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Cjohn 11-09-2012 07:43 AM

cutting cement board
I'm replacing linoleum in our bathroom with tile, and am planning to install 1/4 cement board underneath. Our bathroom is really small and has small sections/walls that protrude, and I was wondering if anyone has any tips for cutting notches into cement board. Everything I can find on cement board seems to assume that every room is built for perfectly straight cuts!


joecaption 11-09-2012 07:50 AM

I make the long cuts with a carbite tipped ciruler saw.

Make sure to wear a dust mask.

Cjohn 11-09-2012 07:51 AM

Unfortunately I don't think that will work in my case, as some of the parts that are protruding are only 4 to 5 inches across and a couple inches deep.

joecaption 11-09-2012 08:01 AM

JazMan 11-09-2012 04:58 PM

I have this strange feeling that Cjohn is not interested in buying a CBU shears ($200-300) to do his tiny bath floor. Just a feeling though.:wink:

You can make small "U" cuts into concrete board with even just a razor knife and a few other regular tools, but it can take some time. Alternatively you can cut the larger sheet into smaller pieces so you'd be making "L" instead of "U" cuts. A carborundum blade on a sabre saw is available too.

The easiest and cheap way is to use a side grinder like this.,r:0,s:0,i:88

Some are available for under $40 and Harbor Freight should have one for under $20. It's a tool you'l use many time including to score the concrete board & certain tile cuts maybe.

It does produce dust so use it outside with a fan behind you blowing the dust away. A mask is smart.


Hardwood Head 11-10-2012 11:12 AM

Sawz-all with a metal blade, no dust no fuss

Cjohn 11-12-2012 08:37 AM

You nailed it Jazman--lot looking to spend that much on a $200 bathroom tile job :). Thanks for the tips, it looks like that grinder is probably the best option. Thank you all for your advice!

mnp13 11-12-2012 08:54 AM

I used my RotoZip with a cement blade on it. Very easy to use and really precise because it's small and light.

tacomahardwood. 11-12-2012 05:39 PM

Drill about a million holes it and connect the dots with a chisel . Tinme consuming , But the least of buying a bunch of tools , Also a scribe will work , Just scribe it about 20 times till you work a weak spot , Drill the corners

Bumpr1080 11-12-2012 11:32 PM

I just finished a huge siding/trim project with 1/4 hardi plank. we used a simple diamond cement 7.5" circular blade for our miter and table saw. Works just fine.

Cjohn 11-13-2012 07:18 AM

TacomaHardwood--Did you use a special drill bit?

JazMan 11-13-2012 08:17 PM


Originally Posted by Cjohn (Post 1051097)
TacomaHardwood--Did you use a special drill bit?

Yes, he probably uses one that will last long enough to make a million holes.:wink:

You're not actually thinking of doing that are you?


Cjohn 11-14-2012 07:10 AM

I have to cut out a hole for the toilet flange as well, and I was thinking some drill holes would work best for that, unless there's a better option?

JazMan 11-14-2012 08:38 PM


I have to cut out a hole for the toilet flange as well, and I was thinking some drill holes would work best for that, unless there's a better option?
I already gave you the answer in post #5 above. Use a grinder if you have one. Of course drilling a bunch of holes will work too.

In the old days when Wonderboard first came out we didn't use or know of all these many tools available today. We made a hole by first scoring the surface and embedded mesh with a regular utility knife or laminate scriber, and then tap with a hammer to complete the hole. So, I recommend the grinder with a fan blowing or a jig saw with appropriate blade.


gregzoll 11-14-2012 08:52 PM

Instead of Cement Board, the better option is Georgia-Pacific's DensGuard or DensShield I used DensShield for our bath floor, and it is easy to work with, and holds up as good as Cement Board.

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