Little House shed roof questions

[moselle]

I'd really like to make a 12x18 (actually 12x16 but that is an easy fix) little house but I want to make it with a shed roof.
What I would like to do is have one side be 2"x4"x8' and the other be 2"x4"x12'.
I am on a very limited budget so:

1. I would like to build up the rafters with 2x6s doubled and spaced either 16" or 24" apart.
Is this possible?

2.On the 12' side, would I need extra support like doubled 2"x4"x12' or 2"x6"x12' or singles are okay?
(I will probably have the entry door and 2 standard windows in that wall)

3.I would like to have a loft over the higher half of the Little House.
Would I use 2"x10" for the loft floor just like the floor joists?
Do I need ledgers or can I just tie into the wall 2x4 studs?

4. If I decide not to have a loft, could I  have the entire space open above without extra support?

[jraabe]

The Little House plans show a shed roof layout although it is not as steep as the one you are wanting. You could frame the tall wall with full height studs at 16" o/c and then attach a ledger (2x4) to this wall at the bottom of the loft joists. Now nail the joist to each stud and toenail into the ledger. This makes a solid connection and stiffens the tall wall. If you don't put in the loft I would still do a joist tie every 4' (which could be a doubled 2x8 to read as an open beam). Most building departments limit the height of an unsupported wall to 10' (without engineering).

I would do single rafters for the roof and make them deeper so you can get in more insulation. That said, your double 2x6 is probably OK (@16").

For a 30 lbs live load and a 12' span my chart shows you would use 2x8 @ 16" or 2x10 @24" - unless you can get select structural DougFir, then you can use a single 2x6 @ 16".

PS - You have probably seen this sketch of the same thing posted earlier: http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1146318321/3#3

[Amanda_931]

Unsupported wall?

does that mean no joists in the loft areas, no similar but wider apart pieces spanning the other areas?

[moselle]

The Little House plans show a shed roof layout although it is not as steep as the one you are wanting. You could frame the tall wall with full height studs at 16" o/c and then attach a ledger (2x4) to this wall at the bottom of the loft joists. Now nail the joist to each stud and toenail into the ledger. This makes a solid connection and stiffens the tall wall. If you don't put in the loft I would still do a joist tie every 4' (which could be a doubled 2x8 to read as an open beam). Most building departments limit the height of an unsupported wall to 10' (without engineering).

I would do single rafters for the roof and make them deeper so you can get in more insulation. That said, your double 2x6 is probably OK (@16").

For a 30 lbs live load and a 12' span my chart shows you would use 2x8 @ 16" or 2x10 @24" - unless you can get select structural DougFir, then you can use a single 2x6 @ 16".

PS - You have probably seen this sketch of the same thing posted earlier: http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1146318321/3#3

I didn't see that sketch but that is exactly what I am referring to.
So Everything I thought is about right.
Thanks for allowing me so much of your time.

BUT, now I think the wife and I and going back to a normal roof.

Here is another question (and I have been wondering this for a long time so it could cover most things)

I can get a good deal on 4x4 posts and I am wondering about the rafters.
If, and I am not sure of this, the Little House calls for 2x4 rafters at a 12/12 pitch on 12' wide could I use 4x4 posts and remove half of the originals?
For example if the original plan allows 2x4 rafters at 12" center could I run 4"x4" posts every 24"?
I am wanting to do a open ceiling exposed beams etc (I have fogotten the style name right now)

The other question pertains to normal or posts rafters, must I have a bird's mouth cut or can the rest on the top plate with metal brackets supporting them?

Can girts lets say 8' up on a 2"x4"x12' be let ins(notched) or that is a bad idea because there is only 2" left of the stud?

Amanda, "Unsupported walls" may mean no crossmember support (ie 2nd floor floor joists) with the entire space open from floor to ceiling.

From what I understand, you should have some sort of crossmember support about every 4 feet after a certain height.

[John Raabe]

I think you mentioned earlier that cost was a consideration. A beam and decking ceiling is quite a bit more expensive than a single rafter system. Just compare what you need to do below.

As a rough rule of thumb you can replace a single rafter system (let's say 2x8 @ 24" o/c) with doubled rafters twice as far apart (4x8 @ 48" o/c). These will be exposed to the interior. Then you cover the beams with 2x6 T&G decking and foam insulation to whatever your core value is for the roof. Usually R-30 which is 6" of R-5/in pink or blue board. Now you can put down roof sheathing (usually with long deck screws or some other way of attaching it to the decking), and finally your roof.

RE: wall framing. I would build a 12' high wall with 2x6 which would allow notching for 2x ledgers. Can you even find 12' long straight 2x4's?  :-/ (If so, a 1x ledger is sufficient if you are also nailing at each stud.)

[PEG688]

RE: wall framing. I would build a 12' high wall with 2x6 which would allow notching for 2x ledgers.

Ah make sure that 2x is only [highlight]net 1 3/8"[/highlight] If you live in the land of anal rentative building officals/ inspectors.


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


G/L PEG
 

[moselle]

Hi John and Peg.
Thanks again for all the great info.

John brings up a great point, straight 12' 2x4s.
A problem indeed!

Peg, I am okay about the anals.
None around here.
No inspectors either.  

Oh, my other question.
Do you guys birdmouth cut your rafters or use a strong tie device on the plates?
(I really would love to avoid the birds mouth cuts  )

Thanks a lot!
This is going to be a great music studio!

[PEG688]

Birds mouths when ever possible , they "lock " the rafters in sort of .  Here in PNW we also use hurricane ties , generally H-1's ,

  or H-2.5 if the H-1 won't fit / work due to other framing members being in the way .

 

 If your in  tornado / earthquake / hurricane arae they are a good thing.  

[moselle]

Peg,
Definitely will be buying some of those and making birds mouth cuts.....whether I want to or not.

Back to the shed idea for a sec.(still up in the air about this final choice.
I looked at John's sketch again.
What height tall wall?
Looks really high.

I did a couple of calcs and came up with a 4/12 pitch on a house that is 12' wide with a 12' tall wall and 8' short wall which would require me to double up some rafters unless I wanted to use 2x12s?
I think rafters came out to around 17' without overhang :-/
Is this right?
I still love the idea of the shed roof because of the extra space, simplicity, no ridge to mess with.
But, now wondering if the cost of the extra long rafters makes it a little more difficult on the pocket book when comparing a normal roof.

Thanks all.

[JRR]

I believe roof loading is determined by the horizontal distance between rafter supports, not the rafter length.  I.E, increasing roof slope does not increase rafter loading.  But I'm a novice, so hopefully others will offer comments.

[Amanda_931]

Steeper roofs ought to shed snow better.  but then they're longer.

You can use I-joist type rafters.  Might be easier for venting and insulation.  But not if you want them exposed.  I think Louisiana-Pacific, among others, makes them

http://www.lpcorp.com/lpstructuralproducts/lprimboard/productinformation/faqs.aspx

[John Raabe]

JRR is right - loading is projected horizontally down onto a roof slope. This is also how rafter spans are calculated. The length of the rafter is not used in these calculations.

Also, at steeper pitches an engineer will use a reduction factor based on the fact that steeper roofs are less likely to hold the load.

[fritz]

John, on your sketch, it looks liek the short wall is 8' and the tall is 16'.  Would you do the tall wall the same way as you describe above, or go with two 8' sections? is 2" x 4" x 16'   16o/c going to work for the tall wall?

[moselle]

Steeper roofs ought to shed snow better.  but then they're longer.

You can use I-joist type rafters.  Might be easier for venting and insulation.  But not if you want them exposed.  I think Louisiana-Pacific, among others, makes them

http://www.lpcorp.com/lpstructuralproducts/lprimboard/productinformation/faqs.aspx

Hey, those are a good idea!
That would solve a lot of problems.
Unfortunately, I can't get them in this area.
I wish I could make them myself, I would.
Darn.

So for the shed roof-normal interior with no rafter exposure, I am back to doubling up 2x6s @ 16" center, being at least 17' long @ 4/12 (this is without overhang ! yikes!:-/....looks basically like 20').
Walls- 12' 2x6 tall wall with a 2x4 ledger @ somwhere around 7', and 8' 2x6 short wall in rear.
Any more ideas/comments/tips are welcome.

[moselle]

edit: I mean about 12'7" without overhang.
(don't know where that other number came from.

[John Raabe]

Fritz:

What I don't show in the quick sketch is that the joists for that platform loft (at least some of them) are best if they work as tie beams over to the top of the other wall and lock the sidewalls together. If you did these every 24" that would be enough integration to allow you to platform frame the tall wall in two stages using 2x4 studs.

[Amanda_931]

and I think that that answers my question

(yes, it was a question, even if it didn't sound like one--Can you frame a shed roof as a pair of kneewalls?  with a loft, occasional joists as collar ties between them??)

[fritz]

Hey all, this is a little deja vu -- and a tie to a couple of threads.

First off, I built the deck for the cabin last fall (deck is 16' by 44')   very sweet.





I started and finished the floor(s) for each side of the dog trot last week.  (As a side note, the local farmers used to call my place "the two ponds".......it's now know as "the deck" ...... as in, "what the heck was that feller thinkin' when he built that deck so far from the pond......"

Anyway, I've settled on the opposed shed roof design .. ending up with an approximate 12:5 pitch 14 foot high wall and 8 foot low wall.  The open area with be a gable roof that matches the pitch on the opposing sides.




QUESTION:

I think I understand what I'm reading here and in the other threads, but to support and tie together the tall and short walls..... it seems the options are a loft OR tie beams every 24" or so.  So if there is a 6 foot loft at one end..... (loft joists 16" o/c toe nailed to ledger and nailed to studs....is that enough ....or do I also need to put some tie beams at the other end?

Related threads:

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1134788948/0

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1146318321/0

I'm still very open to ideas and any suggestions...I've visited this site off and on since ...well a very long time ago.  I learn every time I visit.


I'll work on some photos......

[glenn-k]

Some of John's plans go to bracing every 4' where there is not a loft.  

Shed roofs don't always require the ties when short walls are used  as they don't have the outward forces of the gable roof, but in your situation the tall wall is going to make this into a big sail so I would want them.  I would also want to semi-balloon frame the tall wall for strength.  These are just my thoughts, and you should wait for the pros to jump in here.  I am a steel guy and am familiar with bracing and rule of thumb ideas for forces.    

Other than that I know nothing....... nothing.

[jraabe]

Yes, I will stick with what I said in 2006. Tie the walls together with joists that sit on a ledger AND are nailed into the full height studs on the tall wall. These should be a max of 48" o/c but could be less depending on your stud layout. Where you want a loft, double these on each side of the stud and use an interior spacer joist to end up with a built up beam that can support your decking.

[fritz]

thanks, both for the information -- and the walk down "Hogan's Hero's" memory lane.

[glenn-k]

Where's that stuff come from anyway? :-/

Guess I'm just crazy.