In this series, local architect and brownstone expert, Brendan Coburn, offers an in-depth look at everything you need to know about historic New York City rowhouses. Here we have a summary of a worst case scenario renovation.
This home presented us with a nearly worst-case scenario for structural degradation. The house has a south facing garden wall which is ideal for gardening and interior sunlight, but was very damaging for the masonry wall on the North East side of the building. The wall literally had no more than gravity holding it up since its mortar had long since turned to dust and its actual bricks were decaying.
South-facing facades are particularly susceptible to degradation due to daily freeze/thaw cycles in the winter and early spring. The wall is heated by the sun during the day, but then re-freezes at night creating a cycle of contraction and expansion. Over the long term, this cycle causes fissures in the mortar that traps moisture inside the wall. Trapped within the wall, the moisture freezes, then expands and ultimately forces the mortar to break down. If left un-checked, the integrity of the wall is destroyed and the damage occurs at an ever-increasing rate. The right way to maintain a brick wall in this environment is to re-point it every 20-40 years, depending on its observed condition. The wrong way is to apply any sort of “waterproofing.”
Check back next week for a summary of your best case scenario renovation featuring a Prospect Heights rowhouse.