I was reading the thread on the Kerdi shower system and it got me wondering why nobody ever mentions the roll-on membranes like Red Gard and Mapei.
I’ve used Kerdi and I’ve used Mapei’s Mapelastic product. Both have performed well. I’ve also used the Mapelastic with fiberglass mesh reinforcement as a substitute for Ditra.
I’m not advocating for one or the other. Just puzzled why Mapei and Red Gard are completely off the radar in these discussions?
From work boots to power tools, these favorite picks make perfect gifts for moms and women who build.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
Kerdi is a whole shower waterproof system. The hitch with the roll on system, as far as I can see is what happens at the joint at the base of the shower? I guess you could bridge it with the fiberglass mesh?
Is this what you are doing. This would seem to be a lot less expensive and faster to install than kerdi.
I've done Kerdi in the past and while it's a nice system, I always have trouble getting the mortar to stick well on horizontal surfaces. I do like the preformed pan and the adjustable drain.The roll-on Mapelastic is so much more user-friendly. It dries to the touch in about 1/2 hour and you can keep rolling on coats to get it as thick as you like. It's rated for a shower pan, but I've never used it there. Usually I use it on a tub surround and under a tiled floor. For my money it beats Ditra as an isolation membrane hands down.I guess Kerdi might be better for spanning gaps and joints on a rough wall.Anyway, my original question was trying to get at the reason why nobody brings up the roll-on products. Do Breaktimers reject them as inferior, or are they just not familiar with them?
I've used the laticrete black goo over a spun poly-olefin mesh. And a guy I worked with for quite a few years uses it all the time. It's messy and stinks, but it works well. I use it alone on vertical concrete backer board surfaces and in addition to a vinyl pan liner under a mud bed. The drains are a PITA. I think that's kerdi's main advantage.Steve
Edited 2/13/2009 10:41 pm by mmoogie
Do Breaktimers reject them as inferior, or are they just not familiar with them?
personally I say inferior. Based on nothing but my own perceptions.
But ... that's what I do. I use building methods and materials I personally feel are better.
I do use redguard, as a back up in certain situations. Like when I'm building a traditional shower, membrane, mud bed floor ... and backer board on a shower seat.
I run the membrane up and over the seat. The backer has to be screwed. The screws pierce the membrane. I screw "high" and place for best end results, but a coat or two of red guard over the whole bench helps me sleep at night.
I'd never rely on it to waterproof the pan, so to me, it's inferior.
I buy and use kerdi as a proven system. I install the kerdi over drywall, as it's intended. Either the system works or it doesn't. Don't see the need for kerdi over backer.
I'd never think of coating some drywall in red guard or any roll on product and think it'd be waterproof ... so I'd consider it an inferior product in that usage also.
I also think ditra is a far better isolation membrane than any rolled product.
read the directions and limitations ... red guard isn't meant to span any real crack.
hairline cracks, sure ... but no real world crack that actually needs attention.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Okay. Roll-ons may be good enough, but Kerdi and Ditra are bulletproof. The peace of mind factor - I get that. A callback for a leaking shower would ruin your whole quarter.
Well, you got me thinking now about the roll-on products. How are you spanning the wall to pan joint?, with mesh?It would seem to be faster and cheaper than kerdi. I have yet to use the drain that comes with the Kerdi kit, as all my clients have found it to be aesthetically very unattractive-so I end up having to improvise anyway at that juncture.A typical kerdi kit runs me about $400.A gallon of Redguard costs $50.Not sure what the fabric goes for.Which Mapelastic product do you actually use in the shower? Is there a instructional dvd for a shower install.With Kerdi you can use drywall, but I typically end up using hardibacker on the valve wall anyway as added insurance. Installing kerdi with my roofing nailer is really fast anyway. HD, now has a hardibacker like product that goes for $7 for a 3x5 sheet.
Edited 2/15/2009 12:44 pm ET by yojimbo2
"Installing kerdi with my roofing nailer is really fast anyway."
I hope that was a typo. Did you mean that installing your hardibacker with a nailer is fast?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
yeah, that is what I meant.
I've never done a shower pan with the Mapelastic, but Mapei sells "Mapeiband" inside and outside corner fabric, which is just like the "Kerdiband" fabric used in the Kerdi shower system. There’s no installation DVD I’m aware of, but there are detailed instructions you can download as a PDF.A 1-gal bucket of Mapelastic costs about $35 and covers 40 sq ft at 40 mils thickness. The product I've used is "Mapelastic HPG". A roll of their fiberglass mesh costs about $50 and covers 55 sq. ft.The most recent job I used it on was a tub enclosure in a small bathroom. In the past, I’ve just rolled on the Mapelastic and caulked the gap at the tub/wall intersection with silicone. In this case I had to replace the bottom 12” of wall around the tub and wanted a crack isolation membrane to protect against movement. So I embedded the fiberglass mesh in the wet material and added another coat for about 50 mils total thickness. Total time spent- about 1 hour. Total materials cost- about $45. I also used leveling compound on the floor and used the Mapelastic and mesh as a waterproof uncoupling membrane. One gallon of Mapelastic and one roll of mesh was enough for both walls and floor (small bathroom). The stuff stretches up to 150% and can be walked on in 6 hours, tiled over in 16 hours. Once cured, it’s very tough and near impossible to tear or pull off.I have a hard time seeing the functional difference between this product and Kerdi, other than the vastly lower cost and far quicker installation. If you rolled it out 40 mils thick over a non-stick surface, let it cure, and then peeled it up, you’d have a 40 mil thick sheet of rubber just like the shower pan liner material you buy by the roll. Wouldn’t you? Am I wrong?
I am definitely going to check out the Mapei material. I went to there website: http://www.mapei.us/They have several items that appear to be applicable in a shower. Thanks for the info.
Metacrylic makes a cloth that spans cracks and gaps. While it is intended for roofing along with their elastomeric roll on material, the cloth might work well in a shower application. I've used mesh a couple of times (when I ran out of the cloth) and the cloth is WAY better. I've had the mesh work well with the elastomeric paste but I try to use the cloth whenever I can.
We used the Metacrylic elastomeric roof material to waterproof the drywall behind the hot tub. Two coats just rolled on. It was easy and so far it works well. We also rolled it on the bathroom floors (and garage) under the concrete as an extra sealer.
One problem with the elastomeric - it doesn't dry when cold. Warm rooms or summertime for applications. The Mapei two part system might be better. Also I don't know if the Metacrylic is approved for showers. I'm not sure what the tile guy used for the showers.
Eric
yojimbo,I'm suprised you find a lot of folks don't like the Kerdi drain. I think it's my favorite part of their whole system.I like your idea of the kerdi + redgard system.I know for a fact there are dozens of showers in these parts where the kerdi is only brought up the walls a couple of feet (this is on backerboard), and I have not heard of any problems w these showers.Harry
I have certain clients, I would describe as having high end tastes, or what other people would deem design snobs, who when I have presented the kerdi drain, have said "no way".Schluter has definitely worked out their shower system, especially the drain and the pre-sloped pans. I just wish that they gave you the option of being able to easily adapt another type of drain to their system. All this would involve is threading the throat of their proprietary drain.The other thing I don't get with the Kerdi drain is that there don't appear to be any weep holes, so as the everything under the tiles, and above the kerdi remains wet-it never drains-unless I am mistaken. I guess this is not an issue.
Take a look at Schuleters new installation guidelines. The have come up with adapters that let you use the old style clamp down drain with the KerdiAs to no weep holes, they are not needed as water never gets to the mud bed.
Hey if that is the case, that would be so sweet.
Some nice options but the question I have is this, If you use the schluter system for a shower they tell you not to tape the joints,something to do with the fabric bonding to what ever backer you are using. That said would not these roll on products also cause a bonding problem with the thinset/fabric fron the schluter system. I'm doing one now and don't need any leaks later. Thanks
I don/t know. I would stick with the complete kerdi set up and not experiment, especially if this is a one time deal.
I use RedGard on every shower I do, however, I have never poured a concrete pan so I wouldnt know its limitations there.
I use it as a selling point when remodeling tub/shower surrounds. "You see Mr. HO after we install the concrete backerboard we roll on a rubber membrane as an added line of defense against water penetration. At this point you could realistically take shower with just the membrane and have no worries of water getting into your walls."
Of course that comes with an added cost.
As far as where the backerboard meets the tub, if theres a nailing flange, we run our cement board down to the flange so it basically sits on the flange, then we fill the reaining 1 1/4" with thinset.
No flange. Put a big ol honkin bead of silicone around the perimeter and set the cement board on that.
After these we RedGard the whole thing, taking our time around the base to make sure we get it good and tight in there without being too sloppy. That stuff is no fun to clean up if you're sloppy.
I did some research on the Mapei roll on material.
I could not locate an online retailer. My local big box carries Mapei HPG, but not the Mapeband, which is their proprietary tape for spanning joints. I could get them to special order this for me.
The Mapeband comes in rolls, inside corners and outside corners.
There is a proprietary drain, but I did not see that listed on the Mapei site. I guess you can special order that. Not real clear on what you would do to adapt a standard drain to the Mapei roll-on material.
There are no pre formed pans.
There are no assembled shower kits. I think that this may have to do with their not being any online retailers for Mapei products( I could be wrong on this, if I am please point me in the right direction).
I think that is the crux of the issue with Kerdi being more popular, they just have their system dialed in for the client. With Mapei, you definitely have to hunt for their products, there is no installation DVD, etc-but, it definitely looks like it would cost out to be a 1/4 of the price in labor and materials.
I just did a kerdi shower install yesterday, it is very time consuming. Cutting the material to fit, mixing the thinset, putting everthing on, and the curb takes a while. I did two showers yesterday, one was a neo-angle, I figure it took me 10 hrs.
I am thinking maybe combining a Schluter pre-formed pan, with with Kerdi on the pan, curb, up the walls about a foot, Kerdi in the joints up the wall, and then Mapei HPG on the walls. This would greatly reduce the Kerdi material cost, but you would have to wait to roll on the Mapei so that the thinset would have time to cure.
I think your hybrid Kerdi/Mapei idea is a good one. I always find putting the kerdi on vertical surfaces difficult, so the Mapei on the walls would be ideal. The more you work with it, the more confident you'll become with it.
"I always find putting the kerdi on vertical surfaces difficult,"Are you using drywall knives to squegee the kerdi down? It is advisable to round the edges of the knife to avoid cutting into the Kerdi. I also use a wetter than usual mix of thinset-I find this helps as well.
For a full custom tile shower - pan on up, I use the Kerdi system. Tub surrounds- Redguard over CBU/hardibacker are fine. If there are going to be leaks, its going to come from the pan, not the wall.