10' Walls

Started by georgevacabin, September 22, 2007, 07:40:43 PM

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georgevacabin

Hi John,

Looking at the 14x24 Nash Cabin in the gallery.  They state that 10ft walls were built.  Does this change anything else in the plans if you extend the walls to 10ft?  I like the idea of the extra loft headroom.  

Thanks!

John Raabe

#1
Looking at the early framing pictures of the Nash cabin (near the bottom), you can see that the loft floor is not only attached to the 10' sidewall studs, but has an internal centerline beam supporting 1/2 the loft load and carrying this load to a post in the center of the cabin. This is different than the simple loft of the Little House plans where the loft joists sit on top of the wall plates.

If you did 2x6 wall framing you could use the notched in ledger used in the 20' wide 1-1/2 story cottage and run the loft joists full span to the outside walls thus eliminating the center post. You cannot notch a 2x4 wall for a 2x ledger to carry a loft joist (but you can do a 1x ledger). Alternatively you could attach a 2x ledger to a 2x4 wall with lag screws and either have the joists go over the top or sit in hangers.
None of us are as smart as all of us.


georgevacabin

Hi John,

Thanks for the reply.  My apologies for the newbie questions.   :D

I want to go with the 2x4 framing to stick as close to the plans as possible.  So I think I will op for the 2x(?) ledger attached to the 2x4 wall.  If I understand you correctly, I can build the ledger and then build the loft per the plans? (ie, without the centerline beam).  Is there an image that you could direct me to that shows how this might look?

Thanks for your help and patience!

MountainDon

Changing to the 2x6 walls won't change much except take away 4 inches of interior space. More insulation might be a plus too. Depends upon use  :-/

Just because something has been done and has not failed, doesn't mean it is good design.

georgevacabin

Thanks MD.  

So what does the notched in ledger on the 20' wide 1-1/2 story cottage look like?  I purchased the LH plans.  

Again, sorry if these questions are lame.  I picked up the recommended framing book today.  ::)  Just trying to get things together for kickoff on Thurs.


MountainDon

Here's an example for ya', courtesy of Paul, aka PEG

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1144724922/0

don't worry about some of the flaming controversy further into the post, it's just blather. This is done all the time.
Just because something has been done and has not failed, doesn't mean it is good design.

georgevacabin

Thanks MD (and PEG),

I do remember seeing this thread.  I think that at my skill level (and existing tool level  :D ) I will stick to the 2x ledger with lag screws.  2x what is recommended for the ledger is my next question  ;D.  

Thanks so much for your help.  I'm really excited - although I'm backing off of my expectation of getting the external framing done in a weekend.  Now I'm shooting for four walls on a foundation :D!

glenn kangiser

Looks like PEG let in a 2x6 in the tutorial.

Note that if you don't do the let in you have a couple of issues to deal with.  The 2 x 6 will be sticking into your room.  The lags alone will be less strong - about 450+ lbs each holding strength as I recall.  Holes between joists may be harder to seal.

That said, others have successfully lagged the ledger on.  IMO the let in job is a lot cleaner looking.  The router does a cleaner job but you can do it with the Skilsaw, a hammer and a chisel.  In absence of a chisel you can make the multiple kerfs as PEG showed and knock out the pieces with the claw of the hammer.  

You could try it on a practice piece to develop your skills... or you could just lag it on as you wish.  These are just suggestions. :)

Sorry for degrading his methods, PEG. :-/ :)

"Always work from the general to the specific." J. Raabe

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georgevacabin

Hey Glenn,

Thanks for the feedback.  I think that I would still feel more comfortable using a lag screw.  

Any thoughts on what size ledger should be used if I stick to the 2x4 framing?

Please keep the ideas coming! :D


glenn kangiser

2x6 would give good spacing on 3 screws.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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John_M

I agree with Glen here.  The let in ledgerboard is really easy to do.  And it will look A LOT better when you are finishing the cabin off.

One thing I have learned in building my cabin is that you need to look into the future as far as finishing things off, instead of just "getting things done" right away.  Just some advice, that is all!

Good luck!
...life is short...enjoy the ride!!

georgevacabin

Thanks again for the feedback Glenn/John_M. - point well taken!

MarkAndDebbie

Just to be devil's advocate... (I'm doing the let in ledger - I practiced on my shed's rafters. Using the same technique to cut the rafter so as to let in the outrigger (?? I think that is the right name)). If you use reasonable nice wood, the ledger will just look like trim - think rustic crown molding. Or if you use joist hangers and sheetrock (not my thing) you will have a good surface to attach the ceiling to under the loft.

Glen - if you were concerned about the lag screw weight, could you run the joist on top of the lag bolted ledger and then next to the stud and through-bolt the joist to the stud?

georgevacabin

Hey M&D,

Thanks for the input.  This will not be a primary residence for me.  Mainly a hunting cabin in the fall and a place for the family weekend getaways in the spring and summer.  Not really concerned about the ledger-look.  ;)

That being said, you made me think  :-/ :

Glen - could I do what M&D suggest?  Joist on top next to stud and attach to stud? Sounds doable.  But will it be safe.

Also, in the LH plans where it indicates an open area for the kitchen.  I'd like to close it off for a bedroom.  Would the framed out walls beneath the loft add support?

Thanks!!!!!!


glenn kangiser

#14
Not the lag screw weight, but the amount of weight the lag screw can support.

In round numbers without making me think too hard, wood can support about 1000 lbs per square inch -- allowable fiber stress -- or the allowable pressure on the wood.  A 1/2 inch lag screw inserted into the wood will have a certain amount of it holding but it will also have the outside inch or so pushing down on the wood below.  Figure if one inch long x 1/2 inch wide is pishing down then that is about 1/2 square inch or 500 lbs support load allowed.  This is just rule of thumb stuff I go by to figure loads in my head -gathered here and various places.  3 screws spread a bit and predrilled so as not to split the wood could support near 1500 lbs (actually less - I rounded my rule of thumb figures).

Saying you have a 20 foot wide house - joists on 24" centers - load  40 lbs per square foot, (may not be the right load but close enough for this exercise) - each joist is responsible for 40 square feet of floor - 20 x 2' - so 1/2 load to each side = 10x2'x40lbs=800 lbs plus dead load of about 5 lbs psf so say 900 lbs.  3 screws are good for about 12 to 1300 lbs in actuality -- what would happen if overloaded?  Probably not total failure but maybe split studs - loose joists - creaking - uneasy feelings walking over it.  It may not even go that far considering that things may be stronger than what it is calculated at for failure but could be pushing it.

I'm sure John uses much better numbers than I do but this should give you an idea of the logic behind the reason the let in is better.

...and rereading your post - yes - through bolting is stronger - from my experience of working with engineers on my jobs -- I am not an authority. :)
"Always work from the general to the specific." J. Raabe

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MountainDon

#15
Through bolting the joists to the wall studs as well as having a lag screwed ledger would add definite strength. Keep the bolts through the joists in the lower 2/3 width for best results.

Depending on how you plan to finish the interior walls you could also add a jack stud under the ledger to assist. ?? :-/


Glenn, good "round" numbers.   :)
Just because something has been done and has not failed, doesn't mean it is good design.

glenn kangiser

Anything you add by way of attachment to the stud will add strength - even nailing.  I don't know the figures.

Ken Kern stated -from memory that a 16d nail plain held around 90 lbs but it seems a ring shank or screw nail was more like up to 900 lbs - maybe withdrawal strength -- but - you can't get the shear strength if the nail doesn't hold.

The walls under the loft could add strength but would transfer the load down to the bottom floor which is only supported at the sides -- still all in all one thing stiffens another until it all becomes one strong mass.  Engineers don't always cnsider some of the added strengths of interior walls but their addition of strength cannot be denied.
"Always work from the general to the specific." J. Raabe

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MountainDon

Not to belabor the point, BUT if you do go the lag screw route do be certain to drill the proper shank size hole in the ledger with the appropriate sized pilot hole in the stud. Not drilling pilot holes in all but the wettest of lumber will almost always lead to a few splits here and there. And don't overtighten.
Just because something has been done and has not failed, doesn't mean it is good design.

glenn kangiser

Quote


Glenn, good "round" numbers.   :)

Thanks, Don.  Coming from you, that means a lot to me. ;D
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

MountainDon

#19
 :)
BTW, I don't think there are any published tables of shear strengths for lag screws. Lags are generally ungraded unlike hex head bolts with their varied head markings.

A figure of approximately 60% of the tensile strength would be a point to calculate from for a standard carbob steel screw/bolt. And if I were calculating/estimating lag screw shears I'd use the "minor" dimension, the smaller dimension of the lag between the threads just below the unthreaded shank area. If that's clear?  :-/

JMO

Pumpkin hour, G'nite
Just because something has been done and has not failed, doesn't mean it is good design.


glenn kangiser

May not be - I round that out too --- steel tensile strength about 50000 psi.  Figure the cross sectional area of the screw at that rate -- or another method -- how many 1/2 inch screws will fit into an inch - 4 -- but realizing that they are a bit undersized -no corners as they are round, drop it down a bit.  50k divided by 4 gives about 12.5 k dropped a bit to 10k so I estimate the tensile strength of the 1/2 inch lag to be 10000 lbs.

"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

MarkAndDebbie

QuoteNot the lag screw weight, but the amount of weight the lag screw can support.
;) That's what I meant.  ;D
Both lag screw to hold up the ledger and through bolt into the stud. Through bolt if you are concerned about splitting the ledger with the weight. Just to be clear you wouldn't want to skip the ledger and just through bolt to the stud - especially if you are spacing your joists greater than 24" (doubling them every 4' is an option in the 1.5 story loft plans).

John_C

#22
I've had a Consolidated Dutchwest (Now Vermont Castings) catalytic stove for 20 years.  I bought the smallest one they had and it heats my ~1800 sq. ft. house very nicely. Great stove.  The only problem I ever had was wrestling it out of the pickup truck and into the house by myself.
:)

georgevacabin

Thanks everyone for your replies and great insights!!!

I'm going with:

2x8 joist @ 24"o/c per the plans
2x6 ledger using 3 lag screws (with pre-drilled shank size hole)
through bolts to wall studs (bolted through lower 2/3 of joist.)

Thanks!  

MountainDon

Quote
2x6 ledger using 3 lag screws (with pre-drilled shank size hole)
PLUS pilot holes in the wall stud
Just because something has been done and has not failed, doesn't mean it is good design.