How to install Aquachek Bathroom plasterboard?

Question

Good morning

Looking at plasterboarding a fully stripped bathroom in prep for waterproofing, plumbing, tiling etc.

Planning on using gyprock aquachek 10 mm thick for both ceiling and walls.

https://www.bunnings.com.au/gyprock-csr-3600-x-1200-x-10mm-4-32sqm-aquachek-plasterboard_p0732568

Should stud adhesive be used given that is a wet area?

The Gyprock instruction video also recommend putting 10mm spacer between floor and lower gyprock panel to allow for expansion.

Is this still the case for gyprock Aqua check?

(I believe when I stripped the bathroom the original plasterboard ran all the way to the bottom, beneath the tiles and subfloor?)

And how does that then work with waterproofing?

photos attached.

Thank you in advance.

Jan

JacobZ · Answer

Hi Jan (@jdbunnings),

Construction methods definitely change over time, but the most current information supplied by CSR is that tiled walls should be mechanically fastened only.

Information about the screw spacing for a fastener fixing application can be found on page 26 of The Redbook 2 -

Please note that there are different requirements based on the weight of the wall covering. Your tiles should have a per square metre weight shown in their specifications which will guide you about which method to use, but usually it would just be easier to go with the highest level, which is fine for tiles up to 32kg/m2.

This means a screw every 100mm along the butt joins (left and right edge), a screw in every stud along the recessed edge (top and bottom) and a screw every 100mm along each stud through the centre, referred to as the "field" in the table on the right.

Let me know if you have any further questions.

Jacob

jdbunnings · Answer

Thank you,

The walls I've just stripped down were fixed with a combination of glue and nails. I wonder whether that is because it was installed in a different time, or if it was installed incorrectly.

I found the 6mm gap to floor in the installation guide. I am having a hard time finding anything on screw position and distance in there.

Any suggestions/tips for that would be appreciated.

Kind regards,

Jan

EricL · Answer

Hello @jdbunnings

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about plastering your bathroom.

Yes, Aquachek is an appropriate choice for the bathroom walls and ceiling. CSR specifically describes Gyprock Aquachek 10 mm as a residential wet-area wall and ceiling lining and as a suitable substrate for waterproofing and tiles.

I can really only point you towards CSR's own installation requirements and recommendations, as they're the manufacturer of Aquachek. Before you start sheeting the bathroom, though, I would recommend speaking with your waterproofing contractor. They'll be applying and ultimately standing behind the waterproofing system, so it's worth confirming exactly how they want the plasterboard substrate prepared before installation.

In relation to stud adhesive behind the tiled walls, the generic Gyprock installation videos cover general plasterboard installation rather than specifically preparing Aquachek as a tiled wet-area substrate. The relevant document is CSR Gyprock, The Red Book 2: Residential Installation Guide. On page 48, under “Tiled Areas”, CSR states that where Gyprock Aquachek is used as the substrate for tiles, the sheets are to be mechanically fastened with nails or screws, and that adhesive/fastener fixing is not acceptable. CSR also specifies a Level 3 Finish for the tiled substrate. So, for the tiled Aquachek walls, I wouldn't use stud adhesive; the sheets should be mechanically fixed in accordance with CSR's requirements.

As for the gap at the bottom of the Aquachek, the same section on page 48 instructs the installer to cut and fix the Aquachek while leaving a 6 mm gap between the bottom edge of the sheet and the shower base or floor finish. So even though it's Aquachek, it isn't intended to sit hard against the floor. For this application, I'd follow CSR's specific 6 mm requirement rather than the generic 10 mm spacer shown in some general plasterboard installation demonstrations.

The question is how does waterproofing work with that gap? This is where I'd suggest involving your waterproofer before the plasterboard goes up. Aquachek itself isn't the waterproofing layer; it's the substrate onto which the waterproofing system is subsequently applied. CSR's wet-area instructions address flexible sealants, wet-area joint treatment and waterproofing over the face of the Aquachek, while also directing installers to follow the waterproofing membrane manufacturer's instructions.

Your waterproofer may have specific requirements for the 6 mm clearance, wall-to-floor junction, internal corners, sheet joints, plumbing penetrations, sealants and bond breakers. It's much better to establish those requirements before the walls are sheeted rather than finding out something needs changing when they're ready to waterproof.

Given the relatively small size of the bathroom, I'd also consider having the Aquachek professionally installed in coordination with the waterproofing specialist. The plasterboarding is a relatively small component of the renovation, but it becomes the substrate for the waterproofing, tile adhesive and tiles. Having the plasterer work to the waterproofer's specifications should provide a cleaner handover between trades and greater confidence that the substrate has been prepared correctly and in accordance with the relevant requirements.

Here is a link to The Red Book 2: Residential Installation Guide, starting at page 48, “Tiled Areas” and the adjoining wet-area installation details. Please refer to page 74 for ceiling fixing methods. I'm sorry, I did not see a reference to the angle plaster, please speak to your waterproofing agent in regard to this.

Let me call on our experienced members @Nailbag, @DIY4Knuckleheds, @Neilson95, and @Lev61 for their recommendations.

If you need further assistance, please let us know.

Eric