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additional story over Existing 4" masonry + 4" brick wall for residential building

additional story over Existing 4" masonry + 4" brick wall for residential building

additional story over Existing 4" masonry + 4" brick wall for residential building

(OP)
I would like to get some opinions on existing residential single family dwelling unit.

It has 8" CMU walls in basement and embedded 2X joists and 4" CMU + 4" brick above at first floor. Now owner wants to put additional story (second story) on it. In this case what is the best solution?

Also sometimes existing 8" plain masonry walls will not satisfy lateral earth pressure requirements per code.

Any opinions are appreciated.

thanks in advance.

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

To me, it would depend on whether I felt the 4" block and 4" brick were acting together as a multi-wythe wall. If there are row lock courses or if it's constructed with a solid collar joint, I might feel okay treating it as an 8" masonry.

For buildings in the US, refer to the empirical provisions in IRC R606.2.1, "The minimum thickness of masonry bearing walls more than one story high shall be 8 inches (203 mm). Solid masonry walls of one-story dwellings and garages shall not be less than 6 inches..."

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

If it is 4" of masonry veneer tied to 4" of CMU, no to the addition.

Mike McCann
MMC Engineering

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

(OP)
Well,

I think the way I see is, if additional 2x6 wall can be built inside that goes all the way down to basement footing in that case exterior cmu+brick will become just veneer. it will require flashing at top where second floor starts and 1" gap between existing masonry and new 2x6. So all new load will not get transferred to existing masonry. Also there are helifix retrofit ties that can be used as brick ties to new stud walls.

In the basement 8" CMU is there where additional 6" solid CMU and additional footing (widedned by epoxy grouting rebars to existing footing) which will get additoinal strength to foundation wall.

Looking forward to extend this discussion and thank you all for chiming in.

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

So then, do you intend to take all the new lateral and uplift forces through the same new stud wall?

Mike McCann
MMC Engineering

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

(OP)
Yes. The new 2x6 wall will have sheathing to resist lateral forces(panelized construction)and will be anchored down to footing at basement slab level.

The existing one story masonry wall which was supporting roof will be braced at top with clip angles at top of each studs and it will become just veneer and supporting self weight.

This way i am not transferring any new load to existing structure and new structure is completely self dependent except for footing which i will be enlarging.

RE: additional story over Existing 4" masonry + 4" brick wall for residential building

That's not a bad plan as long as the new structure is designed with the existing as a veneer. Anytime I've tried recommending something like this it gets tossed out due to the floor space loss.

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