which should be as "impermeable" and/or as "layered" as possible. The roof's "architectural diaphragm" is a key constituent of the "drainage system" for the architecture promoting a "whole system" design, and extending the longevity of the structure.

Dome architecture in general is a challenge in many areas, both structural and biome location. Earth bags, and any other system that emulates the vernacular is usually much more successful, especially when built in areas that have similar traditional building systems. When a client that has predilections for "dome architecture" both aesthetically and tangibly, I recommend a vernacular form as much as possible, or a facsimile there of...like stone, brick, adobe, earth bag, or perhaps even some of the less proven like woven with cobb, etc.

Chris Steen wrote:Interior humidity can generate a lot of moisture, even if 100% of ground moisture was kept out and your dome roof was 100% waterproof.


Excellent point again...

Interior humidity is almost always generated by elements (usually organic) that occupy the space. This concept of moisture "rising" into a structure...in most (98%?) cases is a misnomer, and not a effect of ground moisture at all in my experience and observation. Even in location built directly over or on the edge of water seldom suffer much from this proximity to "liquid water" ever affecting in ambient external humidity over what living in the space itself generates. I make this statement and observation on having seen and been part of several historical restorations - reconstructions of "Mills" that basically sit in the water. If "rising moisture" was the issue many seem to believe it is the grains ground/milled, and produced there would mold and decay as quickly as it was manufactured. I would also suggest that places like Venice Italy would have horrid issues with the alleged "rising damp" and other moisture related issues...it does not...and its millenia old - stone sitting on wood - foundations are only now being undermined by rising sea levels and tidal shifts...not this "rising damp" or "ground water" issues. So, if a structure is designed with a proper applicable material elements and excellent draining within the foundation matrix (where applicable) there is seldom (if ever?) issues with interstitial moisture "rising" into the structure, as would be fostered exterior to the living envelope by any elements of cohesive diffusion.

Chris Steen wrote:Metal roofing with a vent would be best in my opinion, out else a durable breathable lime plaster with periodic maintenance washes to seal any cracks.


Excellent, or a equivalent method like stone/slate or clay tile or related reticulated and overlaying system.

As for synthetics...there are many, but I would rather not go into that long list, as most are not applicable to a natural or permaculture build.

Regards,

j
 
Christopher Steen
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Jay C. White Cloud wrote:Hi Kevin, et al,


Chris Steen wrote:Metal roofing with a vent would be best in my opinion, out else a durable breathable lime plaster with periodic maintenance washes to seal any cracks.


Excellent, or a equivalent method like stone/slate or clay tile or related reticulated and overlaying system.

As for synthetics...there are many, but I would rather not go into that long list, as most are not applicable to a natural or permaculture build.

Regards,

j



Hopefully I quoted this correctly.
To roof tile means sacrificing breathability without heavy framing to raise above the fibercrete. But I like metal personally.
Synthetics are what they are. But I just scored a few grand of gaco to durably seal ferrocement. If its laying to waste, and I use it, well that's sustainable.

Jay, I really enjoy your posts. But I find I favor scroungy resourcefulness to use something appropriately from the waste stream in order to build sustainably, otherwise, my vernacular geographical construction would be cliff dwellings or tipis. Can't do that unless I pumped Papercrete on that tipi, bit alas not vernacular. And to not be so experimental, it would be spray foamed and stuccoed

I think half of permaculture is debating. Just keep it breathable and not to wet. Adding lime in the mix is wise. Don't put any fibercrete that'll hold moisture against bales.

Earthbag Chris
 
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