NYC Townhouse Structure Sistering Joists

by | Last updated May 31, 2020 | Published on May 8, 2016 | Renovations, Townhouses

When renovating a townhouse in NYC you can find hidden or unknown structural problems that can require structural repairs such as sistering joists and the installation of new joists, headers, and trimmers.


In this post we will look at two townhouses we renovated each of which need structural work. One was a townhouse renovation in Manhattan and the other was a renovation of a Brooklyn Townhouse.


Manhattan Townhouse Fire Damage

We were working on a small interior renovation of a Manhattan Townhouse when we found some unexpected issues during construction. When the contractor removed all the plaster from the ceilings, we found fire damage. The previous owner did not inform the new owner when. See the picture of the burnt structural joists below.


Townhouse Renovation fire damage

Townhouse Renovation Fire Damage Joists


Fire damage repair is serious business and needs to be handled properly. These burnt joists are a problem and would either need to be removed and replaced or sistered.

Sitering Joist

What is sistering joists?

Sistering joists is the process of placing a new joist next to an old joist as additional support. This is a structural reinforcement where you add sisters to the original structure as opposed to replacing weak or damaged joists.

The upstairs floor was severally unlevel requiring resetting the floor. Additionally, we found one joist that had a large structural crack that we also sistered.

If you would like to read more on the subject of fire damage repair we have another post you should see: Fire Damage Restoration NYC.


Townhouse split joists

Townhouse Renovation split joists

NYC Townhouse Structural Repair 

As we conducted structural work, we corrected a dip in the floor at the location of the burnt joist. We did this by jacking up the existing joists before connecting it to the new joist. Caution when doing this. As Newton’s third law states “every action has an equal and opposite reaction.” The joists above needed to be jacked, but the floor below was a wooden joist floor. By putting the jacks on the floor and pushing upward, we would also equally be pushing downward. New structural damage could emerge from this action, possibly inflicting hazardous conditions. We had to install a new temporary beam. (See the picture below) to use as a support for the jack.

Townhouse Structural Repair

Temporary beam for jack (joist resetting and repair)


Installing the temporary beam allowed us to use it for the jack. We didn’t care how much we bent the beam, because it wasn’t going to stay. New beam pockets were put in the wall as temporary supports. The beam pocket was later refilled with bricks. We kept all the bricks that where removed. We also made new beam pockets for the new permanent joists. Once the new joists were installed, we bolted them to the existing joists. (See the final product below.)

Townhouse Joist repair

Sistering joists in the Manhattan townhouse renovation


Pleasant Surprise

The general contractor was removing all of the interior plaster from the walls down to the brick. As he removed the plaster on the wall facing the street, he discovered an original stained glass window likely around a century old with original wood framing in practically pristine condition. (See photo above.). At some point the original brick facade had been covered with stucco covering the window from the outside. It had then been covered with lath and plaster on the inside. The work must have been done when the front stoop was removed many years before. We can only speculate why the window had been covered on both sides. It was a great find and the homeowner was certainly thrilled.


NYC Townhouse Original Window

NYC Townhouse Original Window


Always plan ahead for contingencies when renovating

While you can come across great finds while renovating a landmark townhouse, you can also encounter unexpected work such as structural damage. Either way, there are always surprises while renovating, older buildings in particular. What this obviously means are unforeseen expenses to any budget, which is why setting aside an additional 15% to 20% of a job’s budget is advisable.


Brooklyn Townhouse Bearing Wall Removal

Townhouses can have interior walls that support or relive the floor joists. We renovated a Broonklyn Townhouse that had such condition. This required adding flitch beams and sistering joists. If you want to read more please see another post we wrote on NYC Townhouse Interior Wall Removal.

Sistering Joists in a BK Townhouse

Sistering Joists in a BK Townhouse


You will need a permit to remove a wall if it is structural and in most cases even if it is not.


Structural Repair NYC DOB Codes and Regulations

Structural repair work will require a Structural Engineer. The engineer will assess the existing conditions and determine a course of action. the engineer does calculations and prepares structural plans and details. These must be filed with the NYC DOB. Additionally you will need “Special Inspections” for the work. these are inspections done by private inspection agencies. In some cases the engineer can do the inspections themselves.

You can see our homepage to learn more about us: Architects New York: Fontan Architecture.


NYC Townhouse Structural Repair Work

In this article we reviewed a few examples with regards to structural work in NYC Townhouses. This post does not assume to cover every possible issue or condition, but provide a general overview of the topic.


Thank You for reading our blog post on Townhouse Renovations.

I hope this was helpful. If you want to discuss a specific project with an architect please feel free to contact us directly.


Contact Fontan Architecture


Jorge Fontan
Jorge Fontan

This post was written by Jorge Fontan AIA a Registered Architect and owner of New York City architecture firm Fontan Architecture. Jorge Fontan has earned 3 degrees in the study of architecture including two degrees from the City University of New York and a Masters Degree in Advanced Architectural Design from Columbia University. Jorge has a background in construction and has been practicing architecture for 15 years where he has designed renovations and new developments of various building types.

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