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Forum / Residential Code Discussions /Weather Barriers
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Robert Rice
(3/1/2007 11:37:42 AM)
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Weather Barriers

Due to the lack of clarity in the application of weather barriers and the problems associated with mis-application this topic is for open discussion. The intent will be to hopefully come to a concensus on what we expect to see in the field. I won't pretend to be the expert in this area - merely the moderator of the discussion.

The basis of this discussion would be, for example, Section R703.2 and the referenced Table R703.4. Specifically, items "Hardboard Lap Siding" and "Fiber cement lap siding" both require "Sheathing Paper". Section R703.2 defines "Weather Resistant sheathing paper".

The last code, 2003 ODSC based on the 2000 IRC, was not as clear in the Table.

Per current code, it's required. It seems that the bigger questions are do we/how do we inspect.

Please share your thoughts/concerns.

Also, would someone offer to draft up a statement that clearly identifies the code reqmt's and our stance as SOC-ICC.
Robert Rice
(3/9/2007 7:17:58 AM)
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RE: Weather Barriers

Isn't there an approved barrier, or several that meet a particular ANSI standard that does substitute for the barrier? I've never seen one, but I believe I've seen them advertised.

Dale B
Robert Rice
(3/9/2007 7:18:51 AM)
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RE: Weather Barriers

If you read the ES Report for tyvek for instance, they will state that their product "...complies with, or is a suitable alternative to what is specified in, those codes listed in Section 1.0 of this report, subject to......" (Section 1.0 refers to 2003 IBC/IRC and 1997 UBC)

See ESR-1993 online.

The code (IRC) says in section R703.2, "...or other approved weather-resistant material shall be applied of studs or sheathing of all exterior walls as required by Table R703.4."


(3/12/2007 11:45:09 AM)
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RE: Weather Barriers

I have enclosed a directive from Richard Rogers at the state level referencing "Fiver cement lap siding"LMike Broomfield-Ader Cement Siding Memo- BO.doc ________ Page1
To: Building Officials Other Interested Parties
From: Richard S. Rogers Structural Program Chief ri gcrs state. or. us
(503) 378-4472
Subject: Fiber Cement Lap Siding — Approved Weather-Resistant Materials
In response to inquiries within the state, Building Codes Division (BCD) wishes to clarify that the Oregon Residential Specialty Code (ORSC) does not allow “fiber cement lap siding” to be installed directly against either studs or sheathing.
ORSC section R703.2 states;
Asphalt-saturated felt free from holes and breaks, weighing not less than 14 pounds per 100 square feet and complying with ASTM D 226 or other approved weather-resistant materials shall be applied over studs or sheathing of all exterior walls as required by Table R703.4. Such felt or material shall be applied horizontally, with the upper layer lapped over the lower layer not less than 2 inches. Where joints occur, felt shall be lapped not less than 6 inches.
Exceptions: Such felt or material shall not be required;
1. In detached accessory buildings.
2. Under panel siding with shiplap joints or battens.
3. Under exterior wall finish materials as permitted in Table R703.4.
4. Under paperbacked stucco lath.
With few exceptions, ORSC Table R703.4 clearly requires either “sheathing paper” or other approved weather-resistant materials, as noted above, to be installed under fiber cement lap siding.
Furthermore, BCD is unaware of any manufacturers installation instructions which permit the omission of a weather resistant barrier in this type of application.
Thank you for your assistance in assuring that these products are properly installed.
Greg S
Robert Rice
(3/13/2007 8:51:25 AM)
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RE: Weather Barriers

Thanks to the language in the most recent code, it's clear that it should be there.

The questions that arise from that are;

Do we inspect the installation?

Do we understand how it is to be installed/flashed/etc.?

Do we gain additional liability by inspecting?


These were the type of unanswered questions brought up during our meetings.

Robert Rice
(3/15/2007 2:07:33 PM)
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RE: Weather Barriers

Food for thought:

IBC states that information should be on the drawings,
106.1.3 Exterior wall envelope. Construction documents for all buildings shall describe the exterior wall envelope in sufficient detail to determine compliance with this code.
The construction documents shall provide details of the exterior wall envelope as required, including flashing, intersections
with dissimilar materials, corners, end details, control joints, intersections at roof, eaves or parapets, means of drainage, water-resistive membrane and details around
The construction documents shall include manufacturer’s installation instructions that provide supporting documentation
that the proposed penetration and opening
details described in the construction documents maintain the weather resistance of the exterior wall envelope. The supporting documentation shall fully describe the exterior wall system which was tested, where applicable, as well as the test procedure used.

The IRC (R106.1.1 & R106.1.2) doesn't state it as clearly but, does say that the drawings should " in detail that i\t will conform to the provisions of this code..." and,

R106.1.2 says that the manufacturers installation instructions need to be on site for inspection.
This, of course is not only talking about weather barriers but, could include them.