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spencerin
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# Posted: 29 Apr 2022 12:03pm - Edited by: spencerin
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The aforementioned rebar would need to be below the frost line as you don't need it where freezing liquid could grab onto it.....
Use large compacted gravel as your footer, assuming you're using wood posts, as it allows for better drainage in the hole. They also make what I think are plastic footers, too. Not sure how durable those are, although certain plastics can be very strong. But the point is to allow for better drainage over a concrete footer.
The guy in the video does say the footers weren't dug deep enough.....
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yoopermike
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# Posted: 29 Apr 2022 12:27pm
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Great thanks for all your help. Now I need to figure out what size built-up beams and joists to use, and how many piers. Is there an easy to read chart somewhere for all this info? Sticking with 12x16 build, medium sand bearing capacity is 2000, possibly 3000, rafters and joists 16"oc going the short way (12ft span, but with significant overhang on roof), probably a beam across middle just to add extra support for joists in middle of room to keep it not bouncy. The green log walls will initially weigh about 12000lbs before drying (so half that once dry), and roof and floor systems and woodstove and other stuff inside should bring total weight to what, 18k? And up here snow load is 50, though a friend said build to 60. I am never away for too long so raking snow off the roof of such a small hut isn't an issue.
For floor I was going to nail osb to underside of joists and fill joist bays with pink stuff, vapor barrier on top and 3/4 ply on top of that, and eventually make maple flooring on top of that sometime down the road. If porkies attack the osb I can always attach 1/4" hardware mesh outside the bottom, but I think osb or plywood underneath will keep mice out of the insulation while still allowing the insulation to "breathe," if I am not mistaken.
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Tim_Ohio
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# Posted: 29 Apr 2022 12:47pm
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I covered the underside of the floor joists with overlapping, white roofing tin. I drilled holes in it for venting. After completing that part of a project, I read an article, or someone pointed out what I thought was a better way. Someone had used vented soffit and fitted it between the joists from above. They did have to create ledges for it to lay on, which is a little more work. But, the work was done from above, unlike in my situation, where I installed it from below, on my back. So, you might consider doing it that way. I'd think since it is
perforated, you could adjust it to serve as support for the floor insulation, keeping the insulation right up against the floor, not unlike the way it sits in a wall. I had to support the floor insulation, to keep it up. Also, I used mineral wool since it's less prone to attract rodents. I'm not sure about your other details of load. That's a lot of weight. Do you have a plan for setting all of the heavy stuff yourself?
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yoopermike
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# Posted: 29 Apr 2022 12:58pm
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8" diameter vertical logs, I can lift them up one at a time and screw them in.
Roofing tin underneath sounds good, but won't ants, etc. get through your drilled ventilation holes or did you put a piece of screen in there or what?
Mineral wool might be good idea, but depending on joist size I would need to go up between the joists to get it up against the floor. Pink stuff takes up more space per r-value I think, and is also cheaper, so if joists are 2x8 or 2x10 all that is needed is something under the joists to support the insulation.
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Tim_Ohio
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# Posted: 29 Apr 2022 01:33pm - Edited by: Tim_Ohio
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Carpenter ants are the biggest concern, but what is most important is the ventilation. No house or cabin is impermeable to insects. Keeping rodents out is the major issue. Most cabins don't even have anything covering the underside of the floor joists. As long as you are in the wilderness, you will have insects. It's as good as it gets. Repellents help to keep them at bay.
For instance, I threw moth balls under the cabin to keep animals from wanting to burrow, such as ground hogs. The odor repels them. A kind of skirt helps to. I haven't gotten to that yet. Here is what I built.
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yoopermike
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# Posted: 29 Apr 2022 01:53pm
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Oh that looks nice. Also, when calculating weight I forgot about the fact that the south wall will be half windows. Recalculated green weight of walls should be 9 something, but as I will be putting the logs up as I go, many of them will have had plenty of wind and sun and should be significantly lighter by the time we start getting snow.
Another thing, I have a large amount of reflectix which I used to insulate a canvas tent I lived in over the winter (was a long winter but mild, only got to -20F a couple times, but more -5s and 0s than normal). What can I reuse this for?
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spencerin
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# Posted: 29 Apr 2022 09:43pm - Edited by: spencerin
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Putting 1/4" hardware cloth underneath, over the plywood/osb, is a good idea for rodent prevention, if you can do it. Imagine what a pain it would be if a rodent got through the plywood/osb into one of the bays with insulation.....
There are span tables and deflection calculators online that can help answer your questions. But, people generally place piers 4' apart. And you may or may not need a support beam in the middle of your joist runs to support them. If your floor joists are spanning 12', it looks like you could forgo a middle support beam if you use 2x8s, for example.
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yoopermike
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# Posted: 29 Apr 2022 11:14pm
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Great, so two sets of 5 piers spaced 4ft apart and no center girder. Should I put a pier halfway between the 12ft non-load bearing walls and maybe a smaller beam that direction (so beam around perimeter) because those end walls will still weight a bit being of 8" logs?
I worried about sag or bounce in the middle of the floor but it's such a small space 2x8 or even 2x10 if I want to go overboard should provide firm floor according to span charts. Not like I am moving around a lot in 12x16 space and it's just me and the dog and maybe one visitor now and then. The only other weight issue is the 400lb stove in the corner but I can double up a joist there in addition to doubling the end joists and just cut batts to fit the resulting smaller bay. Is thermal bridging an issue I should be concerned about or no? Looking to insulate as cheaply as possible but without creating moisture issues that compromise structural components. I lived in a tent on a deck and the floor is cold, and once lived in an apartment that was below grade at floor level and likely poor to no floor insulation, and am tired of really cold floors, but I have no idea what floor system would be sufficient and so my thoughts are likely overcompensating (r30 floor probably unnecessary) because of recent experience (r1).
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spencerin
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# Posted: 30 Apr 2022 01:19am - Edited by: spencerin
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Yes, still put a pier(s) on the 12' side. Not sure what you mean by putting a smaller beam in that direction, though.
A 400 lb. stove spread over multiple floor joists is nothing. No need to double-up joists or anything like that. Look at it this way - would you have any concerns with 2 adults standing in the same spot together on a floor?
Thermal bridging happens and it happens all the time in homes without comprising structural components. If you're not sure what r-value insulation to put in the floor, you can find recommendations online. It's largely based upon geographical location.
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yoopermike
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# Posted: 30 Apr 2022 01:36am - Edited by: yoopermike
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For beam, got beams across 16ft walls either end where load bearing walls are. Would a beam under other 2 walls, to complete perimeter, have any structural advantage? Or just run middle pier up to double joist on those ends?
Idea is that a pier halfway between those 12ft walls could either extend all the way to double joists on the end, or support a smaller beam (than those across 16ft walls) to add some strength under the double joists to help support those walls.
Also, what do you think would be best re-use of the reflectix I have? Overlap and staple under rafters and nail ceiling material under that? Or top of floor joists and nail subfloor on top?
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spencerin
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# Posted: 30 Apr 2022 02:27am
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I see. I don't think it really matters because the double joists supporting the 12' walls are themselves acting like beams, no? I suppose to make it look uniform around the perimeter you could put true beams there, too, but I'm not sure it's necessary from a structural point of view.
Is the Reflectix their bubble-foil type stuff, or their paper-thin, shiny, reflective material?
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yoopermike
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# Posted: 30 Apr 2022 06:54am
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Bubble foil.
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spencerin
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# Posted: 30 Apr 2022 07:58am
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If you feel the need to reuse it, then put it on top of the joists, seal the seams with their tape, and screw the subfloor over it.
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DryCreek
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# Posted: 30 Apr 2022 12:48pm
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"Mineral wool might be good idea, but depending on joist size I would need to go up between the joists to get it up against the floor."
1)Mineral wool, IMHE, is easy to peel in layers of arbitrary thickness, so it's fairly easy to use a 5.5 layer and 2.75 inch half layer or whatever, if you want full depth insulation.
2)If you don't need it full depth for thermal reasons, you could leave a gap except for making it full thickness around the perimeter.
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yoopermike
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# Posted: 2 May 2022 10:49am
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Would it be better to triple up 16ft 2x10s for the beam, or triple up smaller lengths staggered together, or does it have any impact structurally or with potential for warping? To move 16 footers I would need to rent a trailer, smaller sizes in bed of truck, but I may need to rent a trailer anyway to get some other larger items moved.
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spencerin
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# Posted: 11 May 2022 12:16am
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Better to use lumber that's 16' long. Where's the beam going? A triple 2x10 can carry a LOT of weight. Might be overkill......
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yoopermike
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# Posted: 31 May 2022 01:20pm - Edited by: yoopermike
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After much deliberation, I decided not to build with logs--too much work to side them flat and too heavy. So going with stick built 2x6s, which means my foundation wont need to be nearly as beefy. Is the following plan okay, or any elements overkill? I was reading the code book and awc span calculators to come up this.
12x16 with shed style roof 3/12 north wall 7ft south wall 10ft. Foundation of pt 6x6 on pads 4ft underground with 12-14" above ground. 4 of them under each of two beams, spaced 5'4" (or 5ft if I want to cantilever the beam 6" either side). Posts braced to one another with 2x4 or 2x6, and end posts braced the other direction to the double end joists. Beam made of triple pt 2x8. 2x10 joists 16oc on top of the beams spanning 12ft and toenailed in with rim joist and blocking over the beam. Unsure of whether to cantilever those or not. 3/4 ply subfloor. 2x6s for wall framing 16oc and plywood or osb sheathing, with a lot of windows on south wall (2 that are 2x4 and 1 picture window 4x4, and a row of 2ft windows just before the top of the wall--2 awning windows and a fixed window--so heat and humidity can escape up high and I can also have natural light from those top windows without direct summer sun and close the shades over lower windows) so probably good to use 2x10 or even 2x12 for header? Rafters 2x10 16oc with 2 ft overhang in every direction, attached with hurricane ties if not on all then at least some. 3/4 ply on rafters and metal roofing on top of that. Will at least get some use of my hemlock trees and chainsaw mill cutting boards for board and batten siding and maybe for ceiling material too, attached to underside of rafters.
Code says 42" frost depth, 50psf snow load. No major hurricane or tornado winds are usual here, but 130" snow is avg--I can easily rake the snow off the roof. No plumbing, don't need to worry about enclosing crawl space, just gotta keep critters out of the insulation in joist bays.
Any thoughts? Would it then be possible later to add an addition by using joist hangers on the side of the beam? The built-up beam will just be nailed together but I can always add lags or bolts if I later need to hang something of their side, right? What about an addition on non-load bearing side walls, I wouldn't be able to just hang off the end joists but would need to dig for a couple posts close to the building right?
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