Getting the rough ins right is the key to a smooth bathroom renovation

Watching The Block recently, I chuckled as the site foreman Keith was hounding the contestants for their plans so he could start on the plumbing and other rough ins (the electrical and plumbing wiring and pipes to be installed before the internal linings to the frames) when they’d barely started on the ground floor room renovation. They were complaining they barely had time to work out the day’s challenge, let alone plan the upper floors. It hit a chord as I’d been discussing the same thing with our builder today on one of Property Bloom’s house renos.

The rough in process is so important, but seemingly quite ‘boring’. You need to work out where you want pipes and drains that will support the more sexy fittings and fixtures that will come later as part of your bathroom renovation.

To get your wet areas right it’s all about the rough in, to ensure you can then position and connect the PC items in the right spot.  'PC' is the term for a prime cost item – toilet, bath, mirror, vanity, taps etc. If you get the rough in right, then the actual fit out should be pretty easy but you need a good imagination or some experience to ensure your dream design ends up the way you want it. You also need to know what fittings you will use so their specifications can be given to the plumber to refer to during the rough in, so planning ahead is essential.


On a house reno we are currently working on, our beautifully restored 1.7 metre claw foot bath, that we found locked away behind an ugly fibro casing, is sitting in one of the bedrooms where we are painting the base after it was re-enamelled. I couldn’t just pick it up and carry it into the bathroom to position it as it’s bloody heavy, so we measured it and traced its position on the yet to be waterproofed bathroom floor, marking out the location of the plug hole so the plumber knows where to position the waste.


While we're not changing the location of the toilet, it is being replaced with a more modern and stylish back to wall system – so the toilet waste will move a little. When installing a toilet, you will need to know the "set out" and position of the water inlet. This measurement will help you choose the size toilet you need to buy and which sizes to avoid. 

For an S trap installation (where the waste outlet is positioned on the floor) the set out is the distance measured from the finished tiled wall to the centre of the waste outlet on the floor. The set-out can vary greatly depending on the age of the house. Most new homes will have a standard set-out of about 140-165 millimetres, which will enable most toilet suites to be installed. However, if the set-out is more that 200 millimetres or less than 100 millimetres, it will limit your choice of the type of toilet you can buy.

We are working on a timber floor rather than concrete slab, so it’s a little easier to vary the position of the toilet’s waste area but you certainly need to get it right when working with a concrete slab, as the plumbing rough in is done before the slab is poured.

It’s also important to have the tapware delivered early as your plumber needs to chase in the hardware to the walls – this is also part of the rough in process.

As well as our main bathroom, we have a powder room, where we are installing just a toilet and wall mounted modern wash basin over a polished timber floor. We’ve tried to focus on a single feature piece for each bathroom – the claw foot bath is it for the main bathroom, against a floor to ceiling tiled marble look feature wall and the 750 millimetres wide wash basin beneath a large pendant light for the powder room.

Whatever your bathroom design, take time in the initial planning stages to work out the PC item positions and talk to your plumber about the rough ins so that your bathroom reno turns out smoothly.

Jo Chivers is director of Property Bloom, which manages property development.


Jo Chivers

Jo Chivers

Jo Chivers is director of Property Bloom, which manages property development.

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