I've been seeing those concrete-looking hardboard slabs at Home Depot and Lowes over the past few years but never needed to use them. However, I'm now finishing a new bathroom and we decided to use this backerboard material in the shower stall, to make a firm base underneath the ceramic wall tile.

This backerboard is probably best known by the trade name "Durock," which is trademarked by US Gypsum. (The same company owns the trademark on "Sheetrock," I think.) I used two pieces of Durock and several pieces of a competitive product called "Hardiboard." The brochure that came with the Hardiboard said that the stuff is 90 percent concrete and 10 percent cellulose fiber. It also said that these boards are "impervious" to moisture and will not rot or soften when soaked.

I'm not sure about Durock, but Hardiboard comes in various thicknesses. All the stuff I got was 1/2-inch thick. Home Depot has Durock in two sizes: 36 x 60 inches and 32 x 60 inches. Lowes has Hardiboard in 36 x 60 inch slabs, but at various thicknesses from 1/4-inch to 1/2-inch thick.

This stuff is HEAVY. I did not weigh it, but my seat-of-the-pants estimate is that a 3 x 5 foot piece of Durock/Hardiboard is as heavy as a 4 x 8 sheet of Sheetrock, possibly heavier.

This stuff is also fairly miserable to cut. Although both Durock and Hardiboard literature say that you can score it and snap it (much like Sheetrock), a friend said he tried this and it was a dismal failure. I bought a special saw blade for my circular saw and that is what I mostly used to cut these concrete boards. This worked beautifully, except that it is noisy, dusty and uncomfortable, what with all the concrete particles being thrown by the spinning saw blade. Wearing goggles is an absolute necessity.

I will write more about this in the next message.

--Bob

Here's the rest of my story about working with ceramic tile backerboard:

I had to cut a couple of holes in this stuff and I did not have the right tools. I tried a jig saw but the blade dulled very quickly. I ended up using a masonry drill bit and making a lot of little holes, then breaking out the larger hole. I should have run to the store and gotten a Roto-Zip bit for my Roto-Zip tool; this is the easy way to cut holes in these concrete boards.

Durock and its ilk are attached to walls and floors using special screws that are quite expensive. As I recall, a pound of screws costs $15-20. According to both Durock and Hardiboard literature, studs must be 16-inches on center. (This meant that we had to rip out the wall that my now-fired contractor built, as it was 24-inches on center, and rebuild the wall correctly. The contractor-installed framing had other problems anyway, so rebuilding the wall killed two birds with one stone.) Screws are installed every eight inches. The screws are self-drilling and do not require pre-drilled holes.

The screws have ribs under the head that automatically chew out a recess for the screw, so that it's possible to get the screw heads flush or below the surface of the concrete board. In practice, this was easier to do with Durock than it was with Hardiboard, but neither was a huge problem.

Working with these concrete boards was very hard work. The boards are heavy and that's just the tip of the iceberg. Screwing all those screws takes concentration and muscle; I was absolutely worn out after cutting and installing these concrete boards on the walls of my 3 x 5-foot shower stall. I slept like the dead last night... which I guess is a good thing.

Once the Durock and Hardiboard was installed, my wife taped the seams using mesh drywall tape and a concrete-type spackle called Versabond. It will be ready for tiling today, although we probably won't get to it for a couple of days.

My tips on working with Durock and similar products:

1. Wear goggles when cutting and screwing!!

2. If possible, cut the stuff outside to minimize the dust in the house.

3. Think ahead about the simplest way to handle these heavy boards. I stacked them outside, cut them a few feet away and carried the cut boards into the basement. This kept the dust and the worst of the weight outside.

4. Have the right tools to cut and drill this material.

I wasn't looking forward to working with Durock but I'm glad that it's now all done. It should make for a much more stable and water-resistant base for ceramic tile than Sheetrock. Hardiboard seemed easier to work with than Durock and when a screw sunk properly into the Hardiboard, it was a work of art. The Durock seemed to fracture slightly and gave me the impression that it couldn’t stand up to the pressure. Regardless of which product I used, working with these cement boards was hard, dirty and strenuous work.

Let me know if you have any questions about this stuff and I will answer what I can.

--Bob

Here here!

Hardibacker boards and Durarock ARE indeed heavy and equivalent to concrete when trying to cut. The 'simple score and snap' is a dreamy proposal. Try getting a dozen scoring blades and eat your Wheaties. You will literally score a simple cut 20-30 times before it will be snapable (on 1/2" board). When you have cutouts, I too found that masonary bits work much better but they too dull quickly. Just finished breaking off my Jigsaw masonary bit after probably 10 linear ft of cutting. It almost makes me want to be a "mud man" so that I don't have to cut this damn stuff.

cramby

I just picked up some 1/4" hardiboard for a bathroom floor I'll be installing (marble tiles). The Home Depot salesman told be to install the hardiboard by using flexbond in addition to a box of screws. I assume that flexbond is a type of thinset.

Is it overkill to cement the boards down in addition to screwing them down. Thanx for any help.

What type of floor are you installing this on?

My husband says that if it's a wooden floor then you'd need to screw it on and use the hardiboard, also. But he thinks that if you try to screw it down on another type of base, you'll likely get chips.

I hope Bob or Larry will reply to this post, too. Their advice is invaluable. My husband also mentioned mastic, but I'm not sure what that is.

Hold on for real professional advice.....

good luck,

Lorace

Here is a link to Flexbond that will tell you more than you want to know.
http://www.custombuildingproducts.com/ProductCatalog/SettingMaterials/LatexPortlandCementMortars/FlexBondFortifiedThinSet.aspx?user=arc&lang=en

I wouldn't use it between the Hardiboard and the sub-floor. If you want extra adhesion beyond the screws I would use a waterproof construction adhesive.

Larry

All good info, but I need to know the type of circular saw blade to use on Durock. I am making a durock Heat-Shield for the rear of my wood stove and tiling it over so I need to cut it to size. Thanks

I purchased a carbide tipped masonry blade for my circular saw...cost for a good one was about 60.00. It cuts like a charm but does create a lot of dust so be safe and wear a mask and goggles. Outside is best, if you dont wear a mask...be prepared to hold your breath until you can leave the area after the cut...not recommended. Its nasty stuff. Good luck.

I just put down cement backerboard in our half bath and I couldn't get the screw heads even. I also have one piece that is about 1/4 inch higher than the one next to it. I tried hammering the screws in the rest of the way, but no luck.

Do I need to start over--or can I use an extra layer of the tile adhesive to even the floor out? And the same solution for the screw heads? I'm planning on installing tiny 3/4" tiles that come in 1 foot squares. They were expensive and I don't want to waste them/revisit this project in a few months...

Any help/past experience with such a problem? Please reply!

-Sara

Replaced the green board that had crumbled after 25 years of service. Used 3x5 Hardibacker Moldblock 1/2" panels over 15 lbs roofing felt, stapled to studs.
I had excellent results by using a 1" diam. bi-metal hole drill to cut the shower head, faucet and tub spout pipe openings. Only use a (cordless) var.speed drill, because you need looow RPM. Also replace the centering drill bit with 1/4" masonry bit if you have to make a lot of holes. I used the roofing felt first to locate and cutout pipe/faucet holes, then as a template for the holes to be drilled in the Hardiboard. (Eh, before you tack anything to the studs...)
I had the same problem (earlier post) of setting the special Hardibacker screws flush, also needed plenty of pressure against the panel to avoid gap between panel and stud. Fixed this problem by pre-drilling pilot holes in panel and using countersunk. All this work requires a var. speed drill; to control RPM, to adjust the clutch and precisely tension the screws flush and save your hands from blisters.
Did not use tiles, but Glasteel fiberglass wall panels (liners) fastened with FRP adhesive to the Hardibacker base. Their plastic trim moulding strips in the corners and above the tub (embedded with silicon sealant) made the whole thing 100% water/mold proof and "professionally" finished.
First get and read the DIY datasheets from Glasteel panels (HD) or Sequentia structoglas FRP (LOWES), PL FRP adhesive and Hardibacker moldstop panels. Did I mention 100% water and mold proof?
Don't forget, the rear wall goes up first (above a 60" long bath tub). Leave a 1/8" vertical gap between left/right side panels and the rear panel for silicone sealant fill. Run masking tape first, you don't want silicon on the top Hardibacker surface at this time.
Finally, I installed white PVC moulding trim at the top edge (fastened to studs behind with small/long screws) and a new shower door. Happy,happy,joy,enjoy!

Just wanted to ask that I am considering using Hardiboard for a floor installation (ceramic tile). I want to use the 1/4" dia. thickness since the tile is also 1/4" diameter and don't want it to raise too much above the adjoining floors (wood laminate). Is hardiboard ok to screw down to particle board? Do you have to insert a screw every 8-12" each direction or so? Can it be walked on for a few days when the tile finally arrives i.e.special order from Lowes? The subfloor (particle board/wood slat flooring underneath)is level and in good shape. Tell me your opinion. I will be cutting the board outside with a circular saw w/a 8" fine tooth blade (80T). Thanks.

Use a grinder to cut Hardibacker and Durarock. This is the easiest and most proficient way to cut these. The less gaps you have at your seams the better. We usually fill the small seams with silicone 2 or redguard if you wanna get serious with waterproofing. Hardibacker is best for somewhat level floors because it gives you a extremely flat surface to work with. Plus lifetime warranty versus 30-50 year with durarock. Why cheap out? Float the sub-floor with thin set before you lay hardibacker down to fill in any dips. Always nail on the marks of the hardibacker. Don't cheap out on the thin-set. Better thin-sets are much easier to work with (won't dry out) and hold stronger. If the floor is really bad you must lay a concrete or mortar bed to level the floor. This can be tricky, Don't cheap out here or you will come back the next day when it is dry and it will be cracked everywhere...it needs small rocks in it to keep it from doing this. Always vacuum the dust before you lay tile of float the floor. The thin set will set to the dust and won't stick to the hardibacker. It will make the floor sound hollow when you knock on it. Pay close attention to how you fold your shower liner corners. Always fold them up. Anything else?

Whoa, IMHO the grinder is a terrible idea for all except a few really good pros. My local home improvement store tiler recommended a grinder for a recent tile project - I also picked up a diamond blade to ease the cuts on the backerboard. What happened? - the grinder bucked all over the place, gouged here and there and to top it off, doesn't have adequate safety over the blade. Unlike a circular saw, the grinder is not held in place by gravity working with the tool design - you sort of hold it mid air while only the blade engages the cutting surface. Plus, you need to go over the same line more than once (assuming you can work a straight line w/ the thing).

Bottom line - you need superior strength to keep a grinder in line. After my experience, I learned a friend of a friend lost his finger using a grinder to cut the stuff!!! Too risky for me. I'm only 118 lbs so I don't have much weight to throw against a feisty power tool, but can handle a typical circular saw / drill / power tool / floor sander no sweat.

My solution? Well, there are rolls of orange under tile barrier called Ditra (not everyone stocks this) - very thin, very light, very easy to use and cutting is a breeze! (Alternatively, a circular saw w/ appropriate blade is a better choice for cutting backerboard.