Thread: FRT or Equivalent Protection

I will admit that I don't do it consistently (I know, be consistent), but in some cases I will write that I failed to observe a fire resistant/retardant treated sheathing in the attic spanning at least 4' where adjoining dwellings (townhouses) meet. I then go on to recommend that 5/6" drywall be added to achieve the recommended fire rating. I have the code to support it, but I dont want to be the only guy out here writing it. And as I understand it, there could be the chance that the treatment was applied to the exterior side of the sheathing and it would be impossible for me to view the rating in the course of a non invasive home inspection.

I killed a deal the other day with this very same observation and I know I lost that Realtor. I'm okay with that as long as I am not being too anal.

Any thoughts?

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You are not being too anal, you are being too lax if you do not write it up ... when it is needed.

IF (big *IF* there) there is a parapet wall which is at least 30 inches high above the roof, on townhouse has a wall ending at least 30 inches higher than the roof of the lower townhouse adjacent to it, and, (for Type V construction - which is what almost all -if not all - houses are, Type V construction) 1) there are no openings through the roof withing 4 feet of the fire wall, and 2) the roof is a minimum Class B roof covering (asphalt composition shingles are Class A), 3) and the roof sheathing is either fire retardant treated or protected for 4 feet from each side of the wall.

You are referring to looking for that last 1), 2), 3) listed above. Don't forget to look for the other options if that is not there. In some areas, parapet walls are the preferred method, in other areas, it's protecting the roof sheathing, other areas prefer to use architectural design and step the roofs (one story next to a two story next to a one story next to a higher roof one story, etc.)

If you "lost" the Realtor for doing your job, you didn't "have" anything to begin with.

Thanks Guys,

I think I just needed that reassurance. I knew it was the right thing to do.

Jerry (or anyone else),

there are no openings through the roof withing 4 feet of the fire wall

where do I find that requirement specified? Is this any roof penetration (DWV, HVAC, chimneys, access hatches, etc.), or just some types.

Thanks

Michael,

From the IRC.

- SECTION R317
- - DWELLING UNIT SEPARATION

- - - R317.2 Townhouses.

Each townhouse shall be considered a separate building and shall be separated by fire-resistance-rated wall assemblies meeting the requirements of Section R302 for exterior walls.
- - - - Exception:A common 2-hour fire-resistance-rated wall is permitted for townhouses if such walls do not contain plumbing or mechanical equipment, ducts or vents in the cavity of the common wall. Electrical installations shall be installed in accordance with Chapters 33 through 42. Penetrations of electrical outlet boxes shall be in accordance with Section R317.3.
- - - R317.2.2 Parapets.

Parapets constructed in accordance with Section R317.2.3 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 are at 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 (762 mm)above the lower roof surface.

- - - - Exception:

A parapet is not required in the two cases above when the roof is covered with a minimum class C roof covering, 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 a minimum of nominal 2-inch (51 mm) ledgers attached to the sides of the roof framing members, for a minimum distance of 4 feet (1220 mm) on each side of the wall or walls. (Jerry's note: How can this extend to a minimum distance of 4 feet if there is an opening through it? See additional code sections below from the IBC for additional information.)

- - - - 3. A parapet is not required where roof surfaces adjacent to the wall or walls are at different elevations and the higher roof is more than 30 inches (762 mm) above the lower roof. The common wall construction from the lower roof to the underside of the higher roof deck shall have not less than a 1-hour fire-resistence rating. The wall shall be rated for exposure from both sides.

(The protection offered by the fire retardant treated roof sheathing or it protection of gypsum board is lost if there are openings through it.)

From the IBC.
- 705.6 Vertical continuity.

Fire walls shall extend from the foundation to a termination point at least 30 inches (762 mm) above both adjacent roofs.
- - Exceptions:

- - - 4. In buildings of Type III, IV and V construction, walls shall be permitted to terminate at the underside of combustible roof sheathing or decks provided:

- - - - 4.1. There are no openings in the roof within 4 feet (1220 mm) of the fire wall.

(There will be no "continuity" if there are openings through the protected area. At least not unless they are protected with an approved and rated fire stop system, which would cost too much for that (as compared to the no-cost-involved of just putting the opening a minimum of 4 feet from the side of the fire rated wall.)

Thanks.