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  • Coverage of RedGard

    I was rolling some RedGard (liquid-applied, elastomeric membrane for tile installations) out this morning. I actually pay attention to the directions, and was going for the recommended wet film thickness (2 coat) of 93 mils for waterproofing application.

    The bucket of RedGard says that it will cover 35-40 sq ft per gallon as a waterproofing membrane. Hmmmm.... I wasn't getting that kind of coverage. Made me wonder enough to find a calculator.

    35 sq ft at a wet film thickness of 0.093 inches is 468.7 cubic inches. A gallon is 231 cubic inches. So, if you follow the label directions, you will get about HALF the coverage they claim. Can't cheat the numbers.

    Now, this stuff isn't cheap. But what's worse, I imagine many guys will look at the coverage on the container, buy that much material, and apply it all until it's gone. That's what I usually do, anyway. Problem is, the material comes with a lifetime guarantee.... when installed exactly per the instructions. So if you ever (God forbid) have a claim on a tile job, they will come and measure your film thickness (the dry film thickness is half of the wet film for this particular stuff) and tell you that you didn't apply it thick enough.

    Could be an honest mistake. The person that calculated the coverage for the company (Custom Building Products) might have considered the dry-film thickness instead of the wet film. With this material, it makes a big difference. Even so, I'm not trusting the coverage information on the containers anymore.

  • #2
    Re: Coverage of RedGard

    I think they are giving the coverage amount of a single coat. Do "they" recommend 2 coats or is this outside information?

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    • #3
      Re: Coverage of RedGard

      They (Custom Building Products) recommend two coats for waterproofing applications, totalling 93 mils combined wet film thickness. The 35 to 40 sq ft coverage I mentioned is for waterproofing, two coats, at a combined wet film thickness of 93 mils. This is spelled out clearly in the "coverage" section on the bucket.

      If you're using the RedGard as an anti-fracture membrane, the instructions call for a single coat at a minimum wet film of 30 mils. The coverage for anti-fracture at this wet film thickness is stated as 110 sq ft. At 30 mils wet film, covering 110 sq ft takes 475 cubic inches. Again, this is a little over 2 gallons, not one gallon.

      Better buy twice as much RedGard, either way!

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      • #4
        Re: Coverage of RedGard

        Me thinks I would be contacting the manufacturer for clarification on the coverage. (No pun intended).

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        • #5
          Re: Coverage of RedGard

          I shot them an email. It really doesn't need clarification.... the coverage stated on the package is quite clear. But I am interested in what they have to say. I'll report on their comments when (if) I hear back.

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          • #6
            Re: Coverage of RedGard

            Well now, if your coverage is half of what they claim on the can there seems to be an issue. I'll be interested to hear what they have to say.

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            • #7
              Re: Coverage of RedGard

              Interesting stuff! I applied a coat of RedGard to my 80sf concrete bathroom floor last night as an anti-fracture membrane and I was literally scraping the bottom of the bucket to get enough to finish and I'm certain I was pushing the thickness in the end. As you mentioned I should of been able to get 110sf. I applied the product with a v-notch trowel as suggested in the instructions and smoothed the ridges with a 22" wide trowel (texmaster magic trowel great tool) then checked the wet film thickness in a few spots. I tried the 3/8 nap paint roller also and got poor results. It covered the film with bubbles and did not lay down a sufficient wet film thickness. I tried rolling back and forth, and only in one direction before going to the trowel.

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              • #8
                Re: Coverage of RedGard

                No answer from Custom Building Products yet. They claim to answer within two days. I think I might have struck a nerve.

                I notice that on the online data sheet they made some adjustments to the coverage. But the numbers still don't work out mathematically.

                I use a roller just because it's a little neater and easier. I don't get bubbles, but no way am I able to get the full film thickness using a roller. I just use more coats rather than fight with it, keeping track of the wet film thickness of each coat.

                I like Redgard overall. I recently used it on a ceiling over a shower. Using a sticky, modified thinset like Versabond (or Flexbond which is waaay too expensive, but good stuff) it makes a super bonding surface -- much better than thinsetting directly to drywall. I try to avoid backer board on ceilings... it's heavy and the thickness sometimes complicates things at the transition to the un-tiled ceiling.

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