We recently moved into our new home and we are redoing some things that were done by the previous owner.

In the bedroom there is a wall that is covered with faux stones that average about 1 1/2 inches thick. One of the stones is over the central air vent, and even though it has several slits in it that go all the way through the warm air from the vent is mostly blocked.


  1. Is it possible to widen the slits without breaking the faux stone?
  2. Should I take the stone off to do this and then put it back on and mortar it back in place? Can I cut through the mortar with an oscillating tool?
  3. What is the best tool for making the slits bigger? Would an oscillating tool do it without breaking the stone? What about manual tools?
  4. What's the best way to cut faux stone?

Here is a picture of the stone: Stone with slits

Please let me know your suggestions.

  • Would think that a cutting/grinding tool would better control to prevent unwanted cracks/breaks. Will want a masonry/diamond type blade.
    – crip659
    Commented Jan 23, 2022 at 15:19

4 Answers 4



Definitely get rid of that!

Assuming that this "faux stone" is actually one of:

  • Actual stone, sliced thin
  • Concrete, molded and colored to look like stone
  • Ground up stone mixed with "stuff" to color it and molded to look like stone

and not, as I found one reference to faux stone:

  • Foam, painted and cut to look like stone (because you could cut through that very easily with many different tools to solve the problem)

My hunch (but those who have done more of this than I have will surely tell me if I'm wrong) is that those slits were done using a circular saw with a diamond blade as a plunge cut (I think that's the right term).

I would cut it out. The trick is figuring out how big the actual vent behind it is, and exactly where it is.

Get (buy, rent or borrow) a circular saw and a diamond blade. If you don't think you will ever need a circular saw for anything else, you can rent one instead of buying. Do not try this with an ordinary blade - it will not cut well and actually may be quite dangerous.

I'd start with two horizontal cuts across the middle of the existing slits, about two inches apart, centered both horizontally and vertically relative to the existing slits. That should get you a 2" by several inch hole. Then poke around inside to see the extent of the actual vent, mark it on the stone and cut the full rectangle.

Then slap a regular vent cover on it and you're done.

  • 5
    Yes, that looks about right for the method used. Depending on available tools an angle grinder is another option for using a diamond blade to cut stone/concrete, and the blades may be cheaper since they are smaller. Apply all the safety gear, and if you can rip it off the wall and do it outside, better yet.
    – Ecnerwal
    Commented Jan 23, 2022 at 2:08

Safety glasses, earplugs, dust mask if need be.

Stick a prybar in the middle and break out one of the thin slices by prying against the thick slice beside it. Those should come out easily.

Repeat until all those are gone. You now have wider slits. though some breakage was involved.

Then take a (masonry, hopefully obviously) chisel to the thicker slices, or use more prybar in the middle to pry until one of the two on either side of it break, after which a chisel would be more applicable.

IF you can remove the whole thing this might be more convenient and you get to pick where to make this mess, or whether to bring other tools to bear on it. You also get heat without this idiocy in the way of the vent (though you might also find what they were trying to hide by doing this abomination there.)


I have a different take on removing the smaller pieces. My difference is I will use a masonry drill to CAREFULLY drill a small hole in each end of the small slits. This will weaken the connection to the rest of the stone and with careful layout, the ends of the slits could be made uniform by drilling the holes in a straight line across each end. When drilling, you cannot do this quickly, the slower the better. You cannot do this too slow, as soon as you press too hard, the stone will chip away, the drill bit will go places you do not want it to. Then carefully remove the stone prying against the thicker stone by driving a long narrow tapered shim, like a trim and door shim to break out the narrow pieces. Wood will not chip the stone as quickly as metal will.

Last tip, use a drill bit that is slightly smaller that the narrow slits. If the slits are 5/16" apart, use a 1/4" drill bit. Same if they are 3/8" apart.

  • 3
    "You cannot do this too slow" is potentially ambiguous -- from context it means "Do it as slow as you can" rather than "Do not do this too slow" -- but it's confusing because in the previous sentence "you cannot" did mean "do not".
    – nanoman
    Commented Jan 23, 2022 at 15:38
  • @nanoman , I reread this 3 times, just now. That in addition to the many times I already proofread it before posting. There is no "did" in my writing. Just repeating the same thing to emphasize that it must be done slow. Unless you just want to pick apart my grammar, if that is the case, then edit it to your satisfaction. Besides that what part of what I wrote suggest anything else but slow that would be ambiguous?
    – Jack
    Commented Jan 23, 2022 at 16:11
  • 7
    "You cannot do this too slow" means either there is no speed which is too slow or that you must avoid excessive slowness. Commented Jan 23, 2022 at 16:40
  • 3
    Which one? That 60 rpm (for example) is too slow, or 60 rpm is OK? It depends on the intonation of the word "cannot," which of course does not come across in the written word. It could be a regional thing, where cannot is synonymous with must not. Commented Jan 23, 2022 at 17:20
  • 2
    You can never put too much water in a nuclear reactor. (Great SNL skit from many years ago, but can't find a video of it at the moment.) Commented Jan 23, 2022 at 20:24

I would do this backward to the other suggestions.

  1. Look around your home at all the other visible air registers. If they're all the same size, there's a good chance the hidden registers are equal size.
  2. Buy a new register cover/grille of the same size. Something that will suit this room and decor, or is at least paintable to match. OR make a cardboard template of the same size, or temporarily swipe a cover from elsewhere.
  3. Then cut away the fake stone that would be under your new cover or template.
  4. Fit the new register cover - if its intended for a flat surface you may have to make the surround flat with some careful rebating. If the stone won't hold a thread, you might need to use construction adhesive instead of threaded fasteners, which would be hard to get off for cleaning. Perhaps hook-and-loop fastener with adhesive backing will be sufficient.

Another option is to check down the hole and see if you can recess the proper register cover down the hole a lot, essentially under the stone.

Alternate thought - cut away the stone and then hide the hole by using the offcuts as a "bulwark" or "mound". This will permit maximum airflow with minimum noise, though things might fall in easier (dust, pets, children...)

You might choose to be creative - hide it in a fake potplant shelf, or if the hole is on the wall make a small "balcony" if you're crafty.

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