These dramatic images show a house jacking project in the Cambridgeport neighborhood of Cambridge. The intent here is to raise the house high enough to provide a liveable space in the basement area, one which complies with state and local codes for headroom, safe access, natural light, ventilation and drainage. All of these requirements are specifically addressed in the Code.
To this end, the house is cribbed up 16 feet above the bottom of the excavation. The accompanying video shows the footing being poured, and gives a sense of the volume of concrete necessary. The concrete foundation walls themselves will be an additional 10 feet in height above the footing. The difference in height represents the clearance required for the work to be done.
Historically, the City of Cambridge has maintained local codes that are considerably more restrictive than the state code for development of occupied basement spaces. This is because much of the City has a high water table, drains poorly and is prone to flooding and sewer backup. This includes parts of Cambridgeport, East Cambridge and in North Cambridge, around Fresh Pond and Alewife Brook.
Recently, there has been pressure on the City to allow more basement development due to the high demand for housing, affordable or otherwise. Over the last few years, the City Council has passed a series of resolutions, loosening restrictions on single family and owner occupied dwellings. The stated intention of the changes was to permit the conversion of cellars into “accessory unit” apartments, enabling families to grow, host elderly parents or to earn rental income that can help them stay in the City.
These are worthy goals. However, just because it is legal, and in compliance with code, does not mean that it is without risk, if you happen to be in a flood prone neighborhood. Floods don’t happen until they happen, and when they do, they can be devastating. Each project should be modeled individually, to consider the likelihood and the cost of the worst case scenario.