16 x 32 - Starting Out Questions - General

Started by Ross R, May 07, 2010, 09:54:54 PM

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Ross R

Still in the starting stages of planning and I have a couple of questions.

Planning to use the Pier / Post foundation.  Do I have to use treated lumber for the Beam and for the Floor Joists?  I have read of the issues others have dealt with surrounding green treated lumber and it's tendancy to twist etc.  Are there ways to avoid these issues when using green treated lumber?  Also - If I use green treated 2by material and plywood to build my beam are there "constuction adhesives" that work better than others with green treated materials?

I plan to put a metal roof on with purlions running across the rafters.  I would like to close foam insulate the entire roof - does this create any potential "moisture issues".  I am planning to spray foam the entire cabin if I can afford it.  My neighbor sprays the stuff and he is a great guy to work with.

I would like to put up 12 foot side walls and a loft on each end similar to Rob LeMay's cabin.  My lofts may be a little bigger - about 10 - 11 feet.  What are the pros / cons of building with 2x4 vs 2x6 stud walls.  I hate to lose any floor space but if 2x6 add significantly to the overall stability and strength of the cabin that is the way I am going to proceed.

Last (for now anyway) How critical is it to not put any doors or windows in the first four feet of the corners of each wall?

Thanks to all for your guidance.

NM_Shooter

There have been many posts on this if I remember correctly.  I think that if you are 18" or further from the ground, PT wood is not required.  Keep in mind that special fasteners must be used with PT wood. 

-f-
"Officium Vacuus Auctorita"


MountainDon

 w* Ross


The IRC2006 requires PT lumber for beams when they are closer than 12" to the ground. For joists or the bottom of a floor the distance is 18". For ease of underfloor access I would want that as a minimum.

Sprayed in place foam would be great for the under floor area. Also great when sprayed on the underside of the installed metal roof.

I personally believe there is more to be gained with 2x6 walls than the lost floor space.

As for the taller side walls and loft floors, have you given thought to how the roof will be done along with this to control/eliminate the outward forces on the sidewalls? 12 foot high walls with 8 foot lower floor ceilings (to the loft floor) will have large outward forces on the side walls. A ridge beam instead of a ridge board would help with that. That does require proper gable end supports for the beam. Special built trusses can also handle the job.

Codes require brace panels every 25 feet (??) I think. I'd have to check on that. They do not necessarily have to be at the corner. Extra tall walls, ten or twelve foot will require wider panels. Structural OSB or plywood fills the bill. In special cases narrower engineered panels can be used to open up more wall space. I'd look up the code but am short of time right now. However you can find links to IRC codes in the Referral Links section.
Just because something has been done and has not failed, doesn't mean it is good design.

Ross R

Thanks for the information.

Sounds like I may be better off / safer with 8 foot sidewalls- loft floor - and then 4 foot kneewalls in the loft.  Will this take care of the outward pressure concerns on the walls so that I put a ridge board roof on the cabin?

John Raabe

A platform framed knee wall will not be much help with the rafter thrust. A balloon framed loft can help by using the loft joists as a tension member to resist the outward trust of the rafters but most jurisdictions will not let that be the only balancing force. You need to have rafter ties or a truss configuration such as shown in the 20' wide 1-1/2 story cottage plans. Such a configuration is also in the 16' wide studio house that is part of the Victoria Cottage plans.
None of us are as smart as all of us.


Ross R

John,
So if I am understanding you correctly as long as I follow the rafter guidelines for the Studio House that comes with the Victoria plans I should be fine with 12 side walls and my lofts as outlined above? 

I have purchased the Victoria plans and am using the Studio House plans as my guideline.  I was planning to beef up the floor joists and beams a bit since my lofts will be larger.

Soil issues.  So far I have dug down about 2.5 feet and I am in clay.  The lot 200 feet away is sand.  Think I will get lucky and hit sand on my way down??  Here's hoping!!

Thanks
Ross

Rover

RE 4" or 6" studs.
One advantage with 6" studs, is that it can be sprayed first and then there should still be space in front of the insulation to drill and rough-in your electrical. 

Ross R

Thanks

Planning to go with 2x6 studs 16 inch on center.  Seems the pros out weigh the cons for strength and stability.