building separation

huangyhg

building separation
per ibc 2003 sec. 1620.4.5, srss method is used to check separation of adjacent structures, to avoid seismic pounding. i have a new building being constructed next to an existing urm building, and no plans are available of the existing... does anyone have advice on how to rationalize a reasonable delta-m for the existing structure? can it simply be based off the ibc allowable drift limits for a "masonry shearwall building" (ie. 0.007hsx)? obviously hoping for an easy method, to avoid in-depth analysis of the existing structure. this situation must come up all the time in downtown areas(?)
thanks!