I'm the president of a 20-condo association and several residents have been complaining of water coming in and destroying their drywall. The water is coming in at the exact same place in all units and the residents claim they didn't have this problem until we had a company replace all of our siding a few years back.

The owner of the company who did the siding said that we need to caulk around the J channels to keep the water from coming in. I had a company come out and look at it and they said that the problem is that there's no layer of plastic wrapping between the siding and sheathing. He said different counties/cities/states have different codes for siding installation.

Is there indeed a code for this type of thing? Where would I look to find this specific code for my area? What keywords should I be looking out for?

  • The local building department will be able to tell you what the code says, or at least what code they follow.
    – Tester101
    Apr 19, 2015 at 1:18

3 Answers 3


Yes. What he was talking about was the "water-resistive barrier." (WRB) This is typically Tyvek housewrap (a kind of vapor-permeable plastic) or grade D building paper (tar-soaked paper). All wood-framed buildings need one of these, or else any water that penetrates the siding can contact the sheathing, and will quickly rot it out and infiltrate inside. All buildings in jurisdictions covered by a building code are legally bound by this requirement.

If your condo building was re-sided by somebody who removed the WRB and did not put another one, you have an emergency situation on your hands. You need to IMMEDIATELY have someone remove the vinyl siding, replace any water-damaged sheathing, studs, and drywall, and install a proper WRB behind new siding. This is not optional. If you fail to do this, the building could be rendered structurally unsound and effectively uninhabitable due to mold; the aforementioned building materials are highly vulnerable to water. It will cause them to grow mold, become soft, and get eaten by termites.

Another possibility, because the residents say the water is coming in at the same place in each unit, is that the windows were not flashed properly--especially if that place is under any windows. This is a more common error than forgetting the WRB entirely but no less important to fix in a climate where it rains. The solution to this problem would be to make sure the wall's WRB is properly integrated into the windows' nailing flanges. A common error is not lapping the WRB over the top flange, but rather nailing the flange over the WRB--which allows any water flowing down the WRB above the window to get behind the window's flange and into the wall. Needless to say, if there is no WRB at all, the windows are by definition improperly flashed, and could easily be the water infiltration points.

It is highly likely that you have an actionable legal case against the company that installed the vinyl siding if either of these defects can be proven. Unfortunately, any company that will make such galling errors is unlikely to be well-insured.

  • Great response. What if the company claims that there was no WRB there to begin with? Let's assume there wasn't. Is it their responsibility to put on new WRB? About the windows possibly not being flashed, is this also the responsibility of the vinyl installers? Apr 19, 2015 at 0:34
  • 1
    Regardless of whether the WRB is required by code, if they fail to fix the situation, you can sue the contractor for breach of contract for having failed their legal duty to use workmanlike care, as the standard for workmanlike care for your location surely includes a WRB and window flashing.
    – Edwin
    Apr 19, 2015 at 0:48
  • 2
    Absolutely. If they notice there's no WRB and fail to either add one or alert you to the situation, that's simply gross, borderline-malicious negligence, akin to a mechanic who works on a car with dangerously low levels of oil in the engine letting the owner drive off with the car in that state without either alerting them to it or adding the required oil. It's just unacceptable, unprofessional behavior.
    – iLikeDirt
    Apr 19, 2015 at 2:51
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    I find it extremely difficult to believe that no WRB was required until 2012. If there was a code at all, that's, like, one of the most basic parts of it. Almost no point in having a building code if it lets you build so dramatically incorrectly. Caulking the J-channels is like a band-aid on a chest wound. It won't hurt, but if there's no WRB, the real solution is to add one.
    – iLikeDirt
    Apr 20, 2015 at 16:12
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    @iLikeDirt It turns out I was speaking to the wrong person. They dealt with residential codes, but I needed commercial. I spoke with the commercial plans examiner and they informed that it has been code since at least 2011. Thanks for your answer, though I fear our true problems have only yet to begin. May 7, 2015 at 20:38

The actual code requirements depend on your municipality/authority having jurisdiction (AHJ). Also, keep in mind the requirements in lots of places were different several years ago. Some places vinyl siding did not require a wrb below it.

However, the current best practices are that you generally need a vapour barrier, air barrier, insulation, weather resistive barrier (wrb), and cladding (and ideally a rainscreen) in your wall system.

The vinyl siding is the cladding, underneath that you would want a wrb like tyvek (+ flashing).

From vinylsiding.org:

Weather Resistant Barrier

Vinyl siding has always been designed as an exterior cladding, not a weather resistant barrier.

Vinyl siding is designed to allow the material underneath it to breathe; therefore, it is not a watertight covering.

Because of its design and application, it provides a supplemental rain screen that enhances the weather resistant barrier system by reducing the amount of water that reaches the underlying weather resistant barrier.

What Is a Weather Resistant Barrier System?

It is a system that includes water shedding materials and water diversion materials. Weather resistant barrier systems commonly consist of a combination of exterior cladding, flashed wall openings and penetrations, weather resistant barrier material, and sheathing. Effective weather resistant barrier systems will shed the water initially, control moisture flow by capillary and diffusion action, and minimize absorption into the wall structure. The level of weather resistance required is determined by the applicable building code and structure

Best Practice:

To achieve designed performance, vinyl siding must be installed over a weather resistant barrier system that includes

  1. a continuous weather resistant material and

  2. properly integrated flashing around all penetrations and where vinyl siding interfaces with other building products such as brick, stone, or stucco.

Refer to the manufacturer’s installation manual for specific product applications and recommendations. Whichever product(s) you decide to use as part of a weather resistant barrier system, be certain the materials meet the applicable code by contacting the manufacturer of the weather resistant barrier material(s). Always consult the applicable building code for minimum weather barrier requirements in your area. Keep in mind that additional measures may provide better protection against water intrusion than the minimum requirements of the building code.


Depending on the code in your jurisiction, the answer is most likely yes. Around here, the code is based on Uniform Building Code (UBC) Sec. 1708.(a):

All weather-exposed surfaces shall have a weather-resistive barrier to protect the interior wall covering.


...exterior openings exposed to weather be flashed in such a manner as to make them weatherproof.

Vinyl siding is by no means waterproof, or is it intended to be. You might want to call a local building inspector and ask what the code requirement in your area is.

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