Is it acceptable to close the top of a cavity masonry separating wall with blocks laid flat bridging the two leaves?
There should be no rigid connection between the leaves of an RD cavity masonry separating wall other than an appropriate foundation and appropriate wall ties. It is therefore not acceptable to use blocks laid flat to close the top of the cavity masonry wall, either where spandrel panels are proposed or at the roof covering. A flexible closer, such as mineral wool, should be used to close the cavity such that there is no rigid connection between the wall leaves.
