In Cottone v. Zoning Hearing Board of Polk Township, 954 A.2d 1271 (Pa. Cmwlth. 2008), the Court reviewed and restated the principles regarding merger in this Commonwealth: In general, mere common ownership of adjoining properties does not automatically result in a physical merger of the properties for zoning purposes.... On the other hand, adjoining properties under common ownership can merge when a zoning ordinance provision causes one or more of the adjoining lots to become undersized, depending on the facts and circumstances of each case.... The focus of the inquiry is upon: (1) when the properties in question came under common ownership and (2) the effective date of the applicable zoning ordinance. Adjoining lots under separate ownership before a zoning ordinance enactment makes the lots too small to build upon are presumed to remain separate and distinct lots. Should those adjoining, undersized lots be thereafter acquired by a single owner, the burden is on the municipality to show that the new common owner has merged the two lots into one.... Otherwise, the result would be to permit separate development of each lot by any person other than the common owner.... On the other hand, lots are presumed to merge as necessary to comply with a zoning ordinance's lot size requirements where they are under common ownership prior to the passage of the ordinance. It is the landowner's burden to rebut this presumption by proving intent to keep the lots separate and distinct. ... In doing so, the landowner's subjective intent is not determinative; rather, there must be proof of some overt or physical manifestation of intent to keep the lots in question separate and distinct. Id. at 1275-1276. Lots under separate ownership at the time a zoning ordinance is enacted that makes them too small for building are presumed to remain separate. Lots under common ownership at the time zoning is first implemented are presumed to merge, as needed to conform to the zoning ordinance. Further, it is the landowner's burden to rebut the presumption that undersized lots have merged by operation of the zoning ordinance.