Planning a cordwood house???

Started by Rock Knocker, February 14, 2018, 03:15:03 PM

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Don_P

#50
Doodling..



Hmmm, that didn't seem to work. the corrected wall height isn't getting through. well at least for me. I'll try that again later
edit again; there it is, renamed the file, dang caches  d*

Rock Knocker

Well it looks like you're quite a bit better than me with paper and pencil.

You've got the right idea. I'm having trouble visualizing how a staircase is going to get worked in. First I was thinking I wanted a straight staircase along one of the walls(washer&dryer under) but then I figured I might run into problems with head room under the lower ceiling. I am now thinking about a spiral or switchback stair case in the center under the tallest part of the lower ceiling.

Another issue is the roofing, I was thinking about the living grass roof(I've heard good things) but I would need a roof with a significantly shallower angle. That wouldn't be an issue with the lower roof  but it would with the upper roof and head space in the loft. That would be cured with higher walls but I don't know exactly how much higher I would have to go. I do like the higher angled roofs but I would need shingles or steel roof. It depends on my exact budget.

It looks like with the door and windows I would be saving 2 cords of wood with 24" thick walls, after watching Rob Roy's video on youtube again I am thinking about slimming up the walls to 20" to save on a little more wood and add interior space, plus it sounds like a white cedar and perlite wall combo will be very well insulated so 4" may not be missed too much.


Don_P

It's just computer drawing, a different paper and pencil. It makes a pretty picture but the info is what really matters, I got that from your sketch  ;).

Tell me more about the green roof... max allowable slope, weight per square foot, your local snow load per square foot. How do you detail it to keep it dry.

MountainDon

QuoteFirst I was thinking I wanted a straight staircase along one of the walls(washer&dryer under) but then I figured I might run into problems with head room under the lower ceiling.

Run the stairs up a side wall, heading towards the upper level, turn 90 degrees at a landing and head towards the centerline (ridgeline) of the house. Build a dormer at the landing for headroom clearance.
Just because something has been done and has not failed, doesn't mean it is good design.

Rock Knocker

Here's just a few pictures I found online of the green roof.



I don't have the exact details worked out about them but from the little I've seen of them being made is that you put down foam insulation then a heavy duty waterproof liner, I was thinking of heavy duty rubber pond liner then a layer of straw with some black dirt on top and grass seed that. I don't want a flat roof but I am not sure what the max allowable angle would be to make sure it stays put, these pictures show a very shallow roof. Some of the pros about a green roof is water runoff, a lot of the water is caught in the sod and the roots suck it up which keeps water from pouring over the sides. Snow around here hasn't been a whole lot lately, maybe 2-3' feet with some melting in between... Online annual snow reports are saying 3.8' in the nearest large city. I'm not very dead set on the green roof, it just came across as a surprisingly viable option, I will do more researching on that.

MountainDon, I like your stair idea with the bend. For simplicity I would like to avoid a dormer if possible but I think I could get something like that to work without one.


Rock Knocker

I am still trying to figure out a good plan for the post and beams. How far should they be spaced apart?

I've been looking for plans online but almost none of them have the simple type of floor plan I am going for and they don't show measurements, just a CAD drawing.

NathanS

I have a book called "A Timber Framer's Workshop" that I think is considered a good resource for post and beam. It actually does have some basic plans in it.

Timber frames are traditionally made out of a couple 'bents.'

With a sod roof you are going to want impeccable water management details. The sod is actually going to act as a water storage mechanism, and there will always be hydrostatic pressure looking for pinholes to infiltrate. From memory, I believe that if you have 1/2" deep 'cup' of water sitting on the side of a wall, that amount hydrostatic pressure is the equivalent of the wall being hammered with hurricane force winds.

Probably the best way is to create a small gap between the sod and the roofing underlayment. EPDM, then some kind of a mesh material spacing that is held down by the sod.

That's where I would start anyway.

Don_P

You'll need to decide on the roof and nail down those loads more accurately to begin to be able to design the frame. Where my mind is going, the weight of saturated soil with several feet of snow on it has got to be considerable... need a number in lbs per square foot, I would err conservatively there, if it sags and begins ponding it can become a self feeding problem. One more thing to be thinking about is the thick walls and openings. As I moved through the sketch I made, I've put a window and door in it, the first thing I saw was that a door mounted to the exterior to the wall can only swing to 90 degrees before bumping into the thick wall. Mounted inboard would allow more swing or using and outswing door if mounted to the outside. A window in the thick wall is sort of like a tunnel, narrowing the field of view and light. You may want to think about flaring the openings.

I've been bucking the timberframers, and my partner and the client to a lesser degree over the past year as we have been reconstructing a historic log barn. The framers would call for a dimension, I would do the math and come up with a larger size needed and we would argue. I was not copying the original, my reply was that the original members were failing or in serious trouble. I finally asked an engineer friend to check me one day. He asked why I was feeling the need to skimp. From then on I went to the woods and gave them what they needed rather than what they asked for. This past week we surveyed another very similar barn on the same large farm and will begin working on it soon. It is in better condition. It was very likely built by the same person. One of the first things we noticed is the dimensions are a good bit larger than on the first barn. There is one collapsing shed that has smaller rafters just like the first barn, the rest are about the size we put in as replacements in that barn. I suspect we were seeing the learning curve.

Nathan, bent framing probably evolved from cruck frames. Another traditional method was the box frame where posts were topped by timber plates and then the roof system was added to that box. So rather than tipping up heavy bents they were installing timbers one at a time.

Rock Knocker

I see that waterproof membrane, EPDM and rubber pond liner cost more than expected. I will plan on a steel roof for now. My buddy is selling his farm and moving to Florida and we built all of his buildings with rib steel and I know he still has piles of it, I could probably steel roof the whole place for half the cost of these waterproof membranes alone.

So I guess steel roof and high peaks are the way I'm going.

The thick walls for the door isn't a problem, I was planning on an outward swinging oak door with a large wood frame around it that would take a military APC battering ram to get through. The windows might not be the most convenient for letting light in but I can use the extra space as a shelf and in the winter I was thinking if I got around to it I could get some cheap single pane windows to put on the inside for insulation and remove them in the summer. 


Don_P


Rock Knocker

I like how those stairs are looking but I think I would leave some space between that south west facing wall and the lower section of stairs. I would have to extend the lower section but that shouldn't be a problem or I could do a 180 degree switch back, it all depends on the kind of clearance I have with the lower ceiling. I want a bathroom and second room under the loft, so I will need wall space for two doors.

Don_P

Head clearance dictated that last lower step and landing location with that roof configuration with the landing against the wall. You can see it better with the rafter layer turned on;


As you move away from the wall though, at a 12/12 pitch, every foot away from the wall buys you a foot of headroom, so the stair configuration can change, as can the roof height, actually those tails are down in the windows a bit right now at that overhang. Time for a floorplan sketch from you, doodle again is fine. one thing that is going to be kind of a constant is it'll take 14 steps to get upstairs. I wouldn't drop the tread below ~10" deep. They must be at least 36" wide after wall coverings are applied.

Rock Knocker

How would something like this work? Hopefully the stair layout I drew makes sense. Option #1 would have the switchback stairs fully outside of the loft and two room underneath, option #2 would have the higher level of stair set into the two room and loft with the bonus of being under the higher ceiling.


Don_P

#63
You need to land up at the loft on something so option 1 as I see it doesn't work there, the stairway to nowhere  :D. I've done a modification of option 2. It is easier to land against a notch over that center bearing wall between bed and bath. There is a path behind the stairs to the bath on the left.


The sketchup file is here if you want to download sketchup and the file, and then open the file in sketchup. If you make changes save them to sketchup 2016 and post them, where my graphics card stops. Anyone, feel free to play with this and post what you come up with.

http://timbertoolbox.com/cp/cordwood3.8.skp

Bedroom is about 10'6" wide x ~13' deep, bath is ~10'6x10'... carve bedroom closets or more room out of the bath.

Edit, doodled on the skp a little more last night;
http://timbertoolbox.com/cp/cordwood3.14.skp


Rock Knocker

I got a good laugh out of the "stairs to nowhere" comment. I didn't draw that up the best  d* but I figured option 2 was what needed to be done anyways, it will just take a little more fiddling around to make the bedroom and bathroom. Not a big deal to me, it wouldn't bother me to move in without the bathroom even having walls, I will have plenty of time fiddle.

Thanks a ton for the help and I will download that sketchup software hopefully tonight.

Ernest T. Bass

'Smokes Don, I don't know how you can can be so busy and also provide so much in-depth free support here.. It boggles my mind; hat's off to you.

We're 11 years in our cob-mortared aspen-wooded cordwood home in the UP. Actually cutting popple right now for a large kitchen addition we'll be building this summer.

Our family's homestead adventure blog; sharing the goodness and fun!

Don_P

Good to hear from you Andrew, LOL you got the pitter patter all around you, I have more hours of selfish play. Hmm interesting on your aspen experience, actually shortly after this thread went quiet I was in a cordwood/post and beam cabin in TN, very nice. Stone foundation, sawmill lumber and timbers, just about everything from right there. Built by a couple of boys using hand tools as a homeschool project. Each then got to move in to that as part of their life experience, a nice semi independent hardening off time for a growing boy. Predominantly tulip poplar and maple, two woods I would have avoided for the same lack of natural decay resistance and high movement during drying. There was some caulking around shrunken logs but not too bad, no rot visible. The boys now have families and kids, it is a vacation rental cabin now, so it has been there a good while. Keeping things high and dry and having a good hat on is most important.

as a sort of humorous side story on that, the kids grew up around the adjacent little circle mill, the same kind as mine, working it with their Dad. Now that the "old man" is my age he saw 11 grandkids around the mill with his kids working and had an OSHA attack, he bought a bandmill and I bought his old circle mill. I've got the big diesel engine for mine and a friend got his mill and will power it with a tractor which is how I've been running since '93.

hpinson

If you want to do that grass roof you might consider Silicone as well as a membrane.  Good Silicone Primer (APOC® 583 Armor Base®) and Silicone product (APOC® 585 Armor Flex®) is very durable and completely waterproof, and has a surprisingly long lifespan.  A roof like that is just asking for degradation, leakage, and mold. Don't use lessor Silicone products like those available at the box stores like from Henry. Get the good stuff with the high silicone solids count.

Ernest T. Bass

Quote from: Don_P on May 18, 2018, 05:42:49 AM
Good to hear from you Andrew, LOL you got the pitter patter all around you, I have more hours of selfish play. Hmm interesting on your aspen experience, actually shortly after this thread went quiet I was in a cordwood/post and beam cabin in TN, very nice. Stone foundation, sawmill lumber and timbers, just about everything from right there. Built by a couple of boys using hand tools as a homeschool project.

Sounds pretty neat--I'd take cedar any day if it was abundantly available, but Aspen is what we were handed and so far has held up. (Now if you leave the bark on, let it get wet or stick it in the ground it'll be rotten all the way through by the end of the summer.)

I don't get the pitter patter?

Our family's homestead adventure blog; sharing the goodness and fun!

Don_P

The pitter patter of little feet  :D a full house. Although your kids must be growing up fast. We're just a couple of old farts bouncing around the house at night.


Ernest T. Bass

I'm actually the oldest of the little kids, though most of us aren't so little anymore... :)

Our family's homestead adventure blog; sharing the goodness and fun!

Don_P

LOL, my turn to be thoroughly impressed.

Ernest T. Bass

Shucks, I'm 28 now so what I do is no big deal... I'm still resting on the laurels of my 15 y.o. self. :)

Our family's homestead adventure blog; sharing the goodness and fun!

Rock Knocker

Hey! Sorry I haven't been around much. The plan got slowed down when this Minnesota winter lasted into April, then soon as everything thawed out I got crazy busy working on horses.

I plan on having my house up for sale in 2 or 3 weeks and the way the market is going around here I've been told by close to a dozen people that the house will be sold in less than a week, then I will just have to wait for closing.

I've made some progress though, I made plans with a guy to buy around 20 cords of white cedar from him soon as I get paid for the house. I got an ok price at $225 a cord but I am very happy because it was not easy to find and this stuff is aged two years and the bark is ready to come off easily.

I think I've got around 80% of what I am building figured out, I am still stumped on the post and beams though, as to how many I will need and the general layout of them.

JRR

I wonder how re-purposed rail ties would work for stacked cordwood walls?   Such material seems very available as its piled and collected every year from some rail system that I drive near.  Many of these rectangular timbers seem hardly worn.  I would think they would be as dimensionally stable as wood can be.  Cutting and shaping would be a challenge, but cost may well be very low.  I can imagine foot-long pieces being stacked with a thin lather of roofing curing cement as sealer.  A vertical membrane of roofing paper nailed in place, followed by metal lathe/re-bar and thick high quality stucco covering (interior and exterior) would make a wall system that would outlast us all.
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..huh?