First off, this question is a spin-off of this question which I asked recently. Summary: We have several buildings throughout our condo association that do not have WRB. As the answer in the linked question suggests, getting WRB installed is absolutely critical. However, it may be that we are going to have to eat the costs of installing WRB where it does not exist as the contractor may not be liable. This is going to cost our association well into the tens of thousands I am sure and will put everyone in the community in quite a financial pinch.

Therefore, I am researching possible alternatives that will yield an acceptable degree of effectiveness in preventing water penetration. I'd prefer a permanent solution if one exists, not something that requires yearly maintenance like caulking.

  • Have you spoken with an attorney yet? I'm not sure this question is really relevant to the situation if WRB is required by code (as indicated in the comments of the linked question). Any further work would be required to meet the existing code.
    – Comintern
    Commented Jun 20, 2015 at 17:01
  • You also might want to get the manufacturer's installation instructions. Almost every vinyl siding installation guide I've seen specifies a WRB backing - at very least, ignoring the recommended installation procedures would indicate negligence. It likely also voided the warranty on the siding.
    – Comintern
    Commented Jun 20, 2015 at 17:12
  • @Comintern It may be the case that installers didn't replace all siding in 2012 and did a proper install complete with WRB for the siding they did replace. For the siding they didn't replace, we'd have to find out who the last company was to do that and those records are probably long gone. Therefore, if the 2012 installers can't be held accountable, speaking to an attorney would be futile. Commented Jun 20, 2015 at 17:23
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    When tens of thousands of dollars are at stake due to professional negligence, hiring an attorney is never futile.
    – iLikeDirt
    Commented Jun 20, 2015 at 18:12
  • 1
    I would argue that they are absolutely accountable for it. They had to notice that the wall was built dangerously during the course of their contracted work, but failed to inform you. That's clear professional negligence. Call the local contracting board and see what they have to say about, at the minimum.
    – iLikeDirt
    Commented Jun 20, 2015 at 19:00

1 Answer 1


The short answer is that there isn't an alternative that will yield an acceptable degree of effectiveness. Vinyl siding is not intended to create a moisture barrier, and attempting to create a moisture barrier with it could potentially exacerbate the problem by trapping water underneath it. This is almost always specified in the installation instructions (and almost always required by code). For example, in from the CertainTeed Vinyl Siding Installation Guide (my emphasis):

Vinyl siding is an exterior cladding; it is not a complete weather resistant barrier. Before applying siding, make certain the substrate is watertight. In order to be protected from precipitation, the substrate may need to be properly flashed around areas such as windows, doors, other openings and corners so as to shed water to the exterior. See page 45 for proper flashing around windows. The siding alone is not meant to be a watertight barrier.

Caulking only the J-channel is also not sufficient to prevent water infiltration. If you examine vinyl siding closly you'll notice that the bottoms of most siding pieces have drain holes, and runs longer 16` (depending on the manufactured length) will have unsealed lap joints.

If you seal all of these openings, you will likely still have issues. Vinyl siding is designed to allow air to move behind it to allow moisture out from between the vapor barrier and the siding. Sealing it enough that it forms a water barrier would create a moisture trap behind it that could potentially be as bad as not sealing it.

Finally, vinyl siding is hung fairly loose because it expands and contracts quite a bit. This means that you can either seal it well enough that the seals won't break due to expansion (which will make it buckle and warp) or allow expansion and contraction (which will break your seals and provide areas for water ingress).

Any "solution" is basically just going to mask the underlying problem or make it worse. I'd say at this point it's a matter of weighing the long term consequences of not fixing the issue (mold, insects, rot, structural failure) with the short term costs.

  • Correct. You have to eat the cost of doing it right. No way around this. Keeping your incorrectly-built walls and trying to band-aid them is putting the entire buildings in jeopardy. Now that would be a financial burden on your tenants. Don't be penny-wise-pound-foolish.
    – iLikeDirt
    Commented Jun 20, 2015 at 18:13

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