Small House/Cabin Build - Saying No to Tyvek, Roofing felt, Shu Sugi Ban, Keeping out critters Etc.

Hi Mega Brain,

I've been meaning to post designs for a while to get your opinion but july (my build window) is fast approaching and my priorities have been on finishing the framing design and gathering materials, getting lumber quotes form micro mills in the area... so instead of going into the whole she-bang here i'll try and ask my most pertinent current questions while giving a tad of context. I would prefer to do the milling, and be more DIY about it, but I have to do this in a month. Its also possible the border will not open before my window is up...which would suck a lot.

Context:

In New Brunswick Canada - it gets cold here but not that cold for the most part being nearish to the ocean.. -20C in the winter is common enough, +20-25C in summer. Of course it gets colder and hotter, but that's my guess at averages. About 55" of rain/year. Good amount of snow. In an Acadian forest that is amazing. We're building on a south facing slope currently full of beech trees, maple (red and sugar), black spruce in little pockets. Some Ash, some oak. I will be having a few ponds dug hopefully this summer as well at different elevations on said hill (top middle bottom) and will remove a lot of the beech and have it chipped in place as the beech here all gets a disease once it reaches a decent size. If there are good specimens, i'll leave them of course.

Build wants to be as natural material centric as possible. I have no code restrictions in this case (yay rural NB !). I want everything to be super local but there will have to be a couple exceptions.

I would like the walls and ceiling to  (excuse me everybody, I've read the threads on this but i'm gonna screw it up) moisture permeable (can take moisture in, hold it a bit, and let it go outward when heated) ..basically I don't want any material that will cause condensation on the inside or otherwise trap moisture. I don't expect this structure to be 100% draft proof either.

Overall size is around 550 sq. feet on the main floor with a small loft. Wood cook stove as only source of heat for now.

Build is a modified (simplified) post and beam type with 6x6 SPF (probably black or red spruce) as main frame material with some 6x8 and 2x6/8/10/12 full dimensional here and there for specific purposes. The walls will be 6" deep. All eastern white cedar cladding/siding/decking/slats etc. Metal raised ridge roof. The VicWest stuff looks good but appears out of stock everywhere - anyone heard of this issue?

Build will be on piers and it will be vacant much of the winter so the design must freeze without destroying itself and can't rely on actively heated mass - this is off grid, away from utilities.

I'd appreciate if we could stick to the questions and stay off the topic of going bermed, wofating it, or otherwise completely changing the design...i'm set on the methods for a number of reasons pertaining to my actual needs/location.

Ideally I would LIKE to use this building to experiment with woodchip slip, but I won't have time for that kind of thing this year...therefore I'm planning to hold off on insulating the walls, focusing on the floor and ceiling/roof before closing them in and spending next summer's window..or the fall if this 'rona lockdown keeps me working remotely to try the chip slip in the walls (which I will leave open on the inside).

TO insulate the floor i'm thinking of doing the following :
______________________________________
FLOOR BOARDS/DECKING
JOIST stuffed with rock wool
layer of roxul isoboard attached directly to underside of the joists
layer of hardware cloth b/c porcupines etc.
cedar slats to retain hardware cloth (every 1-2' ?)
______________________________________
OPEN AIRSPACE - this should never be blocked off.
Minimum pier height around 12" PLUS 8" of cedar floor beam.
______________________________________
Ground (slight slope) meaning neither water nor frost should accumulate

My research tells me this is OK. No need for plastic under this = hurray !


TO insulate the ceiling :

SKY
______________________________
Metal Raised Ridge Roofing... probably galvanized unpainted/powder coated
furring strips (cedar) 1" deep (long fasteners to make it into the rafters)
(MINIMUM 1" AIR GAP)
ROOFERS FELT (TBC - do I need this? will it cause problems? solve problems? really want to avoid Synfelt...basically plastic)
roxul isoboard again - number of layers TBD.Probably no more than 2"
Cedar Sheathing
Rafters (open)
______________________________
Interior


To insulate the Walls : I plan to leave the walls open on the inside for now with the idea that I'll fill them later. I've been toying with the idea of doing one layer of isoboard here too as "outsulation" - the last layer before the furrows/air gap/siding.

OUTSIDE
_____________________
Vertical Cedar 6-8" Siding: we plan to char these prior a la shou sugi ban.
Vertical Cedar Furrow/Batten
POSSIBLE layer of ISOBOARD (or 2 with offset seams)
Horizontal Furrow/Slats
Post/ Beam Framing (open)
_______________________
Interior
*there will be a gap at the base of the exterior wall/isoboard below the floor the depth of the horizontal furrow/slats. I would plug this with more isoboard.

Questions :

1) House Wrap. I want nothing to do with it, but will my plan mitigate the need for it sufficiently ? If I were infilling with woodchip slip right away I wouldn't be as worried and would just go for it, but isoboard...not sure. Spec says its resistant to moisture so my thinking is, if it gets a bit wet form time to time, its not big deal with a rainscreen gap there to allow for evaporation.

2) Tar paper/ Roofing Felt - i understand this product is not perfectly waterproof. Its also harder to find than it used to be with Synfelt being the new deal. I suspect its far too risky to go with nothing underneath the metal roofing though. Will Roofing Felt trap moisture?

3) Is my plan generally crazy ?

disclaimers: I may not listen to you as I want to experiment to some degree...if I had my druthers i'd fill all cavities with woodchip slip, plant some humidity sensors, and call it a day/ see how it performs over time, but I DO value your opinions !

This structure will likely become a workshop in future years, but I fully expect it to be lived in temporarily or permanently for the next 5 years minimum.

thanks.

j

Hi Jay, nice project you have there!  My limited input is that metal roofing will condense on the inside if air that is above the dewpoint of the roofing temperature touches the underside of it.  So a cold roof and a more humid and slightly warmer air mass will condense.  Maybe that won't happen with your design.  And if it's an exposed fastener roof there could be leaks at a fastener here or there (getting the rubber washers just the right level of tightness is not easy).

Does roxul isoboard block airflow reasonably well?  I'm not familiar with it but I'd want to make sure the floor cavity doesn't easily let air through it.  For my off ground cabin I did fiberglass bats between the joists with 3/8" plywood to hold it in place, block airflow and keep mice out (no porcupines).  I think I had poly under the floorboards to prevent air leaks into the structure but without the plywood the insulation would have been constantly washed of its heat.  This was before my permie days, now I'd probably use rockwool and cheap wood boards...

Thanks for the quick reply Mike - you make a good point.

The semirigid roxul product (actually called comfortboard) doesn't mention anything about airflow though it does say its vapor permeable.

Your suggestions then are :

cover the outsulation completely to block airflow in all cases (including underside) - that's doable and makes sense. Maybe I could do away with the hardware cloth too which will be $$$.

Also I'm hearing that roofing felt would be a good idea. That I figured. Any tips of whether that roofing felt will trap moisture on the interior side?

thanks !
j

Building science that recommends tyvek etc. is based on the assumption of 24/7/365 HVAC conditioned interior.  In your case you need it to BREATHE so moisture naturally migrates out just from daily temperature cycles.

Your roof WILL condense, so a second water (but NOT vapor) barrier is important.  I don't know what the local green option is. Plywood works, tar paper (old or synthetic).

Walls, not so critical with your rain screen air gap, especially if you choose a rockwool board with decent water shedding.

Make sure you flash everything right so you don't funnel water into anywhere.

Jay - thanks for the thorough description of your setting and goals.

I agree with Mike that the metal roofing cries out for something water proof to go under it.  The Roxul material doesn't particularly care about water (duh - its fluffy rock), but water can move through it and water does affect its R value.

For the walls -- less possibility (nill maybe?) of water condensate behind the siding.  I'd just caution that wind and rain can produce some strange outcomes so be sure to manage your exposure with tight laps, eaves, etc.

One thing I don't see stated : some sort of barrier to protect the air gap in your wall and ceiling.  Bugs, birds, pine needles, etc love to get in there.  Fine Mesh, steel wool ... and some fancy plastic products you probably don't want ... do the trick.

I'll also toss out ... cork panels instead of Roxul isoboard?  Not sure about price/availability but 2" of cork insulation is great.  And it sheds water.  Not sure if it should sit under a metal roof without a barrier, but it might be an option to help you keep your design AND avoid synthetic materials.

Jay Peters wrote:The semirigid roxul product (actually called comfortboard) doesn't mention anything about airflow though it does say its vapor permeable.

Your suggestions then are :

cover the outsulation completely to block airflow in all cases (including underside) - that's doable and makes sense. Maybe I could do away with the hardware cloth too which will be $$$.

Also I'm hearing that roofing felt would be a good idea. That I figured. Any tips of whether that roofing felt will trap moisture on the interior side?

I think that comfortboard looks like it might do the trick.  I'd want to severely slow down air passing into and out of the insulation under the building.  Otherwise it will carry away the heat that you're trying to trap.  But it should be water and vapor permeable so that any issues can leak/pass to the outside.  

I'm not sure what to do for porkies.  For mice I was told that they can enlarge a 1/4" hole.  So I just installed the plywood very perfectly so there weren't any gaps over 1/4".  On the corners I used cheap drywall metal corner bead to keep them out.  After installing it I found that it very effectively trapped 3 mice inside that were there before the plywood went on.  So motivated mice couldn't get out of it...  And in the following 5 years I had no mice or porcupine issues.  There were porcupines in the area but I never thought about them being an issue so I didn't plan for them.  Luckily they didn't become a problem.  They do like to eat plywood.....

I know a log home repairing carpenter who swears by old fashioned tar paper.  That's his go to choice for house wrapping and roofing.  It isn't vapor proof due to the material itself and the many seams and staple holes so I think it shouldn't be a moisture trap.  But I'm not an expert...

The metal roofing we put on our house had a anti condensation backing already on it, no idea what it is made of but it did away with the need for any underlay at all. The old roof was underlain with tar paper and then old wooden shingles, basically a bonfire waiting to happen.

I LOVE PERMIES !

Thanks all for the prompt, polite, on point responses

Yes, i will be sure to flash properly and plan a decent overhang. looking at a 12/12 pitch so I'm thinking 18 extension of rafters should do. (concerns with that anyone ? I haven't don the research on eaves yet.)

Interesting lead on the cork board - not familiar with this as an Insulation material. Pretty cool. I'll see what price availability are though I imagine its comparable or more than the board...not that price is my only consideration.

I will definitely be putting max 1/4" hardware cloth maybe backed with steel wool at interstitial gaps you speak of, Eliot - particularly the roof to wall gap where the rainscreen needs to let any moisture accumulated behind, out. I will also need to do something that would let condensation behind metal roof out, without allowing critters in. I was thinking of a horizontal cedar batten with a 1/4" of steel wool sandwich beneath. Really not sure though.

Other than that, I'm feeling pretty confident about the NO TYVEK on walls, and YES ROOFING FELT under the metal roofing.

cheers yall !

j

The building science groups have tested tar paper and it's a top rated  weather barrier. It's more vapor permeable than the house wraps and when detailed properly sheds water totally. Good for both roof and walls. There are two weights in the lower 48, 15# or 30#. The heavier material lives longer but doesn't install as easily. I have pulled 100 years old walls apart and found functioning tar paper. It gets dry and brittle with age so the old stuff won't survive any changes or movement, but left protected, it keeps doing it's job.

On a related note: Wind. Give thought to your weather barrier because there can be a  HUGE difference in your building performance with a wind of, say 15+mph compared to 5mph or calm. The leakier your building, the bigger the affect you'll see. In my sister's 110 yr house with old double hung windows and no insulation, just the tar paper under the sheathing, there is, for the _same_ outside air temperature, a 5-10F drop in temperature inside rooms on the windward wall of the building compared to days when there is little or no wind. This is for three seasons, any time the temps drop below about 50F. Something that's not just noticeable, but needs to be dealt with by either putting on sweaters or cranking the heat up. As I say, a huge difference. So while a building "breathing" has it's positive aspects, I think that with excellent fit and finish on your penetrations and going for "sealed tight" with your tar paper barrier, you'll end up with something just about right. You'll find, I believe, that although tar paper is very forgiving, getting it on tight takes real care. But that's true of most building details.

Sounds like you're off to the races. <g>


Regards,
Rufus

Thanks Rufus - wind was my first reason for thinking .."do i need tyvek ?" which i apparently forgot about when I posted this. Good point. As has been said, I should be able to have my cake and eat it too with respect to vapor permeability if I go with tar paper (which often was called roofers felt where I come from...i think) throughout.. thanks for the reminder. For the price of tar paper, I think I'll probably end up wrapping the thing in that entirely.

thanks muchly !

Dealing with the metal roofing only.
I use a lot in Australia, but I dont deal with snow etc.
Roofing can b ordered with a layer of insulation, foam, attached.
It is a very good product for your purpose.
I doubt it will have any condensation.
As for roof fixings they are easy to keep water proof here.
I dont know if the cold causes you any issues, but I am confident the manufacturers would get it right.
Do They?

I have no building expertise...so will offer you no advice on that, it also means I am ignorant to some of the materials you speak of, so my apologies if I have misunderstood, anything.  I deal with wildlife exclusion, and co-existence with wildlife, and although I do not have porcupines here, I do have some thoughts for you, as it sounds like this will not be a full time dwelling, and vulnerable to Mother Nature's creatures availing themselves of your hard work.  If metal is not offensive to you, consider cladding the entire exterior in metal - walls, roof underside.  Rodent proof, climb proof, fire proof, water proof, but with the contour (rippled or ridged roof panels) it is still breathable, especially if you put battens first and then sheath in metal, just make sure the hardware cloth from below, comes up (from under the floor and over the wall, on the bottom, and from the eaves down on the top) to at least the first batten to keep out insects, rodents and bats.

It is very worthwhile to hit up local Ministry Websites for all (well known and little known) animal/bird species found where you are building so you can plan on building in a way that keeps your hard work safe.  You mention Porcupines as an animal you are looking to keep out, and that is great foresight.  I suggest this needs to be continued for all rodent species, all the way up to the apex predators like bears.  Rodents/birds will avail themselves of the smallest holes, and either be contortionists or remodel to suit.  Mice can fit through a hole the size of a nickel, some shrews and such, a dime; raccoons a hole the size of your fist.  Think about who will want to eat your cabin, sleep in your cabin, nest in your cabin or store food in your cabin.  Now is the time to exclude them.

If I understood correctly, you are using wood chips for insulation.  I would be concerned about settling, moisture, mold and infestation (bug, rodent, bird etc.).  It might be worth considering expanding the use of the rock wool to the entire envelope, floors, walls and ceiling.  The hardware cloth is great on the underside; I highly recommend it be attached with SCREWS through a triple layer (a sandwich of wood, mesh, house), not just mesh nailed or stapled directly to underside of structure; way too easy for most critters to remove.  Always use screws, the groove makes them much more difficult to pry; an animal claw will pry a nailed board much easier than one fastened with a screw. The exposed rock wool on the underside may be plucked, through the mesh, for nesting/bedding material for birds or rodents.  Use of a solid surface may be needed on the underside, or consider enclosing the entire circumference, on the exterior of the stilts, with a metal skirting.

You may want to consider using hardware cloth on the entire exterior, or using metal roofing for siding (my goal is to make structure chew, climb and dig proof and I am not familiar with the product you are planning to use); you can snap single wall, metal stove pipe, or bend metal roofing to fit  around the stilts to fend off the porkies.  Make sure your plan includes securing the windows and doors (heavy metal/wood shutters?); the chimney stove pipe should be long enough that snow pack will not bury it, and absolutely must be capped with a sturdy, mesh cap, screwed in place to keep out weather and critters - a chimney fire due to nesting of animals could destroy all your hard work.  Ensure your structure will keep a bear, wolverine, weasel (the smell alone can make a perfectly good structure ready for the bonfire) or whatever is a known troublemaker(s) in your parts, out when cabin is vacant.  Consider an outward door swing - bears etc., generally like to push or lean on things, and are less likely to try to pull a door open - and do give thought to the handle, if chewed off you could be in a pickle!

Lastly, don't forget your surroundings and how they will be affected by the seasons.  Remove any trees that, if toppled in a storm, or shedding snow/ice could hit you or your structure; this also creates a fire break.  Remember that the level of the ground will change drastically once it snows (assuming you get a several foot accumulation).  A cabin on four foot stilts in the summer could find the "ground" rises 4-10 feet depending on seasonal snowpack - this could mean the cabin becoming completely buried (don't forget to seal the stovepipe), or windows suddenly at 'ground level'.  Not only could this cause moisture issues, especially if ice or snow worked their way into the walls, windows or doors causing rot, mold and mildew; but animals could easily access windows, and/or the roof and do some serious damage, especially if the walls and roof are easily scaled (wood, shingles, siding...).  I do love a set of 'drawbridge stairs' on a tall/high stilted cabin - couple of hinges, a pulley and a good rope can really go a long way with critter proofing, especially if the stilts are metal wrapped.  

Good luck, sorry to take things slightly off topic, hope you don't mind. I wish you well.

Lorinne

Looks on topic to me. Being messed out of you home by tiny critters is _so_ disappointing and kinda queers the whole project!

It's definitely part of making your habitation.  I'm going to have to junk a (formerly) halfway decent car because of mice. I just didn't expect to have leave it "in the country" for so long. And cars are a lot "tighter" than buildings.

Bugs are a bit more difficult, I think. Wood is often dinner.

I think there's a divide in design plans early on between minimalist, where the structure is "skinny" and basically single layer, uninsulated but weatherproof,   OR  fat and tight with insulation, amenities and total attention to detailing and coatings.  The "skinny" structure dramatically reduces harborage and potential food sources and make it much easier to see and remedy, on an ongoing basis, various kinds of intrusions. The "fat" style is a _lot_ more comfortable and useful to most people.

The two legged critters are a little harder to ward off, though.   But they're not so attracted to the "skinny" style, either. <g>


Regards,
Rufus

As above metal oofing will condensate  tar paper is fine. Our house is a similar size very different climate  no snow maybe a couple of frosts  a bit higher off the ground is nice when you want to go underneath to move or add a power point.
We clad ours in sugi weatherboard burnt and oiled with tung oil have a few practices some I didn't burn enough and the wasps love to eat it. Any uv or water will destroy tar paper in quick order.
What rafter spacing  are you planing  1 in battens won't span very far

I wish I had advice to give.  I do wish you well and sounds like you are  wanting to build something I would really like.  I have look at many types of natural building concepts over the years. Many have great ideas and practicallity, but no matter what you choose there are always some issues to over come.   Good luck with your project and if you can post some updates here as you go. I would really love to see what you come up with. .....and when you have all the kinks worked out you can come build me one too LOL.  Just kidding.  Thanks for sharing your ideas.

Shou sugi ban is fun.

A hack (at least for me because I'm a newbie) was to coat the boards in linseed post-char after they'd cooled overnight.

And it was a very very thin coat. The water on coated boards beaded up and just sat on the surface. The boards were from old pallets. It rained before I could hang them.

Board and batten style, as seen on Mr Chickadee's YouTube.

I made a small chicken coop. We've had 1 really intense (for our area) storm so far, and no water or moisture got in the coop.

The coating also kept the char off my hands better.

I probably would have put on a 2nd coat but I ran out of flax seed oil. Doesn't seem to have made a difference this far.

Hi All,

Little update - I got my lumber quote and it is super reasonable. I really love dealing with locals for cash deals when possible and there are lots of 'micro' milling operations in the area.
HOWEVER - I'm concerned about my timeline. Due to the 'rona the border between QC and NB is closed to non essential travel. One estimate for it opening is July but with no place to adequately store my stash of lumber over the winter (and wanting/needing to work it green - i think, more on that later) that becomes a big risk. The downsides of dealing with a small local provider is that the lumber is not sitting on a shelf ready to go, its cut to purpose. So I'm reconsidering my build in the event that my window gets much shorter to be some outdoor features (deck, screened in outdoor kitchen, tinycabin/bunkie)... I'm currently working on a new plan.

But, with respect to these other great posts in this thread :

Rufus - I was looking up installation best practices for the comfortboard to see whether tyvek (or any windbreaking envelope) is recommended with this product - it seems that on most standard installations using this product, it is not used on the comfortboard, but on the sheating. So the layers look something like :

OUTSIDE
____________
siding
furring strips
comfortboard
tyvek
plywood sheathing
framed wall, possibly with cavity filled depending on climate

So the tyvek/envelope is inside the rigid insulation. I find that a bit bizarre and it makes me wonder if the comfortboard has some kind of coating that make this envelope unnecessary..unfortunately I haven't been able to pick that out on the datasheets available from roxul.

Currently I'm thinking of just doing a tarpaper enevelope over the isoboard as you mentioned.


Lorrine - lots of good points. I'll try to address.

Metal is not offensive, but i'd prefer to use less manufactured materials than more, and mostly local. Of course roxul, is not and tarpaper likely is not the lumber certainly is. Although I had thought about trying to find used (collapsed barn) roofing to use as cladding (where if it is not 100% waterproof it will still do good work) at one point, and may still for future structures I think that is out of the question on this timeline and given that I won't be there long enough to hunt much down, and won't be able to bring it with me either (already have a woodstove, windows, doors, sink and other stuff to try and fit in my truck)! Ultimately though, I do hope to take a similar direction once we have the first structure in place and can spend longer periods of time in the area, collecting and preparing for the next build(s).

I don't intend to use wood chip slip for insulation right away, but yes, the whole assembly of chips, clay, water and any moisture remaining in the chips needs to be dried well before winter comes along. For now I will only do a layer or two of roxul comfortboard on the envelope. I would have thought about doing woodchip slip infill in the wall cavity if my work stays online come september, as I'll have more time to prep. With this new strategy though (micro/tiny cabin) I may never bother to insulate any more than a couple layer of the roxul.

With respect to the area and its pests I know them well ! I don't live there now, but did for a long time and the porky is the one i'm worried about. They are known for destroying camps/cabins on woodlots in the area, to the point where the local woodlot owners association has suggested that it could be good to re-introduce the fisher, a natural predator of the porky, if its being a problem (which it is). I'm wary of that though as Fisher's can be quite destructive creatures as well, albeit in a different way. The rest of the wildlife, I think I should be fine with as long as I keep things tight.

I'm also hoping to find out through this experiment (now lower stakes) whether porkies and other vermin like to chew well done wood. I'm hoping the charring process of shu sugi ban also proves a deterrent for critters. I would char anything that would be exposed.

withe respect to the "sandwich of wood, mesh, house" idea, this was my plan for the underside, and I had been considering it throughout at one point..the it became just the underside as I thought about the shou sugi ban being a deterrent, while the underside having exposed rock wool board would have hardware cloth held on by slats with 12" spacing over it, but instead I will cover it completely - no gaps - and am planning to charr it as well and see how it fares. TBD based on my research on the charring method.

Good thoughts regarding height for snow, distance from trees etc. - there have bee microbursts the past couple years in the area in fall mostly and their tendency is to blow down from west to east (ish...) The frequency/ quantity of these blow downs is pretty crazy, but the nature of them has been predictable at least. I will be  paying particularly attention to removing prone species (spruce primarily) off the west side of the construction.

Tom : I'm trying to avoid foam, and have chosen a rockwool product instead. Re: the battens (i think your referring to the roof assembly) - the roof will actually be completely closed/clad before receiving the rock wool board so the battens/furring aren't really structural. Unless your talking about wall battens, but again, they aren't actually structural per se, though having more material there wouldn't hurt.

Kamaar : Thanks for the Shu sugi ban insights ! I shall have to check Mr. Chickadeedeedee on the tube. What are your observations in terms of critter resistance (mammals primarily). Any rodents that like to chew on well done BBQ'd lumber ? DO you boil the linseed ? Did you sand the char at all (pre oiling?). I've heard this is ideal but again I have no direct experience. I'm also thinking that working doing the charring while the wood is pretty green would be key. Let it dry first and I suspect it would burn a bit too readily. I'm assuming that eastern cedar is OK for charring. I just kind of clued in that any examples I've seen using this technique are typically done with japanese and red cedar on the west coast which are quite different than eastern white, so I'll have to make sure this works.

If shu sugi ban is a no go, I'll have to buy in either pine tar, or this crazy stuff... http://valhalco.com/index.php although I doubt it will ward off pests (I still need to read through the literature) and if not hardware cloth over all the rockwool board probably.

Thanks all - I will try to get around to posting plans, and a build thread eventually - for now I think I might rename this thread as it has expanded its scope a bit.

j

I know you said you didn't want to make big design changes but I wanted to at least make you aware of the Log Home Builders Association https://www.lhba.com/ and their butt and pass method of building with whole trees/logs pinned together with 1/2 inch rebar spikes driven vertically into the logs.
They have a lot of experience with all aspects of this design and if you pay for their 2 day course (not sure if they are available now with Covid) you would have access to their collective online wisdom.
There are also several blogs online that go through whole builds. They recommend new builders build a small 20x20 or so structure first to learn the system before embarking on a 30x30 or 40x40 building.
I am not sure green building is their priority but they strike me as fairly green.

PS here is a direct link to their gallery page of homes they have built : https://www.lhba.com/student-homes-gallery

Hi Dave,

Interesting idea and I’m definitely into checking out the info but ultimately the time constraints I have will not allow me to build this way, this time.

Cheers
j

Jay-

2 quick thoughts for you. I don’t know what roof pitch you have planned (and I skimmed all the replies so may have missed it) but I would suggest looking into ice and water shield under the metal, not tar paper. Plywood decking with ice and water and the metal screwed directly on top will be 100% waterproof. Unless you have a very steep pitch (8/12+) I can’t say the same for roofing felt.
There is a lot of new thinking about Tyvek. Do some research, but it’s really better for a building to breathe than to trap humidity. That is NOT to say you should have a drafty house, nor will you if the various layers are installed correctly. Tyvek is ‘supposed’ to breathe, but as was mentioned, it’s intended for a full on hvac design meaning it doesn’t need to allow moisture out.
Good luck with scheduling!

Thanks Julie - Good point regarding pitch.

Trying to keep it steep enough to avoid a product such as water and ice shield, however this experiment may prove to me that water and ice shield is worth the costs.

planned pitch is 12/12.

Should be fine with that steep of a pitch. I realize it’s more costly but I much prefer the ice and water because it prevents issues from ice damming, is waterproof if there are frost /condensation issues on the underside of the metal, self seals around the fasteners that penetrate it, doesn’t tear or buckle, and you don’t need to add a slip sheet between it and the metal. Foundation, frame and roof are the 3 places that saving money rarely pays off, because it’s difficult to go back and change or correct anything.

Not sure what your greater plan is, but just in case it's helpful, you might consider putting up a pole barn/gazebo before starting your house. I did this using 6x6 pressure treated posts (lots of people use 4x4) and gravel to hold them in place. I used some of the not quite perfect live edge 6x6s from my first couple days of milling for the headers, 2x8 rafters and some 1x live edge for the perlons. Metal roof on top with long eaves 20x25. No walls in summer, hang canvas in winter. It has served me well for years now storing all of my extra building materials out of the elements, outdoor kitchen, general shady hang out spot, cat loves it - and it is an absolutely beautiful structure. It also gave me a great, easy and quick project to practice on before really digging in to the main house. I started out using an easy-up, that fell over after the first couple rain/wind storms..

Good points Ryan. I have always advocated building a shed/garage/barn first because you’re going to need that anyway, and it immediately gives you a place to keep tools/materials for the house build, plus a workshop area. You can even set up a corner of that building to ‘live’ temporarily, a bed, small table and chairs, shelves. Maybe a mini fridge and Coleman stove. That seems to work better than trying to have all your tools, materials and work area in the house/cabin being built. Easier to camp out in the barn than have the clutter and mess in the house.

The 1900 wood frame I grew up in had no problem with felt on a 12/12 pitch. I guess that could be viewed as pretty steep; justs looks "normal" to me. But you wouldn't catch _me_ up there! <g>

Forgot to mention. House is just north of Chicago, near the lake, so it gets some weather, including good hard thunderstorms, often.


Cheers,
Rufus

Ryan, Julie - The WHOLE plan originally involved a deck, a screened in outdoor kitchen/ relax away from the bugs space, and  uninsulated, built in a day one room tiny cabin / shed to sleep in. The goal would have been to start with this, then get started on the structure we're talking about here. However the plans have changed (may change again given the situation) and I think we will stick to just the deck, kitchen, "shed" this season if we can get down at all.

The greater plan includes a pole structure but given the time it takes to get to the site from where we live full-time (9 hours) we want to start by making a comfortable living space and build out from there. I also hope to use the lumber in site for the majority of the infrastructure, as there is lots, and it great. But I need to be there to make that happen, whether myself, or by hiring in a guy with a mill. Though I'd like to put a mill under that pole structure in short order !

SO yes, I agree ! And as I said we will reduce the scope of this years plans (even though I *may* end up working online and therefore be able to stay longer) and delete the 500sq/ft cabin this year in favour of insulating the tiny cabin/ shed, using the principles discussed previously in this thread.

Rufus - I've seen much the same in my neck of the woods. I'm not super concerned about the roof other than making sure condensation doesn't build up anywhere it can't be expelled naturally. All the weather here. Sometime very cold, lots of rain and snowfall, ice, lots of wind seasonally. Very common to get hurricane remnants and microbursts giving us heavy horizontal rain. The traditional siding is clapboard or cedar shingles directly over tar paper and mostly not tongue and groove sheathing. Being near the Atlantic, but not right on it makes for some interesting stuff. One thing that's positive is that it gets cold enough that snow sticks around mostly, not living in perpetual slush or snow/rain but it also doesn't stay damn cold for too too long.

j

 Rufus Laggren wrote:
The 1900 wood frame I grew up in had no problem with felt on a 12/12 pitch.  

Yup. That’s a steep roof. The issues are far more UV degradation (for non-metal) and wind than leaks. You can pretty much roof a 12/12 with anything and as long as it doesn’t blow off it’s not gonna leak (short of ice damming). Water rolls off 45 degrees quite nicely.

I think we've somewhat strayed away from the goal of Permies to support the use of healthy materials that are free from toxic gick.  One of my posts above may have initiated that and I'm sorry.  

Indeed - Although I know that tarpaper or whatever you want to call is not exactly wholesome it seems the best option for keeping things dry and not allowing condensation to build up. Indeed i'm trying to keep it as 'natural' and particularly plastic and adhesive free as possible. Even the rockwool is a compromise, but its one I don't feel particularly bad about and it has the properties i'm looking for - I'd prefer to source the material locally, hence the interest in woodchip slip.

cheers

j

I like to think back to older building styles and try to figure out why they worked and if it could apply to a current situation.  For instance, cedar shingles may have an insulating value to themselves that reduces or prevents condensation.  That's just a guess, but how did they deal with this in your area 200 years ago?

200 yeas is hard to find examples. The vernacular is rare in original shape at all, even the newer instances, but it generally looks like timber frame, thick plank sheathing (1-1/2" or sometimes more) pine or cedar siding either as shakes or clapboards. Interior would be plaster with horse hair over slats creating an air gap in between. Sometimes these gaps were stuffed with buckwheat (i remember being told it was grain, but I'm thinking it was probably actually the straw but don't actually know)..

All buildings that needed to be heated would have had uninsulated attics and the cedar shingles would have have often been attached to slats (probably the wrong word here) again, meaning the roof was not completely sheathed.

The roof pitch was always steep on the main home though often the wood/store/hay sheds etc. built off the back had a gentler pitch.

Theres a great historical village that i went to a bunch as a kid and a few times as an adult called Kings Landing not far. A family friend used to be the blacksmith way back. They have a working overshot waterwheel powered flour mill (grinding mostly buckwheat apparently) and I think theres a wood turning shop in there too with a million straps turning machines around the workshop, attached to the main power source and geared up.

(ASIDE)

The vernacular here in Montreal is quite different and very weird and interesting. I'd like to try and break it down at some point in a post. I live in a building that was built in 1913 and is largely original. Just got new windows and doors in the past 3 years (!). I initially thought the electrical was added to replace gas fixtures, but I'm no longer sure. Montreal Light was founded in 1901... The structure is very odd...but that's for another post ! I will say that these buildings do have tar paper over the sheathing as well, which you will find brittle but intact over the weird 2-3x10-12 balloon/timber frame/sheathing combo under a single mostly non structural facade of brick or stone.If it sounds crazy...its cuz it is (as far as i can tell).

(ASIDE COMPLETE)

> Cedar shingles... condensation

Cedar shingles pass a lot of air and that takes away moisture. Also, they used to be installed on horizontal stringers (I'm not sure the word, either) spaced about 8-10" and often w/out any underlayment at all so one could stand in the "attic" or whatever the level just below the roof and see the underside of the actual shingles. _Lots_ of ventilation, both ways. <g> That's what I saw in the attic in Chicago until we finally had to do a tear-off.


Cheers,
Rufus