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Community and Q&A

Fluid WRB at big box stores?

Jhaller | Posted in General Questions on


I am interested in building a workshop/studio 16’x12’x12′ and am interested in using a WRB. I read the wrb in a can article on this website and lots of other information on the subject. When I look at the mentioned products, they do not seem to be accessible in local stores or something that a non-contract professional can find. Is there a Home Depot or Lowes type solution? This studio will be assembled in the order of a 2×4 framed, OSB sheathed, fluid WRB, drain wrap, 3″ XPS and seam sealed, rainscreen, fiber cement.

Can you please recommend a product I can buy online or in a big box store and roll on? Also is the drain wrap necessary after the fluid WRB? It sounds like it is recommended. Trying to avoid the extra cost if I can find a 2 in one solution.

I could go with a peel and stick, but that has some similar issues in availability and what is available is awfully expensive.

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  1. GBA Editor
    Martin Holladay | | #1

    Here's an online source:

    Perhaps some GBA readers know of other online sources for liquid-applied WRBs.

  2. Jhaller | | #2

    Martin, Thank you very much for your suggestion. I looked at this. for my square footage I would need two 5 gal buckets. That is very expensive. Would something else like Hydrohalt @ homedepot or Rubberseal liquid rubber waterproofing and protective coating work?

    Here are the links.


    I'm not asking you to give your approval, but at least the cons why these products will not work or are worth trying.

  3. STEPHEN SHEEHY | | #3

    John- It doesn't look like either of those products is designed for use as a wrb. A little quick math shows the hydrohalt costs about $2 per square foot of coverage, plus labor. You'd need about a gallon per sheet of shesthing. That sounds awfully pricey.

  4. GBA Editor
    Martin Holladay | | #4

    Neither of the products you linked to is intended to be used as a water-resistive barrier (WRB). If you're looking for a WRB, choose a product intended for that application.

    For more information, see Housewrap in a Can: Liquid-Applied WRBs.

  5. user-2310254 | | #5

    John. Your best option may be tape the seams on the OSB. I used Huber Zip tape on my house. But check out Martin's tape test article before you decide:

  6. Jhaller | | #6

    Okay, After looking at the information presented it would seem that my idea is ridiculously expensive. I was advised by a trusted friend to do cavity insulation with Roxul in 2x6 walls and ceiling. I have read a few blogs from this website regarding vented or unvented roofs and vapor barriers/retarders and have a few questions.

    Q: I live in a climate 5 zone (North Central Indiana). I was thinking of using Roxul insulation and having DB+ on the interior wall, then drywall. What kind, if any and WHERE should an outside water, air and moisture barrier go on the walls and roof?

    Q: I'm not trying to meet code for the roof, but just provide some comfort in the summer and winter. with R-23 insulation in the roof cavity, can I use wool fiber board to insulate roof on the outside? I'm not trying to do 6 inches of the stuff, but maybe 2 inches? This also ties into my first question about the WRB as well.

    I saw lots of photos of roof assemblies, but some included a WRB like Grace on the roof decking, a vapor barrier at the bottom of the air gap and a vapor barrier on the inside of the wall. I'm still confused on what I need and what is extra or overkill.

  7. user-2310254 | | #7

    John. There are good reasons for meeting or exceeding code. But I let others respond to your questions and outline why.

    Have you considered using used rigid foam for your project. It is often available at very affordable prices. (See Craigslist or If you are trying to economize but want good performance, this strategy might be worth considering.

    Also... Will your workshop have heating or air conditioning? If so, what type.

  8. Jhaller | | #8

    I have considered using rigid foam on the outside. But I have been reading that with as much insulation as I will have on the inside that I don't want to have an impermeable air barrier on the outside. I know that not all rigid foam can be used as an air barrier, but if you have an example drawing or setup of thin layer of rigid on the outside and fluffy insulation on the inside I would like to see it. I am mainly concerned about getting the order of the layers correct, what goes where. Then making sure the envelop on the interior is sealed properly.

    I am considering a small room AC and Heater to keep things a good temp in the appropriate seasons.

  9. GBA Editor
    Martin Holladay | | #10

    Rigid foam is much easier than mineral wool to install on the exterior side of your sheathing -- especially on a roof.

    If you install the proper thickness of rigid foam, there is no need for the rigid foam to be leaky or vapor-permeable.

    I'm not sure why you wrote, "I don't want to have an impermeable air barrier on the outside." Air barriers are always good. To learn more about air barriers, read this article: Questions and Answers About Air Barriers.

    The usual order (for a wall), from the inside to the outside, is:
    - Gypsum wallboard
    - Studs filled with fluffy insulation
    - OSB or plywood sheathing (ideally, with taped seams)
    - Rigid foam if desired
    - A water-resistive barrier (WRB) like housewrap
    - Vertical furring strips to create a ventilated rainscreen gap
    - Siding

    There are variations, but that's the basic idea.

  10. Jhaller | | #11

    Steve: Thanks, but cannot read the article as I'm not a paying member.

    Martin: Thanks for the information. So based on your recommendation and some extra reading I don't need any vapor retarder on the inside as long as the cavity doesn't get to humid, correct? I have a local dealer of the zip system and am considering using this. Can I put rigid insulation over the zip system with out an additional drainage plane? I am considering just 1 inch of pink f150 insulation and then a 3/4" 1x4 rain screen over that.

  11. GBA Editor
    Martin Holladay | | #12

    Q. "I don't need any vapor retarder on the inside as long as the cavity doesn't get to humid, correct?"

    A. Whether your wall assembly needs an interior vapor retarder depends on the details of your wall assembly and your location. If you live in Climate Zone 4 or anywhere warmer, you never need an interior vapor retarder. If you life in Climate Zone 5 or anywhere colder, you may need an interior vapor retarder (for example, kraft facing or vapor retarder paint).

    For more information on this issue, see these two articles:

    Do I Need a Vapor Retarder?

    Vapor Retarders and Vapor Barriers

    Q. "Can I put rigid insulation over the Zip System without an additional drainage plane?"

    A. I'm not sure what you mean by a "drainage plane." If you install rigid foam on the exterior side of Zip sheathing, make sure that the rigid foam meets the minimum R-values explained in this article: Calculating the Minimum Thickness of Rigid Foam Sheathing.

    Every wall needs a water-resistive barrier (WRB); perhaps that's what you meant by "drainage plane." A true drainage plane requires a rainscreen gap. Rainscreen gaps are always a good idea; for more information, see All About Rainscreens.

  12. GBA Editor
    Martin Holladay | | #13

    You wrote, "I cannot read the article as I'm not a paying member."

    You may be interested to learn:

    1. GBA offers a free 10-day trial membership.

    2. You can become a GBA member for one month for just $15.

    3. Since you are planning to build a building, you might want to consider this point: If you get just one good idea from an article on GBA, that idea can easily save you a lot more than $15.

  13. STEPHEN SHEEHY | | #14

    John: Martin is right. Investing in a GBA membership was among my best ever investments. No matter how good your builder is, no one cares more about your house project than you. The more you know, the better the outcome.

  14. user-2310254 | | #15

    Second Stephen's testimonial.

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