What tiling timber substrate?

[AnnieN4]

I have done a lot of reading and research on Self Level Compound, however remain unclear about damp proof membrane for the toilet floor (stand-alone toilet room, not bathroom)

I have original hardwood floors on the first storey, over a garage meaning there's nothing between the underside of the timber and the garage below. I am aware that a membrane under SLC will usually risk tearing the membrane, however some articles state that timber substrates always require waterproofing prior to SLC. If I use a liquid DPM instead of a sheet membrane, does this fix the issue of tearing? Or would a watertight timber primer do the job, noting I need to prime prior to SLC anyway.

After the SLC is complete, I intend to apply a sheet membrane to waterproof prior to an uncoupling sheet so that I can tile. 

Given I have timber floors, I have been looking at Dunlop Level-Flex Timber Floor Leveller which comes with it's own primer. I'm not sure if this particular primer would be suitable as a waterproofing agent to achieve the above prior to SLC. 

Appreciate any suggestions on method and products, Cheers. 

[EricL]

Hello @AnnieN4 

Welcome to the Bunnings Workshop community. It's sensational to have you join us and thanks for sharing your question about tiling your timber substrate.

You've certainly done your homework in regards to the SLC and DPM. As this is a rather complex endeavour, I've sent Dunlop your enquiry in regards to the compatibility of the products. Since sheet membranes under SLC are prone to tearing, a liquid damp-proof membrane (DPM) is a good option. However, most liquid DPMs are designed primarily for concrete rather than timber, so compatibility would need to be confirmed. 

Dunlop Level-Flex Timber Floor Leveller does come with a primer, but it's specifically designed for adhesion, not waterproofing. Instead, you might want to look at the Dunlop Undertile Waterproofing (which is a liquid membrane) could be used first. Again, it will be necessary to confirm if it can be applied to hardwood flooring or if a primer will need to be used before application.

Your plan to apply a sheet membrane over the SLC before tiling is spot on. That will provide extra waterproofing and crack isolation, especially with the uncoupling sheet. To sum it up, if the process can be simplified by using a single waterproofing product which can take the SLC, it should make the process less complex. As soon as I get a reply from Dunlop, I'll let you know. 

Let me call on our experienced members @Dave-1 and @Jewelleryrescue for their recommendations.

If you need further assistance, please let us know.

Eric

[Dave-1]

Good Evening @AnnieN4 

"Cracks door open" and wooooooooooo grits teeth as whole new subject matter comes up. Sorry I cant help you on this one as I had to go and look up the abbreviations you were using to start with! Always happy to learn new things but cant really offer anything for this instance.

Dave

[EricL]

Hello @AnnieN4 

I've been in contact with the Dunlop technical team, and they did mention the use of the Dunlop 15.9kg Timber Floor Level Flex Kit. However, they mentioned that it is water resistant not waterproof. The flooring sequence that they suggest is to put the cement sheet first, then the SLC and then the waterproofing compound on top. They could not give me a product recommendation in regards to waterproofing the Timber Foor Leveller. They also mentioned that the DPM and the Undertile waterproofing is not ideal for timber floors. 

In this instance, because you are waterproofing this wet area, it will be necessary to engage the services of a certified waterproofing installer, as it will need to be sighted and signed off. I propose discussing your options with the installer in regards to your idea of applying a DPM or something similar to double your protection. The installer will be able to provide you with a more in-depth answer as they are familiar with the rules and regulations of waterproofing.     

If you wish to discuss it further the Dunlop team have suggested to give them a call on 1300 788 780 and look for Maria.

If you have any other questions we can help with, please let us know.

Eric