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Is my bathroom floor ready for waterproofing?

Hi there, I just got new floor laid in the bathroom (James Hardie Secura on timber frame) and just wondering if I can get some advise whether these gaps are acceptable and ready for waterproofing. Here is the gap between the shower recess and rest of the floor (~10mm)

And here between the floor and bottom plate (19mm widest point):

I’m planning to sheet with villaboard so that’s 6mm less gap but still…

The tiler/waterproofer says the gaps are too big and the carpenter/builder says this is build to code and that the tiler is not worth his salt if he can’t deal with it. I’m not sure who is right but it does seem like there is no reason for gaps like that… any advise is much appreciated!

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EricL

Hello @tom138

I'm afraid those gaps are too big. A gap of 2mm at the most would be tolerable as they can filled in with silicone before being covered with a waterproofing membrane. But that gap, there's just no way to cover it. I propose calling the builder back and asking them to refit the panel with no gaps visible anywhere.

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

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

Eric

Nailbag

I'm with the tiler/waterproofer @tom138 & @EricL that this is unacceptable and that the builder (I use the title lightly) should be skilled enough to butt-join all the sheets, both wall and floor. Your waterproofer should also be licensed and as such comes with the skills and qualifications to ensure the waterproofing is done to strict guidelines for you to obtain certification as part of the building approval process for your bathroom. If you haven't paid the builder yet, then I wouldn't be until he makes good the work.

Nailbag

Dave-1

Evening @tom138

Id be going back to the builder and saying "nope" needs to be fixed. Makes my mind hurt looking straight through the floor...

Feel your pain and frustration, worth sorting now tho.

Id be doing the same thing @Nailbag has suggested...

Dave

tom138

Thanks everyone for your suggestions and feedback. It gave me confidence that I was in the right to request rectification.

I also read the JH Secura installation guide and it specifies that gaps for butt joins in internal tiled wet areas are supposed to be 2mm and gap between wall and floor should be 3mm. It also says that JH sealant should be spread over heads of fasteners, which was not done.

To my surprise, after initially pushing back, the carpenter has agreed to come back and re-do part of the floor when I pointed him to the specs from the installation guide. We had a good conversation and he seems to want to make it good. Fingers crossed it is done correctly this time around 😉

Thanks again!

EricL

Hi @tom138

Please don't forget to post a photo update. We would definitely like to see the progress of your bathroom renovation.

Eric

Nailbag

That’s an awesome result mate. I’m guessing the builder probably knew himself already the job wasn’t up to scratch. Sealing the nail heads though I would expect that to be part of the waterproofer/tilers job. As long as it’s done it doesn’t matter 👍

tom138

So… he came back and although over the phone he had agreed to replace half of the sheets, he replaced the worst one and glued slivers to the other ones so there are no gaps now (the black bit is just a shade):

Not sure whether this is a standard way to do this and although it’s not ideal, looks acceptable to me. Main thing is the big gap is gone. Fingers crossed the tiler is happy on Monday 😉

Oh yeah and the carpenter demanded payment on the spot yesterday 😀

tom138

I am making progress. Had a lot of work to do on framing, some of which was in bad condition and needed reinforcement/replacing.

Now I am moving onto sheeting. Walls will be lined with Villaboard and nailed and ceiling with Gyprock Aquacheck and secured using combination of stud adhesive and screws. Shower area will be tiled but most of the bathroom walls just painted (for now might tile in the future).

I have few questions. Firstly - what to do in the corners where the Villaboard wall meets the Gyprock ceiling?

Secondly - I cut this sheet a bit bigger as the ceiling is not 100% square and the corner cracked when I installed the sheet:

Is there a way to remediate this without removing the whole sheet? There is Rockwool insulation underneath. I’ve seen people using expansion foam and then plastering over it? Or should I cut the area and install a new piece in there? The problem is that there is not much to screw it into in that corner, I would have to use a backing board or something.

Also, should I put something like Sikaflex to fill those gaps between the bottom plate and the new flooring?

Thanks!!

MitchellMc

Hi @tom138,

Well done on your progress. Here's the James Hardie Villaboard Installation Guide for wet areas.

The joint between the Villaboard and Aquachek can be sealed with a polyurethane sealant such as Sikaflex 11FC.

I'd recommend cutting out a 100 x 100mm section in that corner and glueing a couple of timber strips to the back of the sheets and stud work across the opening. You can then install a new section of plasterboard and use fillers.

Most gaps can be filled with Sikaflex; remember that it is not a structural element. So, for the gap in your image, it might be best to attach timber to the underside to close the gap and then use the sealant.

Please let me know if you have any questions.

Mitchell

tom138

Thanks @MitchellMc, great idea! I couldn’t get any timber strips as there was insulation in the way so I used a 4.5mm FC sheet as backing

Frustratingly, partly due to a inaccurate measurement (no matter how much time did I take and how many times did I measure) and old out of square/level frame, I’ve ended up with quite a big gap between wall sheet and ceiling in one place (about 1.5cm):

Is this within acceptable tolerance or is it too big? Would you still recommend Sikaflex? I am planning to install simple timber coving/cornice that should cover the gap.

Last question - JH recommends to use the James Hardie Base Coat 4kg for villaboard but this product unavailable in all stores close to me with unknown availability date so can I use Gyprock CSR 3kg Wet Area Base Coat instead? It says it’s also for FC sheets.

Thanks,

Tom

JacobZ

Hi @tom138,

While not ideal, as it's not James Hardie's recommended product, the Gyprock CSR Wet Area Base Coat is a comparable product that can also be used in this application.

This gap should be manageable as it's unlikely you will have too much water hitting the ceiling. As long as the top plate runs the full lengths as backing, you can use the beforementioned wet area base coat to back fill this gap. Once covered with cornice, you will not be able to see it anyway.

If you need any further advice, please reach out.

Jacob

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