I'm going to replace my bathroom carpet with a Vinyl floor, but want to make sure I get it level and waterproofed.

  1. Assuming there's a level subfloor, can I use a regular Aquastop underlay?
  2. Whats the best sealant to use around the edges against the wall?

The bathroom is only 2x2 max and fairly square in shape so seems like i could do this myself! This is my first floor job though so if I've failed to consider anything obvious please let me know and many thanks for any advice!

If it helps here are my choices so far:

  • Glad to hear you are getting rid of carpet in the bathroom. As far as doing it yourself, whenever I have seen carpet replaced in a bathroom, I have also seen rotten/moldy subfloors that need to be replaced since people tend to step out of the bath/shower onto the carpet and allow the water to absorb into the carpet/subfloor rather than completely drying off first. Just keep in mind that you might find this and need to replace it as well when you remove the carpet if planning to DIY--you can always decide to hire someone at that point though. Sep 20, 2017 at 12:31
  • I think the carpet might just be sitting on underlay over floorboards... I'd be comfortable with cutting out a plywood sub to level things out as like I say, the room is nice and square. So subfloor - underlay - vinyl, would that work? I'm finding it hard to find people to do this in my area so considering my own attempt!
    – Andyjm
    Sep 20, 2017 at 12:36

2 Answers 2


Get the installation white papers for the kind of vinyl flooring you're using and follow the instructions to the letter. They should tell you exactly what kind of underlay to use on top of the subfloor if any. For instance vinyl planking without a sticky side (not what you're getting by the look of it) needs no underlay, sealant or subfloor to function correctly as per the installation instructions.

As for sealing the wall surrounding the flooring, I assume that since you had carpet there this is a dry area of the bathroom and not required to be in direct contact with water. You don't need sealant around the wall as the drywall in that area should be greenback/mold resistant anyway. You can just trim, paint and caulk.

Additionally, you're going to need expansion gaps (~3/16") on all sides where the flooring meets a hard vertical plane in order to prevent buckling due to material expansion. This gap will usually be covered by trim or quarter round which you will caulk the portion that meets the flooring to prevent the spread of any water you may get on the ground from getting out of the shower and whatnot.

  • Thanks so much for the detailed advice, I feel a bit out of my depth now though as I've got no idea about expansion gaps and trims/quarters etc.! As long as I can buy the correct materials I might have to find a good floorer to do this one right
    – Andyjm
    Sep 20, 2017 at 12:48
  • Honestly, flooring is very easy. I believe that if you have the desire to do it you can. Like I said, nearly every flooring solution you get now a days will come with detailed instructions on exactly how to install the material. But I also don't know your exact setup. Also expansion gaps are literally just the concept of putting your floor together, in the case of vinyl squares, but cutting them ~3/16" short where they hit a vertical surface like the wall or the edge of the bathtub. This allows for the flooring to expand if needed without buckling the floor. The gaps are covered by trim.
    – cclater
    Sep 20, 2017 at 12:53
  • OK, I'll do a bit more research on the Vinyl to use and have a look under the carpet tonight so see what I'm dealing with! Thanks for filling me in on a few of the basics here
    – Andyjm
    Sep 20, 2017 at 12:58

Glad to see the carpet go, but too much. This is the floor, not the shower (a shower needs more, I'm just saying). You'd apply Floor Leveling Compound (not anything like Aquastop) to any low spots on the sub-floor and then lay your vinyl atop. Finishing by sealing the perimeter with a very thin pinstripe of regular Tub & Shower caulk.

Waterproofed, level, flat and solid for decades. Using anything like Aquastop adds unwanted and very detrimental cushioning or movement. If (by chance), you were thinking of Self-Adhesive vinyl squares, the Aquastop wouldn't do anything to keep the water away from those either...you'd caulk those seams/gaps as well.

  • I have a feeling the carpet and underlay might just be sitting on floorboards - would it be sensible to add a plywood layer on this and stick the vinyl over that?
    – Andyjm
    Sep 20, 2017 at 12:39
  • Not necessarily, but another layer isn't a bad thing at all. Planks are better than plywood and if their joints are still rather tight or close, then you'd just fill those with Floor Leveling Compound too...no affect to the toilet or vanity. Expansion and contraction would be miniscule in such old planks and the vinyl will keep them locked in, possibly unlike the carpet...rubber backed carpet would've been the same as vinyl.
    – Iggy
    Sep 20, 2017 at 12:47

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