The Supreme Judicial Court of Massachusetts found there was no clear answer as to whether water accumulated on a roof is or is not "surface water" in the context of insurance policies. The case is Zurich American Insurance Co. et al. v. Medical Properties Trust Inc. et al, 2024 Mass. LEXIS 289 (Mass. 2024).  

A severe thunderstorm dumped heavy rains on Norwood Hospital, flooding the basements of two buildings and accumulating on the parapet roofs. The accumulated water on the roofs seeped into the hospital itself and caused interior and property damage. Medical Properties Trust, Inc. (MPT), the company that owned the hospital, and Steward Health Care System, who leased the property from MPT, both sought coverage from their commercial property insurers. MPT had a policy with Zurich American Insurance Company, and Steward had a policy with American Guarantee and Liability Insurance Company (AGLIC). Each policy stated that a "flood" included "the unusual and rapid accumulation or runoff of surface waters" (emphasis original). Each policy also contained a specific sublimit for flood damages. 

Both MPT and Steward each filed a formal proof of loss for more than $200 million, well over their respective flooding sublimits. The carriers decided, and the insureds agreed, that the damages in the flooded basements were subject to the flood sublimits. The carriers also claimed the water accumulated on the roofs was "surface water," meaning those damages were subject to the sublimit for flood.