The Great Cabin Erection!

Foam makes sense. But I expect the main vapor barrier will be below the fiberglass insulation?

I know a friend who did a DIY addition to her house, put the vapor lock outside the insulation, ended up getting rained on when the vapor condensed against the cold plastic. I learned then that if I ever was to build something I'd keep that simple physics in mind and keep the vapor lock below all insulation.

halfwise wrote: But I expect the main vapor barrier will be below the fiberglass insulation?

that's what i'd do. i'm in a particularly wet climate but having a separate vapor barrier and air space below each layer of insulation makes a lot of sense to me. otherwise you can expect soggy insulation and rotten roof boards over time. what's the wood treatment you're using forest?

The wood treatment is Bora-care, a brand of borate solution that you dilute with water. I added blue dye for ease of knowing what I already hit. I don't know if it will actually work, but, I mean, it should do something. I freaked out after I found thousands of dry-wood termite wings all over my new construction last fall, so I ordered a bunch and tried to soak every square inch.

The silver is a radiant barrier on the underside of the roof sheathing. I believe it's perforated so that must mean that it's not a vapor barrier as well. I think it's necessary in the cabin because of all the direct sunlight it gets in the summer.

I had been talking to my boss about what to do for proper ventilation, and he had scoffed at the idea of a ventilation channel, saying that it wasn't needed. I decided to go for it anyway, and am using a cheap-o ventilation channel insert that basically allows air to flow into the roof from underneath the eaves, up through the roof between the roof sheathing and the fiberglass insulation, and then out through the ridge vents I've installed already. Basically, you can't see it in those pictures because I hadn't decided to use it yet. (I had to pull out the insulation and put it back in again.)

California has a pretty dry, warm climate. The coast is more humid, but overall it's quite dry most of the year. Perhaps that is why I'm not actually familiar with vapor barriers in my work. I've never had to put one in and haven't seen any when doing demo work. I don't think they're needed here in regular houses.

Except the roof is kind of different. This is rather confusing to me, even after reading some more about it. Basically, as I understand it, I had two main options for my cabin's cathedral ceiling: spray-foam insulation or fiberglass insulation. Spray-foam insulation is, you know, spray-foamed between the rafters on the underside of the roof sheathing. It forms a vapour, air, and thermal barrier. Not much heat travels through it, and no air or water vapour can get through it. Once it's in, you don't need anything else, you're good to go. Cover it up with your ceiling material of choice. This keeps the hot or warm air in your ceiling away from your roof sheathing and rafters.  

But fiberglass insulation is different. It's a thermal barrier, but vapour and air can flow through or around it. The sheet-rock I'm putting on my ceiling is an effective air barrier, but not a vapour barrier. So what you do then is to include an open channel between the roof sheathing and the insulation, and then drill holes or whatever in your soffit and put a continuous ridge vent in your roof's ridge. This allows the hot air in your ceiling to flow out the ridge and be replaced by cooler air from under the eaves in a self-regulating way. This drives the hot air up and away from your roof sheathing and rafters.

As I understand it, this second method keeps my roof cooler overall than the first method, which is a fine thing. But both methods keep condensation from forming on my roof sheathing or rafters when outside and inside temperatures are different from each other. The first method by keeping vapour away from the roof sheathing and rafters, and the second by allowing the roof to breathe out any warm humid air and breathe in cool air that matches exterior levels of humidity.

Does that make sense? I feel like I needed to type this out so I could reassure myself that I knew what was going on here.

I think you're wise to go with the ventilated roof method Forest. It's a little more work to install but it breathes in a much healthier way for the whole house, plus it's a lot easier to track down and repair a leak or rot issue if you ever have one [a serious consideration here in coastal WA with 6-8 ft of rain a yeaar....]

Send some of that rain down this-a-way whenever you feel like it. We haven't gotten rain for weeks and weeks now, right smack-dab in the middle of the "rainy season". It's crazy that you can get that much rain. I remember four years ago we had fewer than 10 inches for the whole year, counting total precipitation. I think with just rainfall we had so little rain that a few years later we had more rain in one weekend than we did throughout that entire winter.

I hate it. I really do. I know that frigid winters suck in their own way, but I sure do miss Minnesota rainstorms in the spring and summer.

I could talk about global circulation and rainfall patterns, but shall opt out.

Forest Shepherd wrote:Send some of that rain down this-a-way whenever you feel like it.

It's your for free* Forest!

*Transportation not included.

Ah yes, back to the only search result for "erection" on the forum.

Sheetrock suuuucks, I've been doing that for quite a while now. Here are some views of the interior. That sketchy scaffolding is coming down as soon as i finish mudding the ceiling.









Below you can see the boards I've cut down for my ladder-stairs to the loft. There's a close-up of the grain. It's very nice, knot-free, vertical grain, old growth Douglas Fir that I cut from a beam. The beam is one of several we pulled out of an old roof at work. It was going to be taken to the landfill, so I feel pretty good about bringing it home.
At first I went to a specialty lumber yard, and they wanted to charge me like 500 dollars for the wood I needed. Yeah right!





Here's what regular construction-grade douglas fir grain looks like, for comparison (the board is 1.5 by 3.5 inches):



I bought a new router, and a bunch of bits for it.



I did a little more painting outside, but I don't really want to take down the scaffolding until I finish the trim and soffit on the dormer.

Thumbs up on reuse of old wood. You can rarely find boards of those dimensions any more; trees are harvested too early.

But I fear your erection has lasted longer than 4 hours. Maybe you should see a doctor?

wow that's gorgeous, are you having wood on the interior walls like an alpine stube?

That, is a fantastic piece of work ! It looks stunning. Love the grain on that wood, looks so silky to the touch. How wonderful to be able to do something like that
{{{ if you knew the jokes in my head right now ! }}}

Or the jokes about the head?

No wood on the inside Figgs, or at least just around the windows and along the floors as trim. But I will try and include lots of wooden furniture and bits and pieces. I might make my own door, and am certainly making the step-ladder out of wood.

> But I fear your erection has lasted longer than 4 hours. Maybe you should see a doctor?

I rarely work on the erection for more than a few hours in the evenings, or in the morning on the weekend. Perfectly healthy I'm sure.

{{I have to say I am impressed Forest- I dont think I've ever seen as quite a substantial erection as yours being handled by just one man   }}

To have kept it going this long all by one's self is a testament to the powers of concentration.

Well I usually wear gloves, so that helps with keeping my skin from getting too damaged.

I'm running low on oil for sharpening my knife though, I'll have to pick up some more in town.

Just a quick update on the stairs. I connected the treads to the stringers with mortise and tenon joints. Here they are, glued and clamped. You can see how the treads are off-set now with each other.

Ah, ladder/stairs!!
That's twice the project of either a simple ladder or normal stairs, but it gets you the best of both worlds (very little floor space used, and hands-free climbing)
Nice job!!!

Thanks!
It has taken quite a while, but they're shaping up nicely. I made a wooden bottom-plate for them to set into where they meet the floor, and another where they anchor onto the wall. It's helped firm them up nicely. Putting the router to good use anyway.
We had an ungainly old set in our barn, but vertical rise between treads was very high indeed. These are only eight inches, which is a comfortable step distance.

Hm... They are on the steep side. I think I have to add a stubby little riser on the front of each one as well to deepen the tread: they need more foot support. Bugger.

stairs that are offset for each foot is a novel idea. I'd never thought about the idea that each foot actually goes two steps on stairs. They do look a tad steep but I don't think you'll really know until you test them.

I did, and was rather disappointed. I definitely could have gone with less steepness. I read up on these stairs and thought that my design was within good parameters: I even slapped together a short "prototype".

A hand-rail will help, and deepening the tread.

Anyway, yeah, alternating tread stairs are really useful in a small house.

I've used some pretty steep ones in Swiss Alpine cabins, and if I had to guess I'd say you'll get used to the steepness pretty quickly, but the handrail is probably a good idea for guests Always best to go down backwards like a ladder (especially drunk ) If you forget and start down with the wrong foot first, things can go bad really fast.....

I don't understand how alternating steps save space. I see it as just a neat idea but it's still the same width as ordinary stairs.

It's not the width, it's the steeper pitch saves the space. The offset treads allow you to walk naturally up a much steeper pitch because the each toe doesn't have to dodge the alternate stair treads. And a steeper pitch means a smaller horizontal component, so less floor space lost under the stairs. Another way I've seen it done is with full treads all the way across, but with cut-outs on alternate treads for the toes to pass.

Ah, now I see.