Buildings Bulletin 2015-017 was released to clarify code requirements for lot line openings, taking into consideration various Building Code and Zoning laws and this release supercedes TPPN 10/1987. Here’s a rundown of the parameters:

I. Distance from Lot Lines
BC Table 705.8 covers distance from a lot line, it limits the quantity of exterior openings based on “fire separation distance” which is measured perpendicularly from the exterior wall to the tax lot line.

II. Glazed Exterior Walls as Rated Assemblies
Glazed exterior walls that are fixed, closed and labeled as fire-resistance-rated glazing and are tested to become part of a fire-resistant rated wall assembly in compliance with the ASTM E119 as requisite for exterior walls for lot line conditions and follows section BC 705.5 (around 1 hour – as per BC table 602) are not considered openings and as such is permitted as-of-right to an unlimited degree.

III. Lot Line Conditions for other than R-2 and R-3
As-of-right openings for other than Group R-2 and R-3 occupancies are not allowed for lot line conditions as per BC Table 705.8. On the other hand, beyond 60ft from adjoining buildings, unlimited, unprotected openings maybe allowed if approved by the borough examiner and the criteria in Part V of this bulletin is met.

IV. Lot line condition for R-2 and R-3
Table BC 705.8 footnote k notes that as-of-right openings on tax lot lines are allowed in Group R-2 and R-3 occupancies as long as they don’t exceed 10 percent of the area of the façade of the section in which they are located.

Such openings also need to be-

• Opening protectives pursuant to section BC 715
• In cases where the R-2 or R-3 building is completely sprinklered, protected by an approved water curtain using automatic sprinklers approved for that use and mounted in concurrence with NFPA 13 as modified in Appendix Q

Such openings cannot be utilized in order to satisfy natural light or ventilation requirements as per part VI(A) of this bulletin.

BC 705.8.2 also denotes that fire window assembly openings must comply with section BC 715 as fire-protection rated glazing. The fire-protection rated glazing within fire windows assembly must be automatic-closing in accordance with BC 715.5.6 if operable fire window assembly are used.

V. 60 feet or more between openings and neighboring building.
Footnote m of BC Table 705.8 provides the acceptable exception for the requisites noted in Parts III and IV of this bulletin for openings adequately far away from nearby buildings that front such openings. An exterior wall that is at least 60ft away from an adjoining building, measured in any direction and at any angle to the nearest point of said adjoining building, including any rooftop apparatus, bulkheads and the likes, unlimited and unprotected openings may be permitted by the Borough examiner provided that:

• The owner shall file a lot line window restrictive declaration against the tax lot in compliance with BB 2015-008 or any of its successor bulletin that requires the owner of the building to immediately close off such openings in case the adjoining building is later changed or any construction be done to come within the 60ft limit. The CO or Schedule A of the said building must reflect the CRFN number for the declaration recorded against the lot.
• The construction documents must include data with regards to the obligations imposed by the declaration.
• Structural and mechanical plans must show that the building will be able to accommodate human occupancy and any additional load in case the exterior wall enclosures needs to be installed.
• Section BC 2113.9 that specifies distances for openings above the top of any chimney must also be fixed.

VI. Windows providing required natural light or ventilation on zoning lots with multiple tax lots.
Section 30 of the Multiple Dwelling Law provides that windows providing natura lighting and ventilation that do not open to a street must open directly “upon a lawful yard, court or space above a setback upon the same lot as that occupied by the multiple dwelling in which such room is situated.”

The term same lot as expressed in this document is interpreted as the zoning lot even if the zoning lot is composed of numerous tax lots. Nevertheless, for the analysis of applicable fire safety requisites for opening protectives, the BC measures fire separation distances or exterior separations to the tax lot line/s.