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Lack of weather resistant barrier under vinyl


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Yesterday I had a 23 year old modular that had the vinyl siding installed directly over the OSB. There was no house wrap and I'm sure no flashing around the windows and doors. The last modular I did was the same as this one. I thought the other one was a fluke, but the buyer of this one said that he had been looking at new modulars, and was told house wrap was an option.

I don't see many modulars. For those who do, is this typical? I'm pretty incredulous.

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Your problem stems from the code and what was required by the code in force where the house is located at the time it was built 23 years ago. The manufacturer would have researched the local codes in effect at the time before starting to fullfill the order for that house. My father built modulars in New York state before he died and the manufacturer was based out of PA. The manufacturer built the mod occording to his local code requirements and that meant that when my father ordered the house he would have to very carefully review the spec sheet on the order to ensure that they'd dotted all of the I's and crossed all of their T's before approviing the order.

Just two code cycles ago here in Seattle Table 703.4 of the IRC did not require WRB under vinyl siding and stated only that vinyl siding must be installed in accordance with ASTM D3679. The Seattle Residential Code now requires a WRB under vinyl.

It's possible that 23 years ago (possibly even today) the codes in PA didn't require WRB (Look at exceptions allowed under R703.2 and then look at Table 703.4).

A manufacturer isn't going to install anything that it doesn't have to if it's going to save on construction cost and increase profits; that's just the way it is.

So, the real question is - what condition is that OSB in after 23 years beneath vinyl siding in a state with winters as severe as Pennsylvania's?



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The OSB was actually OK in the few areas I looked. It was a different story around the windows, but I didn't delve too deeply there, for fear of being blamed for causing damage.

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Regardless of what codes were in effect when the house was delivered, I have to think the siding manufacturer would have recommended a WRB. It doesn't really matter, though, because it's a mess now.

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