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Re: 2nd floor addition

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Dear Gary,

There are several things that you will need to check into.

1.  The existing footings almost certainly will need widening to support
the additional load.
2.  There is no good way of extending the first floor studs up the extra
foot  without bracing the wall at this point.  Might as well take the
existing studs down and install new wall and anchor bolts (number as
required) and holdown bolts into the foundation. This may have
implications for addition versus new construction, I believe some
municipalities consider remodels over a threshold limit as new
construction, and all items need to conform to current code.
3.  Joints in shear walls can occur at other than the plate lines, solid
blocking is required.
4.  Make sure there is room in the plywood sheathing for shrinkage at
the second floor joists.
5.  If in seismic zone 4, you may want to follow City of LA requirements
about shear wall reductions, and use of 3x members at sills and vertical
plywood joints.

Hope this helps.

Patrick Rodgers

GaryD wrote:

> Another simple question (probably) all the wood design experts. I
> thinking about the best way to approach an existing 1 story house that
> is getting a 2nd floor addition. Normally, I would assume that the
> roof gets removed, floor framing is placed, and the 2nd floor platform
> walls will sit over the lower walls just like in a new house. I have a
> situation where we are required to raise the original lower floor
> ceiling height from 8 ft to 9 ft.What are the various methods to
> achieve this? I was thinking that simply adding cripple studs would
> not be good to make up the 1 ft difference because I would be relying
> on a 1 ft strip of plywood when I was taught not to use plywood with
> less than 24" in shear panels. To complicate things, the 2nd floor
> ceiling height is 10'-6" so I would have another joint since I believe
> plywood is only available in 10' max sheet sizes. Thanks for any
> comments . Gary


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