We have been looking at MGO boards but as a new product there seems to be risk and a lack of product warranty, and potentially fire rating (1 hour burn). Same for "moisture resistant" drywall new to market.
Looking at wood lattice cost is high: http://www.lowes.com/pd_429248-199-127738___?productId=4113854&pl=1&Ntt=lattice Zinc coated steel even higher and not ideal due to corrosion.
Wood lattice @ $14 (1/2x4x8 ) or ~.48 Sf is over twice that of drywall @ ~.18 SF unfinished, and we have not got to the material and labor cost of field lime or clay scratch, brown, finish coats (note: the more thickness the more mass and better ability to manage humidity, HVAC loads that can take cost down in the over all design). I'd venture to say that lime or clay mass is better at that than gymsum. finishing the seams of drywall will cost less than 3 full coats of plaster. So lime or clay on lath is getting very high in cost unless some has a way to get it's cost down. Getting wood sticks from the back yard may not be an option for everyone and labor cost to attach them will be very high compared to 4x8 sheets of lattice.
First attachment is a mainstream wall for comparison, second moisture resistant gypsum detail. I'm using Chief Architect Cad Premier V7 software. That is where wall defaults are set. Feel free to correct any of my statements.
We quit selling that material because it don’t last. What we sell is ¾ cedar lattice @ $30 each.
So my design approach is to focus on the envelope first. I just can't seem to get past it after two years of looking at all the possibilities. I think I'm obsessed! or perhaps challenged especially when we start looking at cost, code(safety requirements(structures fire and smoke etc), sub-divisions dos and don't allow), etc...). If your in rural with lots of DIY time or $$$$ where noone cares it is MUCH easier.
So back to walls. I got some studs, American Clay plaster samples (nice looking I'll post some cost soon). Learned quite a bit from there site today, so I'm going to try my beginner hand at plasters to their on-line instructions. Tomorrow I call and have some questions. I'll also call Carmeuse lime about there type O interior mix, and perhaps my friend Bill Bradbury if he's still alive I have not seen out here in a while. He does alot of lime on drywall renovations and has a lime co in Idaho he recommends. That is the other way I design is before I spec it out on a drawing I build it or mock it up, talk to trades with experience. Then I can get a feel for the trades I'll assign to the task. As in clay or lime plaster veneer that can be our plaster/stucco or paint and drywall trades so I can get competitive quotes. If I go all thick lime plaster that is one quote, plaster trade.
I already know the insulation will be mineral wool unless someone know what can beat it, but I'd that differently. As soon as I have my stud and truss cost I'll compare it to Timber bolts(wall and truss timbers combined, see my blog below we did on a commercial job) craned in and if it looks good I'll model it.
Cost, durability, toxicity, sustainability,
Cost is huge, toxicity is hard to place value on in light of all the false green washing out there the average(non-educated) person may not buy it. "natural" might work, maybe, perhaps to some people that go to health food stores like me or chemicall sensitive, small groups not the masses . Sustainability is a new buzz word and a hard sell in America where the average person buys another home or moves every five years. I think getting them to pay more is going to take a very convincing sales staff we do have, but still in reality a hard sell but I do like the word. Nice!
The exterior is tricky since most subdivisions mandate a certain look, color, for siding and roof materials such as asphalt shingles, so some of that is out of my control and unfortunately in the hands of the developer or ACC or common land owners by land contract and law. The best plan I have is 1-direct meaning I will use a structural rated siding like LP or plywood, it has to be stamped by APA or an approved agency in code with an on center spacing to satisfy braced wall code (shear, racking). The OSB is the pic above is gone which I call and improvement. I back yard tested the "fiberboard" LP "smartside panel siding and it held up well in water submersion, I just do like the fact I can delam it with my finger nail at the T&G. Georgia Pacific plywood structural siding I cannot do that. We'll get into more of that later since it also mates directly to mineral wool so we have to be careful. I may put a furring strip rain drain gap there if cost allows. Roxul and Thermafiber spec out house wrap. That is OK since in my mind the interior materials are more important. Probably T&G pine or cedar ceiling, again cost?
I'm just about to try chicken wire as lath, wood is too expensive. I'm also thinking about getting some marbled sand, different clay types and experimenting to drop cost and keep it local.
But yes, it is easy to through ideas out there. This thread is different I hope it looks at reality cost and safety. BTW: If you have an idea don't be shy, I know enough about code and ACCs to identify it's feasibility.
Thanks for the interest, I was not going to not waste my time if there is none. I have alot to do. Behind all this I have a 3,200 SF flex/next generation spec home to get past the dang envelope once and for all. After which I'll run the HVAC loads through some software it should be low, decide the HVAC unit and rest of building design for improvements, cost reductions. So what I will have done is move cost from HVAC to the envelope and provide a more comfortable living environment....not easy!
BTW: By following code we do not have the expense of a PE. Single family US homes for the most part up to a duplex and three stories do not require the stamp of Architect. The software I am using is complex and has a steep learning curve, one can do their own models and drawing's but it takes time to gain the skills.
Terry Ruth wrote:
I'm just about to try chicken wire as lath, wood is too expensive.
For what it's worth, Menard's carries metal lath. At $.52/SF, it's no cheaper.
But 4' chicken wire (poultry netting), now that's just $.20/SF. Presumably, you'd prefer the 4' roll over the 3' roll, so that it spans 16"OC studs conveniently.
Last thing, this also came up when I searched the word "lath". The gaps between the boards are probably too wide for plastering, huh?
I'm trying to figure out how and what charge Kaolin clay has and how well it holds moisture and repels water, Bentonite too. So we know certain clay have a higher ability than others, which ones, high swell, slow shrink/crack, or self healing like lime. I found this bulk supplier so far: http://www.bulkapothecary.com/categories/raw-ingredients/clays/ I'd want as white as possible for a base to pigment. Mix a few clays, add some fine aggregates, a little binder for durability, good to go for a finish or veneer coat.
Had a long talk with American Clay today and got some price quotes I'll post soon. They use a marbled sand and other aggregates, acrylic binder, iron and earth oxide pigments, I need to look for and cost too if anyone wants to help. They prep new drywall with a sealer/primer and add 80 grit sharp edge sand to the primer for adhesion to their veneer clays. Some nice looking walls no doubt.
Cut into strips to work as lath.
In my experience it actually resists moisture pretty well, lasting years in direct contact with soil.
Are natural fibers a possibility? Jute netting , burlap fabric, wool cordage...
There are several choices for the brown and finish coats on drywall. Installers and builders get price breaks, this is retail.
1. American Lime(see attached). Enjarre single coat is the way I'd go for ~ $3.00 SF installed. I have sample panels that are not that durable they say adding an acrylic sealer helps. Bill and I agree it takes down the breathability of the wall. They add sand to primer for a scratch coat then for most of their product line like Loma two coats are required. It can also be sprayed with a 10% material loss.
2. Make up your own with Kaoline, Bentonite, marbled sand or dust or mix a lime type 0 mix according to a lime manufacture or American Lime association usually 1:2:3 (portland cement:lime: sand) on drywall sandy primer base or on sawn lumber lath.
Here are some properties of Kaoline and bentonite clay that would combine well with a 80 grit sharp edge mason sand.
I'd start with 1:2:3 (Kaoline: Calcium Bentonite: Sand)
Kaolin clay has a low positive charge,expansion, shrinkage, adsorption. It is used in paint(the silica and alumina) production to improving the brightness of colors in paint, as well as controlling the texture for disbursement and coatability.
Bentonite (Smectite) has a high negative charge(surface attraction). It comes in the form of sodium bentonite which has VERY high expansion/shrinkage properties and potential to crack if it evaporated. It can be used as a sealant or water barrier in landfills, basements walls and slabs if it has a plastic index < 14 for structural reasons. Calcium Bentonite has less expansion/shrinkage crack potential better for plasters. Bentonite also can be used as a binder. The two can also be mixed.
Surfaces in bathrooms/kitchens/showers may need additional rendering.
3. Use a hot mud or setting joint compound brown coat on drywall and Limestrong finish. This is what Bill uses and I am looking at. I have samples and quotes coming. Basically, the entire new drywall gets a brown coat of mud and the Limestong is set to it. I'm guessing this is going to be less than American Clay @ ~ $.300 SF and a better thicker product. I added 1" to the model below, compared to 1/16 American Clay. Perhaps Bill will be out to explain more of this. He temporarily lost internet service.
Read all about Limestrong here, very impressive: http://limestrongfinish.com/master-of-plaster.html#contact
4. MGO plaster. I'm talking to Premier about. Not for the DIYer. I also recommend staying clear of boards.
I'll be back with model pics...
1. Structural Rated Siding Panel, 19/32, APA or other agency approved to meet braced wall requirements in code. I'm using IRC 2012 as a guide. Check local jurisdiction for amendments. LP is an Engineered wood product and is one choice, it delams easy and I could not get a perm rating out of them. The other best IMO thus far is Georgia Pacific Plytanium with a "Exterior" exposure rating not to be confused with "Exposure 1" has a perm rating of around 1-2. There are other ways to meet braced wall per code but most use method 3 continuous sheathing/siding, and the ACC's require that look. We could look at board and batten or lap but that would be more labor intensive than these panels and more code inspections.
2. 3/4 fur stud rain drain gap prolong the life of siding and allows wall to breath to a ventilation gap I'll detail more later.
3. House wrap changes the pore size of the mineral wool and is a manufacturing requirement for warranty.
4. 1 1/4 Rigid Mineral Wool Comfortboard IS by Roxul. @ 10% deflection it has a compression strength of 745 PSI compared to foam 8-10 psi and it is inert, repels water and fire/smoke better. It can be very difficult to get a hold of in some locations. R-5. Provides stud thermal break and air seal.
5. 2x4x8 @ 24 OC provides R-23. Note: Continuous R value of 30 (23+5+2(cladding). Effective r-value of 25 (high since mineral wool does not degrade much with moisture like others (fiberglass, etc))
6. Drywall (conventional) as discussed above.
7. Plaster as discussed above. Provides hygroscopic mass, humidity/hot/cold buffering, health and beauty!
We meet fire and smoke requirements with the drywall so we don't have to prove the plaster although I will double check. Most ACC's require slabs we use a slab on grade monolythic for cost reductions per IRC 2012. Check local jurisdiction for other requirements such as soil testing to determine depth of footing etc... 4 x 12 x 24 is for estimating purposes only.
Any questions or suggestions let me know. I think we have improved the mainstream wall by far. I'll develop a material list for both to compare cost on where we are at so far. Then we'll build the roof and floors. Look at Timbers, etc....
0 burn if non-fire rated. Fire rated walls are between garages and dwelling’s, addicts, other building separations, etc...
Wall and ceiling finishes shall not have a flame index greater than 200, smoke 450, per E84 or UL 723.
Earth/lime etc has to be over 4 I dunno I never seen a rating for it, and I'm sure it will depend on aggregates. Some jurisdictions want to see all supporting documention including smoke and fire rating's before issuing a permit.
Chicken wire @ $.18 sf falls under “wire lath”..¾ min plaster thickness same as drywall which drives cost of high. We finish drywall at $85 SF hence why it is so popular. Interior paint add $.70..... drywall, prime, paint $1.55 sf hard to beat but not very hygrothermal and it causes high HVAC loads and other health related issues depending on how it is painted and how high the humidity is.
Coat mix requirements note "masonry cement" and lime columns.....
APA structural rated exterior panel water resistant barrier is required for cement plasters. See table R703.4 pg 365/395. I think out house wrap satisfy s this.
If designing 1 direct structural siding to studs as I did above or APA structural rated exterior siding panel a water resistant barrier is required for cement plasters. See table R703.4 pg 365/395. LP wants $1.50 SF for 5/8. GP plytanium wants $1.06 for plywood siding I think is a better choice than LP "engineered" at a ridiculous price.
I studying this Roxul design guide if anyone want to read and compare notes: http://www.roxul.com/files/RX-NA_EN/pdf/Technical%20Bulletins_Guides/Residential/13A76%20ROXUL%20COMFORTBOARD%20IS%20Installation%20Guide%20FINAL.pdf
I'm not sure attaching fasteners through siding and rigid mineral board is going to work for shear in the insulation although the compression allowable for 1.25 thick is VERY high 745 PSI, as I said compared to foam 10 at best. It may be best to use two layers a backer board and siding. OSB is VERY cheap @ $.22 SF (plywood over double that) I don't want to use but it with the labor and matl cost of siding is lower, 3/8 LP @ .63 sf on OSB @ .22 or total $.85 sf, compared to LP $1.50 sf, GP $1.06 sf. This design would also allow what Roxul is proposing attaching furring strips to their insulation. This is a very informative guide. I'm also considering mineral wool underslab. That and a bassault rebar along with fiber reinforcement would stack up to any foundation out there imo and based on my research of large commercial but it is going to take code changes and cost, if laid on the proper substructure. The slab has to be suspended which is the case of foam most do not. So most mainstream designers take a weaker product foam and subject to higher loads than the Engineers at Roxul would with a product that can take over 75 xs the compression, go figure! Roxul is testing it for creep over time is my guess which foam fails miserable and is ignored by marketing hype . I'm getting with Roxul testing soon. I'm also building a test wall mock up to see how well plaster goes on Roxul with nothing or chicken wire although I don't like metal it is affordable and I believe if the plaster keeps the moisture off the metal it will not loose it's zinc coating as fast, that just leaves heat cycles. Hope it last at least 50+ years before there are any issues and if there are it will be deep in the wall. As thin as it is I doubt we see any rust jacking or cracks at the 1-2 " plaster but that is JMO.
I hope readers do not get the false impression that designing a cost optimized "code home" vs. all natural home in rural is less complicated it's not! There is ALOT to know and consider to do it properly.
Here is the braced wall section I have been referring to in code. There are 16 different methods to resist shear or racking. The design above is Method 3 (WSP) "Wood Structural Panel" continuous sheathed. 3/8 is the min thickness from code. Manufactures have their panels third party rated to specify the thickness and stud spacing. Examples: 24/16 means 24 OC roof/walls, 16 sub-floors. Again local jurisdiction may deviate. There are other requirements, many, like 4' max for bump outs, corner bracing, max door and window opening's, strapping, etc....but most use method 3 since it is simply, just sheath all studs which in some areas is over kill. If one wants to cut cost study the wall bracing chapters but then one may end up having to explain to code officials that do not understand and when that happens they can make a builder go get and pay for a 3rd party inspection familiar with the practice and code.
I have samples coming from Roseburg (5/8 duratemp) engineered product that competes with LP to go 1-direct about the same cost. RoyOMartin "smartcore" my distributor tells me for a yellow pine siding has less knots than Georgia Pacific (GP) "plytanium" for almost half the cost. They offer a T1-11 on 4 or 8 OC, or a 12 OC reverse board and batten (RBB) with ship lap edges...The plywood needs priming material and labor we are around $.45 SF, LP and Duratemp do not. More on siding later...
Here is my test wall. I'm no pro plaster trade so I figure if I can do a pro will do it much better. I added a drywall joint and set tape no sanding, level 1 finish and I primed with 1: 1/4 primer:sand. You can see American Clay's sand is very fine. Next I'll add their veneer coat to it per their instructions to about the thickness of two credit cards. Also, I muded the joint and some feild for a limestrong (pumice/lime) product with a mix 1:1:2 (mud:lime:sand) per their instructions and I extended that to Roxul mineral wool with and without chicken wire, I did CW studs. The gap between the chicken wire and roxul varies and needs alot of scratch coat, and the wall would take alot of work to make smooth if that were desired, so far due to the additional labor and material $ I am not seeing much benefit vs a direct to drywall. We'll see.
Also shown is limestrong in the round bucket. Roxul "Confortbatt in cavities @ 16 OC since 24 OC is special order shipped from CAN. Confortboard samples for an exterior insulation wrap and underslab.
So the base coats are done I'll be adding the finish coats soon.
There is a BIG myth that says just because it is made of natural earth type materials it HAS to be safe which is a lie. In many applications, materials taken from mother nature or ground sources without proper processing are more prone to microbial and moisture damage than most of the mainstream materials that are better understood. The word "natural" is as much if not more of a misnomer than the word 'green". If you want a feel for that read WUFI website. The current issues with it is ASHRAE 160 mold source material data accuracy, climate files, layered 3D air flow we are fond of in America but, we are getting there. All building's should go through a WUFI simulation ran by a qualified professional, it has been the backbone or world class designs in Germany for two decades that do not rely on guess work and opinions or a lack of documented empirical data people design to. I have an envelope assembly I am running the simulations on now and will be offering the service in the near future for a price. Your best bet is to hire a pro.
And no do not modify a lab tested concrete mix unless you go back to the lab and have a PE stamp the structure.
My test fixtures are going through freeze-thaw cycles as I monitor them this winter.
Look at some of their summary statements,
In fact, the pumice pozzolan turns the CH into additional CSH, densifying the concrete and making it nearly impermeable.
I'm not sure making concrete "impermeable" is the correct approach, I see a need for it be breathable to dry surface or boundary conditions. Permeability is just one physical property to look at. Hygrothermics is better. I'd like to see more test on how this product reacts to common flooring materials since not everyone wants decorative cold concrete floors. Mag is suppose to be non thermally conductive but the boards I have are. We need a thermal brake so we do not have to insulate, chemical resistance pumice provides another, many (not just long term compression) mechanical properties, others, when is comes to long term "fatigue" in the property we look at not compression. Fatigue life takes into account more than compression. There has been long term studies using fly ash, perhaps not as effective, but it is code compliant. Any pumice or mag company that is serious should seek a ICC letter of compliance.
While chemical resistance is perhaps the biggest benefit to adding pumice pozzolan to concrete formulations, it is by no means the only gained advantage.
In some applications, Hess UltraPozz can replace up to 50% of the Portland cement typically needed, thus reducing, on a pound for pound basis, the colossal carbon footprint standard cement leaves behind.
Take note "In some applications" meaning Engineering is required.
The other approach is to DIY in a mortar mixer under the direction of one of these companies and hope for the best. Premier has some sample mixes on their site but takes no part in a warranty or liability for losses or false claims. I do not recommend this unles you are a professional concrete designer with decades of experience in the design and builds of concrete structures, such a civil engineer or PE.
I'd also someday like to incorporate pumice, mag, FRPs, into a mix but I know it will be a long costly windy road to get it engineered correctly and code adopted so it is on the shelf for now
Now perhaps we see why hidden stick wood construction dominates as opposed to ancient Timber beams that are also no longer in our code books. I guess those resurrecting it must think they have a product to make some money on? This will not work for a sub-divison spec home, only for the wealthy that can afford a custom. I have talked to other builders in other states that agree and do offer it as mainstream.
Timbers are ~$25 Sf, Stick ~ $16. IMO they should be the same > $15. Timbers are 27% of my total construction cost, stick 15%.