Great video.. dont worry about the mess on the fiberglass tub people, it washes off before it dries with warm water and peels/ flakes right off when its dry. Ive been using Ardex products for over 12 years and never had a leak. I use it with/ over wedi pans, curbs and cement board on the walls. Mesh tape the joints and corners. Follow instructions on the 8+9 package. Ive done dozens of showers this way including 2 in my own house 12 years ago. No problems. Ardex products are engineered to last.
Outstanding video, however, a standard 9lb kit of Ardex 8+9 isn't enough to seal an entire 8 foot (~80 sq ft) alcove with concrete backer board. With the recommended 1/8th gaps and stud protrusion I didn't even have enough for a single coat, let alone two. Says it right on the bag too, only covers 70 sq ft of concrete backer, but I still didn't come close. Couldn't have done it without this video though fellas, thanks.
This is a great demo! Steve does such a great job explaining everything! Really wish he was in our area so we could get him to do the bathrooms in our home.
+Carrie Beth thanks. Steve is awesome. He's mostly tied up with huge bathroom remodels which is a huge reason we have Bathroom Repair Tutor. You might like that Carrie. We created it to help support homeowners who want to do a DIY bathroom remodel. What all would you like to do with your bathroom?
Just curious why an alkaline resistant mesh or the ardex mesh wasn't used on all seams and corners??? Any expansion and contraction in the walls will cause the seams and corners to crack which makes the 8+9 waterproofing irrelevant. The 8+9 is only rated for up to a 1/8" crack. Why take the risk and just mesh all seams and corners???
You'll know the difference if you've worked with the different products. Ardex 8+9 is amazingly hard when dried and bonds amazing to the substrate unlike the others.
8×9 doesn't need air to dry, so no chance of accidentally covering it with tile mortar before it cures and then preventing it from curing and therefore not being waterproof. Not a problem if you use the water based ones and leave them for a day, but guys like this who want to tile the same day benefit from a two part like this. Got this info from Tile Coach's channel.
Great video and much thanks for all the home repair advice. Just curious about where the cement board meets the drywall ceiling. Does one finish that off with a corner bead and mud? I am doing a similar project and am tiling to the ceiling.
you could use the 8+9 in the caulking format, like we did between the tub and cement board. It can get messy though and you don't want copious amounts on the ceiling. You'll be tiling over the small gap as well and when you're done you can seal the tile to the ceiling with either silicone caulk or a siliconized acrylic that can be painted.
Love all your videos. I'm remodeling my bathroom, but I don't see any videos that talk about what should be behind cement board if that is the option I decide to use. Wedi and Kerdi are not easy to find at my local hardware stores. So, if I use cement board what goes behind it? Plywood then membrane? Or does the Ardex 8+9 allow me to skip this step? Thanks
A late response and hope your project went well. If your bath walls are the exterior wall then just use regular insulation. If all interior walls you don't need anything.
+ThePdxster I'd have to check the Ardex 8+9 instructions. That said, it would be a rough texture and possibly need a skin coat of joint compound to look flat. You could tile the ceiling 👍
Yes, the original plan was to tile the ceiling and walls, then my wife changed her mind and only wants the tile up to the ceiling. Using Wedi for walls, but don't want to mess with a ceiling replacement due to asbestos. So Ardex for the ceiling. Cannot find anything about painting Ardex.
Thanks, and yes I did talk to their technical guy. No go on the painting, has to be thinset and tile over the Ardex. The good news is my wife changed her mind after I told her the painting won't work and we are tiling the ceiling!
You are doing a great job with your TH-cam channel. Good job! The only thing is bad, your buddy Steve is a mess :) is sloppy. Has knowledge but he need to cover and protect. Avoid scratches /painting in this case the tub. This I saw on the Wedi project you guys did as well when he set the boards and seal...he was a mess :)) Again great job with your TH-cam channel!👍🏻
+Pristine Kitchens & Baths Corp PKB I disagree, these projects are inherently a mess. You have to get your hands dirty to get stuff done. And sure, sealant sometimes gets on the tub but we always clean up. Please understand that no project is 100% neat but that's the point...you don't need to be a perfectionist to get projects going. Plus, our attention to detail is in pretty darn good
This stuff is craaaaaaazy messy lol. I taped more, had more cleaning supplies and a place for everything and still looked like a bomb went off when I was done!
Was their anything in the cracks (such as caulk or thinset) between the cement board before he painted the corners or was it a 1/8" gap that was filled when painting it on? I'm getting ready to do a bathroom and had questions about this process. Thanks.
No, the gaps were less than 1/8" and did't require the caulking or SK Mesh. But, if there are gaps greater than 1/4" then use the 8+9 caulking to fill those gaps then apply another coat. If you want to be ultra sure it's waterproof then feel free to use the SK Mesh in the corners and seams. Our complete tutorial is over on Home Repair Tutor www.homerepairtutor.com/how-to-waterproof-a-shower-with-ardex/ Hope that helps. What kind of shower are you remodeling?
Home Repair Tutor Home Repair Tutor Thank you. I will be taking out a cast iron tub, putting in a shower pan and tile surround for my mother to make it more accessible and less of a trip hazard. One more question--if using cement board and an abs redi niche, so I need to use epoxy to attach the tile or will the mortar work just fine? Thank you again for your reply.
good eye, if the cement board is tight enough there's no need to use the SK Mesh, the 8+9 will suffice. That's where it's a bit different than RedGard.
+Jeff Patterson I was wondering the same thing. I was considering it for my kitchen backsplash near my sink faucet. I'm going to apply tile there, but there is only drywall behind it now. Thanks! Keep'em comin' my friend!
+joseph Gross if the boards are close enough it's not necessary, although we'd recommend the mesh for most installs. I spoke with ARDEX tech support a few times bout this topic and adhered to their advice. Plus, they approved this video
You cant find EVERY product EVERYWHERE. I think these guys do a decent job showing MANY acceptable options. I'm SURE many will argue Schulter is better then Wedi, so then what? "Superior" is a lil over the top.
A little over doing it, no? If the 2 coats are waterproof, why waste time and money on tape (provided you thin setted cement board fiberglass mesh prior) In the end we are trying to prevent moisture from passing to the cement board and hopefully not provide a moist area for mold. It's not a pool, it's just to prevent mold. The job was great, by the way.
Ardex : I woudn’t touch this company with a barge pole. I Bought the WPC kit and the instruction were lacking so I phoned Ardex. They advised to use their P51 sealer on new plaster which I did at an additional cost of £54. The finished job looked good but when I scraped of a snot (small lump) I could see the WPC had not adhered to the plaster. Ardex then said I shouldn’t have used sealer ! and advised me to scrape it all off and re-do it. No admission to their wrong advice or even compensation for the materials let alone my time. 2 WPC kits and 1 P51 = £184. This comment would not upload to a Ardex uploaded video. The plastering was done weeks prior to the application of the wpc.
Backerboard is water proof. What are you water proofing? The tub is waterproof and the tub deck lip is high enough to keep water out. I can see where drywall meets backerboard, though. I have torn out hundred of bathroom tub tile installations that had nothing but basic drywall and didn't have water damage.
+A.W. Baran cement board isn't waterproof, water resistant at best. Tile, grout and thin-set aren't waterproof either. It only takes one failure to ruin a reputation. So spending $100-$200 is worth every penny.
Good product but there are "ready to use", single component fluid membranes out there with no need to mix. Who really knows if you are mixing correctly? Plus, some fluid membranes are both crack isolation AND waterproofing meeting both ANSI standards...one covers concrete cracks up to 1/4"...with just one coat.
Yes but you cant install mesh tape with liquid waterproofing it has to be installed with thinset first. After thinset drys then you can apply liquid WP. Ardex 8+9 you can do both at the same time so you save a whole day.
It's hard to take you serious when you cover the homeowners tub with a small piece of cardboard. For heavens sake, cover it well so you aren't grinding the grit into the tub with your shoes. Ardex products are good but with the sand in the mix, it's going to build out thicker, especially where the tape is added. The walls that probably were fairly flat won't be when it comes time to tile.
+TILE SETTER 191 not arguing your choices just wanted to try this and see how it worked. It's good to have choices since not every town or city has Mapei or Laticrete or even Schluter for that matter. Distribution of materials is still a problem even in the internet age
I thought whole idea of using a mesh was to seal any corners and joints from water ingress and to prevent from cracking, and your video clearly does not show it and it is bad example... . What you are showing here is applying a mesh where it does not have to be. it is wide for a reason ,.... to grab 2 corners of a wall or cement sheets and make it as one.... Once any of these cement board moves it will open up a bit and your corners will get water in it !!! To me bad example !!!
+Jay D this video was vetted and reviewed by ARDEX technical support before going Live on TH-cam. They specifically said we didn't have to use the SK Mesh in the corners because the gaps were less than 1/4". If you read the directions they go over this in detail. You can add the SK Mesh to the corners and seams, it will not hurt the installation. But this is not a bad installation because ARDEX approved it 👍
What is that mesh giving you around the corners or around the edges then ??? to me absolutely NOTHING. Video is wrong. Once any of these boards move (and they will in time) by a tiny bit it will open up the ARDEX coat and you will end up having a crack (under tiles in time) and it will leak there.. I have not seen a single video (apart from yours) where mesh was used this way. I will not change my mind and any DIYer will say exactly the same. Using tape elsewhere is pointless... you may as well tape the whole panel... Don't believe me ... ask ARDEX about your joints isolation
Did you read my last reply, this video was reviewed and approved by ARDEX, i.e. I spoke to ARDEX myself...after all, they're in Pittsburgh where we're located. That said, if you feel more comfortable adding the SK Mesh then go ahead and do it. I'm not arguing that it's a good idea, I'm saying ARDEX gave us guidance on this video and said it was okay to not use the mesh because our cement board seams were butted against each other.
To jd: “once they move”?? No anything with tile should be rock solid. Movement is the enemy of tile. Or the entire tile bed must move as one. Thats why we put cement board on floors & make the floor rock solid. Any movement in tile will fail any protection.
please understand that we make videos showing all the options...not everyone has access to K10 or KERDI or Wedi...but cement board is widely available and Ardex makes some of the best products in the world
Hey friend, I'm about to buy a house, but the neighbors house is very near to the house wall so, there's a very little separation between the two walls, and apparently the house have some leaking problems, you think is it possible to repair from inside of the house?
hard to say, the best thing to do is identify where the leak is coming from. If it's exterior or from somewhere inside the wall you'll need to address that. Ardex 8 + 9 is meant to waterproof your shower or tub walls from water coming from the shower.
Great video.. dont worry about the mess on the fiberglass tub people, it washes off before it dries with warm water and peels/ flakes right off when its dry. Ive been using Ardex products for over 12 years and never had a leak. I use it with/ over wedi pans, curbs and cement board on the walls. Mesh tape the joints and corners. Follow instructions on the 8+9 package. Ive done dozens of showers this way including 2 in my own house 12 years ago.
No problems. Ardex products are engineered to last.
Thanks Brett, good to hear you’ve gotten great results. We agree - Ardex makes solid products
Outstanding video, however, a standard 9lb kit of Ardex 8+9 isn't enough to seal an entire 8 foot (~80 sq ft) alcove with concrete backer board. With the recommended 1/8th gaps and stud protrusion I didn't even have enough for a single coat, let alone two. Says it right on the bag too, only covers 70 sq ft of concrete backer, but I still didn't come close. Couldn't have done it without this video though fellas, thanks.
This series of instructional videos is so informative. Lots of the comments are helping too! Great tutorials Thank you.
This is a great demo! Steve does such a great job explaining everything! Really wish he was in our area so we could get him to do the bathrooms in our home.
+Carrie Beth thanks. Steve is awesome. He's mostly tied up with huge bathroom remodels which is a huge reason we have Bathroom Repair Tutor. You might like that Carrie. We created it to help support homeowners who want to do a DIY bathroom remodel. What all would you like to do with your bathroom?
Great video!
No mesh for the two vertical corner joints?
Thx
could you do an exterior ardex concrete product on top of the 8+9 for the look of a concrete shower instead of tile?
Just curious why an alkaline resistant mesh or the ardex mesh wasn't used on all seams and corners??? Any expansion and contraction in the walls will cause the seams and corners to crack which makes the 8+9 waterproofing irrelevant. The 8+9 is only rated for up to a 1/8" crack. Why take the risk and just mesh all seams and corners???
Thank you for the video. What do you think of using ardex 8+9 on shower pan?
How is the compatibility/adhesion to kerdi and hardi backer?
What is the purple drywall next to the cement board? Ive seen things like that but not a purple drywall? Is it for mold mitigation?
Yes exactly
The guys on global tile,were testing various products ardex 8.9,one of them new to me,
Great job steve,n jeff
Great! Any videos on how to fit cement boards?
Can I use ardex 8+9 over Schulter Kerdi shower pan to make it more water proof?
Hi I wonder if I could use the Ardex 8+9 for kerdi sheet to Abs plastic compotite linear drain
Other than price, what’s your thoughts and experience with Red Guard or MAPEI aquadefense on cement board?
Both are good options. Follow the directions to get the maximum coverage.
Makes me wonder if there's much of an advantage to the 8+9 versus a roll on from Mapei or Hydroban.
You'll know the difference if you've worked with the different products. Ardex 8+9 is amazingly hard when dried and bonds amazing to the substrate unlike the others.
Yeah until you start noticing your grout cracking
8×9 doesn't need air to dry, so no chance of accidentally covering it with tile mortar before it cures and then preventing it from curing and therefore not being waterproof. Not a problem if you use the water based ones and leave them for a day, but guys like this who want to tile the same day benefit from a two part like this. Got this info from Tile Coach's channel.
How bout using it where the cement board meets the cement floor/shower pan. And also coating the entire floor.
Walk in shower ??
Nice video on soldering copper pipe.
+Vic Yuschuk thanks, hope it helped 👍
Great video and much thanks for all the home repair advice. Just curious about where the cement board meets the drywall ceiling. Does one finish that off with a corner bead and mud? I am doing a similar project and am tiling to the ceiling.
you could use the 8+9 in the caulking format, like we did between the tub and cement board. It can get messy though and you don't want copious amounts on the ceiling. You'll be tiling over the small gap as well and when you're done you can seal the tile to the ceiling with either silicone caulk or a siliconized acrylic that can be painted.
Can you put a schluter membrane over the top of Ardex?
The 8+9 yea but all that tape on the wall idk don’t that build up to much and get the wall kinda wonky right there wen u tile or it’s real thin ?
Love all your videos. I'm remodeling my bathroom, but I don't see any videos that talk about what should be behind cement board if that is the option I decide to use. Wedi and Kerdi are not easy to find at my local hardware stores. So, if I use cement board what goes behind it? Plywood then membrane? Or does the Ardex 8+9 allow me to skip this step? Thanks
A late response and hope your project went well. If your bath walls are the exterior wall then just use regular insulation. If all interior walls you don't need anything.
Or the Reguard over the Kerdi?
Hi. Thank you for the video. Have anyone only used ardex S1K and have feedback? This product is one component vs 8+9. Thanks
Not yet but it's probably a great product. We find anything from Ardex to be very good
VERY helpful!!!! New subscriber!!!
+Carlos Sanchez thanks
If you did decide to paint the drywall ceiling with the Ardex, could you then paint over it with regular latex or oil based paint?
+ThePdxster I'd have to check the Ardex 8+9 instructions. That said, it would be a rough texture and possibly need a skin coat of joint compound to look flat. You could tile the ceiling 👍
Yes, the original plan was to tile the ceiling and walls, then my wife changed her mind and only wants the tile up to the ceiling. Using Wedi for walls, but don't want to mess with a ceiling replacement due to asbestos. So Ardex for the ceiling. Cannot find anything about painting Ardex.
+ThePdxster you could call Ardex, their tech support is great.
Thanks, and yes I did talk to their technical guy. No go on the painting, has to be thinset and tile over the Ardex. The good news is my wife changed her mind after I told her the painting won't work and we are tiling the ceiling!
Am wondering how hard is it to get the 8+9 off the tub?😳
You are doing a great job with your TH-cam channel. Good job!
The only thing is bad, your buddy Steve is a mess :) is sloppy. Has knowledge but he need to cover and protect. Avoid scratches /painting in this case the tub. This I saw on the Wedi project you guys did as well when he set the boards and seal...he was a mess :))
Again great job with your TH-cam channel!👍🏻
+Pristine Kitchens & Baths Corp PKB I disagree, these projects are inherently a mess. You have to get your hands dirty to get stuff done. And sure, sealant sometimes gets on the tub but we always clean up. Please understand that no project is 100% neat but that's the point...you don't need to be a perfectionist to get projects going. Plus, our attention to detail is in pretty darn good
This stuff is craaaaaaazy messy lol. I taped more, had more cleaning supplies and a place for everything and still looked like a bomb went off when I was done!
I wonder if I could save $40 and buy a bottle of ardex e90 and a bag of Portland cement and use that. I am pretty sure it's the same thing.
Was their anything in the cracks (such as caulk or thinset) between the cement board before he painted the corners or was it a 1/8" gap that was filled when painting it on? I'm getting ready to do a bathroom and had questions about this process. Thanks.
No, the gaps were less than 1/8" and did't require the caulking or SK Mesh. But, if there are gaps greater than 1/4" then use the 8+9 caulking to fill those gaps then apply another coat. If you want to be ultra sure it's waterproof then feel free to use the SK Mesh in the corners and seams. Our complete tutorial is over on Home Repair Tutor
www.homerepairtutor.com/how-to-waterproof-a-shower-with-ardex/
Hope that helps. What kind of shower are you remodeling?
Home Repair Tutor
Home Repair Tutor
Thank you. I will be taking out a cast iron tub, putting in a shower pan and tile surround for my mother to make it more accessible and less of a trip hazard. One more question--if using cement board and an abs redi niche, so I need to use epoxy to attach the tile or will the mortar work just fine? Thank you again for your reply.
Sounds like a good project J Man, let us know if you have any questions. Ardex makes quality products.
The joints arnt taped?
good eye, if the cement board is tight enough there's no need to use the SK Mesh, the 8+9 will suffice. That's where it's a bit different than RedGard.
Where can Ardex 8+9 be purchased? Is it sold in Lowes or Home Depot?
+Chris Roy we got it directly from Ardex but you can find it at local tile stores. I don't think big box stores carry it
Chris Roy I got mine off amazon but it was the last one in stock
@@robertbrashear9395 stil out of stock.
contractorsdirect.com has it.
can you use it over drywall
You can but we recommend using cement board in showers or tubs? Are you using it in drywall for another reason other than a bathroom?
+Jeff Patterson I was wondering the same thing. I was considering it for my kitchen backsplash near my sink faucet. I'm going to apply tile there, but there is only drywall behind it now. Thanks! Keep'em comin' my friend!
Would you use this product on top of the Kerdi?
where can I buy or find Ardex 8+9 near Downingtown, Pa?
Yes, Mohawk tile in King of Prussia....
what mesh did you use?
+Juliette Perez Calaf SK mesh from Ardex specifically for 8+9
did I miss the sk mesh in the corners?
+joseph Gross if the boards are close enough it's not necessary, although we'd recommend the mesh for most installs. I spoke with ARDEX tech support a few times bout this topic and adhered to their advice. Plus, they approved this video
That's the same thing I was thinking he didn't do any of the seems a long horizontal or the seams in the on the edge why do that not the rest of thm
I think it’s ironic that niche made out of wedi , which is by far superior product
You cant find EVERY product EVERYWHERE. I think these guys do a decent job showing MANY acceptable options. I'm SURE many will argue Schulter is better then Wedi, so then what? "Superior" is a lil over the top.
A little over doing it, no? If the 2 coats are waterproof, why waste time and money on tape (provided you thin setted cement board fiberglass mesh prior)
In the end we are trying to prevent moisture from passing to the cement board and hopefully not provide a moist area for mold. It's not a pool, it's just to prevent mold.
The job was great, by the way.
I'm partial to Red-Gard. Any benefits over Red Gard? I would imagine cost is one but interested in your opinion. Thanks
RedGard is good, I've used it. Ardex dries quicker and doesn't smell like RedGard. So you can start tiling quicker
maybe I'll give it a try on the next project
Ardex : I woudn’t touch this company with a barge pole. I Bought the WPC kit and the instruction were lacking so I phoned Ardex. They advised to use their P51 sealer on new plaster which I did at an additional cost of £54. The finished job looked good but when I scraped of a snot (small lump) I could see the WPC had not adhered to the plaster. Ardex then said I shouldn’t have used sealer ! and advised me to scrape it all off and re-do it. No admission to their wrong advice or even compensation for the materials let alone my time. 2 WPC kits and 1 P51 = £184. This comment would not upload to a Ardex uploaded video. The plastering was done weeks prior to the application of the wpc.
Not with the shluter system.
Backerboard is water proof. What are you water proofing? The tub is waterproof and the tub deck lip is high enough to keep water out. I can see where drywall meets backerboard, though. I have torn out hundred of bathroom tub tile installations that had nothing but basic drywall and didn't have water damage.
+A.W. Baran cement board isn't waterproof, water resistant at best. Tile, grout and thin-set aren't waterproof either. It only takes one failure to ruin a reputation. So spending $100-$200 is worth every penny.
Cement board is NOT waterproof, it's porous and absorbs water readily.
Good product but there are "ready to use", single component fluid membranes out there with no need to mix. Who really knows if you are mixing correctly? Plus, some fluid membranes are both crack isolation AND waterproofing meeting both ANSI standards...one covers concrete cracks up to 1/4"...with just one coat.
Yes but you cant install mesh tape with liquid waterproofing it has to be installed with thinset first. After thinset drys then you can apply liquid WP. Ardex 8+9 you can do both at the same time so you save a whole day.
How will ardex 8+9 perform in a steam room application?
You gonna put a rug in your steam room? You know, to tie it together
It's hard to take you serious when you cover the homeowners tub with a small piece of cardboard. For heavens sake, cover it well so you aren't grinding the grit into the tub with your shoes. Ardex products are good but with the sand in the mix, it's going to build out thicker, especially where the tape is added. The walls that probably were fairly flat won't be when it comes time to tile.
You didn’t seam tape your corners with gray nylon seam tape😮
You did not ship Lap the top tape on the cubby properly-top horizontals tape should have gone OVER the two vertical pics, not under!
How's Steve's back? Looks like tiring work... Great videos though.
I've used This stuff and it is pain in the ass to use. Mapea,laticete,tec make way better sealants at a way better price for sure.
+TILE SETTER 191 not arguing your choices just wanted to try this and see how it worked. It's good to have choices since not every town or city has Mapei or Laticrete or even Schluter for that matter. Distribution of materials is still a problem even in the internet age
I thought whole idea of using a mesh was to seal any corners and joints from water ingress and to prevent from cracking, and your video clearly does not show it and it is bad example... .
What you are showing here is applying a mesh where it does not have to be. it is wide for a reason ,.... to grab 2 corners of a wall or cement sheets and make it as one....
Once any of these cement board moves it will open up a bit and your corners will get water in it !!! To me bad example !!!
+Jay D this video was vetted and reviewed by ARDEX technical support before going Live on TH-cam. They specifically said we didn't have to use the SK Mesh in the corners because the gaps were less than 1/4". If you read the directions they go over this in detail. You can add the SK Mesh to the corners and seams, it will not hurt the installation. But this is not a bad installation because ARDEX approved it 👍
What is that mesh giving you around the corners or around the edges then ???
to me absolutely NOTHING.
Video is wrong. Once any of these boards move (and they will in time) by a tiny bit it will open up the ARDEX coat and you will end up having a crack (under tiles in time) and it will leak there..
I have not seen a single video (apart from yours) where mesh was used this way.
I will not change my mind and any DIYer will say exactly the same.
Using tape elsewhere is pointless... you may as well tape the whole panel...
Don't believe me ... ask ARDEX about your joints isolation
Did you read my last reply, this video was reviewed and approved by ARDEX, i.e. I spoke to ARDEX myself...after all, they're in Pittsburgh where we're located. That said, if you feel more comfortable adding the SK Mesh then go ahead and do it. I'm not arguing that it's a good idea, I'm saying ARDEX gave us guidance on this video and said it was okay to not use the mesh because our cement board seams were butted against each other.
To jd: “once they move”?? No anything with tile should be rock solid. Movement is the enemy of tile. Or the entire tile bed must move as one. Thats why we put cement board on floors & make the floor rock solid. Any movement in tile will fail any protection.
Steve add some pics to Instagram
Thanks, this project was done awhile back
An exkutchin ? Bwahhhh! Wtf my guy are you for real
Pittsburghese, LOL!
That tub is fucked now. Good luck getting that ardex off.
+Kevin Pence it came off no problem
What the F..k are you doing man.
just use a K10. water proffing with poly silicon.
please understand that we make videos showing all the options...not everyone has access to K10 or KERDI or Wedi...but cement board is widely available and Ardex makes some of the best products in the world
Hey friend, I'm about to buy a house, but the neighbors house is very near to the house wall so, there's a very little separation between the two walls, and apparently the house have some leaking problems, you think is it possible to repair from inside of the house?
hard to say, the best thing to do is identify where the leak is coming from. If it's exterior or from somewhere inside the wall you'll need to address that. Ardex 8 + 9 is meant to waterproof your shower or tub walls from water coming from the shower.
Can i use artex on top of kerdi membrane which is put over backerboard for 100% waterproofing