# Forum Home Renovation Waterproofing  fall with adhesive?

## boasha

Gday and thanks to contributors for all the Information I have gleaned from previous threads. There are some questions I have though that need some further clarification. so firstly, assuming my underlay ( water rated composite on 6mm underlay) is level, can I create fall with adhesive? its a small bathroom. and whilst on this question, if it was at all practical to do so, why not put slight fall on the underlay? there seems to be alot of talk about sitting moisture leading to " that smell" so why not encourage its flow. 
secondly, if I have complete coverage with waterproofing does this not create an issue with the adhesive? like you would not pva to a painted piece of timber.  
third, and though not really a question but a request, I can see a pdf in the library for wet areas, thats great, anybody know of any other good resources for diagrams and so on for wet areas? 
 thanks folks

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## phild01

Not sure what you are dealing with but I think you are talking about 6mm fc over floorboards.  You want to create fall over this with an adhesive.  Personally I don't like the use of underlays in a bathroom.  Other threads have dealt with creating thin bed falls with levelling compound and sand.  As for the underlay, why create a flexible lamination with the substrate when a new scyon or compressed cement would be far superior.  Personally I also advise against creating a levelling compound thin bed over underlayment like this.  You really need to direct adhere to the underlay.  Thick bed adhesives may give some fall but in a shower you probably need more than they can offer.  Adding sand to megalastic may help improve the thickness. 
Strictly use cement based adhesives over waterproofing compounds like SE-7 or powdermastic - they will work.  Ready mixed adhesives will not set properly with non-porous surfaces.  To avoid the smell, let your tiling be direct to the waterproofing. 
Suggest checking the Hardies site for their pdf instruction for wet areas.

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## Oldsaltoz

> Gday and thanks to contributors for all the Information I have gleaned from previous threads. There are some questions I have though that need some further clarification. so firstly, assuming my underlay ( water rated composite on 6mm underlay) is level, can I create fall with adhesive? its a small bathroom. and whilst on this question, if it was at all practical to do so, why not put slight fall on the underlay? there seems to be a lot of talk about sitting moisture leading to " that smell" so why not encourage its flow.  As long as the board is very well fixed this is not a problem, fixing through a wedge of glue might be. 
> secondly, if I have complete coverage with waterproofing does this not create an issue with the 
> adhesive? like you would not pva to a painted piece of timber.   Waterproofing products are designed to have a good adhesion rating, look for the CSIRO approval or BRANZ approval on the product when selecting it.  
> third, and though not really a question but a request, I can see a pdf in the library for wet areas, that's great, anybody know of any other good resources for diagrams and so on for wet areas? 
>  thanks folks

  You could try the link below and download the hand book on waterproofing.  Good luck and fair winds.   :Smilie:

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## boasha

thanks for the input guys, makes sense with the cement based adhesive. looking forward to getting stuck into it. knowing I am doing it properly, this will be the last time I use a 6mm underlay mind you, the extra piece of mind with the scyon type products seems to be well worth it.

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## wspivak

Better be careful with scyon products as there are a number of complaints with the product that have cropped up since its release.  First and foremost is that priming over scyon cannot be done with standard general purpose primer, and you would need to use something like Gripset OP primer or an epoxy primer to ensure adequate adhesion. 
Inside a bathroom it's otherwise usually not too bad a product - outdoors on the other hand there are other issues with scyon...  Waterproofing products, Waterproofing supplies. The WaterStop Shop® - Home

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## phild01

> Better be careful with scyon products as there are a number of complaints with the product that have cropped up since its release.  First and foremost is that priming over scyon cannot be done with standard general purpose primer, and you would need to use something like Gripset OP primer or an epoxy primer to ensure adequate adhesion. 
> Inside a bathroom it's otherwise usually not too bad a product - outdoors on the other hand there are other issues with scyon...  Waterproofing products, Waterproofing supplies. The WaterStop Shop® - Home

  Can you expand on the outdoor waterproofing issues, or maybe a link?

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## wspivak

Scyon is essentially a tongue and groove system made out of a cellulose cement material with a "waterproof" thin coating over the top.  The problem is that the edges are not sealed and during construction work often times the actual coating is damaged prior to wateproofing.  So when it rains or ends up with water on it, you end up with water under the waterproof thin coating, saturating the cellulose sheeting, which can then cause one or both of the following>1. delamination of the coating from the board and/or 2. saturation of the board leading to warping. 
Now this on it's own whilst an issue is bad enough, but what then happens is when you try to waterproof over the top of it (assuming you've managed to prime it correctly), can then lead to the primer not acting as intended and the membrane subsequently either delaminating or possibly preventing the membrane from drying/curing in a timely manner as there may be excess moisture in the substrate. 
Hope that helps.  Waterproofing products, Waterproofing supplies. The WaterStop Shop® - Home

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## phild01

> Scyon is essentially a tongue and groove system made out of a cellulose cement material with a "waterproof" thin coating over the top.  The problem is that the edges are not sealed and during construction work often times the actual coating is damaged prior to wateproofing.  So when it rains or ends up with water on it, you end up with water under the waterproof thin coating, saturating the cellulose sheeting, which can then cause one or both of the following>1. delamination of the coating from the board and/or 2. saturation of the board leading to warping. 
> Now this on it's own whilst an issue is bad enough, but what then happens is when you try to waterproof over the top of it (assuming you've managed to prime it correctly), can then lead to the primer not acting as intended and the membrane subsequently either delaminating or possibly preventing the membrane from drying/curing in a timely manner as there may be excess moisture in the substrate. 
> Hope that helps.  Waterproofing products, Waterproofing supplies. The WaterStop Shop® - Home

  Yes it is a wood fibre composite (cellulose) material in part.  The install instructions do indicate sealing the edges with a metal primer and stopping up holes with polyurethane.  I am waiting for some hot fine weather to get on with things, the rain won't let up enough here!
I was hoping you might have had something to show what you say has actually happened.

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## wspivak

I can only tell you what I and others in the waterproofing industry have seen happen on site.  I haven't actually got any pictures as it's not really something that occurred for me to take when I last saw this happen - so take it as anecdotal evidence based on industry experience. 
Having said that, yes, you're supposed to seal the joints with polyurethane, however, this doesn't always occur in a timely manner, and certainly doesn't protect the cellulose from scratches that occur on the waterproof film as a result of accidental damage and/or wear and tear during the building process. 
Bear in mind that if the joints are damp/wet, you're going to have a hell of a time caulking with polyurethane without either first drying the joints out or using an appropriate primer.  Alternately, get your hands on a good quality MS Polymer based sealant such as the Soudal Multibond MS35 or T-Rex which work on damp/wet surfaces. 
Hope that clears things up a little  :Smilie:   Waterproofing products, Waterproofing supplies. The WaterStop Shop® - Home

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## phild01

I discussed this with Hardies technical and the person advised against using an epoxy primer but urged me to contact the waterproofing technical depts instead.  I rang Cromellin and they have no reported issues with their Wetite product, but if still concerned recommended Powerflex or WB2K.

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