Howdie, so I'm in the research phase of designing a straw bale wrap around my double wide mobile home. From what I've learned so far, we need to extend the eaves, make sure there's a small space between the straw bale wall and the vinyl siding of the actual house and make sure there's a stem wall that keeps the bales high enough. We live in western PA where temperatures get down to 0 and go up to 100 and there's about 40 inches of rain a year. Keeping in mind the frost heave, drainage and that it's not load bearing, can I get away with just a rubble trench and earthbags filled with gravel for the foundation/stemwall?
Isaac Hill : If you are talking about an existing Double wide Mobile Home then it sets on piers that set on a Concrete slab, Usually the company that delivers
the home comes to the site to inspect it to ensure it is ready for the delivery !
This increases your options, if your double wide is less then 15 years old it is probably quite well insulated and still tight enough that you have a few more options.
Underneath the trailer and inside the skirting is an area where some quick exploring can pay big dividends ! You want to get in under there and check the condition
of the bottom of Your Home ! If the sheathing installed under the trailer is in good shape with no holes or sheeting panels that have failed due to a water leak -
You can stack your hay bales behind the siding and under the trailer!
Keep in mind that most Fossil fuel fired forced-air Furnaces get their combustion air from under the trailer and that you will need to extend the piping that brings
in from under the Double wide to outside of the skirting !
You would do this with a complete straw bale wrap also !
I suggest this path to you as you will be placing a new roof over top of your existing roof, and plan on cabling tour homes roof to the ground as you will not want
to use nails or lag screws to secure your new roof to the top of your trailer, as you will ruin its water tightness and potentially cause leaks !
You will also have to extend your chimney and at least one Sewer pipe vent from its location on top of your home up through your new roof !
- and then there is the need to keep the straw dry or start growing mushrooms in your hay bales !
This is where I set back and watch for the other comments of your fellow members, irreguardless you need to check for a concrete slab under your home and
the condition of its sheathing ! And plan your Furnaces make-up air supply !
Laid flat, they would take the compression fro a 10ft strawbale wall. But could you find thoses in the states? No idea! I know what is needed, either an air gap, or a non moisture wicking material under the bales, onto which moisture transfered through the bales can't condensate.
But to tell you from 3000 miles away. dat's not simple.
Lots of confusion about bale design....you DO NOT want to use impermeable plastic anywhere or wrap bales in plastic tarps. Plastic PROMOTES wicking or capillary action due to it's closed pore structure and because it is not hygroscopic like clay that absorbs, holds, manages relative humidity differences of the material - atmosphere without wicking unless if it's saturated which takes alot depending on thickness. AAC "aerated" or "air entertained" in an insulation of concrete has decent "Equilibrium Moisture Content" (EMC) or this ability, plastic is VERY low, clay very high. Air en trained concrete has lower compression rating's, so it needs to be looked at from not only compression but shear wall (wind, seismic) or "environmental loads" along with live (people) and weight (dead) for building safety. Bales skinned do very well structurally but it depends on loads, meshing or wood reinforcements may be needed.....Just FYI...Issac's design is "non-structural".
As long as water (different than moisture drive) is draining away from the foundation it is no threat.
You can set bales on rubble trenches with nothing else since it provides drainage and insulation to move the dew point to rock, some use foam and plastic which is a mistake. If you create a sill gap between the bales and another foundation (AAC or concrete stem walls for crawl spaces) the air flow keeps the surfaces warm and from dew, by wicking and evaporation before fungi can set in (<48 hours drying required). The earth bags skins should be high perm just as the bales (clay). That is why the gap is needed to the vinyl house, that will only work if you have a drain plane from the roof out a flashing otherwise you can trap moisture in. otherwise the bales need to breath both direction and be protected like stucco-plaster does. With the gap the dew or cold condensation should accumulate on the vinyl or rain should drain out. Not the best inner skin for bales but good enough if you design to vent to a high flow (soffit, ridge, etc), open to the interior plaster would be better since it can regulate indoor humidity and breath. To do this better tear out the old walls if you can afford it. Bales offer r30-50 and mass effect insulation and moisture management with clay renders. This high insulation and slow moving heat transfer dries bales out fast before fungi sets in.
Perlite drains well but it needs a means to do so. You could put a sill (1x 2's) on the bags fill the gaps with more perlite to aerate-insulated the bale interfaces, set the bales on the wood sills. That is acceptable to 2015 IRC.
You lap over the gaps with clay-lime-high perm/EMC and hygroscopic skins,wire mesh gaps to keep critters out, and you have a breathable wall and foundation that should sustain for centuries. The first bales built in the states are like this never needing any plastic or foam, why reinvent the wheel. Nebraska, USA, is the state home of the bale "Load Bearing Wall"....Some never even put a stucco on them since the perm rating of the bale or ability to absorb and adsorb water is very low 2-4 perms, but the cows ate the early European settlers home....well everyone has to eat
Terry, have i said that i wanted to wrap bales? Nope!
I just said that i thought it would be best practice to use plastic bags for the earthbag foundation of the non bearing walls, as this would stop moisture wicking, and advocated the use of something under the bales to form an air gap, so they wouldn't get moisture via condensation. Tho i'm not extremely keen on having gaps around bales. Actualy, if the bales are to be covered with wood siding and an exterior air gap, i would stick thoses directly against the vinyl, because condensation never happens on the hot side of a wall. And that vinyl doesn't let moisture out from the inside of the house.
If rendered with lime or mud, i would not, as the moisture escaping, from wherever, would be slowed by the render.
Air entrained concrete blocks are load bearing. They make whole houses out of theses you know It's just, that theses blocks are "convenient". Same width as a bale on edge, load bearing, critter proof. Water proof.
I would never use bales directly on a rubble or gravel trench. I would raise theses at least 18 inches from the ground. Exept in places like AZ, NM, south algeria or moroco. But i live in France! Furthermore where i live, there's snow, so no bales near the ground!
If you do not get your foundation right and you extend your eves to the bale walls you have load bearing walls from roof loads where ice dams can also occur, people can walk, wind can up-lift, etc. You need water and ice shield non toxic depending of roof cladding.
Some up there in NW are getting R50 walls, R60 roofs (most heat escapes here) with frames and let in bales combined like this situation, using high density blown in with toxic fire retardants that produce out-gassing and fungi. Your insulation if it is food fungi fiberglass batts, plastic lap siding, probably carries a food for fungi that combined with heat (which BTW moisture accumulation on walls is not that depend on temperature, more relative humidity) can attack the bale wraps if you have a path. I'm going to take a guess that your double wide design has a plastic vapor "barrier" behind drywall and the wall is suppose to dry outwards through sheathing gaps that is probably not tape for an air seal, and laps in vinyl siding. You need to verify that before any advice can be given here. As I said toxic factory products and natural materials do not do well together so, the first step in this situation is to understand the current design intent?
If you are finding that all this is complex, a good engineer that does understand this would be wise investment.
Study the material and feel free to jump in the discussion with comments and questions. We are getting into capillary action now for which there is little quantitative research for, but the test data above shows very little effect on strawbales that is why they do not need to be elevated like people think and rubble trenches have worked throughout history, if drainage and renders designs are correct. We do not want to wrap per-lite or rock or any other natural material in plastic period. Lets let the factory builder produce toxins, formaldehyde's, food for mold, mildew, fungi, rot, into their homes not natural permie ones.
Reading the data above, it should lead to asking for it to supports myth and opinions about the need for factory products in natural building's which I think you will find MANY opinions for a very little data to support it.
Issac, find out if and where there is a plastic barrier or retarder such as house wrap, it's location in your walls, roof, foundation if possible, along with a rough sketch of your eve/over hang connections, current vents such as soffit, ridge, so you can be given the proper advice. If you are being code enforced by an AHJ you will need to follow it or hire Engineer's to comply.
Do you have clay on site?
At 40" of rain per year, I would not build with bales, but utilize one of the light straw clay styles. I would leave the interior of the trailer wall alone and remove the exterior PVC cladding. The tie-back the mass wall to the trailer frame. You could use wood or standard brick ties. While you have your exterior open, seal the air leaks and shore up any insulation problems. Install a wooden bond beam at the top of the mass wall and attach your, hopefully very long eave extensions which could probably be 2x4"s. You will have to remove the last sheet of sheathing from your roof in order to sufficiently access your trusses to tie into them at least a foot before the top plate, so you don't get too much cantilever pulling up on your roof. Install HS24 hurricane ties at each eave extension to tie them to the top plate.
I have lived in mud, stone and wood for over 20 years and I couldn't recommend it more!
These guys are claiming to have generated the next gen '3' strawbale design for the cold climate of the NW by inset r-30 bales with a stick blown in r-20 cellulose wrap that gets them to a r-50 wall that is blower door testing @ 1.5 ACH...They use drywall as "airfins", door, window, to bale plaster transitions. The stick frame takes all the loads, I like inset timber better. They eliminate an exterior stucco, cut the bale strings spread and feather the straw out, and tie them to the studded stick frame, pinned and staggered, and lower the need for stuffing labor. Deep wood roof trusses and r-60. I talked to Jacob McArleton author of "The Natural Building Companion" ( I read and highly recommend) and builder of many SB NW homes about clay-slips low r-1.7/inch pointing out the benefit of mass effect there is no testing for except the video we seen lately by the chemist calls for lab testing your clay to get there and prevent mold. He thinks it is too risky since he can not get to r-50 with confidence. A guy like Ace could prove the slip up there, probably not a good idea unless you really know your stuff.
Problem with HD cellulose are fire retardants, setting over time loosing r-value......I'd go with some mineral wool in 2x6's to get the r-20 ish wrap, inert, more natural, but they have a cellulose company in town and are out to combine natural with mainstream stick for this "Next Gen 3" concept I don't see taking on International acceptance.....perhaps only in cold harsh climates.
Remember though these pros mentioned above have produced many net zero natural homes which can be a challenge with a double wide.
For me, talking about air entrained concrete, was just convenience. And, even if it has lots of grey energy in the making, concrete is not that un natural. It's made out of mud and stones. Ok, calcinated etc. But still, it's not as bad as petrochemicals.
I'm sorry, i haven't read the links. But, i'm dubious about putting strawbales directly on earthbags. Or a rubble trench. Tell me good old stone foundations. Bricks, yes too. Cob, may be. I haven't seen more than two structures made out of earthbags, and both felt damp.
Obviously you know your code. I don't even know mine for strawbales in france. But there's something we agree on, no plastic wrap on a house! That's heresy!
Bill, permie bro, do you want to respond to that last post or you want me to? Hey, I need to get back to the breathable wall thread thanks for sticking with me on it, I need to do some more research and get back on it. It has woke up my knowledge, even reading some of the SIPs claims with MGO which are up coming up.....I hope to address and find better alternatives with it and geo-polymers. I wonder what happen to Jay, kinda miss the em We got more Timbers coming in and I'm heading back to that 6 million $ job site Monday you can view in the Timber section. What a moisture mess! SIPs wrap.
Isaac, I lived in southern Philly, Media, few years back in 1994, the summers get hot and humid. Sweat like a pig! Love the place tho.
Satamax the code I posted is IRC, international and proven, take the time to read it and the links on bale moisture properties. I've been designing structures and systems for over 30 years, Bill and Jay lots of field and inspection experience, ask questions.
Ok, still digesting all that but here's what I got so far: The walls are (from inside out) 1. drywall 2. fiberglass insulation 3. Studs (obv with gaps) 4. Cardboard with shiny part facing in 5. Vinyl siding, so it seems as if there is no plastic besides the vinyl. I could take off the vinyl and tie the bales to the beams, but then I need to figure out to do with all that siding... but that can be done.
In regards to foundation, it seems that a rubble trench and gravel or scoria filled earthbag stem/pony wall with permeable bags and earthen plaster would work, no?
As far as venting, there are no soffits or anything, I plan on installing those too though.
Isaac, what year is your double wide? I'll draw up a proposed design sketch when I got some time and we'll let Bill critique it of a design I think will work assuming you are not being code enforced. Are you?
Do you have an attic or vaulted? Tomorrow I'll tell you how to find out if you are needing to pull some permits for structures and energy codes. If codes and permits are needed that is a game changer! Right now it looks like IRC 2009 and IECC applies unless something changed in 15 which I doubt, they may have went to 12 or 15 which would be good for bales since it is in it.
All right got it. I have some material take offs I need to work on tomorrow for a big job I am on, I see what county you are in...if I remember right PA is broken out to townships what is your township or better yet if you know what Building and Safety (B&S) jurisdiction or office with a phone number where the inspector are that governs your local building codes that would help....If not I'll sign up to help you figure that out but it may be next week before I can find out. We need to find out what building codes apply (IRC 2009, 2012, 2015 and IF an energy code (IECC) is being enforced). That is the first step in the design process. AHJ (Authority having jurisdiction) is a term we use for this, I used above.
Wow, thank you for all the help! We're in Ohioville TWP, . This is the kind of stuff I get really confused about... when it comes to how plants grow, I got it, but when it comes to how bureaucracies operate, I am at a loss...
"To oppose something is to maintain it" -- Ursula LeGuin
Issac, you are being governed by the state adopted code IRC 2009 meaning that you will have to pull permits, structural since you are creating a load bearing wall with eave extensions, and perhaps energy IECC 2009. Your AHJ is very small, the lady I talked to had no idea what IRC, IECC, strawbale, etc, meant and she would be part of review process and your plans you have to submit. Getting them to adopt 2015 bale code is going to be a real challange...there is another path you can go, get a PE (Professional Engineer) stamped drawing and use their third party inspector name MDIA you and everyone else regardless of new construction or additions, etc, have to pay, but, you have to understand enough to help them understand, and it is going to cost to design. In that case they would not be reviewing your plans since it is stamped...that is specified in CH R104.11.
Unfortunately, I recommend finding something more conventional like a stick built with roxul or other intert insulation more common and understood in your area. You will have to follow code in all design aspects so it may be beneficial as I said above to hire an Architect that understands it, or read it yourself. It takes alot of research and time unless you already know it. A good General Contractor that has worked with the Architect may be a good idea. You do not need a GC or stamped Architect drawing's to pull the permit and do the design just to be clear for residential. If you do not want to deal with them or code you can hire an Engineer, but she did not even get that nor was she familiar with R104.11.....so I can see building or doing anything in your area outside the "norm" a real challenge since they have no in-house inspectors or qualified people...sounds like budget issues so same people do lots of jobs.
Only requires a skin permit. If awnings are used for roof the 'hat', no inspectors needed.
In his 1984 Fine Homebuilding article, Hughes explained why it was perfectly acceptable to wrap poly around a house with Larsen trusses: “Research in Canada has shown that as long as there’s at least twice as much insulation (in R-value) on the cold side of the vapor barrier as on the warm side, no significant condensation will occur in the wall under normal circumstances.” - See more at:  This combined with a light straw clay fill, seems do able.
I didn't do it. You can't prove it. Nobody saw me. The sheep are lying! This tiny ad is my witness!
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