I'm installing CoreTec One vinyl plank flooring as a floating floor over slab in a three-season porch. I don't think my situation is as bad as that described in How can I prepare uneven concrete basement floor for vinyl planks? The slab is even at a macro level (no visible dips or hills). However, overall the cement has a texture like a lightly-textured ceiling, a bit rougher than most sidewalks. I worry that laying the plank over this is like laying it on a bed of nails with many points of contact but a lot of unsupported area in between. Do I need to do a skim coat of self-leveling cement to even this out before laying the planks?
Flooring – How smooth does the floor need to be to lay vinyl plank over it
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I'd question how waterproof you need this to be. Will there routinely be water sitting on the floor? If not, you may be over-engineering things.
That said, off the top of my head, one option for waterproofing the subfloor would be to paint on Redgard:
It's a 'paint on' waterproofing membrane that you'd typically use behind tiles on cement board and the like.
In your position, I'd try a fine toothed blade in a table saw for cutting the vinyl planks. As long as the material keeps moving past the blade, I wouldn't expect a problematic amount of melting/gumming.
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Best Answer
You can download the DIY installation instructions here, which contain a lot of guidance on the subfloor requirements, as well as instructions. They say concrete is a suitable subfloor, although they are probably referring to a typical interior floor rather than a broom finished surface.
There are also several caveats for concrete. It needs to be level (i.e., smooth/flat) to within 3/16" per 10 foot radius, and not have a moisture problem (the planks won't be damaged, but the moisture can collect under them and wick to walls and cause damage).
Ceramic tile (with grout lines), and textured vinyl are suitable subfloors, so the the surface irregularities in those surfaces aren't considered a problem (but they provide more support surface, that is less pointy).
The planks are rigid, so irregularities won't telegraph through them. They have a cork bottom layer which should conform to the small points in the surface. The planks don't expand or contract, which would mean that they don't move in relation to the rough surface, which might abrade the bottom, although they still want you to leave an expansion gap around the perimeter, so who knows.
If you are concerned that the surface is rougher and more irregular than a typical concrete floor, the best bet is to ask them directly. They have a toll-free support number, 844-743-7439, that you can call to get their recommendation.