28' x 36' log cabin project

[akadiesel]

So I've been working on plans for a small cabin for way too long now! Thought I'd already be working on it but since I've never done this I'm having to learn what I can and can't do by code. Being short on time and money doesn't help either! On top of that, me being the first person to ever walk into the building inspectors without detailed drawings all stamped by engineers doesn't help!!
Not having the knowledge, like most here, on timber framing and post and beam or the time and resources I'm having to go with the milled logs. Not a kit. The plan is to put first sill log directly on the foundation wall and ledger the floor to the inside 2.5 inches above the bottom of the sill log to run wire. Haven't figured out what would be best to put between foundation and sill log so it's not to have to use pressure treated wood. Now stack up seven more rows and set my main beams for the loft. That'll give me my required 84 in ceiling height. That'll be 2 x 14 ft side to side and a 16 ft (maybe more )  from the rear wall to a post. Haven't figured out yet how to do that to be legal and satisfy inspectors that don't have a clue! I'd like to use EWP  for all the beams if possible, moneywise. I'll have to recheck my calculations but I believe it'll work with 6 by 10s or maybe 12s with another post in the middle of the 16 footer.
I may want to go to 8 by beams just for the look since they'll be a wall separating the sides and font of one. Next will be floor joists on both sides space no more than 4 ft. That's all I can go without a rubber stamp!  Four bys will work here but I'm thinking six bys would look better. Again I have to figure out the best way to attach them to the beam in the center. 2x6 T&G spruce for flooring. Now come up several more rows of logs before thinking about the roof. Wall just has to be tall enough so a 9 or 10 slope roof will give me headroom at the top of the stairs. I had planned on an open cathedral ceiling but money and not wanting the big stack of insulation on top Plus the 4 ft rubber stamp rule

 I'm thinking conventional roof with 2x10s and some beam set under that just for looks if that's possible.
Going to post a floor diagram and a few pictures and take a break and do some work.

[Don P]

First thing catching my eye is the same "standard 2' kneewall" we've heard of recently.
Folks, a kneewall is not standard, it is a problem. The roof is not tied at its base and there is no way to tie it together there. Codewise you'll be in chapter 8 of the IRC, basically, if the roof cannot be tied in the lower third of roof height then it must hang from a properly designed ridge beam. Your posts under the second floor need to extend to the ridge to support that large beam., trace those posts all the way to foundation elements.

Most modern milled log homes, the logs sit on the floor deck. This is stronger than ledgering the floor inside the log crib and also makes wiring easier. Use a treated sill, attach it as per chapter... I think 4. BTW, those inspectors know more than you think, don't make them prove it  ;).

[fluidpowerpro]

Can you set trusses on a knee wall? 

[Don P]

Yes, but any configuration I'm thinking of would be a head banger there.

[akadiesel]

 Don P,
 I pretty much agree with everything you said. Proper ridge beam properly supported on the end walls, supported with that extended post going to the foundation which also I believe needs to be adjustable to allow for wall shrinkage. I think it needs at least one more support towards the other end. And whatever we want to call those walls wether short walls, knee wall, or whatever, I think they should be tied together in at least several places. I've wondered about maybe some posts up the interior side of the walls to a beiam spanning the width. Or would the post be worthless as it can only be attached to the wall in a way to allow for shrinkage?
 My mind has been obsessed with all this and I appreciate your critique and thoughts on solutions!

[snobdds]

I wish I could post up my plan on this forum, they were developed by an architect and engineer for our deep Wyoming winter.  

We used 12 foot walls, with the loft at 8 feet, to give a 3 foot knee wall.  The rafter attach on top of that.  We used normal collar ties, but the rafter ties were actually on the outside of the main structure.   It has survived lots of deep winters and this past winter was crazy up there. 

Here is a thread I did a while back.  I should update it one of these dats.

https://forestryforum.com/board/index.php?topic=113025.0

[akadiesel]

  Honestly I don't know if I would have ever thought to come up two or so foot above the loft if I hadn't gone into a log cabin sales center model that had done it and I saw how much more usable loft room there was.
 Realistically, without the several rows of logs, it's the same situation.  So is what we're calling a problem, really the wall or is it the ceiling joist or lack of??

[akadiesel]

SNOBDDS ,
  Nice! I'm going to have to look at it again later when I can project it onto the big screen TV!

[Don P]

This has turned into a stream of consciousness, there are 3 posts since i started writing this so I'm bouncing around a little here.

The lack of low ties means there is unrestrained push against the walls. The prescriptive code solution is a ridgebeam that the roof hangs from.

When I see a 2 or 3' kneewall I ask, can we make it a 5' kneewall? If the answer is yes, I can usually get rafter ties down into the lower third of roof height, and life is good, a ridgeboard roof will work. Dormers are another option

Where are you, by which I mean, what is your design snow load?

One thing that does help, there is a prescriptive log home standard recognized by the code... if you can work within those prescriptions, no engineer required. You do have to show sufficient plans to demonstrate that you are prescriptive.

At 28' wide... can you lose the kneewalls and put a 12/12 roof on it, that would give about 17' of useable width upstairs. Those tall cathedral rooms, look good on paper, they do not live all that well. I have one house that has a million dollar living room, tall TF cathedral room very nicely appointed, open floor plan with an adjoining dining room under the second floor. Time and again I've paid attention, people gravitate to the dining under that lower ceiling rather than sitting in the 25' tall great room. Just like pups, we kennel up.

Yup you can do wall stiffeners if it goes that way.

These codes I know pretty well and am quite happy to clear up or explain any of that, its just a lifetime of contact with it. I'm trying to get a food manufacturing permit and inspection, that set of codes is driving me to distraction, I do understand the feeling.

[akadiesel]

Don P
  I'm in northeastern NC. Close to but not in the mountains. Roof needs to be l/180 and 30lb plus dead load. I may state a few things wrong since this is kind of like learning a new language! And I know you know your stuff just from using your calculators some. Do I have questions!?!! That's kind of funny since I've never felt stressed before until trying to find out where all these answers I want are hidden. I really like to know how to figure out the answer and I have a lot. 40 years ago I could have done all those equations in my head but those days are gone! I am currently a somewhat retired pipefitter, boilermaker, welder, rigger, etc so I can relate to a lot of this stuff.
 As far as the building goes, it's just on paper now, and really not much of that. I will have to learn/ figure out how to do any required drawings.
Changes are possible and I am way past plan b at this point! Of course there's a little lady that has to be happy at the end also. We've even considered something stick built but since all pretty much be doing everything by myself, and having a boom truck it seems stacking logs would be easier for me. And closer to what I would prefer in the end.
 Back to the roof. I've never considered not having a ridge beam. I had to go back and look when you mentioned a properly constructed ridge beam as I had only seen the minimum 1-in and height requirements. Rafters. Would really, really like to have an open ceiling, not a high one, but for the cost of t&g and the 8-in or so stack of foam on top. It's still an option.. that route I was thinking 20 ft or so total rafter length. That would be right at 18 ft actual with two fit overhang at about a 10 slope. Cross ties and some cross beams at the bottom. 
 Okay if I go to stick built I really have to check and see what lengths I can find. I'm going to send this much and take a needed break why you absorb all this dribble. It struck me earlier that maybe a hybrid of a sort would be possible and have the best of both worlds?

[Don P]

Cool, you're just below me somewhere. Those skills and toys will come in handy.

Looking at the post in the picture above, from this wall to the post is 20'? I'm trying to see what the worst ridgebeam will take. The rafters will bear half on the ridge and half on the wall, as viewed on the level. So that longest ridgebeam is supporting 20' long x 14' wide=280 square feet. The loads are 30 psf snow +10 psf dead load. 280 square feet x 40 lbs per square foot =11,200 lbs on a 20' span.
We're pretty much outside of solid sawn wood for that. I used the manual entry beam calc and entered LVL strength numbers, Fb 2800, E 2.0 Fv 280 .. it looks like a 3 ply 14" deep LVL would work. It would end up 5-1/4" thick x 14" tall and if you can set it I'd order 36'ers and avoid a splicing situation.  That's just the ridge, the rafters could be exposed with T&G/foam, etc or it could be stick framed with 2x12's and fiberglass. If it is exposed a glulam would come in at a similar size and at that height they look enough like a solid sawn beam. You can go either way there.

The loft floor is going to be 40 psf rather than 30, same dead load. That 16' beam needs a wall under part or a post somewhere, which it looks like it has... lets see the floor plan.

This is a cypress home near Ruffin. Being poor and on the road, we used pump jacks and spooky small ropes to lift those green 6x12 loft and ridgebeams into place.

[akadiesel]

Don p,
  Now that's wild! Nobody in the entire world knows where rRuffin is! And it's not on the way to anywhere unless you happen to come to see me!!

[akadiesel]

Don P 
 On the loft floor, building inspector told me 360 and 30 being it's considered second floor. That post is at 16 ft. I'd like another foot or two but that's cutting into somewhere else. And without doing the equations, I had originally figured that ridge beam would be somewhere around a 4x12 or 4x14. Are you using nominal or actual figures?
  Let's keep that roof thought. I was thinking if did a stick roof that 2x10s would work. I haven't looked hard but I'm only seeing local r30 at9.5 inches thick. That's 8 rs short. Foam on top? Now let me throw this out which actually the building inspector threw this out while we were talking.BTW I didn't mean to imply that they didn't know anything. I think that they really would like to be as helpful as possible. It's just that like they said they've never dealt with any kind of cabin not a kit with detailed drawings and all the stamps on it. But he suggested the possibility of some somewhat decorative beams below. I haven't really tried to figure what may or may not work like that. Taller ridge beam for sure and I'm sure some technical issues. As you mentioned earlier, yes I've read the 2017 400 several times but that doesn't mean I remember it all! The 2018 IRC says that any Log members must conform to the 2017 400. And like you said the 400 only requires the ridge beam and wall plate attachment. That could be taken to mean the individual members or the system as a whole? Also I'm told that a beam constitutes a log member. Is there a size of beam that draws the line on that? Also the only condition in the 400 that could affect me as to engineered status  would be if I exceeded the 4' rafter spacing limit. FWIW I've never been opposed to paying a reasonable fee for the engineered but have not been able to find anybody around. And if I'd paid one in the beginning I wouldn't have learned anything! And I wasn't sure in the beginning, if I can say it right, maybe the motivation behind everything. I think we're pretty much on the same page, kind of like irregardless you have to be code bu t you also have to feel like you did it right! Like maybe not but I felt from day one that those two walls should be somehow be tied together more to follow. Oh yeah I'll throw out a floor plan .
Please bear in mind though that it has been changed and rearranged and changed again. Everything's not exact and I just threw those beams up not trying to space them right and everything. I've got a lot more I'll have to go through and get something a little better

[akadiesel]

 

 

[Don P]

There it is, we don't need a 16' beam, the bedroom wall is the support for the center of the loft floor. Do stack the joists over the studs... over the 1'st floor joists and girder (which has 2 floors bearing on it (crawl or basement?)), and carry the load to adequate footings. I'm kind of talking you through accumulating and tracing the load paths to ground as a way I think. 30 psf for "sleeping rooms" is code, you will not find many designers or engineers doing that any more. There's less complaining if it is all designed to 40psf live and at least l/360. No tile in that loft.

L/180, L/360... these are the allowable deflections under design load and very often control the beam sizes rather than strength. For a roof, it can sag as much as 1" in 15' of span where a floor is only allowed 1/2" in the same span. They are a serviceability limit rather than a strength limit.

I've stick framed roofs with 2x12's for some time now to get enough insulation in, on at least a couple they had us go either over or under the 2x12's with 2x2's to get adequate vent room with fiberglass. Which means, you can't put foam over the top to get more R's because there is a vent channel, the foam wouldn't be helping you. Over my head, on the ceiling here the foam is inside, under the fiberglass and osb screwed thru the foam to the rafters, then I could shoot the T&G everywhere and you can run it in any direction over that osb. I did a simple pattern in the living room.

If you want to do a beam roof we can get you there with another code reference, WSDD, Wood Structural Design Data, in the publications at awc.org. There are heavy timber beam tables in it. I've never had a desire to go wider than 4' oc and it does get tougher but it is not impossible if that is a big desire. Dad's roofs were often "Plank and Beam". On a number of them there were 2 gable walls and 2 or 3 pairs of beam rafters at up to 12' centers with heavy timber glulam decking on top. 

I'm not sure I'm understanding the log beam question, A log can be designed as a beam and it'll need to be larger as spans and loads increase, same as a sawn beam. log beams are stronger than sawn beams because we aren't cutting through all those strong fibers to create an easy to use shape. 

[akadiesel]

Don P
I'm going to have to reread most everything in the morning with new eyes. The beam question:
Since it's a cabin and by definition logs can be round, sawn rectangular and many other shapes, I have been told that using beams for rafters and such makes the roof a log structure. True or false?

[Don P]

Code-wise, that would be false. The log walls make it a log structure. If you would like to build it without an engineer, stick to the prescriptive log standard, ICC 400 for the parts it addresses. 

The roof, yup I'm glazed over too but I don't believe the log standard addresses the roof. If you use heavy timber we need to find another way. I think we can get there prescriptively using WSDD. 

Or another way to think about that question. What the residential code says in the opening paragraphs is, roughly, that if you follow what is in the IRC it is approved design. It then goes on to say that any elements that are outside of those prescriptions need to be designed according to accepted engineering practice. Then somewhere around chapter 14 is a list of referenced standards and documents, that is "accepted" stuff. That is why I'm looking there for the roof beam sizes. Those tables are prescriptive by reference.

If I put trusses on a stick frame or a log house it does not become a truss house requiring engineering of all elements, only the trusses are stamped. Only those items that are not prescriptive require outside design. 

[Don P]

Let me work over that last thought a different way. I think there is a misunderstanding about how those referenced standards get used.

Use the IRC for any parts of the residence that it can cover. That is your master code, always return to it as quick as possible.

When there is some element that is not addressed in the IRC look to see if there is a referenced standard that does address that portion of the build. For instance I've described foundation elements from the IRC, an IRC floor and then we hit the logs... go to the log standard ICC400.

 At the top of the log wall go back to the IRC if stick framing the roof. With the exception that a ridgebeam is non prescriptive, it needs design. If its an LVL or glulam the supplier will engineer that for free as service of the sale. If heavy timber you or an engineer does the design. You are not a licensed design pro so the BO has to use good judgement, are you within your expertise. In rural NC on your residence, you will get a lot of grace if you present well. 

If you want to use heavy timber up there go to WSDD. Or, another up my sleeve, the AITC standard is in chapter 14, I'm not pulling it out if we can get there easier. If you want log rafters use the log design values from 400. If you want to use milled "logs" for the rafters, those are really heavy timber so WSDD and some conservative measuring of dimensions.

Then right back to the IRC to sheath and insulate, wire, plumb, trim, decks, etc. Even if it is log, the standard only handles those elements... but it is a residence, the IRC is our main code. If we fail to find an acceptable referenced standard or if any of that gets above someone's comfort level, then bring in an engineer.

[Hilltop366]

Question...

Would there be a issue with using a wall or post to support the loft?

Thinking that the log walls are going to shrink in height and the post or support wall is not or very little. I guess a post would be easier to adjust but a wall would be more challenging.

I'm thinking making the entire roof attached to the log walls only would cause less issues later, perhaps some long logs fastened to the walls every 4 to 6 feet or so would prevent spread and still have a "open" ceiling. (with no knee walls) One post under the loft that is adjustable and walls designed with a space at the top for log shrink.

Stair placement in smaller buildings can be tough, it's hard to get enough head room and not have the stairs in the middle of the room or a winder/landing with a turn towards the centre. Something to watch out for.

[Hilltop366]

Another option would be a vertical log building. Here is one that a friend built recently, 16' x 24' it was under the required size for a permit where he lives in New Brunswick.



 

 

 

Not sure how the detail at the bottom of the log is going to work out for rot....time will tell.

He made it with a 50cc chainsaw and a ATV with log arch and bought the 2x rough cut from a local with a band mill for the floor and roof framing. The logs are flattened on both sides.

[akadiesel]

Don P  
 After spending a good bit of time replying to everything, it wouldn't post and I ended up losing it.
 That's pretty much the way I was thinking what codes when, other standards and all.
 After a while I'll get back and I think we need to back up to the beginning for a minute so we see everything the same from the ground up.

[akadiesel]

So some years back I bought an acre near Madison, about 30 minutes from Ruffin, with well and septic on the small part of buildable land.  Not allowed to put my 40 ft gooseneck there and live in it while building something so find a nice place to rent in Ruffin. Love it here. Nice old farmhouse on 150 acres, but got to think something more  permit. Start learning how to use this limited home architect program just for a visual of what we think we'd like. Go to see about a permit and it's not as easy as it used to be we now go by the 2018 Irc. I start reading and learning then go to measuring and crap, better drop down from 38 ft to 36 ft. I only say all this because here is the stress part that entered. There's barely enough room for a storage building much less any kind of shop. I have stuff in West Virginia where I'm from. A lot of stuff. What to do? What to do? Don't see any alternatives but drop a bunch of money in something where I'm just not going to be happy. Only say all that so you'll understand why some of these decisions on building are as easy as they could be! Okay, trying to learn rules and all on beams and such I end up here checking out your calculators. Figure I should join maybe learn more. Make a little post for whatever reason. Never even expecting a reply, I got to say it's pretty mind-boggling where we're at now. Speaks volumes!
  Now looking at my floor plan. Tried to be as simple as possible while keeping the center part of that model home in Mebane North Carolina in mind. So I thought foundation, put up walls to the loft, put in the loft beams, several more rows  of logs, get a roof on and now maybe it'll quit raining??!!  That unknown length and amount of rain, plus a good chance of having to stage all my material there is why I thought to leger the floor in then. So looking at my floor plan, at least in my mind, there are no supporting walls. I was thinking to set them in as thin as possible to accentuate the beams. Or even leave under the loft open and call the loft of bedroom. Not all that happy with the bathroom as is but run the other way the stairs were an issue.  Maybe I need to rethink some stuff before moving up to the roof we're talking about?

[akadiesel]

Don P
  On the bright side, you know what city I'm in. You're pretty close to knowing exactly where to send the bill 🤣

[akadiesel]

Don P
 Rereading some of your posts, a few questions. When you were doing the math to figure out the load on what you termed the heavier 16 or I guess 20 ft heavy length. I would have thought it would have been full length. Is that because you have to throw in the weight of the loft due to the post or what? I know you're right I'm just trying to understand. And somewhere you said no tile in the loft. I didn't catch that meaning

[akadiesel]

Don P
 Reread that and actually you said the longest. Still confused. And you said the 10 lb dead load. I'm curious how you derive that only because I probably misunderstand the proper way.