HomeMy WebLinkAboutB17-0162_RESPONSE TO PARTYWALL AND ROOF OVERHANG_1497299880.pdf
Date: 06-09-2017
RE: RESPONSE TO ROOF OVERHANG AT PARTYWALL QUESTION FROM TOWN OF VAIL R17-0161 and r-
17-0162 located at 2655 Davos Trail in Vail, Colorado
JR Mondragon and planning department.
The architect was asked to provide a detail for the portion of roof that has an overhang that protrudes
from the east unit, across the party wall/property line and into the west unit’s property. The owner is
the same on both sides of the party wall and will allow the projection of the overhang. A party wall
agreement will be drafted between the owners regarding the maintenance and integrity of the wall
and the roof overhang. This length of roof that has the projecting eave is only 17 feet of the the total
depth of the building. I will address the response referencing 2015 IRC:
SECTION R302
FIRE-RESISTANT CONSTRUCTION
R302.1 Exterior walls. Construction, projections, openings and penetrations of exterior walls of
dwellings and accessory buildings shall comply with Table R302.1(1); or dwellings equipped throughout
with an automatic sprinkler system installed in accordance with Section P2904 shall comply with Table
R302.1(2).
The project is a Primary/Secondary residence with an automatic Sprinkler System
The wall between the units is constructed as 1 hour rated assembly on each side of the party wall/ lot
line. Wall construction follows the Gypsum association’s WP 3810 assembly. Each wall is a bearing
wall and independently structured.
From table R302.1(2)
PROJECTIONS | Fire-resistance rated | 1 hour on the underside b, c | <2 feet
The footnotes read:
b. The roof eave fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of
the eave if fireblocking is provided from the wall top plate to the underside of the roof sheathing.
c. The roof eave fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of
the eave provided that gable vent openings are not installed
This part of the code/table refers to projections within fire resistant construction. Projections of <2 feet
are allowed with the 1 hour on the underside. Being further reduced by footnotes to 0 hours and does
not allow for eave venting. This is consisitant with the proposed detail and we are surpassing by
adding 5/8” type ‘X’ Gypsum Wall Board on the underside of the roof overhang and behind the fascia.
No venting in this eave is proposed.
While the project is a Two-Family Dwelling, we have reviewed and complied to requirements for a
parapet wall in R302.2 Townhome construction. The current detail complies with the following section
of the code regarding walls with parapets <30” tall. See below
R302.2.2 Parapets for townhouses. Parapets constructed in accordance with Section R302.2.3 shall be
constructed for townhouses as an extension of exterior walls or common walls in accordance with the
following:
1. Where roof surfaces adjacent to the wall or walls areat the same elevation, the parapet shall extend
not less than 30 inches (762 mm) above the roof surfaces.
2. Where roof surfaces adjacent to the wall or walls are at different elevations and the higher roof is not
more than 30 inches (762 mm) above the lower roof, the parapet shall extend not less than 30 inches
(762mm) above the lower roof surface.
Exception: A parapet is not required in the preceding two cases where the roof covering complies
with a minimum Class C rating as tested in accordance with ASTM E 108 or UL 790 and the roof
decking or sheathing is of noncombustible materials or approved fire-retardant-treated wood for a
distance of 4 feet (1219 mm) on each side of the wall or walls, or one layer of 5/8-inch (15.9 mm)
Type X gypsum board is installed directly beneath the roof decking or sheathing, supported by not
less than nominal 2-inch (51 mm) ledgers attached to the sides of the roof framing members, for a
distance of not less than 4 feet (1219 mm) on each side of the wall or walls and any openings or
penetrations in the roof are not within 4 feet (1219 mm) of the common walls.
We are making the argument that, if a fire started on the lower wall (west unit), below the eave,
1. The soffit is protected by 5/8” type ‘X’ Gypsum Wall Board.
2. There is fireblocking between the roof rafters and protected with an added layer of 5/8” type ‘X’
Gypsum Wall Board on the blocking, and
3. We have 4’-0” distance from the partywall of 5/8” type ‘X’ Gypsum Wall Board on the underside
of the roof sheathing.
If we look at
R302.3 Two-family dwellings. Dwelling units in two-family dwellings shall be separated from each other
by wall and floor assemblies having not less than a 1-hour fire-resistance rating where tested in
accordance with ASTM E 119 or UL 263. Fire-resistance-rated floor/ceiling and wall assemblies shall
extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to
the underside of the roof sheathing.
Exceptions:
1. A fire-resistance rating of 1/2 hour shall be permitted in buildings equipped throughout with an
automatic sprinkler system installed in accordance with NFPA 13.
This section of the code states that the walls need to be only 1/2 hour since we have an Automatic
Sprinkler System in accordance with NFPA 13. The single layer that is applied to the underside of the
soffit which provides fire resistance from that side.
Thank you,
Jeffrey P Manley AIA
Martin Manley Architects
jeff@martinmanleyarchitects.com
970-328-1299 (direct)