The Interplay between the Amended RPAPL 881 and
The NYC Building Code
On December 5, 2025, Governor Kathy Hochul signed major amendments to the New York Real Property Actions and Proceedings Law (RPAPL) § 881, which governs access to adjoining properties during construction. In contrast to its brief predecessor, the revised statute explicitly enumerates specific construction installations and cross-references construction codes and regulations. Consequently, understanding and properly applying the new law requires significant engineering insight. The following analysis examines the modified text to offer practical engineering clarifications to legal practitioners navigating these disputes.
Significant Legislative Changes
The amended RPAPL § 881 shifts the justification for entering an adjoining property from “mere necessity” to the necessity to repair or develop a property in a “commercially reasonable” manner. By codifying the definition of an adjoining property owner’s “refusal,” the statute creates a clear path for court intervention.
Most notably, the revised statute now allows structural elements to be installed permanently on neighboring property when required by applicable code, regulation, or local law. Under the prior version of RPAPL 881, courts generally treated the statute as authorizing only temporary protective installations. By characterizing underpinning as “permanent encroachments,” previous judicial decisions had denied access outright.
These changes have drastically intensified the need for specialized consulting engineering, especially as the statute refers to “good construction practice.” The statute now requires both developers and adjoining property owners to produce rigorous technical analysis regarding proposed and alternate construction methods and building code compliance to avoid access disputes.
Permanent Installations – Underpinning and Alternate Methods
Under the amended statute, the threshold for permanent entry is whether the installation is “required by code, regulation, or local law,” shifting the burden to engineering consultants to identify the precise code triggers and to demonstrate whether technically viable alternatives exist. There is ambiguity as to whether the statutory standard of “good construction practice” applies to all measures listed in RPAPL 881 or only to additional, non‑enumerated measures proposed by the applicant. The statute now expressly codifies that the licensee must reasonably compensate the adjoining owner for “loss of use and enjoyment,” including any “diminution in value” caused by the access, further elevating the role of technical and valuation evidence.
It is therefore useful to examine in more detail what permanent encroachments might genuinely be “required by code, regulation, or local law.” The most common installation that has been the subject of court action is underpinning. New York appellate courts have treated underpinning as a permanent structural intervention, and, as late as 2025, declined to authorize it under RPAPL 881 as then written.
NYC Building Code Section 1817.4.1 provides:
1817.4.1 Underpinning.
If the foundation loads are to be transferred to a lower bearing level, underpinning consisting of concrete piers, drilled piles, jacked piles, bracket piles, or similar engineered systems to transfer the existing building loads below the bottom of the proposed excavation shall be installed.
Section 1817.4 further provides:
1817.4 Suitable methods of support.
Where a method of support for an existing building is required, such underpinning or alternate method of support shall be designed as a permanent structural element specific to the building using the methods described in Sections 1817.4.1 through 1817.4.3. The underpinning or alternate method of support shall be installed in accordance with the provisions of this chapter and Chapter 33 and shall be inspected in accordance with the provisions of Chapter 17.
From an engineering standpoint, the question becomes: in what cases must foundation loads be transferred to a lower bearing level? When the design of a new building or alteration places the proposed foundation at a lower bearing level than an adjoining existing foundation, excavation in the vicinity of that foundation is highly likely to disturb the supporting soil and reduce the bearing capacity of the existing footing. In such situations, carrying the existing loads to an undisturbed bearing stratum becomes necessary as a matter of sound engineering practice. Chapter 18 itself does not explicitly enumerate the scenarios in which such load transfer is triggered. The construction activity necessary for installing a new lower foundation creates this need.
An analysis of the NYC Building Code reveals the connection between Chapter 18 and Chapter 33 on this point. Section 1817.4.1 dictates that if foundation loads are to be transferred to a lower bearing level, underpinning or similar engineered systems must be installed, and Section 1817.4 requires that such systems be designed as permanent structural elements. Chapter 18 thus defines the nature and performance of underpinning, but not the conditions under which load transfer becomes mandatory. The operative trigger appears in Chapter 33.
Section 3309.4 (“Soil or foundation work affecting adjoining property”) provides, in relevant part:
3309.4 Soil or foundation work affecting adjoining property.
Whenever soil or foundation work occurs, regardless of the depth of such, the person who causes such to be made shall, at all times during the course of such work and at his or her own
expense, preserve and protect from damage any adjoining structures, including but not limited to footings and foundations, provided such person is afforded a license in accordance with the
requirements of Section 3309.2 to enter and inspect the adjoining buildings and property, and to perform such work thereon as may be necessary for such purpose. If the person who causes
the soil or foundation work is not afforded a license, such duty to preserve and protect the adjacent property shall devolve to the owner of such adjoining property, who shall be afforded a similar license with respect to the property where the soil or foundation work is to be made.
Section 3309.4.1 then states:
3309.4.1 Additional safeguards during excavation.
The following additional requirements shall apply during excavation:
- The person causing the excavation shall support the vertical and lateral load of the adjoining structure by proper foundations, underpinning, or other equivalent means where the level of the foundations of the adjoining structure is at or above the level of the bottom of the new excavation.
Thus, in cases where the new foundation extends below the bottom of the adjoining foundation, the code expressly requires the person causing the excavation to support the neighboring structure by underpinning or an equivalent system. Chapter 33 goes even further, imposing this duty “whenever soil or foundation work occurs, regardless of the depth of such,” underscoring that the obligation to preserve and protect adjoining structures is not limited to deep excavations.
The Chapter 33 language focuses heavily on the active construction period, noting that these safeguards apply “during excavation.” In forensic engineering practice, however, structural damage and settlement often manifest long after foundation work is complete, especially where transient construction‑stage movements have pushed a structure closer to its tolerance limits. Section 1817.4 Suitable methods of support seems to address this problem by requiring such underpinning or alternate method of support shall be designed as a permanent structural element specific to the building using the methods described in Sections 1817.4.1 through 1817.4.3.
Moreover, Section 3309.4 introduces a critical shift in liability: the absolute duty to protect the adjoining property rests on the person performing the excavation, at that party’s expense, provided they are granted a license to enter. If the adjoining owner refuses access, the legal and financial obligation to preserve the structure devolves to that adjoining owner, who is then entitled to a reciprocal license onto the excavator’s property.
In the author’s experience as an engineer, courts and agencies have rarely compelled adjoining owners to undertake and fund protective work themselves in response to such a refusal, notwithstanding the formal language of Section 3309.4. The amended RPAPL 881 appears designed to address this practical gap by clarifying the consequences of refusal and providing a structured mechanism for court‑ordered access conditioned on defined protective measures and compensation.
The choice of support method—underpinning versus alternate systems—and the determination of what is both safer and commercially reasonable will often be contested between engineers representing each side or litigated in the context of an RPAPL 881 proceeding. Alternate methods of support include systems that do not physically encroach, such as interior rakers, soil improvement, or fully within‑lot secant or tangent pile walls, although these may carry different safety profiles, construction risks, and costs. Ideally, the selection among alternatives is driven first by safety and good construction practice, and only in the last instance by commercial feasibility.
There have been numerous accidents, some very serious, associated with underpinning installations. In response, the 2022 NYC Building Code introduced a detailed set of requirements for underpinning, particularly in Chapter 18, and Section BC 1817 (“Underpinning and Alternate Methods of Support of Buildings and Adjacent Property”) now spans several pages of text. These provisions require rigorous analysis of underpinning and its effects on the adjoining structure, coupled with enhanced inspection and monitoring obligations. If properly implemented, these requirements should significantly reduce the frequency and severity of underpinning‑related incidents. Effective review and design, however, demand an engineer with substantial experience in underpinning procedures and in the specific types of structures being supported. GMS reviewed the effectiveness of the new code to prevent accidents. An analysis of NYC ECB violations for the years 2024 and 2025, when the 2022 NYCBC code was in effect, did not find any instance where underpinning produced significant damage to an adjoining building.
Permanent Installation – Demolition
In several cases adjoining property owners opposed or objected to some demolition requirements included in the Section 3309.8 Adjoining walls, especially those related to inspection and proper anchorage of joists in the wall. The new RPAPL 881 seems to dismiss such opposition, when joists are lacking anchors installing new permanent anchors in wood joists is clearly required by code. Anchorage of joists has been a code requirement for over 150 years and is essential for improving the stability of the existing building.
Temporary Protective Installations
The statute enumerates various activities and temporary installations required to protect pedestrians, neighboring properties, and occupants that may trigger the need for access. Many of these measures—often prescribed by NYC Building Code Chapter 33 (Safeguards During Construction or Demolition)—are detailed in site safety plans and have long formed the basis for privately negotiated license agreements between developers and adjoining owners. Such agreements typically include indemnification and related provisions to compensate the adjoining owner for loss of use or damage.
Imprecise Language
The courts and the construction and engineering community will have to provide clarity on what is and how to apply the commercially reasonable provision.
The current statutory phrasing is imprecise in some other respects. For instance, it can be read to permit temporary sheeting or other support‑of‑excavation (SOE) elements to be installed on adjoining property whenever the cost of remaining entirely within the developer’s lot is deemed economically unreasonable. Similarly it is not clear the scope of the relocation of “other equipment “ on the roof.
The diminution of value provision is expected to be a subject of debate, as it is not clear if it pertains to both immediate, physical damage to adjoining property and the long-term, consequential impact on its future development potential. For example, subterranean anchorage (such as tiebacks) encroaching under neighboring property may necessitate, or be deemed to create, additional construction expenses and restrictions when that property is improved. Therefore, the clause must clearly define whether it covers only immediate structural damage or also future costs.
Under the amended RPAPL 881, engineers will also be called upon to analyze potential diminution in value associated with permanent encroachments, residual settlement risk, and constraints on future development of the adjoining parcel.
Whether the provisions regarding permanent installations will withstand constitutional scrutiny remains unresolved; as recently as 2025, a New York appellate court characterized underpinning as a permanent installation and refused to approve it under the pre‑amendment version of RPAPL 881.
Conclusions
As a result of the new amendments, court decisions regarding access, underpinning, and alternate support systems are likely to be heavily influenced by technical engineering and construction arguments, set against the backdrop of “commercially reasonable” development and “good construction practice” as those terms are gradually defined in the case law.
Written by Dan Eschenasy