I did a shower in Hardieboard sealed with two layers of Redgard. Should I still seal the grout lines even though we used Redgard underneath?

  • 1
    I always seal grout so it will be less likely to get stained. Redgard is good but make it bullet proof by sealing the grout.
    – Ed Beal
    Jan 26, 2016 at 0:16

2 Answers 2


You don't have to. It is completely up to you. Sealing the grout is doing absolutely nothing as far as water-proofing your current setup. I Redgard/HB many showers/tubs and here is what I do:

  • unsanded - gets sealant. In my opinion it stains easily, especially below level where water constantly hits.

  • sanded - don't seal it. It looks better unsealed and this grout allows you to "sand" out a stain.

  • epoxy - no sealant of course.

  • Agree, one should not count on grout sealer as any form of waterproofing. The "sealant" referred to in other answer for CBP warranty is not the grout sealer. Jan 26, 2016 at 6:16
  • @JimmyFix-it - if you can't count on it to prevent stains how can it really be sealing water... He has HB/Redgard... if there is water getting in bad places he has bigger problems.
    – DMoore
    Jan 26, 2016 at 6:18
  • Yes, but his question relates the use of grout sealer to his application of Redguard, implying some sort of waterproofing value to the grout sealer, which is not correct. It should never be relied on for that purpose, even though it may give some stain resistance. Jan 27, 2016 at 3:19
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    @JimmyFix-it - exactly. Using grout sealer used to be more important as a lot of installs weren't done water tight. Even HB without redgard if done right it would be really really hard to leak. Add on an 1/8" of rubber and we can move past sealer as a water barrier. I know it works if applied right and applied every x amount of months/years... but that never happens right.
    – DMoore
    Jan 27, 2016 at 3:41
  • @JimmyFix-it - Then what are they referring to? Sealer is to prevent stains. I'll have to admit, I kinda stopped reading after Should I seal grout. I don't care what comes after that, my answer is yes. - Is it harder to sand out stains on sealed sanded grout then non-sealed, DMoore?
    – Mazura
    Jan 27, 2016 at 7:02

I always seal the grout, whether or not I'm after one of Custom Building Products' warranties:

A complete CUSTOM Shower Installation System of products must be used including Shower Slope, Shower Base, ANSI A118.4 Bedding Mortar, Sealant, and suitable CUSTOM RedGard Waterproofing and Crack Prevention Membrane to qualify for this limited warranty. –CBP

(I've no affiliation with CBP. If other companies offer similar warranties, I'd love to know about them.)

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