Townhouse eave and soffit separation detail

[BayPointArchitect]

How should the soffit and attic / eave area be detailed and constructed to prevent the spread of fire from one townhouse to the other without building a 30 inch tall parapet?

Thanks

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

 

[classicT]

R302.2.2 (paraphrased) 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 E108 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.

In looking at the attached detail, a couple things to mention.

1. No openings are permitted within 4-ft. A fire-resistance rating is not provided.
2. The soffit, unless parallel to the lot line, is not required to be of fire resistant construction. Openings within the soffit are again not permitted within 4-ft of common wall.
3. Be careful with the use of termonology; per drawing, fire resistive wall is denoted as a firewall. Firewalls, per the IBC are structurally independent, etc. The IRC uses fire resistance rated wall or assembly, and IBC would require fire partitions or possibly fire barriers.

 

[Builder Bob]

I have seen two hour shaft walls used and terminated against the highest roof with four feet of protection on either side. That way the homeowner can hang pictures etc without hurting the fire separation. also water lines and electrical can run in this furred out wall.

 

[BayPointArchitect]

Your answers confirm what I was thinking.

In order to satisfy the strict requirements of the code, a layer of 5/8" Denglas wraps around the soffit, fascia, and top of roof trusses where located within 4 feet of the fire-rated separation. Fire-treated plywood could also be used in lieu of the 5/8" Denglas.

Thanks Bob and Ty.