If you work on construction projects in New York City, you hear “20 feet” a lot.
Twenty feet from an adjoining building.
Twenty feet from an unenclosed perimeter.
Twenty feet of roof protection.
Windows within 20 feet.
Equipment within 20 feet.
It sounds like one simple rule.
It isn’t.
Several provisions of NYC Building Code Chapter 33 use a 20-foot distance, but they apply to different conditions and can require very different types of protection.
That is why simply drawing a 20-foot line on a Site Safety Plan does not necessarily answer the question.
The real question is:
What is within that 20-foot area, what work is occurring above or adjacent to it, and what protection does the code require for that specific exposure?
1. Adjoining Windows Within 20 Feet
One of the most common conditions involves windows on an adjoining property.
Under BC 3309.14, when exterior construction or demolition creates an unenclosed perimeter, windows on adjoining private property that face the work and are within 20 feet or less of that unenclosed perimeter must generally be protected, subject to the applicable exceptions. (New York City Government)
The word “face” matters.
A window located within 20 feet of the project is not automatically subject to the requirement simply because it falls inside a 20-foot radius.
The orientation of the window relative to the work should also be evaluated.
For example, a window directly facing an exposed slab edge may present a very different condition from a window located on a wall perpendicular to the construction exposure.
This is why adjoining elevations should be reviewed, not just the site plan.
2. Adjoining Roof Protection
The 20-foot measurement also appears in the requirements for protecting adjoining roofs.
When construction or demolition occurs above the roof of an adjoining building, BC 3309 requires protection of the adjoining roof, skylights, roof openings and rooftop equipment under qualifying conditions.
Where the work is at least 48 inches above the adjoining roof, the prescribed roof protection generally extends horizontally based on the height of the work above that roof, up to a maximum of 20 feet, unless DOB requires a greater distance because of a unique hazard. (New York City Government)
This means the protected area is not always automatically 20 feet.
For example, if the highest working level is only 10 feet above the adjoining roof, the required horizontal protection may correspond to that lesser dimension.
As the building rises, however, the required area can increase until it reaches the maximum established by the code.
That is why adjoining roof protection sometimes needs to evolve as construction progresses.
3. Adjoining Equipment and Occupied Spaces
Another condition involves mechanical equipment and spaces on adjoining property.
For qualifying major-building construction or demolition subject to site safety requirements, Chapter 33 contains provisions addressing mechanical, electrical and similar equipment, as well as publicly accessible adjoining spaces, located within 20 feet of an unenclosed perimeter. (New York City Government)
Examples may include:
- HVAC equipment
- Rooftop or yard mechanical units
- Electrical equipment
- Occupied yards
- Terraces
- Publicly accessible areas
- Other spaces exposed to construction above
The appropriate protection depends on the actual condition.
It may involve overhead protection, catchalls, scaffolding, engineered protection, controlled access or another solution acceptable for the specific exposure.
4. A 20-Foot Controlled Access Area Is Not Automatically the Same Thing
This is where things often get mixed together.
A project team may identify an adjoining area within 20 feet of active work and immediately assume that a 20-foot controlled access zone solves the condition.
Sometimes restricting access can be part of the solution.
But a Controlled Access Zone, or CAZ, is not automatically interchangeable with required physical protection.
If an area must remain occupied or accessible, simply placing barricades and signage may not satisfy the applicable requirement.
Similarly, if rooftop equipment must continue operating, closing the entire area may not be practical.
The protection strategy needs to correspond with the actual hazard and the applicable code provision.
5. Hoists Can Create Temporary 20-Foot Exposure Conditions
Construction hoists are a good example of why this issue should be reviewed by phase.
A future condition may show an engineered scaffold, enclosure system or other protection along a façade.
But what happens before that system is fully installed?
There may be a period during construction when:
- The building continues to rise
- The hoist run is incomplete
- The permanent or engineered enclosure has not yet reached the active floor
- An adjoining property remains exposed
- Windows, terraces, roofs or occupied areas remain within the potential hazard zone
Those temporary conditions can easily be missed if the Site Safety Plan only illustrates the project’s final logistics configuration.
A protection strategy should consider the sequence of construction, not just the completed condition.
6. Engineered Enclosure Systems Can Change the Analysis
Chapter 33 recognizes certain site-specific engineered enclosure systems as alternatives under specific adjoining-property protection provisions.
For example, current code language provides exceptions in certain circumstances where an engineered enclosure system acceptable to the Commissioner covers the full exposure where work is occurring. (New York City Government)
This can significantly change how adjoining-property protection is handled.
But the key words are:
the entire exposure where work is occurring.
If the enclosure does not yet extend to the active work level, or if gaps exist because of construction sequencing, the adjoining condition may still require separate temporary protection.
Again, the construction phase matters.
7. The Site Plan Alone May Not Tell the Whole Story
A 20-foot condition is three-dimensional.
A plan view can tell you the horizontal distance between buildings.
It cannot always tell you:
- Which windows face the work
- The elevation of an adjoining roof
- Where terraces or setbacks occur
- Whether rooftop equipment is exposed
- How high the active working level is above the adjoining property
- Whether an enclosure system actually covers the exposure
- Whether an adjoining area remains occupied
That is why Site Safety Plans often need to coordinate site plans, floor plans, elevations and sections to properly illustrate adjoining-property conditions.
A Simple Way to Review the Condition
When we identify an adjoining property within 20 feet of active construction, we typically start by asking:
What exactly is inside the 20 feet?
Is it a:
- Window?
- Roof?
- Terrace?
- Yard?
- Mechanical unit?
- Pedestrian area?
- Occupied space?
- Another active construction site?
Then:
What work is occurring adjacent to or above it?
And finally:
What protection applies to that specific condition?
That approach is much more useful than treating every 20-foot exposure the same way.
The Bottom Line
In NYC construction, 20 feet is not one rule.
It is a distance that appears in several different Chapter 33 protection requirements.
The correct response depends on the exposure.
A neighboring window may require one type of protection.
An adjoining roof may require another.
A terrace, courtyard or mechanical area may require something completely different.
And the answer can change as the project moves from excavation to superstructure to façade work.
The goal of a good Site Safety Plan is not simply to show a 20-foot line.
It is to understand what that line actually affects.
At Canonvex, we review adjoining-property conditions as part of the overall construction logistics and Site Safety Plan process, including how those conditions may change throughout different phases of construction.
Measure the distance. Then understand the exposure.
1 comment
Thank you for the information