Appeal 8507

705.5 Fire-resistance ratings

Exterior walls shall be fire-resistance rated in accordance with Tables 60 I and 602 and this section. The required fire-resistance rating of exterior walls with a fire separation distance of greater than 10 feet (3048 mm) shall be rated for exposure to fire from the inside. The required fire-resistance rating of exterior walls with a fire separation distance of less than or equal to 10 feet (3048 mm) shall be rated for exposure to fire from both sides

This project is the conversion of an 1886 Victorian house in a historic neighborhood. The house has been altered throughout its 126 years. There is evidence it has housed single family, duplex, triplex, fourplex and a boarding house. The current conversion is from a permitted Duplex to a fourplex.

The structure is being developed as a Type Vb construction fully sprinklered per NFPA 13r.

The combined occupant load for all four units is 14. The lower level unit with an occupancy of 4 will exit through a separate door and is not connected to the upper levels.

Existing balloon framed wall construction with metal siding, original T&G sheathing, 2x4’s at 16”o.c. and cavity space filled with batt insulation with new 5/8” Gypsum wallboard type “X”. Blocking added at floor and ceiling junctions.
Which provides a one hour wall from the interior. Per 720.1(2) 16-1.1

Adding a sprinkler system throughout the structure in compliance with NFPA 13r
Upgrade the structural integrity of the structure for both seismic and gravity to current code. The upgrade includes the addition of a new foundation and shear walls in the basement tied to the existing brick foundation, framed wall and floor framing.
Adding fire alarm system with sprinkler flow activation and notification in each dwelling unit.
Adding hardwired interconnected smoke alarms between dwelling units.
Adding One hour fire rated enclosure at exit stair.
Adding One hour fire rated wall separations between dwelling units.
Adding One hour fire rated floor ceiling separation between floors.

The primary wall of the adjacent structure is 74” from the wall of the structure in question. There is a bay on the adjacent structure which projects approx. 24” towards the property line.

The upgrade of the exterior wall to conform with this section would require the removal of the existing sheathing and siding, and historical trim.

The exterior siding was upgraded to aluminum siding sometime in the past, this should limit flammability of the exterior surface. We understand it has minimal effect on the fire rating of the wall.

The structural upgrade to current code in conjunction with the addition of the fire sprinkler, fire alarm and smoke detection systems, combined with relatively short travel distances within units and travel paths to an exit will provide a reasonable level of protection of the building occupants.

The combination of fire sprinkler systems and new construction will also provide additional protection of the adjacent structure.

We request that the upgrade of the construction details relating to fire and life safety, structural systems, sprinkler and alarm and smoke detection systems be considered equivalent protection of life and property for this wall rating.

705.8

705.8 Openings. Openings in exterior walls shall comply with Sections 705.81 through 705.8.6.
705.8.1 Allowable area of openings. The maximum area of unprotected and protected openings permitted in an exterior wall in any story of a building shall not exceed the percentages specified in Table 705.8.

FIRE SEPARATION DISTANCE DEGREE OF OPENING PROTECTION ALLOWABLE AREA
0 to less than 3 Unprotected, Sprinklered (UP, S) Not Permitted
3 to less than 5 Unprotected, Sprinklered (UP, S I5%

The property line in question is between two 1886 framed houses. The separation of the two primary walls of the structures is 74” at the front corner and 78” at the rear.

The adjacent house has a windowless bay which extends towards the property line approx 24”.

We have investigated the property line and believe it to fall somewhere between 30” and 37” from the west face of the subject property.

Given the age of the properties and nature construction practices at the time we believe the intent was to locate the two main walls equal distance from the property line, or 37”.

It should be noted that the two houses are identical in original floor plan and have a primary structural core of nineteen feet on twenty-five foot wide lots.

Alteration of the exterior façade would trigger a historic design review.

We therefore feel that the wall in question should be considered greater than three feet clear to the property line, allowing unprotected openings / sprinklered for 15% of the wall area.

Our overall Opening area for this wall is currently 8%, with the lower level floor at 11%, and the main level and upper level floors at 6%.

We request that the fire separation distance at the wall in question be defined as 3’ with Unprotected / Sprinklered allowable Opening of 15% of the wall area.

1208.2

1208.2 Minimum ceiling heights. Occupiable spaces and habitable spaces shall have a ceiling height of not less than 7 feet 6 inches (2286 mm). Bathrooms, toilet rooms, kitchens, storage rooms and laundry rooms shall be permitted to have a ceiling height of not less than 7 feet (2134 mm).

Our current understanding of the 1886 masonry footing / foundation is that it bears at approximately 84” below the current bottom of joist.
The new One hour Fire, STC and ITC rated ceiling floor assembly will extend approximately 1” below the existing joist
The structural upgrade calls for a new interior perimeter foundation and slab along with new perimeter shear walls inside the existing foundation walls.
The top of the new concrete slab will be at or slightly above the bottom of the existing footing could limit our clear head room in the living, dining and bedrooms to 7’- 0”+
The new finish floor will be 36” below grade with adequate natural light and ventilation.
The new space will be fully sprinklered.
The ceiling will provide one hour separation to the unit above with STC and ITC of 50.

We intend to excavate the basement area as low as practical without impacting the structural integrity of the existing foundation. Preliminary site investigations indicate that the bottom of footing varies.
He have used 7’ as a benchmark for the new top of slab.
We could see a situation where we may have a portion of the ceiling at or below 84” and will not know until we have full prepared the excavation.
The new work will provide a spacious light and open space with upgrades to current sprinkler, fire alarm, smoke alarm, structural, life safety codes.
Preliminary investigations indicate that the sewer connection will limit the final depth of the slab.

We would like to request a variance in the ceiling height to accommodate potential field conditions.