Well I tried that route and the problem with a real licensed and insured contractor is that none of them I contacted wanted to "finish" a job started by someone else.

I have faith in my friend and to be honest he seems like my only hope in getting this done without tearing out the bathtub an starting over. I know that's an option but does the pictures above really warrant that?

My friend has done tile work and plumbing jobs before although mostly for bars and businesses. He admits he's never installed a bathtub before. But the tub is in and the CBU is installed and waterproofed with RedGaurd. Looking back he said he probably shouldn't have put the mortar in there, but he says it will be fine once tiled over.

So point taken about hiring a real contractor but what would be the next best choice? Would it be advisable to RedGuard the mortar before he starts tiling? Or is this project ruined now with no hope of being resistant to mold and mildew once finished?

Do you have access to the tub installation manual/instructions.

Yes, I believe so. Its a Kohler Expanse 5ft (left hand drain) tub. Got it at Home Depot and it wasn't cheap. I can go on their website or I may even still have the directions that came with it.

So after reading more about MAPEI mortar used to fill in around the tub flange, it states it mold and mildew resistant.

I also see it's not to be used over waterproofing membrane, like Redguard. So luckily we haven't went any farther with it.

So the bottom line is I'm asking if it would be OK if we did this...

Just do the tile job like any other tile job using a good modified thinset mortar such as VersaBond.

With the walls already waterproofed with several coats of RedGuard, once tiled over using proper thinset, grouted and caulked at the bottom with 100% silicone, why wouldn't it be OK?

In other words, despite cracked and ugly looking mortar around the tub flange, there used to be nothing there. So what difference does it really make?

Is that mortar really going to cause problems once it's tiled over or is it likely to be fine and only I will know its there?

I think the real question here is: Are you feeling lucky?

Seriously, though, why risk it? I’d think you would be able to remove that mortar without damaging the tub if you took the proper precautions. So do that and start over with the waterproofing. I mean, you wouldn’t be out that much money and even if you would be, well, that’s the brakes. Heck, you seem to be reasonably interested and willing and/or able to learn about the technical aspects of this project so why not just do it yourself?

BTW, do you have any in-process pics showing the first guy’s work—I mean, are you sure what he did is up to snuff?

Its tile mortar the same stuff that goes behind the tile when its installed its fine. Tile and move on..

The first guys work was done well but I don't have pics. He put insulation behind the Hardy board, taped and mudded all the seams, made furring strips for the CBU so it mounted properly around the tub and adjacent walls, did a thin primer coat of redguard followed by two thick coats, and also installed the tub well in a bed of mortar and secured the flange to the studs.

Like I said, I liked him, he was a good guy. He worked hard and did so at a very reasonable cost. Just a shame he fell on hard times in his personal life and is being incarcerated.

I'm not totally sure why but my guess is it's due to one too many DUI arrests.

He recently fell asleep at the wheel and got in a bad one-car accident and my guess is that's what got him sent up the river.

Thank you Elizabeth B, that is exactly the mindset I had but wanted to hear someone else say it. I don't see why this mortar, albeit ugly, would cause any major problems but trying to remove it might be a nightmare. So I think I'm just going to leave it as is and a you said, move on.

When you are using something like Redguard you should use Redguard and fiberglass tape to create a waterproof seal between the backer board and the bath. Exactly how you do that will depend on the sort of flange you have. I've seen some people overlap the flange with the backer board and some keep the backerboard 1/16" above the flange. When I did it I had a cast iron tub with a thick flange and just kept the backer board 1/16" above the flange. Then put some painters tape on the tub deck to protect it and stuffed Hydroban into the gap and then embedded fiberglass tape.Then the tile goes on and the bottom 1/4" or so is below the backer board and is about 1/8" above the tub deck. Then the usual recommendation is to seal that gap with caulk, but I always think if water does get behind the tile then it won't have a way to weep out into the tub..........

Thought I posted earlier today. A rehash:

The Mapei Premium Mortar that your second guy used is a mastic. That's why you can't use it to adhere tile over a membrane like RedGard.

Mastic does not undergo a chemical reaction to cure and create a bond like powdered thinset. Mastic needs to see free air so it can dry and harden. If you sandwich it between two air impermeable materials like RedGard and procelain tile, the drying process can be drastically slowed. So please, don't use that product to tile this shower.

It looks like your first guy did fine work. The RedGard is an even and deep color, not a transparent whitewash we see so many times on these forums.

I'd recommend you give a once-over to check the mastic that the new guy put in. Make sure it did not slump and bulge out proud of the face of the backerboard as it dried. If it did, pare it back flush with a chisel or another sharp edge. If you have extra RedGard, once the mastic has dried, you could paint over the mastic to bring the RedGard down on to the tub's flange, giving a solid waterproof membrane from ceiling to flange. You don't have to, but it'll help insure that the mastic never sees water.

You mentioned Versabond. Versabond it a lightly modified thinset, that will work fine for bonding your tiles to the RedGard.

Good luck with the remainder of the installation.

Thanks MongoCT, your reply helps a lot and concurs with several others here that the mastic packed in against the tub flange, in the gap from the bottom of the backerboard to the tub deck, shouldn't be a problem.

We realize now that it shouldn't have been put in, but we checked and there are no bulges in the mastic beyond the face of the backerboard.

Thank you for also addressing the question I asked in my original post:

"But I'm wondering should we try and RedGaurd where the new mortar is or will it be fine once tiled over?"

If we do apply RedGuard, would it be advisable to attempt to fill in the gaps and cracks in the mastic (that happened as it dried) by using a small brush and try and get the RedGuard in there with the bristles of the brush as well as applying at least two coats?

That's what I'm debating now: RedGuard the mastic first then tile as usual, or just leave it alone and tile over as-is. I'd have to buy another small bucket of RedGuard and not sure if it's worth the cost and effort.

These paint on membranes are advertised as being able to span cracks. I'd worry a bit about the stability of the mastic though. So I would use some fiberglass tape across the gap as well as the Redguard.

I hear you on the stability concern. After-all, its attached to a smooth fiberglass tub surface. But I've pushed on it with my fingers and despite the slippery-smooth tub surface, it seems to have bonded well. I'd try and remove it if I knew I could do it without damaging the tub. But it's in there now so I guess it's best to try and deal with it the best I can.

If it's solid I'd just treat it like any joint and overlap it with fiberglass tape and Redguard.

Waterproofing to tubs isn't exactly easy. Back in the day poly sheet went behind the CBU and there would be a small gap between the CBU and the flange and the poly came through that and over the flange. Then tile went on the CBU and the bottom bit of the tile was below the CBU and was just above the tub deck. That way water could run down the poly and into the tub. Now that people are putting barriers on top of the CBU they have to come up with a waterproof way to connect the flange to the CBU or just ignore it. On my tub the CBU was basically rested on top of the flange and the Hydroban and fiberglass tape was used to waterproof the joint. Then the tile was installed down to the tub deck and that gap was caulked......but now that seems wrong to me because any water that gets on to the Hydroban has nowhere to go. That said these are vertical walls and I bet the amount if water getting behind the tile is small.

Can you explain how you would go about using some fiberglass tape across the gap and the Redguard? The top of the tape overlaps on the backerboard and bottom of the tape touches the tub surface, or just above it?

Like I mentioned above, right now the mastic doesn't protrude past the face of the backerboard. So I'm asking because I don't want to create an added surface at the bottom that isn't level with the rest of the backerboard. Covering the gap with fiberglass tape and Redguard seems like a good idea but just concerned it might stick out slightly.

You should be fine "as is".

I'm simply not a fan of mastic in a shower or shower surround. The part of your walls that will see the most moisture is the bottom course of wall tile. Direct from spray, and indirect as water sheds off of the wall.

If it was me, and I'll admit you certainly don't have to do this, but I'd RedGard it. As Jeff wrote, RedGard can bridge small cracks. Paint the cracks to fill. Allow to dry. Then a first coat, dry, then second coat.

When done, to store your RG? Tamp a piece of saran wrap down over the opened RedGard to cover and to be in contact with the surface. Add a splash of water on top of the saran wrap. Reseal, place it on a shelf. It'll be good for a while in case you have a future project. And take the price of the new RG out of your friends bill. lol

To see what I did go to 5:38 in this video. I used Hydroban rather than the Kerdi products. How you deal with the backer board to flange transition will depend on the their relative positions. My CBU was on top of the flange so we used fiberglass tape and Hydroban. Painters tape was a guide used to make sure the tape would be hidden by the final tile and that not too much Hydroban got on the bath....however I still had lots of clean up to do with a razor blade to remove lots of little speckles as that stuff really sticks to enamel.

There are good examples using Kerdi here, you can do the same thing with Redguard/Hydroban and fiberglass tape as they are speced to span 1/8" gaps.

go to 5:38

https://www.youtube.com/watch?v=hs9w6VEM_pc

and 12:04 here...although this guy isn't the tidiest

https://www.youtube.com/watch?v=OTf2gG-J-o8

Run for the Hills!!

Get a licensed contractor in which you can visit the work they have already done before you hire.

The two mentioned are suspicious at best.

Water is the house's enemy = MOLD.

I would not trust anyone with that unless it is a licensed contractor.

We have had clients rip out newly installed tile, etc due to this.

The work done by the first guy looks ok, it's the use of mastic by the second which could be an issue as that is not a material that plays well with lots of water.

in regards to the post by T.F.W.

Hiring my friend was a mistake. I see that now and I have now decided to forgo having him finish the job. He is talented with wood and metal and has done some really nice work for bars and business. But he admitted he's never installed a bathtub before so I'm not going to have him do the tile. I don't want to have this issue ruin a friendship.

Also, T.F.W is right, the folks telling me its fine and move on with the tile job as-is makes me feel like all is not lost. But his and other professional's comments here make it sound like even the first guys work wasn't done correctly.

I don't want to argue the importance of hiring a licensed contractor, which clearly is not the path I took. But several have said the first guys work looks fine. I wonder, if there wasn't any mastic around the tub flange, would the pros here still be suggesting I rip it all out?

That's a legitimate question. Just because the first guy wasn't a licensed contractor does his work constitute ripping it all out and starting over? And if not, how does the mastic create such an issue that now it needs to be ripped out completely?

Again, legitimate questions I would like to know before i decide to start over or move on. The tub alone cost $750. But if it's a total disater and it's clear problems with mold are bound to happen shortly after, then it's coming out.

The first guy used PEX for the plumbing and I looked through my phone and found about a dozen more photos of the work in progress. Not sure they'll help answer the question of ripping it out but I have added the photos below.

It's good to have pictures. One comment on the insulation. It looks to be faced with a vapor barrier, you don't need that as you have the Redguard. When I did my bathroom my contractor used unfaced insulation on the interior and exterior walls as he was putting Hydroban on the CBU. on the exterior wall. Also a good exhaust fan vented to the outside is a must....and probably code.

Is that another problem that the insulation has a vapor barrier face?

Note last picture above has a hole cut in the ceiling and the grill for the fan is leaning against the tub. Exhaust fan in ceiling is now installed and will be vented to one of the roof vents to the outside.

Following...Is vapor barrier + red guard a "moisture sandwich" or does that not matter if it's not an enclosed shower with glass, such as a steam shower?

The people saying rip it out have probably never done a bathroom before. Its not a mold sandwich that insulation is not aiair tight waterproofing . Just buy the right thinset for a wet shower wall that can be installed on a vapor barrier like red guard and move on..

The insulation isn't that tight so it's not as bad as having 6 mil poly behind the Redguard. The worry with two vapor barriers is that the space between becomes stagnant and damp and you get mold. Depending on where you live and whether it's an interior or exterior wall you might be just fine. I think these issues usually happen when you don't use a professional......and they still might occur with a professional.

From examining at the latest photos I posted above, would it be possible to take the backerboards down that's been coated with Redguard and remove the tub without damaging it?

When the tub was dry-fit it looked really nice and there was no gap at the front where the left side apron of the tub met the wall. But when set in a small bed of mortar for the final install, the gap was as you see it in photo #4 above.