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Anybody familiar with old cement board?

We just bought and I just started renovating an old (c. 1910) house that was completely renovated in 1974 or so. It's our third house of similar vintage, so I have had some practice.

The closets still have (mostly) original horsehair plaster on lath walls, but the rooms have been refinished in a product I've never seen before. From the stud side, it looks like approx. 5/16 inch gypsum wallboard with a paper backing, but then in the middle there's another 5/16 inch layer of what looks like cement, then a very smooth 1/8 inch finish layer. It's crazy heavy, as you would expect, and rock-hard. It's also in great shape as it has been covered with wallpaper for decades, possibly since it went up.

So is this 1974-vintage cement board? And a couple of follow-up questions:
It sanded and took plaster and paint very well in the first room I did, but I want to tile the bathroom and don't know if I should just scour and clean the surface or put up a backerboard. Cement backerboard on cement board sounds like overkill overkill?

And finally, when I stripped (about 4 layers) of wallpaper before painting the first room, the final layer was a navy blue/black-and-tan vertical stripe on paper so thin I can't imagine it was hung after it left the factory. I don't know if this was for easier install or if somebody was selling pre-finished cement board in 1974. Any suggestions or cautionary notes would be most appreciated.

Re: Anybody familiar with old cement board?


It sounds like you have a product that was an intermediate successor to lath and plaster. It was nailed up like drywall and then a skim coat of real plaster put over the entire wall. There was no need for a scratch coat of plaster as with lath and plaster. It came in unusuaul sizes, something like 4 feet by 2 feet, rather than 4 x 8 sheets like modern drywall or blue board. I think blueboard became the norm in later years. Blueboard is hung like drywall, but then a skim layer of real plaster is put over the entire surface. Blueboard seems to be more popular in the North-Eastern U.S. than in the rest of the country.

Hank Bauer
Re: Anybody familiar with old cement board?

I would say that it is Rock Lath 3/8 inch with a brown coat of gypsum plaster3/8 inch and a white finish coat.If it is Rock Lath it is 16 inch by 4 feet.

Re: Anybody familiar with old cement board?

yup rock lath, and a whole lot cleaner to remove than old plaster and wood laths

Re: Anybody familiar with old cement board?

I appreciate the help guys. I haven't taken much out, so can't verify the 4-foot lengths, but 16 inches is right.
The finish plasterers did an amazing job. It's smoother and more even than a lot of drywall, still.
Will it take a nail, or should I use screws for replacing baseboards and the like?
Thanks again,

Re: Anybody familiar with old cement board?

I've had thick hard mortar over rock lath where it would turn a finish nail. You'll find out for yourself if it's that thick and hard.

Re: Anybody familiar with old cement board?

very true about trying to nail to concrete board, you can try it but i wouldnt use a 18 gauge or 16 guage nail, those two gauges of nails are almost guarenteed to fishhook and come back at you, if you do try to use a finish nailer upgrade to a 15 gauge angled nailer, better quality models will shoot through even light gauge steel stud

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