masonry/wood structure shearwall combination & code requirements?

[eng003]

This may be difficult to describe without a sketch but I do not have one handy so here it goes: I have an existing 2 story old wood framed structure to which a one story cmu masonry addition was added. On about 50% of one of the addition wall was the original wood frame 1st story wall. Client wants to add a second story on cmu addition. Addition originally designed with flat minimal slope roof trusses for 40 psf live so adequate for floor loads. Roof currently used as deck area and masonry was extended up as railing. They want to continue up with block but now I will have a two story block structure with one shear wall line being a combination of masonry then original old wood construction?? then a tiny segment of masonry. I seem to remember asce 7 having comments about using a wood shearwall for resisting masonry but maybe this was just for seismic?? I have not seismic but high wind. Thanks for any advice!

 

[CELinOttawa]

This will be unlikely to have been designed properly. High wind is similar to seismic in that stiffness matters. Your CMU walls are far stiffer than the old wood, and thus must take the whole of the load. Now it will also have to take the new loads as well as everything already assumed.

You can hope that you have ungrouted masonry, since whatever you have is likely insufficient. That way you can do whatever you want in terms of reinforcing the existing and work out a standard existing lap anchor for retrofit situations (there are a couple of okay examples available online).

Effectively you're going to become the EOR for everything involved. Check, retrofit, replace or substantially upgrade all of the following:

- New to existing roof joint
- New to existing foundations (you'll likely need bigger than you already have)
- Existing CMU to existing old timber (ensure connection can transfer the loads involved)
- Existing CMU to New, as well as to new floor
- New floor to existing timber system/roof

ASCE 7 I believe is the yank load code for this situation. Best of luck.