# Forum Home Renovation Bathrooms  Waterproofing around bath tub

## Pepscobra

Hi All, 
long time visitor, first time poster.
Thanks for all the great info and advice here. 
Currently undertaking a major bathroom renovation in an old (circa 1930's) timber framed cottage.
Have replaced floor joists and installed new sycon flooring. 
Got a bit carried away last week and installed the new bath tub in its new hob without applying the waterproofing membrane first.
Its all cemented and siliconed in, so no taking it out now. 
Is it a problem that the waterproofing membrane won't run under the edge of the bath?
Is it ok to just paint up to it?
Then tile and silicone seal again around the edge? 
Thanks.

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## sol381

I take it  youve installed the bath by notching out the studs and sliding the bath in and just building a frame at the  front  to support it..   if its a drop in bath then id say you will have to pull the bath out.. the tiles slide under the lip and the bath sits on top of the tiles...some pics might help...

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## Pepscobra

Thanks for the reply.
Yes, studs have been notched about 20mm. 
This is the detail from the CSR Gyprock Residential installation guide; it shows the tiles butting up to edge of the bath.   
But I didn't run the waterproofing under the bath, as shown in the detail. This is what I'm worried about now. 
Here's a photo of the bath installed in the hob:

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## perf

Thats a poor detail from CSR in my opinion. The tiles could or should be under the bath at an unnoticeable fall so the detailed silicon seal is more vertical than horizontal. (its just a neater no worry finish)  If its not an option to remove the bath , then its all about damage control. Fortunately not real lot of water gets on the hob anyway ( I am presuming there is not a shower into the bath).  I would suitably prime the timber using the primer recommended as part of your chosen waterproofing system and then waterproof. I would then cover the timber with villaboard or equivalent and sika the the joint up against the bath as well.  After the frame is lined with suitable chosen cladding , I would waterproof again and overlap into you plastic angles. I would sleep rather well after this system applied.

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## sol381

never seen it done that way.. cant say it would give a neat finish..id use villaboard instaed of aquacheck  as well.. the villa not only goes vertically but also horizontally on top of the stud(not shown that way in the diagram) waterproofing is done on top of the villa not on the stud as shown as well...villa  then angle then waterproof then tiles then bath is the standard way of doing it...theres normally a bit of water when you hop out of the bath and just siliconing it may not be enough..might have to try and get the bath out as it may save a lot of work down the track when you have a water leak...

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## Pepscobra

Thanks for the feedback. 
Taking the bath out isn't an option at this stage. It's fixed in there good and proper and now all the wall sheeting has been installed also. 
Originally I had set it out for the tiles to run under the bath lip, but when I saw that CSR detail I adjusted it. 
I'll have to make the best of the situation and go overboard with the waterproofing membrane to ensure a good seal around the bath edge.

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## mudbrick

Wow that looks like a heavy duty frame to hold a bath. If you can't move the bath is it possible ( however painful ) to pull the top timber rail off the frame on both sides and plane it down, or trim the tops of the studs then nail the top rail bck on at the correct height to allow the waterproofing to be done according to the drawing ? 
If this bath isn't going to be used every day i'd probably just continue on and finally sikaflex the gap between tile and bath edge, and hope it seals. What's the worst that can happen?

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## intertd6

The bath install is defective & doesn't meet the standard, if you don't rectify the defect now it could cost you more in the long run.
inter

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## Pepscobra

Hmmm... Looks like I've got a bigger problem then I thought  :Frown:  
Does the detail pictured above meet standard at least?

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## Pepscobra

Ok, so last night I've started to chisel/gouge a recess in the timber under the lip of the bath. 
This will enable me to brush the waterproofing in under the bath. 
I'll apply numerous coats and polyester matting just to be sure.

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## Pulse

a defective install won't pass certification I think  
Sent from my iPhone using Tapatalk

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## Pepscobra

certification is the least of my worries.
I just don't want to have any water issues down the track.

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## GDOG

I've never installed an angle under the lip and then waterproofed before installing a bath.  In 90% of cases the bath supporting walls are only fixed down permanently at the same time as bedding in the bath therefore it is not practical anyway.  As mentioned by others, I install the bath (lip) about 17-20mm (depends on tile thickness) higher than the wall by the use of a whaling plate (just timber on edge)  fixed on the inside of the wall supporting the bath inside further than the lip.  The top and side of the supporting walls are clad with villa (6mm) then wet sealed.  The laid tile finishes under lip relatively snug with a bit of fall out.  A good silicone caulking job then follows.  Have done baths this way for 20 years (except the membrane, relatively new) and my first boss who taught me had been doing it this way for his 35 years in the trade.  Neither of us have ever got a call back once.  Waterproofing a bath is nowhere near as important as tiled shower bases.  Kids splash around in the bath but if done correctly, the water runs off the supporting walls onto the floor.  Now that is where you'll get water damage if not wet sealed correctly. 
Nearly all manufacturers of membranes will only guarantee their products for 10 years.  Not much piece of mind there. There are some really cheap ones out there to avoid. Also this talk of not passing certification is not an issue.  Who will inspect it?  Not sure of your situation but it seems like it's just a reno on your own house.  On a new house build in my world, there is no inspection of waterproofing.  It's left to the builders discretion.  Not many builders will skimp on this though.  I know I always use a top notch polyurethane product. 
I often wonder though how a novice can do it.  As a professional, I was required to complete a course in the application of waterproofing when it became mandatory. Yes it's not rocket science but knowing the process, the bond breaker (very important) and how and where to use the reinforcement web/mat helps.  I suppose you tube solves that though. there are demos on absolutely everything on there.  Not many are right or appropriate for the novices region though which is the problem.

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## Pepscobra

Thanks GDOG, your post is most encouraging. 
A couple of questions if I may please... 
what angle/fall do you install the edge tiles on?
what waterproofing membrane system do you recommend? I'm looking at the Dunlop wet area stuff.

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## GDOG

+  

> Thanks GDOG, your post is most encouraging. 
> A couple of questions if I may please...
>   /
> fwhat angle/fall do you install the edge tiles on?
> what waterproofing membrane system do you recommend? I'm looking at the Dunlop wet area stuff.

    The fall is very minimal and over your distance, I'm talking 1-2mm.  Enough to run out not in so anything under level is enough.  The top corner tile may need to be mitred if you have too much fall rather than using one L shaped tile that if falling out on one plane will cause it to kick up on the other.  If using one L shaped tile it should fall diagonally to the corner with the corresponding tiles not perfectly lining up but unnoticeable.   Hard to explain but seems to work in practise.  
As for the product, if it is only for the bath, floor and shower walls assuming a shower base is being used and providing you're not on a second story and have used villaboard, use whatever as it's not that vital but if you are doing a tiled shower base, on the second floor or using plasterboard :Shock:  it's another story.   I always use Davco k10 plus. water based polyurethane, resists re emulsifying if constantly pooled with water that some others do.  Don't bother with 'aba superflex' an acrylic based product that is half as thick as the k10 plus.  Have not used anything else.  The k10 costs about $100 for the small 4 litre tub which will only do a 1m x 1m shower base and 2 walls with 2 thick coats.  
Like most things, you get what you pay for (excluding aba products, overpriced)

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## phild01

The K10 is good, Also Cromellin which doesn't need another primer product.

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## intertd6

It is really important that a water proofing (WP) angle goes under the lip of a bath as it doesn't rely on the bond of a sealant to waterproof around the bath perimeter that moves considerably every time the bath is filled. A certificate stating that the waterproofing has been done complying with the standard is required for certifiers & such, if it's a backyard job then who ever does it takes the risk, most professional builders or tradesman doing bathrooms would make sure the WP is done properly to the standard as it is very expensive to rectify leaks at a later stage as they are responsible for a least 6 years of warranty. To do it properly the waterproofer has to do the WP in two stages & I still come across installers that think it can be done in one stage, but I haven't yet been shown how thats possible.
inter

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## GDOG

> It is really important that a water proofing (WP) angle goes under the lip of a bath as it doesn't rely on the bond of a sealant to waterproof around the bath perimeter that moves considerably every time the bath is filled. A certificate stating that the waterproofing has been done complying with the standard is required for certifiers & such, if it's a backyard job then who ever does it takes the risk, most professional builders or tradesman doing bathrooms would make sure the WP is done properly to the standard as it is very expensive to rectify leaks at a later stage as they are responsible for a least 6 years of warranty. To do it properly the waterproofer has to do the WP in two stages & I still come across installers that think it can be done in one stage, but I haven't yet been shown how thats possible.
> inter

  I've pulled out old baths that have been in for 5o + years without a sniff of any water damage.  In fact, I don't think i've ever seen water damage on a bath frame or surrounding area unless a shower is involved.  These standards you speak of are relatively new and we survived without them let alone any form of waterproofing.  A bath is nothing like a shower and these standards are good in theory but not in practise.  As I mentioned earlier, these bath supporting walls usually need to be fitted permanently at the same time as the bath install.  Hard to clad and wet seal first.  The way I do it, the supporting timber is back very close to the inside of the bath.  Smothered in silicone prior to the fit to take up any slack and hold the bath secure.  Then the tile being tight under the lip supports that edge aswell so have never had a properly prepared silicone seal give.   
That's the problem with these standards we have to abide to. Not just waterproofing either, Most are written by suits with out practical experience and are catered for the worst in the industry.

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## intertd6

ive been fitting drop in baths & spas for 15 years that meet the standard showing an upturn under the lip, it's not hard at all to do properly, when I first started in the building industry 38 years ago there was no such thing as a WP standard at all & bathrooms leaked so regularly they introduced a WP standard for those that hadn't been shown how to WP at TAFE as part of their trade training. The way you say that you fit baths doesn't meet the standard.
inter

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## phild01

I tend to think some standards are over the top but this one is a must for the shower areas.
  Also think fire ratings can be a bit over the top (more to do with insurance than saving lives).

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## GDOG

> ive been fitting drop in baths & spas for 15 years that meet the standard showing an upturn under the lip, it's not hard at all to do properly, when I first started in the building industry 38 years ago there was no such thing as a WP standard at all & bathrooms leaked so regularly they introduced a WP standard for those that hadn't been shown how to WP at TAFE as part of their trade training. The way you say that you fit baths doesn't meet the standard.
> inter

  They are not a drop in bath as it's checked into the walls.  A drop in bath to me denotes an island that a bath can be sat in.  This type you mention is fully tiled prior to a bath even coming onto the scene. (using a smart waste) As the builder overseeing the whole project from start to finish,  I'd prefer all plumbing be ran in the walls prior to a bath even coming on site.  I don't risk damage to a fitted bath from the plumber, bad enough all the trades to follow.  Now this plumbing makes it impossible to 'drop' in the bath. The supporting walls need removing to enable the bath to go underneath the mixer or the like. Although, in hindsight, there is nothing stopping a small 12mm angle being nailed to the supporting walls about 20mm under the lip then once fixed in position, butt villa up to it then wet seal through my then 10 or so mm gap.  Hard but not impossible. 
A bath is nothing like a shower with any water damage usually reserved for the floor below which was caused by water running off the hob and drying oneself, The tile hangs through under the lip about 20mm with fall.  any water that may get passed the what you call the sure to fail seal would be next to nothing and evaporate.  As mentioned earlier these standards are because of all the dodgy builders out there cutting costs and poor workmanship.  Surely you can admit some standards are over the top.  The membrane is guaranteed for only 10 years, It has a lifespan of probably 15 then. Sometimes old school know how is vital for longevity.

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## intertd6

Your advice is contrary to the standard & wouldn't be eligible to be covered under a WP certificate, as your method doesn't comply.
inter

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## GDOG

> Your advice is contrary to the standard & wouldn't be eligible to be covered under a WP certificate, as your method doesn't comply.
> inter

   okaaaaay then,  It does withstand the test of time regardless what your standards say.  How does the waterproofing membrane go after 10-15years?  It's only just becoming known. You seem such a stickler for the book that you struggle to think outside the box.  We are talking about a bloody wall/hob mounted bath on a lower floor not an insitu base on an upper level.

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## Pepscobra

Any difference between the Davco K10 Green and Grey?

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## GDOG

> Any difference between the Davco K10 Green and Grey?

  No idea, maybe it's an acrylic, fibre reinforced, for external use, roofing and retaining walls.  Google it maybe.  Stick to the k10 plus I reckon for showers, It's the green one with the consistency of very thick custard

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## Pepscobra

Sounds good, might give the K10 a go.
I assume its compatible with all tile adhesives? 
Is there a good flexible adhesive that would be recommended over others?

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## Pepscobra

Sorry for all the questions... does the Davco K10 require installation of a reinforcement fabric at joints in the plasterboard?

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## GDOG

> Any difference between the Davco K10 Green and Grey?

  No idea mate,  maybe it's an acrylic, fibre reinforced, designed for external use like balconies, suited to roofing and retaining walls.  Google it maybe.  Stick to the k10 plus I reckon for showers, It's the green one with the consistency of very thick custard.   
Also in your case I would rough up the bottom 10mm of the bath lip resting on the frame.  Use a rotary tool or sandpaper.  Clean using acetone or metho, when dry use this adhesive/sealant  Ardex CE 20 P,  to caulk a good 5mm bead onto bath and timber frame.  This product is white and sticks to everything and won't let go.  Similar to sikaflex/soudal but supposedly superior. Very hard to finish neatly but not a concern as it's not seen.  About $25 a tube though.  Clad frame with villaboard and repeat the caulk over that.  Wet seal, tile then caulk another bead up against the tile and bath but this time using silicone smoothed over with  soapy water and an icy pole stick. 
Now I know this won't meet inters standards and you'll receive no certification but I guarantee it won't leak or move.  That is 3 separate caulks against the bath. There is more than 1 way to skin a cat. 
If the plasterboard joins haven't been taped and filled I would. (should be villaboard by the way) I use the deck web (fabric) on every internal corner, any joins/change of substrate such as from the shower bases morter/concrete onto the pvc puddleflange.  If in doubt use it anyway.  Make sure you still do the bondbreaker (neutral cure silicone, not acetic) on every junction, crack, change of substrate.  Another tip when wet sealing is brush on the first coat vertically then do the second coat horizontally. 
I use a glue called maxset, there are 2 or 3 versions of this but you can use the purple bag for everything bar a shower base.  That's for the black bag  Compatible with k10.  It comes in the 20kg bags and costs about $30 a bag.  Good workability and pot life.

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## Pepscobra

Thanks GDOG. 
Do you mean Ardex CA 20 P...?

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## GDOG

> Thanks GDOG. 
> Do you mean Ardex CA 20 P...?

  Yes sorry. It is pretty sensitive to air it even has a ring pull lid on the bottom for shelf life.

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## intertd6

> okaaaaay then,  It does withstand the test of time regardless what your standards say.  How does the waterproofing membrane go after 10-15years?  It's only just becoming known. You seem such a stickler for the book that you struggle to think outside the box.  We are talking about a bloody wall/hob mounted bath on a lower floor not an insitu base on an upper level.

  I'm struggling to understand how if you do bathrooms, how they get certification which actually complies with the standard.
inter

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## GDOG

> I'm struggling to understand how if you do bathrooms, how they get certification which actually complies with the standard.
> inter

   You struggle to think critically and sound like a bloody robot.  Just forget about it because you will keep saying the same crap Blah blah blah standard this, certification that.  Are you able to think for yourself or just repeat the wording in the standards.  I'd hate to see you overcome a problem on site.  You'd be lost.  The sign of a competent tradesman is overcoming problems that the draftsmen draw as they have no practical experience.  On paper doesn't always equate to 'on site' which is your problem.

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## intertd6

> You struggle to think critically and sound like a bloody robot.  Just forget about it because you will keep saying the same crap Blah blah blah standard this, certification that.  Are you able to think for yourself or just repeat the wording in the standards.  I'd hate to see you overcome a problem on site.  You'd be lost.  The sign of a competent tradesman is overcoming problems that the draftsmen draw as they have no practical experience.  On paper doesn't always equate to 'on site' which is your problem.

   One of the biggest problems on site, are so called tradesmen who can't adjust to change, I normally send them down the road quick smart when the stupid excuses or arguments come out for them not complying with current standards or levels of workmanship which are needed these days, it just comes down to self discipline to achieve what some seem impossible. I must have been hiding in the site sheds over 38 years to not have seen & solved just about every problem imaginable in the construction industry, working for myself through to the once largest construction organisation in this country doing some of the most sophisticated projects around the globe, its quite funny when someone's wingeing about not being able to comply with a simple WP standard detail which other tradesmen manage to quite easily around the country, it just doesn't seem professional to me to go below a standard which is often the bare minimum.
inter

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## GDOG

:Roll Eyes (Sarcastic):

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## Watters

> 

  Resurrecting this thread. 
I have created a bath hob which is a sort of island, so the bath is not recessed into notched studs, nor do I want to do that for aesthetic reasons. 
Below is a photo of the arrangement and a diagram of what I'm thinking of doing. Would appreciate input thanks, GDOG?

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## phild01

Watters, take care with the tiling around the bath as splash water will pool and be a source of annoyance.

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