Framing question for the 1 1/2 story

Started by duglyuckling, July 09, 2008, 11:19:04 PM

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duglyuckling

We have started framing our 1 1/2 34' cabin using 10 foot sidewalls on Mayne Island in the Southern Gulf Islands of B.C.  Can we frame the gable end walls at the same 10 foot level and construct and stand the gables on top?  We are using an engineered ridge beam supported by a post running up adjacent to our partitioning wall. Does building the gable end walls in two parts cause any concerns such as a hinge point issue?  This is important because the gable end walls support the beam which supports the structure.  The beam is actually in two parts - a 3 1/2 x 16 23ft section, and a 3 1/2 x 9 11 ft section - which join at the post.   Our building inspector would not allow us to use the site built trusses unless the project was engineered, so we switched to an engineered ridge beam which seemed to make him happy, and saved us both time and money.  The reason for the question is that it seems simpler to build this wall in two pieces - the weight of the wall is far more management, and maintaining square seems that it might be more straightforward.

John Raabe

Yes, you can frame the gable end walls with the same 10' studs as the sidewalls. The project below (with the site built trusses) has the same famed gable walls you would do. Since you have a beam bearing point in that wall you will want a solid built-up post (three or four studs) with solid bearing all the way to the foundation. That means blocking at the floor system to get the loads to the sill plate and heavy headers if you have a window or door opening under the beam.

None of us are as smart as all of us.


duglyuckling

Hi John:
Thanks for the quick response.  Just for clarification, our design in gable wall is - engineered beam supported by built up post going to heavy header (3 2x12's with CDX plywood) over 40" wide window supported by double 2x6 cripple studs going to another heavy header over 74" French doors to sill plate (made of dbl 2 x 12's).   The foundation is post & beam (all concrete) with a pier centred directly under the engineered beam.  I guess the question is - should we add piers under cripple studs at sides of the French doors or (and I'm probably dreaming) would the load have dissapated and be carried by the rim joist?  The built up post supporting the beam at the partitiong wall carries through to a 24x24x8" cement footing pinned to solid rock.

John Raabe

I've said it before, but I do not feel comfortable redoing modified engineering for plan changes. There are just too many ways to make an error of visualization or other misconception, not to mention the fact that I can't know the local conditions and local codes. To be safe you should go back and check this with the engineer who did the ridge beam design.

The post and pier foundation layout in the plans is designed for a gable end wall that is not load bearing as it carries only half the load of a normal 24" rafter bay and the weight of the wall framing. The site built trusses carry all the roof loads to the sidewalls. You have a pretty hefty point load coming down the gable end walls.

If you want a non-engineered opinion I would suggest a triple built up joist/beam supported by 2 piers (at third points) rather than the single pier at mid-span. That will provide a beam and pier loading about equal to the sidewalls and a stiff enough beam (from the nailed together joists) to carry the point loads to the piers. Of course, you probably already have the single pier installed at the center of the span. ::)

Best wishes on this.
None of us are as smart as all of us.