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Ridge Vent near Common Wall of Townhomes

F

Fort

Silver Member
Joined
Jan 12, 2012
Messages
128
Location
California
In CA, 2010 CRC.

Townhomes, at the common-wall, where extends up thru attic to bottom of roof sheathing.

The code is silent on whether penetrations are permitted in the fire retardant roof sheathing 5/8" type x gyp. when using that exception. (see below).

Questions:

1). Is a continuous attic vent permitted within this 4'-0" zone near the common wall ? Is your answer based on code section reference, or judgement of AHJ?

2). Are other types of penetrations permitted, such as plumbing or hvac ? Is your answer based on code section reference, or judgement of AHJ?

Code Citation:

R302.2.2 Parapets. 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:

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.

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 68 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 (1219 mm) on each side of the wall or walls.
 
1) the ridge vent is permitted to run the entire length of the roof. The fire retardant sheathing is not permitted to be removed within 4 ft of the common wall. Judgement of the AHJ based on the IBC requirements

2) No penetrations with 4 ft. Judgement of the AHJ based on the IBC requirements

Historicaly we used the UBC for all construction till 1995 when CABO was adopted. Nobody noticed that it was not a requirment of CABO so it was still being required until a new employee studying for his IRC cert noticed it wasn't required by the 2006 IRC. The BO at the time made the decision that since the IRC was silent on the subject that under R102.1 he would establish the policy that the IBC would be followed. We haven't changed it and nobody has challanged it.
 
Fort,

I say "no", the ridge vent is not allowed in the 4 ft. zone, because it is not

a fire resistant rated product. See Section R902.1 in the 2006 IRC:

R902.1 - Roofing covering materials.

Roofs shall be covered with materials as set forth in Sections R904 and

R905. Class A, B or C roofing shall be installed in areas designated by law

as requiring their use or when the edge of the roof is less than 3 feet

(914 mm) from a property line. Classes A, B and C roofing required to be

listed by this section shall be tested in accordance with UL 790 or

ASTM E 108. Roof assemblies with coverings of brick, masonry, slate,

clay or concrete roof tile, exposed concrete roof deck, ferrous or copper

shingles or sheets, and metal sheets and shingles, shall be considered

Class A roof coverings.

The 4 ft. dimension is there to protect the other property owner from

spread of the fire.



.
 
I when reviewing and inspecting a townhouse without parapets and the exception of FRT plywood is used

prohibit any and all penetrations of that 4 foot area, be it ridge vent, skylight, plumbing vent, NO PENETRATIONS ...

As a DRP thats the way I designed them as a CBO thats the way I inspect them.

want holes ther then build the parapet.

COMPLIANCE IS THE ALTERNATIVE.............
 
A parapet is required by the code to try and prevent, or at least slow, a fire from spreading to the adjacent unit. The 4' on each side of a common wall alternate is permitted, but is also expected to accomplish the same task of preventing, or slowing, the spread of fire. anything that reduces the total of 8' of fire-resistive construction should not be permitted. There should be no ridge vents, roof vent, plumbing vents, exhaust vents, etc. permitted within 4' of the common wall on either side.
 
Architect1281 said:
I when reviewing and inspecting a townhouse without parapets and the exception of FRT plywood is used prohibit any and all penetrations of that 4 foot area, be it ridge vent, skylight, plumbing vent, NO PENETRATIONS ... As a DRP thats the way I designed them as a CBO thats the way I inspect them. want holes ther then build the parapet. COMPLIANCE IS THE ALTERNATIVE.............
Click to expand...
And you base this on which section of the code?
 
Big Mac said:
A parapet is required by the code to try and prevent, or at least slow, a fire from spreading to the adjacent unit. The 4' on each side of a common wall alternate is permitted, but is also expected to accomplish the same task of preventing, or slowing, the spread of fire. anything that reduces the total of 8' of fire-resistive construction should not be permitted. There should be no ridge vents, roof vent, plumbing vents, exhaust vents, etc. permitted within 4' of the common wall on either side.
Click to expand...
And you cite which section of the code?
 
Posted by Architect1281: I when reviewing and inspecting a townhouse without parapetsand the exception of FRT plywood is used prohibit any and all penetrations of that 4 foot area, be

it ridge vent, skylight, plumbing vent, NO PENETRATIONS ... As a DRP thats the way I designed

them as a CBO thats the way I inspect them. want holes ther then build the parapet. COMPLIANCE

IS THE ALTERNATIVE.

Posted by brudgers: And you base this on which section of the code?
Click to expand...
Posted by Big Mac: A parapet is required by the code to try and prevent, or at least slow,a fire from spreading to the adjacent unit. The 4' on each side of a common wall alternate is

permitted, but is also expected to accomplish the same task of preventing, or slowing, the spread

of fire. anything that reduces the total of 8' of fire-resistive construction should not be permitted.

There should be no ridge vents, roof vent, plumbing vents, exhaust vents, etc. permitted within 4'

of the common wall on either side.

Posted by brudgers: And you cite which section of the code?
Click to expand...
They could cite Section R317, # 2, the Exception, from the 2006 IRC:

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.

If there are penetrations into the 4 ft. zone, then the roof is not covered (completely)

with a Class C covering, nor a non-combustible roof decking underneath.

IMO, if someone wants to penetrate the 4 ft. zone, then submit the type of

non-combustible materials that will be installed for review and approval by the BO.

All of the residential type of ridge vents that I have seen are plastic and are very

combustible.





.
 
That is asinine.

By that logic the IBC disallows roof penetrations on buildings of Type I and II construction unless the roof covering is non-combustible.

Or rather, "By that illogic..."
 
Code compliance can seem asinine at times. It is a fire safety issue and the correct call is as described above. You don't have to like it.
 
The citation given by Globe Trekker was from the IRC. The IBC uses similar language to disallow penetrations within 4' of a fire wall - Section 760.6, item #2.

Good Grief Brudgers, buy a code book, maybe even a commentary.

I will say my farewell since I see the forum is now going to be a subscription only. I fully understand why this needs to happen but sincerely wish the economics were different. At any rate, I would like to say thank you to the sponsors of this board for the access I have been granted until now and I must say, I will miss most of the participants. Take Care - Fight the good fight - Have a good life.
 
Fort said:
In CA, 2010 CRC.Townhomes, at the common-wall, where extends up thru attic to bottom of roof sheathing.

The code is silent on whether penetrations are permitted in the fire retardant roof sheathing 5/8" type x gyp. when using that exception. (see below).

Questions:

1). Is a continuous attic vent permitted within this 4'-0" zone near the common wall ? Is your answer based on code section reference, or judgement of AHJ?

2). Are other types of penetrations permitted, such as plumbing or hvac ? Is your answer based on code section reference, or judgement of AHJ?

Code Citation:

R302.2.2 Parapets. 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:

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.

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 68 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 (1219 mm) on each side of the wall or walls.
Click to expand...
See pages 23 - 24; says the IRC had not previously placed any restrictions but the 2012 prohibits openings or penetrations within the 4 ft. area.

http://www.iccsafe.org/Store/Documents/TOC/7101S12-sample.pdf

R302.2.2 Parapets.

Parapets constructed in accordance with :Next('./icod_irc_2012_3_par045.htm')'>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 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 (1219 mm) on each side of the wall or walls and there are no openings or penetrations in the roof within 4 feet (1219 mm) of the common walls.

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-resistance rating. The wall shall be rated for exposure from both sides.

Francis
 
Last edited by a moderator:
Big Mac,

I hope that you will reconsider and stay with us, ..maybe even

rob your kids piggy bank if you have to. :D

.
 
Big Mac,

You will still have access to this forum, just as you do now, you aren't a sawhorse, so nothing changes. The change is that in order to remain a sawhorse, or become one for the first time, requires a "subscription, rather than the donation system that JAR was trying to stay with. The forum will still be open to the public for viewing, and posting if you are registered. Subcriptions are required for sawhorses.
 
This is great info.

It answers my question, the code was silent on the issue, and is now explicit.

THANKS Francis !
 
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