Brick & Block / Concrete Floor - Do I need to tank?

[Ripmaster]

Hi. First post. Fount the forum whilst searching for cutting tool hire info.

I am currently building a new house and have planned a wet room in the main bedroom en-suite. Construction is block work and concrete floors throughout. My question is, do I need to tank? My builder/plasterer and tiler all say that they don't think it is necessary. Bathroom designer says that I should (up to 5 feet high) to be on the safe side. Plan is to plaster the walls (sand and cement scratch coat) and cast the linear call in the sunken wet area. The drainage is via a 1100mm QuickDrain at the back. the entire bathroom will be tiled floor to ceiling in ABK porcelain tiles with 2mm spacing and Mapei grouts. Any advice welcome. Thanks

 

[david campbell]

i would tank the entire wet area especially since theres no windows and it'll be an expelair or similar fiited

 

[diamondtiling]

Your 'tiler' has said you do not need to tank a wet room? I would be more worried about him.

:incazzato:

 

[Diamond Pool Finishers]

you need to find a pro-tiler off this forum IMHO mate :lol: with advice like that , who needs enemies :lol:

 

[White Room]

You say sand/cement scratch coat, is there a finish to go on it or just left as a smooth render

 

[Diamond Pool Finishers]

buy the way hi:welcome:to the forum mate

 

[Ripmaster]

Thanks all for the welcome and prompt feedback. Any advice on the best product?

The bathroom designer has mentioned some liquid tanking product although I forget what it was called. The builder/plaster thought that it would not be needed as they thought it was just a case of going over the top since the room is on the ground floor and thought that the tile shop was just trying to sell me more stuff 🙂

Wet rooms, at least of the type I'm planning are not run of the mill stuff in my neck of the woods it seems, so lots of hands on experience might be thin on the ground from local pros. The tilers being considered are very good at the actual cutting and installing, and I only heard 2nd hand that they did not think tanking was necessary so I will have to double check that again to be sure. But I will certainly ask the question of them again and ask for justification.

The concrete slab obviously has visqueen underneath, there is also another layer of insulation with visqueen on top underneath the C25 screed that has been poured on top of the slab. The wet area is also quite large 1.2M square with a Clearwater square shower head recessed into the ceiling so the amount of water going to the side walls would be minimal I would have thought. The shower areas is 1.2m*2m with the drying area having underfloor heating and additional screed. So maybe this is why they think spending on tanking is a waste of money. All the internal block walls in question are 9'' hollows too, so no chance of any water bridging to the other side....But I will probably tank it to be on the safe side if that is still the consensus from the pros here.

Here are few pic of what I hope it will look like at the end.

​

Thanks again for all the advice.

PS: There will be two extractors in the bathroom. One directly above the wetroom area, another for the rest of the bathroom. Wetroom vent will only come on when the shower is used and other will be disabled at that time via automation to avoid air flow 'conflict'. Not shown in the pics, there is a velux in the ceiling above the back wall where the sink and box will go. Althought will not be opened much as only really there for some light.

 

[White Room]

That looks nice:drool5:

 

[diamondtiling]

A room like that will not be cheap, it looks fantastic. Applying tanking is not just for a 1st floor bathroom or wetroom, it should be used in all bathrooms. It does not just protect from leaks through to a room below, it protects the whole structure as in the walls and floors and gives a 100% failsafe if installed correctly. It amazes me when builders think it is just for making more money and when wanna be tilers think it is a gimmick. Ask yourself this, do you want problems in the future? the obvious answer is no, so dont risk it at this crucial stage.
If you are unsure of the tiler then now is the time to change them.

You could always ring me.................:smilewinkgrin:

 

[wetdec]

Take on board all the comments as they are all relivant experienced opinions.

My question is, do I need to tank?

My answer would be no.......


..

 

[Ripmaster]

Take on board all the comments as they are all relivant experienced opinions.

My answer would be no.......

..

Thanks wetdec, would you mind expanding as to why you think no. I'm curious as your are the first to agree with my builder on this - He'll have a field day as I'd told him all the advice I received so far as to tank - I'm just keen that the job is done properly so would appreciate your thoughts.

Thanks again for taking the time.

 

[DHTiling]

I would tank.. constant wetting of the substrate can cause damp to travel and is a haven for mould spores...

It is better to just have the adhesive bed getting wet , rather than the whole substrate ,be it concrete floor or block walls..

I know what my preference would be.

 

[White Room]

Tend to agree with Dave, with the render being strong but brittle if there is any movement/settling down in the subtrate it will travel thru to the tiles.

 

[heavytrevy]

lmao,

Water will easily go thru the blockwork.
I seen plenty without tanking and the resulting water stains and mildew on the other side is pretty bad.

I would tank above the height of the rose , use a liquid tank , ardex make good ones.


i can link you some detailed waterproofing instructions if you like.
you will need bondbreakers in all the corners and of course a waterstop at the doorway.

Trev

Take on board all the comments as they are all relivant experienced opinions.




My answer would be no.......


..

 

[Ripmaster]

Hi Trev, any links greatefully received...

I assume you mean the doorway to the shower area, rather than the doorway to the bathroom. The shower is nowhere near the entry door to the room and is sunken into the floor so would need to fall asleep and block the drain to cause enough of a flood to reach the door I would have though :yikes:

 

[heavytrevy]

Both , only takes a washcloth or a block of soap .


Im off to work atm , when i get back later on i will send you some info thru.

Regards
Trev

 

[jay]

hi interesting i would tank but if your in doubt set up a sprinkler in shower cube and let it run for a couple of hours and then see were water has gone then when dry waterproof or tank walls and floors let dry and try sprinkler again even with tiles on walls and floor some moisture will get through (grout joints) waterproofing stops it from going further //:8:

 

[heavytrevy]

here ya go
http://www.bsa.qld.gov.au/SiteColle...s/Tech Info/Waterproofing Standard AS3740.pdf

if you still have any questions dont hesistate to PM me.

Regards
Trev

 

[diamondtiling]

Take on board all the comments as they are all relivant experienced opinions.




My answer would be no.......


..

Hi Tony, I don't understand why you would advise not to tank in this situation? Or any wet area? What are the reasons why you advise against it mate?

 

[wetdec]

Hi m8

First off its not advice its an answer to the question the man is asking given the situation. Generally on new build concrete walls I wouldn’t push tanking as solid walls are rarely suceptable to joint fracture as dry wall carcassed walls are. Solid walls stand a lot longer and have infinitely more time to move during the drying process. On an old property where decay has taken place then the answer would be yes inorder to stabalise the surface that may be cracked or damaged.

The majority of water ingress derives from cracking at transitions, that is corners and wall to floor points not through grout line failure. The ingress as its spoken of is water leaking at transitions and moisture penetration at grout line. The latter is a concern obviously but moisture ingress predominantly goes through the drying out process during shower down time where as leaks are leaks.

There are all kinds of reasons lent to why you should tank but the main one being “ to secure a wet area so preventing water damage to surroundings due to substrate failure “ and is directed at dry build systems and the problems that can arise from leaks into floor voids, electrics etc where tanking is a must.

Back to the question, the room in the picture has its corner block work bonded so if it moves it will all move, and there is no direct strike area. Later we are advised that the floor will be the strike area as the shower head is ceiling and central.

Looking at it from here I would say fix Dura-CI before your tiles over the poured screed, as it appears the drop in the floor will not be brought to level and possibly hold water tape the wall floor transition. As for the walls they are to be rendered, then covered in adhesive then tiles and grout tanking imo will not be of benefit, if you want belt and braces put waterproofer in the render.


Hope this helps a little.

 

[jay]

Hi m8

First off its not advice its an answer to the question the man is asking given the situation. Generally on new build concrete walls I wouldn’t push tanking as solid walls are rarely suceptable to joint fracture as dry wall carcassed walls are. Solid walls stand a lot longer and have infinitely more time to move during the drying process. On an old property where decay has taken place then the answer would be yes inorder to stabalise the surface that may be cracked or damaged.

The majority of water ingress derives from cracking at transitions, that is corners and wall to floor points not through grout line failure. The ingress as its spoken of is water leaking at transitions and moisture penetration at grout line. The latter is a concern obviously but moisture ingress predominantly goes through the drying out process during shower down time where as leaks are leaks.

There are all kinds of reasons lent to why you should tank but the main one being “ to secure a wet area so preventing water damage to surroundings due to substrate failure “ and is directed at dry build systems and the problems that can arise from leaks into floor voids, electrics etc where tanking is a must.

Back to the question, the room in the picture has its corner block work bonded so if it moves it will all move, and there is no direct strike area. Later we are advised that the floor will be the strike area as the shower head is ceiling and central.

Looking at it from here I would say fix Dura-CI before your tiles over the poured screed, as it appears the drop in the floor will not be brought to level and possibly hold water tape the wall floor transition. As for the walls they are to be rendered, then covered in adhesive then tiles and grout tanking imo will not be of benefit, if you want belt and braces put waterproofer in the render.


Hope this helps a little.

can see were you are coming from and tend to agree on some // but if your going to do this sort of a bathroom and you want to eliminate all possible future problems ( moisture in blockwork poss leaks bacteria growth slower floorheating pos efflorescence in grout ) for the few extra dollars i would waterproof and have peace of mind but that's me if you do go the waterproofing or tanking way you cant beat wet dec
:8:

 

[wetdec]

if your going to do this sort of a bathroom and you want to eliminate all possible future problems ( moisture in blockwork poss leaks bacteria growth slower floorheating pos efflorescence in grout ) for the few extra dollars i would waterproof :8:

Well then lets tank the ceiling incase we get a hole in the roof......:smilewinkgrin:



..

 

[grumpygrouter]

Well then lets tank the ceiling incase we get a hole in the roof......:smilewinkgrin:



..

....business opportunity, prior to laying insulation?????

 

[jay]

Well then lets tank the ceiling incase we get a hole in the roof......:smilewinkgrin:



..

good idea
if it was your bathroom wet deck you wouldn't tank or waterproof
if it was mine i would



once tiled if a problem occur es and only if do you patch and hope for the best or rip it out and start again didn't realise he wanted to tile ceiling:lol: