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no wrap under vinyl siding


John Dirks Jr
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I am still looking for any info that is from one of the manufacturers that states they rely on OSB being a weather restive sheathing.

I was recently had a case that covered a hundred townhomes built 14 to 15 years ago under the 91 UBC.

Mark

The only information I've seen is the APA OSB product guide that states that there are exterior rated OSB products. I believe the LP SmartSide products are OSB overlaid with a treated resin paper.

The only OSB panels I see used as sheathing are rated Exposure 1.

Download Attachment: icon_adobe.gif APA OSB exposure classification.pdf

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Peter

thanks for the info

I see that was published 2009.

The LP products are as you say and I find them to be a very substantial product.

If installation instructions are followed these products will last but the problem

I often see is that the clearances are not maintained and that is where the degradation starts.

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  • 2 years later...

No posts to this in a while, but earlier this was described as the tip of the iceberg issue. I seeing this problem in a subdivision where most of the houses where built by same builder with the following: faulty vinyl siding transitions, no building wrap, osb behind under vinyl. Is this a nightmare?

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Should mention, the observed problem location, is 100 miles or more from my published location. Code enforcement where I live is very good.

However, very concerned that code enforcement where this situation has been sighted not so good. Also I have observed that at least in one case the OSB totally degraded when exposed to small amount of water in 7 years.

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Should mention, the observed problem location, is 100 miles or more from my published location. Code enforcement where I live is very good.

However, very concerned that code enforcement where this situation has been sighted not so good. Also I have observed that at least in one case the OSB totally degraded when exposed to small amount of water in 7 years.

I would say that 90% of the homes in my area built prior to 2009 with vinyl siding will not have a WRB, including my home which was built in 2005. Unless you start pulling off the siding you really have no way of knowing what is going on. I have used moisture meters on many homes that did not have a WRB around penetrations, etc and it is not very often that I find hidden wet or damaged areas. I can't tell you why they are dry, but the vast majority are.

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A lot has happened in my world since this thread was originally started.

We have investigated quite a few more individual homes and town home units

Even though the 2000 and 2003 IRC got it wrong on WRB requirements behind vinyl siding and the defense tries to use this argument, we have been successful in pointing out the flashing section of the code requires counter-flashing.

Without a WRB that laps the flashing. The flashing is not properly protected and acts as a funnel instead of a protective flashing that directs moisture back to the exterior as code states.

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In my area the lack of an wrb behind vinyl was standard until required by the IRC. My house was built that way in 1990 (with OSB). Over the years I have removed much of the siding when I replaced windows. I only found minimal deterioration below one window. I think this installation generally performs well because the wall sheathing can dry quickly.

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In my area the lack of an wrb behind vinyl was standard until required by the IRC. My house was built that way in 1990 (with OSB). Over the years I have removed much of the siding when I replaced windows. I only found minimal deterioration below one window. I think this installation generally performs well because the wall sheathing can dry quickly.

Water should not ever get to the OSB. If it does, you have a problem.

Regardless of what code was in effect when any house was built, the siding manufacturers have always recommended secondary moisture barrier be installed as part of their siding system.

I've gotten into debate with a builder or two over the years. When they tell me moisture barrier was not required by code, I respond with the following;

"What is the brand name of the siding? Lets have a look at their installation instructions."

I never hear back from them and the conversation ends.

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I believe that older installation instructions for vinyl siding do not require a wrb behind the siding. I recall looking at this a while ago and seeing the requirement for a wrb a bit before it was required by the IRC (if I recall correctly). This was standard practice in my area for close to 20 years with OSB and there has generally not been a lot of problems. Whole different story with stucco.

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We keep debating as to whether or not WRB was required behind vinyl siding by the code or by the manufacturer?s installation instructions.

Vinyl and steel are very leaky and something needs to protect the building envelope from moisture intrusion into the interstitial cavities. These products were originally designed to be a quick side over the original without remove product. You did get some protection from the original siding in this process.

In the late 80?s a lot of builders in my area and all over started using vinyl without WRB behind. The code called for WRB on all weather- exposed surfaces. . It goes on to describe the insulation of such a WRB and its omissions. It speaks of waterproof panels and water-repellant sheathing as being exceptions. One thing many do not consider is if using a water repellant sheathing or waterproof panel the joints need to be taken care of making them water-tight or proof otherwise it doesn?t work as a weather-proof assembly. This is where the problems come in. Water gets in and creates problems, attorneys get involved and some kind of wins and the other loses.

All of the UBC stated WRB on all weather-exposed surfaces; and that does include the gable ends above the heated wall areas. Io have heard all of the excuses; ?we don?t need it on the gables or garage walls only on the heated occupied walls?. You ought to see the way this defense works when the case is litigated.

Weather Protection 1982 UBC

Sec. 1707, (a) Weather-resistive Barriers. All weather-exposed surfaces shall have a weather-resistive barrier to protect the interior wall covering. Such barrier shall be equal?

91 UBC the same section 1708. (a)

97 UBC the same section 1402.1

99 don?t have it

IRC 2000 same as IRC 2003

IRC 2003 R703.2 Weather-resistant sheathing paper.

Exceptions include: 2. Under panel siding with shiplap joints.

3. Under exterior wall finish as permitted in Table R703.4.

Horizontal Aluminum ?no?

Steel ?no?

Vinyl siding ?no?

IRC 2006 Section 703.1 Finally starting to get it right. Table R703.4 WRB required under everything

In the 2000 and 2003 a case can still be made that flashing needs to be counterflashed with a WRB in order to properly divert moisture back to the exterior.

I realize this can bring debate but we have successfully argued this need for a WRB behind all claddings and damages were awarded to my clients in several cases

I welcome all critiques of this post as it makes my case better the next time it comes up in a case.

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  • 2 years later...

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