View Full Version : Making holes in cocrete backerboard

11-14-2006, 06:31 PM
I am curious as to how to make small holes for plumbing in concrete backerboard, I know you can score the hole and carefully bash it out, but is there an easier way? Is it possible to use a router with a carbide striaght bit or something along those lines?


11-14-2006, 07:39 PM
Carbide bits work, a jig saw will work, and carbide drills, too. Or, use a carbide scoring tool and then knock it out. A small router like a RotoZip with a carbide bit will work, but don't rush it - it will get hot. A diamond tool works better. If using HardiBacker, a jig saw will cut it (and dull it). Watch out for the silica dust when cutting the stuff - it will get everywhere and is a known carcinogenic - cut it outside upwind.

11-14-2006, 08:51 PM
Hmm lots to think about, thx :)

11-14-2006, 09:26 PM
Try a 1 3/8" carbide-gritted hole saw. You can use it to make the proper size holes in cement backer board as well as the ceramic tiles. You need a drill with 1/2" chuck. If I need to enlarge a hole, I use a Dremel or Rotozip with a Carbide bit.

You can get a cheaper version of this at Lowes without the fancy spring ejector.

Here's a link for more info:


11-15-2006, 05:24 AM
If you need to cut it in place, use a "shop vac" keeping the hose a couple if inches from your cut. Will reduce the dust to next to nothing.


11-15-2006, 05:29 AM
For just plain old 1/2" durock (or similar concrete board) I just use plain old wood-bore spade bits and or hole boring bits. Nothing fancy, and works fine. Just go slow to keep it neat. ;)

11-15-2006, 07:52 AM
If it's "plain old CBU", you can perform manually. Just scratch it out manually by twisting a sharp pointed object on the spot.

I did this with an old steak knife. It worked. :D

The time you take is not significant for one or two holes. The big advantage is little dust. You can keep a wet sponge on the CBU too. Power tools create dust. CBU dust can often be invisible, but you will see it later on all your furniture and floors, and you will feel it in your eyes, nose and lungs.


11-15-2006, 10:12 AM
Wear eye protection, use a dust mask, and set up your work table outside if possible. If you're drilling holes in place, just shut the bathroom door and vacuum up the mess after. I like to use a bed of cardboard or something similar to protect the tub when I'm working in the shower area.

I think standard wood bits will wear out prematurely if used on abrasive materials. A good gritted holesaw makes professional looking holes and can be used on anything but metal. It also never gets dull (or so the manufacturers say).

Steak knife?

I thought I was the only one who gave low-tech answers around here. :D