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attic sheathing

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[#1] Posted: 06/22/2012 - 5:46:41 PM
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The townhome was built in 1985 but recently had a new roof installed which included all new sheathing. My guess is they tore off FRT plywood. They installed OSB all the way to the firewalls on both side of the attic.

Shouldn't they have at least run a section of fire rated plywood on the edges butting up to the firewall? Are there any code references that apply to this?

Thanks.





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John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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[#2] Posted: 06/22/2012 - 6:36:56 PM
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There's a few options to the FRT. They could have installed firesheet on the underside of the rafters for a distance of 4' from the firewall. Another is to extend the firewall above the roof deck.

Without any of those, the firewall loses it's rating.

Marc

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[#3] Posted: 06/22/2012 - 7:07:57 PM
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FRT plywood was a problem.

http://www.homeinspector.org/r...wood.pdf

Bob Kenney
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[#4] Posted: 06/22/2012 - 7:39:11 PM
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That's my guess. Bad bunch of FRT plywood.
Kurt in Chicago

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[#5] Posted: 06/22/2012 - 8:09:03 PM
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Thanks for the input and I'm aware of the possible issues with FRT. It's not that it was replaced that I'm questioning. I'm questioning the OSB (not fire rated) butting up to the firewalls at the adjoining units.

On another angle, considering all the sheathing was replaced, that constitutes structural work, correct? Therefore, would a permit be required normally?

John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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[#6] Posted: 06/22/2012 - 8:25:09 PM
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Quote: Originally posted by Marc

There's a few options to the FRT. They could have installed firesheet on the underside of the rafters for a distance of 4' from the firewall. Another is to extend the firewall above the roof deck.

Without any of those, the firewall loses it's rating.

Marc


Marc, neither of these was done. So, to regain the rating for the firewall, is there a retrofit or does the job have to be torn off and done again?


John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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[#7] Posted: 06/22/2012 - 8:27:06 PM
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Quote: Originally posted by rkenney

FRT plywood was a problem.

http://www.homeinspector.org/r...wood.pdf


Thanks Bob, the document was helpful.

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[#8] Posted: 06/22/2012 - 8:39:52 PM
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706.6 Vertical continuity. Fire walls shall extend from the foundation to a termination point at least 30 inches (762 mm) above both adjacent roofs.

Exceptions:

1. Stepped buildings in accordance with Section 706.6.1 (see below).
2. Two-hour fire-resistance-rated walls shall be permitted to terminate at the underside of the roof sheathing, deck or slab, provided:
2.1. The lower roof assembly within 4 feet (1220 mm) of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour.
2.2. Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.
2.3. Each building shall be provided with not less than a Class B roof covering.
3. Walls shall be permitted to terminate at the underside of noncombustible roof sheathing, deck or slabs where both buildings are provided with not less than a Class B roof covering. Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.
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,
4.2. The roof is covered with a minimum Class B roof covering, and
4.3. The roof sheathing or deck is constructed of fire-retardant-treated wood for a distance of 4 feet (1220 mm) on both sides of the wall or the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by a minimum of 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a minimum distance of 4 feet (1220 mm) on both sides of the fire wall.
5. In buildings designed in accordance with Section 509.2, fire walls located above the 3-hour horizontal assembly required by Section 509.2, Item 1 shall be permitted to extend from the top of this horizontal assembly.
_____________________________________________________
706.6.1 Stepped buildings. Where a fire wall serves as an exterior wall for a building and separates buildings having different roof levels, such wall shall terminate at a point not less than 30 inches (762 mm) above the lower roof level, provided the exterior wall for a height of 15 feet (4572 mm) above the lower roof is not less than 1-hour fire-resistance-rated construction from both sides with openings protected by fire assemblies having a fire protection rating of not less than 3/4 hour.

Exception: Where the fire wall terminates at the underside of the roof sheathing, deck or slab of the lower roof, provided:
1. The lower roof assembly within 10 feet (3048 mm) of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour.
2. Openings in the lower roof shall not be located within 10 feet (3048 mm) of the fire wall.

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[#9] Posted: 06/22/2012 - 8:56:29 PM
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Bill, 706 is on track but I think the one you posted is from 2009. Unfortunately, the local jurisdiction in question is still in 2003 IRC. I'm digging there now. The '03 version if a bit different on the topic.
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[#10] Posted: 06/22/2012 - 10:51:30 PM
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the pic doesn't appear to be a "firewall" assembly?

as i understand gypsum board firewall assembly: all gaps and penetrations must be filled with taping compound, fireproof sealant or stuffed with non-combustible material

i've slung more 5/8 type x and mud than i care to admit

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[#11] Posted: 06/23/2012 - 12:56:23 AM
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Quote: Originally posted by John Dirks Jr

Bill, 706 is on track but I think the one you posted is from 2009. Unfortunately, the local jurisdiction in question is still in 2003 IRC. I'm digging there now. The '03 version if a bit different on the topic.
For 2003, see R317.2.2 Parapets.

"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 on each side of the wall or walls, or one layer of 5/8-inch Type X gypsum board is installed directly beneath the roof decking or sheathing for a distance of 4 feet on each side of the wall or walls".

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[#12] Posted: 06/23/2012 - 05:48:46 AM
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Quote: Originally posted by Bill Kibbel

Quote: Originally posted by John Dirks Jr

Bill, 706 is on track but I think the one you posted is from 2009. Unfortunately, the local jurisdiction in question is still in 2003 IRC. I'm digging there now. The '03 version if a bit different on the topic.
For 2003, see R317.2.2 Parapets.

"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 on each side of the wall or walls, or one layer of 5/8-inch Type X gypsum board is installed directly beneath the roof decking or sheathing for a distance of 4 feet on each side of the wall or walls".


Thanks Bill. As a matter of fact I found that one last night and wanted to respond but the forum went down.

http://publicecodes.citation.c...r004.htm

I'll be checking with the AHJ to get their take on the situation too. I'll let you know what they say.

I'm thinking the entire sheathing change might have required a permit as well and there are no permits on file for that work at that property. Now, even though it was built in '85, if permit required work was done in 2012, wouldn't that mean that adhering to the current adopted code would be required? IE 2003 IRC R317.2.2 Parapets.

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[#13] Posted: 06/23/2012 - 05:58:32 AM
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Quote: Originally posted by BADAIR

the pic doesn't appear to be a "firewall" assembly?

as i understand gypsum board firewall assembly: all gaps and penetrations must be filled with taping compound, fireproof sealant or stuffed with non-combustible material

i've slung more 5/8 type x and mud than i care to admit


It appeared to be double layered gypsum with staggered joints. I saw gaps with another layer underneath. Would that make a difference as to the requirement of taped joints?

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[#14] Posted: 06/23/2012 - 07:48:04 AM
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Quote: Originally posted by John Dirks Jr

Quote: Originally posted by BADAIR

the pic doesn't appear to be a "firewall" assembly?

as i understand gypsum board firewall assembly: all gaps and penetrations must be filled with taping compound, fireproof sealant or stuffed with non-combustible material

i've slung more 5/8 type x and mud than i care to admit


It appeared to be double layered gypsum with staggered joints. I saw gaps with another layer underneath. Would that make a difference as to the requirement of taped joints?


material, fastener spacing, sealing all seams and gaps is/was required on every gypsum board firewall assembly (gbfwa) i've ever seen or built

a fire marshal explained, "stopping air passage, stops flame spread" simple physics

imo & documented, it's not a tried & true UL tested gbfwa without these details, just unit/space separation in that case

this may assist
http://www.usg.com/rc/system-c...A100.pdf

aside: the backside visible would also be a deal killer for this as a gbfwa
different paper has not met or would not meet the test requirements

any ahj that would pass that as a gbfwa doesn't care or understand the potential ramifications

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[#15] Posted: 06/25/2012 - 10:56:09 PM
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And just in case anyone isn't clear on the potential ramifications...

Here's a photo I took recently while on vacation, showing what's left of a 4-unit townhome.

Click to View

97.87 KB

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[#16] Posted: 06/26/2012 - 06:33:00 AM
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Quote:

Here's a photo I took recently while on vacation, showing what's left of a 4-unit townhome.

Click to View

97.87?KB


I may be wrong, but it seems to me the purpose of the code is to allow sufficient time for evacuation, not to save the structure.

A long FD response time (remote, inaccessible location), lack of water, weather, prevailing wind, etc. Ultimately fire will take everything, code or no code.

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[#17] Posted: 06/26/2012 - 1:32:34 PM
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The photo is from the middle of Vail, Colorado. I doubt that fire department response time or resources were a factor. Obviously, it was a major fire (it even spread to the next building over) and when Mother Nature goes on a rampage it's best to keep your distance. But the point is that fire spreading from one living unit to the next is a very real concern with devastating consequences.
Garet Denise
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