Little House Plans Question

Started by MountainDon, February 04, 2008, 09:28:44 PM

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MountainDon

This is directed specifically to John, but anyone's comments, ideas, etc are welcome. This is a somewhat odd query from this sometimes odd builder.  ::)

I have 2 questions basically; one with reference to floor joists and the other to ceiling joists.

I have the Little House plans and all along have been planning on a 14' wide version, using 2 longitudinal 6x12 built up beams as the main support girders. Some recent developments here are making us wish to increase the width slightly. I know that wider usually, if not always, means a change to the foundation; moving the main beams out under the long walls and likely including a center beam as well.

However, all I need is an extra foot, making it 15 ft wide. Yes, I know that's a seriously weird number when it comes to construction, but that's okay. Here's what I'm thinking...

Use the same two - 6x12 built up beams, as the main supports.

[1]
Place them 13 ft apart, at their centerline.
Use 2x10 floor joists mounted on top of the beams (wanted for insulation value, R30, as well as stiffness)
The joists would be trimmed to 14'9" to make a 15' wide at the outside of the rim joists.
(my deflection calculator says the above would be okay)

3/4" T&G sub flooring
2x6 wall studs, 8 ft, @24" OC (1x interior wood walls and 7/16" OSB exterior sheathing with 1x siding over)
NO loft. That would eliminate the loft loads from the long walls.

Probably a 5:12 or  6:12 pitch roof; 7/16 sheathing with 26 ga. metal roofing over top.

[2]
the same calculator indicates that 2x8 (24" OC) ceiling joists might be ill advised with a 15 foot wide cabin design.  ?
I could go to 2x10's in that case.
The ceiling would likely be 1x T&G on top of or below the joists.  :-\
Blown in cellulose ceiling insulation of R30 - 38

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

John Raabe

I see no reason to challenge your 15' extension of the Little House. The deeper floor joists could handle both the cantilever and the extra roof loads as well as the interior 12+' joist span. Your girders are loaded a bit more heavily perhaps, but would be plenty strong and should have little deflection. This is especially true if you do not have extensive loft loads. 
None of us are as smart as all of us.


MountainDon

#2
Thanks, I was thinking it wasn't an overly large change, considering the joist size upgrades and an actual reduction in the cantilever amount, plus no loft loads.
K will be happy, so I will be happy. :)
Just because something has been done and has not failed, doesn't mean it is good design.