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How to protect timber shower frame?

Hi there,

Currently building a stud wall for my shower recess and am using H2S treated LVL studs. Just wondering if there is anything I can paint them with to offer a little more protection in the case of a leak in the waterproofing membrane of the shower?

I have used marine epoxy in the past (bote-cote) to treat outdoor timbers and while it is excellent stuff, it is quite expensive.

The shower and bathroom will be waterproofed and tiled by a licensed tradie for what its worth. I just like to be extra cautious when it comes to timber in wet areas. I am not in any rush to finish this wall as I am waiting on contractors to finish other work in the bathroom, so happy to take my time and get this right.

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EricL

Hello @bigkid

I understand your desire to take that extra step to protect your timber stud frame in case of a leak in your shower area. However, in most Australian homes, fully waterproofing a timber stud frame inside a wall is not recommended. It often causes more problems than it solves. What is recommended is controlling moisture in a way that still lets the wall dry out.

Here’s the balanced view.

The good (why people consider it):

The idea comes from wanting to protect timber from rot, mould, and moisture damage. In very wet areas like showers, a properly installed waterproof membrane on the surface (behind tiles) is essential and required by the building code. Some also think that sealing the studs themselves adds an extra layer of protection if water ever gets past the tiles.

The bad (where it goes wrong):

Timber-framed walls need the ability to breathe and dry. If you coat or wrap the studs in a waterproof barrier, you can end up trapping moisture inside the wall cavity. In Australia’s mixed climates (humid summers, cooler winters in many regions), moisture can enter walls from both inside (steam, humidity) and outside (rain, vapour). If it can’t escape, it sits there and this is when rot, mould, and even structural issues start.

It can also interfere with how wall systems are designed to work. Plasterboard, insulation, sarking, and membranes are meant to manage moisture in layers not by sealing everything airtight.

The ugly (what can actually happen):

If water does get in (and realistically, at some point it often does through a failed grout line, small leak, or condensation), a waterproofed frame can trap that moisture against the timber. Instead of drying out naturally, it stays damp for long periods. That’s when you see hidden rot, black mould, and damage that isn’t obvious until it’s extensive and expensive to fix.

There’s also a compliance issue. In wet areas, Australian standards require waterproofing in specific locations (e.g., over the wall lining), not inside the wall cavity on the framing. Doing it differently can create problems with warranties and inspections. My best advice is to follow the recommendations of your tradie and to make sure that your waterproofing membrane is applied by a trained, registered agent.

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

If you need further assistance, please let us know.

Eric

Dave-1

Good Evening @bigkid

Wooo I was interesting seeing @EricL 's response :). Mainly because as soon as I read what you had concerns over, that same list pretty much filled out with the sdame answers. My short answer was that the potential to cause more issues down the track by doing it, than it actually getting wet and rotting. With the same thoughts as to preventitive stuff we all want to do :) I would really suggest to stick to what the Australian rules specify as they are stringent and there are technical reasons why they exist.

Dave

Nailbag

Hi @bigkid

There is no need of marine epoxy (bote-cote). The internal frame only needs to be standard MGP10 framing pine. This is then lined with and/or Aquacheck plasterboard and blue-board as required with the joins and corners sealed with jointing tape. Then the room would be professionally waterproofed by a certified waterproofer so that tiling can begin.

Nailbag

bigkid

Thanks @EricL @Dave-1 @Nailbag for the prompt responses and solid advice.

So my next question is how about just coating say the cut ends, tops and sides of each piece, and leaving the bottom raw for breathability? Or still no just leave the waterproofing membrane to do its job?

I probably should have mentioned the external bathroom walls are cavity brick, so yeah porous, not sure if that makes any difference or not.

Nailbag

Hi @bigkid

Let the waterproofing do its job 👍️

JacobZ

Hi @bigkid,

I'm with @Nailbag on this one. There's no real need for it. As long as the waterproofing membrane is applied to the outside of the sheeting without any pinholes, gaps or tears, then that will be sufficient.

Jacob

bigkid

Ok thanks for the info, one last question then. For timber selection, H2 or H3 treated pine? There seems to be a lot of contradicting opinions about this on the internet.

Some say H2 is fine for periodic wetting, others say only in well ventilated areas. Some say H3 is a must for wet area framing, others say it’s an unnecessary expense and too prone to warping as it dries out.

Part of this build includes a shower ledge that sits between rendered brick walls so cant imagine that will get too much ventilation. I can’t build this ledge from brick unfortunately due to an odd waste pipe situation.

JacobZ

Hi @bigkid,

In Australia, bathroom timber is specified under AS 1604, and H2 treated pine is the standard for internal framing, including bathrooms. H3 isn’t generally required, but can be used where there’s a higher moisture risk or poor ventilation. In your case, that enclosed shower ledge is one of those spots where H3 could be a sensible upgrade, but it’s not strictly necessary. In saying this, as you are already planning for the worst in terms of a leak, using H3 would be worthwhile in the event that there is a leak.

Keep in mind that compliant waterproofing is far more important than the timber treatment itself. The treatment is only going to come into play if the waterproofing fails, which should be the primary focus.

Let me know if you have any further questions.

Jacob

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