How to install a bath frame?

Hello.

We plan on installing an inset bath (pressed steel) in the back of this bathroom (where there is no floor / joists). The plumber has roughed-in, and will be back to fit off the bathtub once the frame is installed.

Can I build a frame and anchor the upper horizontal lengths to the brick walls, and then nail the bottom horizontal lengths to the sill plates? Would it be better to cut some joists or put in a subfloor?
Can I use regular 70 x 35mm framing timber, or should I use 90 x 45mm? Assuming I can use 75 x 3.15mm nails with either option?
Many thanks

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MitchellMc

Welcome to the Bunnings Workshop community @alex_89. It's fantastic to have you join us, and many thanks for your question about installing a bathframe.

Given that this is a bathroom and is considered a wet area, you'll need to waterproof it. Waterproofing must be completed across the floor and up the walls to a height specified in building codes. I suggest installing a subfloor to achieve this, and it would be best to speak with a licensed waterproofer to better understand how you can achieve compliance while also mounting your bath. It will likely be a case of installing the sub-floor, then the wall sheeting, waterproofing, and then constructing your frame for the bath.

Please let me know if you have any questions.

Mitchell

alex_89

thanks for the reply @MitchellMc

I have talked to a tiler who will do the waterproofing/tiling once the bath is fit out by the plumber. he was happy to waterproof and tile onto rendered brick, doesn’t absolutely require sheeting. i also believe because it is an inset bath, the waterproofing doesn’t require a subfloor under the bath.

i was more wondering about supporting the weight of the bath/person sitting in bath/ water inside bath.

can the bath frame rest on the sill plates and be anchored into brick?

Can I use regular 70 x 35mm framing timber, or should I use 90 x 45mm? Assuming I can use 75 x 3.15mm nails with either option?

thanks.

alex_89

this diagram shows the bath on a slab, but we are not on a slab

and this shows the attachment to a brick wall, which is what we will do

MitchellMc

Hi @alex_89,

Technically, it sounds like what you're proposing would work, and 70 x 35mm should be sufficient. However, given that you'll need joists to support the bottom of the bath, I personally think it would be a more straightforward approach to install a subfloor and then construct a frame for the bath on it. If you are installing joists to support the bottom of the bath and have to add a subfloor to the rest of the room, the cost would be relatively minimal to continue the subfloor to the end of the room. Creating a frame on a solid subfloor will be a more robust solution than attaching your timbers to the wall and sill plate.

If you've checked with your trades, and they are happy with your proposition, you're golden. My concerns were that your waterproofer would prefer a more traditional approach, as seen in this guide: How to waterproof a bathtub.

Mitchell

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