Can I slick finish cement bd w/thinset?
Fonzie
| Posted in Construction Techniques on
This is a basement bathroom – some pipes showing – nice but not fancy. Customer wants inside covered with cement board/ slick finished, painted with paint for cement. One wall is brick (exterior) and we plan to put 1 in R board under the cement board and attach with cement screws. Two of the other walls are brick (interior) and we plan to use a combination of thinset and cement screws to attach. Fourth wall is framed.
Here is my question: do you think it is possible to use cement board, thinset and fibreglass tape on joints and end up with fairly smooth walls? If this isn’t going to work I’d like to know it now.
Replies
I think it'd be tough to match the feathered joints with the textured board for a finished look. One further step might take care of it though...parge the whole wall with stucco after doing the joints as you outlined.
I have successfully skim coated/parged concrete surfaces with the cheapest thinset home depot sells. I think it was made by custom products. Another time I tried the same with some top quality latex modified thinset and couldnt trowel it smooth. It kept sticking to the trowel.
Good luck, and the moral is it may pay to go cheap on the thinset.
karl
You might try a micrograin cementious floor patching compound designed to be sanded smooth to a feather edge. I've used it to tape cement board joints because you can get very smooth, flat joints, which helps get better tiling results than with less smooth thinset on theses joints (I know you won't be tiling and would need more stuff--it relatively expensive).
You might try a micrograin cementious floor patching compound
That sounds like interesting stuff.
Who makes it?
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
yourcontractor@aol.com
One product of this kind is called "Micro Finish" and it is a cementitious skim coat and patching compound. It is made by Para-Chem (http://www.parachem.com).Cement board should never be taped with joint compond, that defeats the purpose of using cement board (read the instructions on any cement board product). Thinset or other common mortars are not fine-grained enough to tape joints smoothly. I think using a product like this is far better than durabond and joint compound for this kind of application, but is much easier to work with (far smoother) and easier to sand on taped joints than thinset (thinset is not really designed for taping joints or being sanded).
Thanks for the info on the micro finish. I'll check it out.
re: taping compound or d bond on cement board...............I know that wasn't directed at me!
I've done some silly things in my life but................
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
yourcontractor@aol.com
durobond over backer board works just fine.
done all the time.
I tape it with mesh, no problems ever.
floats out nice and smooth ... can't tell where the plan change was and they didn't like the final tile price. Happens all the time when I sub tile. No big deal.
only "problem" is ... usually I get the CBU/durobond so smooth ... that the rest of the wall ... the drywall portion ... looks bad in comparison .. usually me or the painter skims the drywall with duroband so everything in that plane is the same.
Jeff Buck Construction
Artistry in Carpentry
Pgh, PA
I think a couple of weeks ago someone here posted that they had "hot mudded" the interior of a shower prior to tiling.
Yikes! I didn' even bother to respond to that one.
My experience with d bong and cbu is that it doesn't always adhere well. I like to give the cbu a quick coat of WILLBOND or something similiar before coating those areas that are beyond the range of the tile work.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
yourcontractor@aol.com
What is Willbond?I'm with you on keeping the durabond and joint compound away from the cementboard. If those products are just fine then why not go back to hanging drywall in the shower.
it's the base that disintegrates if you use drywall..doesn't happen with cement board
i'll just muddle on .. screwing things up as i've always done...
heh, heh, hehMike Smith Rhode Island : Design / Build / Repair / Restore
Mike,I am sure your methods have served you well. From what I have gathered here, I would rather learn how you do things, than try to persuade you to do things my way (at least nine times out of ten).Of course, this could be the tenth time. I am just advocating taping cement board joints, esentially the way the manufacturer reccomends--with fiberglass mesh tape and thinset (or if you want it smooth with a super fine cementitious skim coating and patching product).Durabond and joint compound might occasionally compomise an installation (maybe 1 in 100, I don't really know). If something does go wrong, I don't want it to be because I ignored the product instructions.The Para-Chem product I have been trying has the smoothness of durabond, but is a cement-based, polymer fortified product--the best of both worlds.Cheers
bass... i think you're right..
this original post is for cement board that is NOT a tile base.. for some reason they're using it as a wall base finish material.
in our tile / plaster transitions.. we prefer to let the cement board intrude a little into the plaster wall area.. the alternative is for the plaster wall to intrude into the tile area ( not good ) or to have the tile end exactly at the joint.. ( hard to do )...
given those choices.. we have our plasterers lap onto the cement board
as for cement board as a tile base..we'll comply with the mfr. as you so correctly point outMike Smith Rhode Island : Design / Build / Repair / Restore
............glad we got that straightened out.
I was beginning to wonder who was reading what!
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
yourcontractor@aol.com
OKI sorta got off on a tangent here (and that never happens on this forum).I just figured that if moisture was enough of an issue to call for cement board, then the finish work (taping and skim coating) should be just as moisture proof (that's why I reccomended the cementitious skim coat product--though it would be more expensive).
here's a shower with Durock on the walls butting up to blueboard with skimcoat plaster..
the Plasterers made the transition from blueboard to durock.. here at the tile joint.. and also at the corner with the ceiling..Mike Smith Rhode Island : Design / Build / Repair / Restore
I can't see anything ...
there's a big hand in the way.
Jeff Buck Construction
Artistry in Carpentry
Pgh, PA
that's the hand of a craftsman ....
View ImageMike Smith Rhode Island : Design / Build / Repair / Restore
I get it.Looks good.You might try the Para-Chem Micro Finish on the joints in the shower sometime and tell me what you think.On the topic of blue board, the inspectors here and some letters to Fine Homebuilding have both suggested switching back to regular drywall where cement board in not required. What do you think?And on a completely different note, I was asked today to build a display case for a large doll collection. I suggested something that looks like a nice bookcase (something I know you are familiar with). As a variation on the theme, I further suggested that it could be made to look like a doll house/display case or even a series of doll row houses (a la San Francisco). They want a glass front and access from the back it move dolls in and out, and lighting, etc. Any suggestions, sources? (I know this should be another thread).
queen victoria's dollhouse in Windsor Castle is big enough to live in..Mike Smith Rhode Island : Design / Build / Repair / Restore
This one will be more along the dimensions of a bookcase (10' w x 7' h x 1' deep). Really just a display case, but maybe with that doll row house mottif.Edited to say: Now I've really hijacked the thread, unless I build the doll display out of cement board and skim coat it with durabond.
Edited 3/2/2005 10:05 pm ET by basswood
might work.. if the dolls are the Village PeopleMike Smith Rhode Island : Design / Build / Repair / Restore
WILLBOND (sp)
I believe it is manufactured by Thorocrete (sp?) and should be available at any good mason jobber.
It is a thick pink water soluble (before cure) liquid. Stick your nose in it and you think elmers or yellow glue. It's proerties and behaviours are nearly identical, although I have never tried glueing wood together with it.
I had a job to remove a tile floor that was falling up because the contractor that did the install did not fasten the ul well. I scaped up all the tile, put 16 million screws in the underlayment, and after scraping down the high spots of left over thinset rolled on willbond prior to setting the new tile.
You need to patch in some plaster or broken out stucco, apply willbond first.
Great stuff, I always keep it around.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
yourcontractor@aol.com
I'm not talking about durobonding IN the shower ...
I'm talking about outside the shower or above the tub deck ...
then the HO's decide that a whole wall of tile is too much ... and they just want the tile in the shower/wet area ... but ... the job had the CBU's installed over the whole wall ... because tile was spec'd instead of drywall.
Then ... ya just tiile where they want it ...
then skim coat the cbu with durorock to make for a nice .... now painted ... finish.
Jeff Buck Construction
Artistry in Carpentry
Pgh, PA
OKSorry, I misunderstood.I've seen others do the durabond in the shower, and as I said above--most of the time that probably works fine too. I just prefer to follow the instructions, just in case...of course this is coming from the guy who used white tile mastic on a shower ceiling. So who's the expert here?
this stuff,
http://www.quikrete.com/catalog/VinylConcretePatcher.html
will feather to a thin edge and has a fairly fine grain - is this what you mean?
That product would go on smoother than thinset, so it might make taping cement board joints easier than using thinset. The product I have been experimenting with is:"Micro Finish" cementitious skim coat and patching compound by Para-Chem.http://www.parachem.comI should say that I am not a tile setter by trade (I am a trim carpenter who tiles mostly floors and backsplashes in kitchens that I remodel). I am sure there are tile pro's who get thinset to make nice smooth joints. I have struggled to get thinset to work for me on fiberglass taped cement board joints. I have been trying out other products to see what works. This seems to be a reasonable compromise.
are these the bath walls or the shower walls?
what's the point of the CBU?
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA
fonzie... we often have cement board butted up against blueboard in our baths..
the plasterers fibertape the joint and just keep on troweling right thru.. in other words they skim-coat the cement board just like it was the blueboard.. so the tile guy will have no transition problems
my point is this: why use thinset ? why not use Durabond ? and joint compound for your final coat ?.. that's what i would do if i was trying to get a nice finish on cement board
course... there's always ...........D-mix
me too
It seems like the joint compound would be the weak link in moisture defense - am I wrong? I was reading about the D mix - that sounds interesting.
I agree What's with the thinset? It's too sticky to trowel smooth anyway!
I can see why you would do this in a basement. If the sheetrock gets wet you will have a tearout and mold issue. If the cement board gets wet you probably won't have mold (maybe on the framing but at least there's no paper faced mold food like there is with sheetrock).
I would be inclined to use joint compound and just deal with repairing the joint compound if it gets wet. The cement board allows moisture to pass through which is a good thing on a basement wall. Don't use the cement board substitutes that have waterproof facings -- they cannot breath like cement board.
Billy