Author Topic: MO 20X40 Cabin  (Read 4123 times)

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Offline NathanS

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Re: MO 20X40 Cabin
« Reply #25 on: October 07, 2017, 04:54:46 AM »
This one stuck with me - 90% of walls with no overhang in British Columbia have water damage vs 25% with 2' + overhang.


Wall problems as a function of the overhang size from a field survey.


https://buildingscience.com/documents/digests/bsd-013-rain-control-in-buildings

Offline retiredmarine

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Re: MO 20X40 Cabin
« Reply #26 on: October 07, 2017, 06:35:09 AM »
Don,  Your full of good news!  LOL  But your right, you and AK said the same thing before.

 
If you are going to do it Cape Cod style put a common truss on the ends and balloon frame to the ceiling chord of the truss 


Does that mean frame the wall like normal but then frame up from the top plate to the ceiling chord of the common trusses?

Ok so I'll rethink the overhang (thanks Nathan for the graphic).  What's your preference drop trusses or notched? If I did the overhang is there some sort of architectural guide as to the size based on the building or is just and "eyeball" thing?

Offline Don_P

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Re: MO 20X40 Cabin
« Reply #27 on: October 08, 2017, 12:55:19 AM »
Does that mean frame the wall like normal but then frame up from the top plate to the ceiling chord of the common trusses?

Here is the rule, understand and memorize it;
A stud shall run unbroken between points of lateral support.

That vertical stud runs as one single stick from floor (lateral support) to ceiling(lateral support). There is no top plate running through space. Can you get away with building it wrong, yup, usually! is there any reason to build it wrong, can't think of one.

The points of lateral support are sheathed planes, beams... stiff elements. When I run into a hinged wall I've built a "plant shelf", a horizontal beam a number of times to provide some lateral support, I've also embedded steel plate in between the plates... that really doesn't provide that much stiffness at these widths unless it gets very heavy. point is, that is the tough way, trying to fix a floppy wall. Don't build it, run the studs solid between rigid planes.

The only downside of framing a tall wall is stud lengths, I suspect you are getting above 16' for a few in the middle, not the end of the world. Generally when the wall is getting special order studs tall the engineers start drawing 2x8 studs... hey if it was easy anybody could do it  :D

You can loft the tall wall out on the floor. Getting even more basic, I've also slid the last truss over to beside the wall temporarily. Screwed my dropped top plate to the top chord, measure stud by stud and build it right there. then unscrew and slide the truss over to layout.

There was the time Michelle and I were lifting a tall wall we had built on the floor. As it was rising against some serious local gravity and we were walking it up the true physics of the situation started to become crystal clear. We were going to get overbalanced and this thing was big enough to treat us like bugs. Happily I heard the crunch of gravel. We got our new recruit to grab a push stick and heave against the top plate and up we went.  The next day we decided to frame the opposite wall in place  d*. anyway, something to be mindful of as heavy things get about 2x your height and more.
« Last Edit: October 08, 2017, 01:36:01 AM by Don_P »

Offline flyingvan

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Re: MO 20X40 Cabin
« Reply #28 on: October 08, 2017, 06:13:46 AM »
That brings back memories..

   







     The wind howls through here and that wall is basically a giant sail.  It doesn't budge, creak, or vibrate even in the strongest windstorm. 

Find what you love and let it kill you.

Offline retiredmarine

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Re: MO 20X40 Cabin
« Reply #29 on: October 08, 2017, 08:16:54 AM »
That's one tall wall flyingvan...  Yea I checked the code and looks as though the gable ends will have to be 2X6s and without my own "Michelle" its going to take a bit of work..  Sounds like some Egyptian ingenuity  will be needed in the form of levers and a fulcrum. Guess I'd better call the truss folks too and add two regular trusses and eliminate those "bad sail" trusses.

HOLD EVERYTHING...  If I use two more standard trusses and frame up to the bottom chords it looks as though the center stud (the highest) would be a stud around 13'.  The bottom chord is a bit less than 5' high and with an 8' wall that means I may be able to get by with 2X4s.  and I can place the truss and frame up to it.Why do I have the feeling that Don is reading this saying.. "Duh, i told you that to begin with"?


What say you folks about the overhang? "What's your preference drop trusses or notched? If I did the overhang is there some sort of architectural guide as to the size based on the building or is just and "eyeball" thing?"
« Last Edit: October 08, 2017, 08:38:12 AM by retiredmarine »

Offline NathanS

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Re: MO 20X40 Cabin
« Reply #30 on: October 08, 2017, 10:20:27 AM »
if i am following everything, dropped gable wall 3.5 or 5.5 inches with 2x4 or 2x6 outriggers is much superior to notching out a rafter.

The wood frame construction manual stops prescriptive code at a 2' overhang, Don gave me great advice on my roof for all of this by the way, I am basically regurgitating things he has told me to do last year. I did standard rafters, 16" on center. I skipped the first inboard rafter and doubled the next, that way my gable overhang was 32" inboard and 24" out, more weight resting on the inside.

I have some pics in my thread on how I framed my 2' overhang and Don has an old thread where he does it too.I

In terms of looks.. Drawing on sketchup is a good start. At the eaves, a 12-12 is going to put the end of the fascia at 2' below the top plate, id make sure it doesn't cover up the Windows in a weird way.

Offline retiredmarine

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Re: MO 20X40 Cabin
« Reply #31 on: October 09, 2017, 12:20:01 PM »
Nathan,  Great build you have there, and lots of very useful information.  It was a lot of fun to walk though your build post by post - Thanks! Now I have no data to support my thought here but hear me out.  I would think that notching the outside rafter or even notching the first two would help on any potential hinging the gable wall might want to do.  I think this because you'd have more of the overhang and truss surface to nail together with instead of toe nailing the overhang on the first truss.  Again no data, just a thought.

Definitely going to replace the "new" end truss and just go with 2 more standard trusses and frame up to them.  Of course that means I need to decide if I'm going to notch or have the dropped 3.5".  decisions decisions.  Also I think a 12" overhang should be sufficient.   

Offline NathanS

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Re: MO 20X40 Cabin
« Reply #32 on: October 10, 2017, 03:34:25 AM »
Working with trusses, there isn't really anything that's safe to notch. I think for the overhang it is pretty mandatory to frame the double top plate of the gable wall 3.5" low.

You can't use standard trusses for that reason, and you can't notch anything out. Engineering aside 2x4 is already a pretty small piece of wood. I am pretty sure if you have the truss company make you a truss dropped 3.5" the bottom cord needs to be in plane with ceiling so that 'hinge' is well braced. Personal opinion, I am not sure that is going to save much work in terms of framing out the gable wall.

As an aside I don't think that notching a rafter for outriggers does anything but weaken that piece of wood. A couple nails vs the amount of torque created from that hinge point to notch... it's probably like breaking a toothpick.

Offline dablack

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Re: MO 20X40 Cabin
« Reply #33 on: October 10, 2017, 04:15:38 AM »
On the first house, I built the barge rafter as a ladder assembly.  The gable end truss was full height and the barge rafter depth was about 16".  No notching.  It was nailed outside of the gable wall and the 2x4s were vertical to fight the droop.  I made sure the plywood sheeting crossed over the hinge point to help support. 

On the 2nd house, the gable end trusses were 3.5" shorter.  Again, I built the barge rafter assembly on the ground and it looked like a big ladder.  Used my electric winch to pull it up on the roof upside down.  Attached them (upside down) to the inboard full height truss with hinges.  Then I just lifted them and then fell into place.  This time I had 18" overhang.  To lock the gable end truss to the 2x4s crossing the top, I used Simpson Strong Tie H1Z ZMAX Galvanized 18-Gauge Hurricane Ties.  They worked great and no notching required.  This was all a one man job.  Let me know if you want some pictures.  I will find them and link to them in one of my old threads. 

Austin

Offline retiredmarine

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Re: MO 20X40 Cabin
« Reply #34 on: October 10, 2017, 12:41:49 PM »
Nathan - Sound logic, thank you.

Austin - Yes please I'd enjoy seeing the pictures of your "upside down ladders"  ;D

Offline Don_P

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Re: MO 20X40 Cabin
« Reply #35 on: October 10, 2017, 02:38:06 PM »
This is a sketch I had,



Edit, I must even hate to draw blocking... there should be blocking in between each pair of lookouts over the wall, I see I drew in one and left it up to you to do the rest  :D

Offline dablack

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Re: MO 20X40 Cabin
« Reply #36 on: October 11, 2017, 04:01:52 AM »
Here is the "ladder" built upside down. 



Here I am winching it up on the roof.



Here is how one of the hinges look once the assembly is in place.  You line up the assembly upside down and mark the house and barge rafter, then scoot the barge rafter out of the way and attach the hinge to the house, scoot the barge rafter assembly back in place (on top of the hinges) and attach the hinge from underneath.  I think I used three hinges to be safe.  Then lift and flip it to the outside of the gable end wall.  HA!  Easy. 



This first one, was built a little rough.  The next three were all ready trimmed and finished so no work in the air was required. 



Austin


Offline tugdor

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Re: MO 20X40 Cabin
« Reply #37 on: October 12, 2017, 08:39:52 AM »
dablack, that's brilliant. Tucking that away for future use.

Offline retiredmarine

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Re: MO 20X40 Cabin
« Reply #38 on: October 12, 2017, 12:49:12 PM »
New end truss!!  The designer was pretty embarrassed when I told them they needed to relook at the end trusses.



I'll frame up from the floor, its not that high.

If I had them built dropped then the heels would have to had to come up... more wood.. more cost.. more weight.  No problem thanks to Austin I'll be building the overhang as an "upside down ladder"!!  ;D