Tub Surround Waterproofing

[Melanie0303]

Hello all. Hoping for some advice.

Hubby put up Wonderboard Lite cement board on three walls for alcove tub/shower. One of the three walls is an exterior wall and has poly over insulation. We now have to waterproof before having porcelain tiles installed.

Having done extensive reading, it appears we would have to slash through poly covering insulation if applying a surface membrane to cement board? (We're in Winnipeg, Manitoba).

We haven't taped/mortared the seams yet on the cement board.

Also, what is recommended membrane? I've heard about kerdi membrane, Latricrete Hydro Ban or Hydro Barrier, and Redguard. Doesn't look like the big box department stores carry the Latricrete line so not sure where to purchase either.

Thanks so much for any replies!

Melanie

 

[ShowerDude]

This has been debated, re-debated, and pasted all over the web for years. Likely has you confused???

both your questions come down to you or your contractor(hubby) to make the call, but either way you break a rule and that discussion already has been answered...still confused.....?

You simply have to make an educated smart decision "for yourself". You can cut or not cut your poly.... either way you will make someone mad and further confuse and always second guess your self.


If you use a surface membrane, liquid or fleece applied membrane, and it gets properly PROPERLY installed, the chances of that being compromised and water getting between that and your poly is the concern and its slim.


If I used a liquid I would pick a reputable brand such as you have mentioned above and focus on a good installation by reading instructions twice and taking your time.. Liquids can pull off if you set a tile and a few days later attempt to remove said tile and replace it, you likely will compromise the liquid maybe even the fleece . A pro sets tile and doesnt need to be pulling them back off the substrate very often anyways, and also would know how to correct any damage occured!.

If you install membrane properly and set the tile once PROPERLY you likely will not compromise waterproofing and never have an issue in which case the poly doesnt matter in regards to the drama youve been reading about...


For you and your hubby a liquid likely the easier route to take without knowing your skillsets. In regards to avaialabilty, simply get away from the big box stores and start calling your bigger tile vendors and find the Professional product line you choose. All this stuff can be ordered online as well.

the biggest key to liquids is cleaning and prepping you need VERY CLEAN Cement board that also must be properly blocked and installed ( see vegas recent post on small bathroom remodel) Then pay close attention to the MFG installation specs.

still confused? you simply need to make up your own mind......Good luck & share some pics with us all if you can...

 

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[Melanie0303]

Thanks RedShoe...do we still tape seams with fibreglass mesh and mortar before applying liquid membrane?

Here are some pics of the project.

Also, how do you deal with transition between cement board and drywall? Also have a corner to deal with on smaller of three walls (visible in 1st pic) of cement board...can a corner bead be used? and is it over mesh and mortar? how about where cement board meets ceiling?

Sorry for the myriad of questions! Any and all help/advice much appreciated!!!

 

[ShowerDude]

Yes you need to tape and thinset all of those joints and let dry before cleaning and waterproofing. follow cement board mfg specs first, then jump to the waterproofing mfg specs.

The transistion to drywall should see a mesh tape and thinset at seam, your liquid waterproofing can later extend beyond wet area/tile line and later you can skim over it touch up with drywall mud outside the wet area.. Yes corner bead can be used, make sure its galvanized and use zink plated screws anywhere you will have tile and thinset. No drywall screws.

at the ceiling I usually tape and thinset both , I will usually treat the ceiling much like a wet area and waterpoof it, then skim it with drywall mud and prime/ paint accordingly for a wet area. In low overhead areas the showers steam will rise into your paint so plan for that.

good luck, pay attention to MFG specs and dont overthink things. be clean and methodical you will win. ! its good to know you are concerned about these details....

 

[Vegas_sparky]

Welcome. You'll get great advice here, Melanie. Take your time to make sure its right, and you'll end up with a great job at the end. Don't skip the little details. They can make/break these builds.

RSCB mentioned my current project. I'm no expert, but I'm doing the best I can.

https://terrylove.com/forums/index.php?threads/small-bathroom-remodel.58397/

Now you need to decide if you'll be putting poly behind the remaining board, or putting a waterproofing product on the surface. You're not too far into it to pull the board, and slash the poly. Some, or all, will have to come down. I had no poly to pull, but did remove the paper faced vaper barrior from my existing wall insulation, which originally performed the same function as your poly.

 

[JohnfrWhipple]

I would not slice the vapour barrier.

Is the tub installed against the cement board? How is the cement board fastened? I see no screws.

 

[JohnfrWhipple]

One of the best products you can use for your tub's shower walls is made by Ardex and called 8+9. Once installed it looks like this.

​

This is an undermount tub so different that your install. Sealing the Ardex to the tub deck tile edge is the key part. I have used everything from kerdi Band. hydro band Band. Sk 25 mesh and on.

Ardex 8+9 bites well to wonder board lite but bites better to WonderBoard lite that has first been taped and flat trowelled.

If you prefer a sheet membrane over a cement based product then Laticrete's hydro Ban Sheet membrane works well.

Just pick a waterproofing material that has no thin-set restrictions. You do not want these lower grade products in your home's shower.

 

[Melanie0303]

Thanks for all of your replies!

John:

Rock on screws were used to faster the cement board. A 1/4" gap was left between cement board and tub flange and filled with caulk.

Can you provide more details about how you achieve:
"Sealing the Ardex to the tub deck tile edge is the key part."

Also, where would Ardex or Latricrete products be available in Winnipeg?

 

[JohnfrWhipple]

Call Ardex and Laticrete and ask. I live and shop in Vancouver.

On my most current project I used some kerdi fix and Hydro ban sheet membrane band. Your making something like a sandwich. You need to add ingredients in the right order.

Kerdi Fix sticks to the tub.
Hydro band Sheet Membrane Band stick to Kerdi Fix.
Ardex 8+9 sticks to that.

The build can be done all at the same time. I would first set the HydroBan Sheet Membrane band into a bead of Kerdi Fix. Then set the remainder to the wonder board with 8+9. Then coat out the entire surround with 8+9. Wait a half day and add a second coat. Done and Done.....

The industry guidelines from the TCNA and TTMAC are out to lunch on this detail. My approach is much better. A year or two after I started showing this Schluter followed suit with a similar detail. You could use Kerdi all the way but then you would be using an inferior product in my opinion. Kerdi is best left for lab like settings and not used on real job sites.... lol Can you tell I hate this company?

I would love to walk you through all the steps but I do do this shower design as a part time business. Unlike lots of other people I do like to get paid somewhat for these pro tips. But I just gave you my system in a nutshell. And I have pictures all ready online showing it.

 

[JohnfrWhipple]

Before you buy any Ardex products anywhere make sure you understand how to read the date codes. Those German's make it hard and have a secret coding system.

As for Laticrete - they make it easy. The made on date printed in regular english (no code) on the top of the bags... You could skip 8+9 and do the same process with Hydro Band.

I ask my clients to . If you have blocking in place then I skip the taping of the backer board and use reinforcing mesh (in your case SK25 or hydro Ban mesh). If you have proper blocking then you can skip the reinforcing mesh all together. But It is nice to double down on the inside corners - especially if they are on outside walls.

Your vapour barrier question is so old. The TCNA has not even booked a date to start a study. There will be no info in the next five years is my guess. I'm a voting member or the ASTM and in the past two years the group that covers this has only debated the testing methods for roofs. No study groups for vapour barrier sandwiches.

If you board right - which you did keep your waterproofing from going rift to the ceiling. Stop it at 7' or so. Then moisture can breathe out the top. Same on the sides.

 

[Melanie0303]

Thanks again for the advice!...much appreciated.
I have sent out an email to Laticrete. Looks like the Hydro Ban application is straight forward enough.

Are you saying that with the Hydro Ban we would not have to mortar/fibreglass tape our cement board seams (just seal with Hydro Ban without fabric)?...they are quite small. Then again there's the gap between cement board and ceiling to fill.

 

[Jadnashua]

Some of those products can bridge a gap, the largest is generally considered to be 1/8". It's not a bad idea to use reinforcing band on the corners, and it often can work out best to use it at the tub/wall junction. You DO want to tape and mortar the board seams AND LET IT CURE WELL, if you're going to use a liquid surface membrane. But with a sheet membrane, the membrane acts like the reinforcement tape, and you can do it all in the same step. IOW, you do not need to tape the seams before applying a sheet membrane.

FWIW, Schluter has been selling their Kerdi shower stuff for nearly 30-years...if it was so bad, they wouldn't be in business. John's hate of Schluter products, and he recommends KerdiFix...maybe because it works, as does their other products, seems selective. The man has no shame...choose your product from a company with a good track record, and follow their instructions - it will work. It's not hard, but it is detail oriented, and is easier if you've done it more than once, but the learning curve isn't horrible, and a DIY'er can afford to take their time.

 

[Melanie0303]

Thanks again everyone. I have one other question about our project.

Our cement board on a corner does not meet up with the width of the drywall (about 1/2 " shy). Should the cement board be redone to be flush with the dry wall to form the 90 degree angle or can a trim be used to cover the gap?

Took the following two pics to demonstrate:

 

[JohnfrWhipple]

Does the tile wrap around the corner of the other wall? Is the wall with drywall staying that way?

Have you seen my post on a nice looking outside corner? Many people finish with a nasty tile edging. They work sometimes but add a lot of chrome or plastic to a typical job.

If you are leaving it drywall then I would utilize my J Bead approach and make the corner sexy. Or if it's getting tiled all the way around then I would use a mesh and thin-set to reinforce that corner. Something larger than 2". I cut my strips about 6" and often set one side one day and the other side the next.

On this project you can see a combination of Laticrete Hydro Ban Sheet Membrane and Ardex 8+9 in action. The shinny bit is a J Molding that the tile meets up with. Follow the link above to learn more on this detail. There is a secret tip or two shared there.

Notice how the tile meets up with the J bead. The painter needs to prime and paint it out.​

 

[Melanie0303]

Wow...nice! So a j bead would compensate for that gap.

 

[JohnfrWhipple]

Wow...nice! So a j bead would compensate for that gap.

No - you would need to cut out some drywall and re-patch it with a larger piece. Sometimes you can not add the ply detail easy so I use a mud on version of a JBead not a screw or nail on version. Study the link above closer and you can see