When planning a bathroom renovation or building a new home, most people focus on the beautiful, visible details like timber tones, benchtop finishes and tapware. But behind every stunning vanity is a set of carefully considered technical elements that make the whole thing work—and allowances are a big part of that.

So, what are allowances?

Allowances are the space and clearances built into your Bombora timber vanity to make room for things like plumbing, basin installation and drawer movement. These “hidden” details ensure that everything functions as it should, from your pipes fitting neatly behind the drawers to your basin sitting securely in place.

At Bombora, we have several standard allowances in our timber vanities, based on years of experience building custom bathroom furniture and collaborating with plumbers, architects and builders. Understanding these will help you feel more confident during your design process and avoid costly surprises during installation.

Basin Waste Cutout

Our Standard: 100mm diameter
This is the hole we cut into the top of your vanity to allow for the basin waste to pass through. While many basins only need a 40mm opening, we provide a 100mm cutout to make things easier for your plumber, especially when working with solid timber tops, which are often thicker than standard cabinetry materials.

What to check: Refer to your basin’s specification sheet (available from your supplier or included in the box) to ensure that the 100mm cutout suits the base of your basin, especially if it doesn’t sit flush with the benchtop.

2. Rear Plumbing Cavity

Our Standard: 80mm space between the back of the drawer and the rear cabinet panel
This space at the rear of the vanity gives your plumbing enough room to sit comfortably without interfering with the drawer function. It’s a small but important consideration that helps ensure smooth operation and a clean fit.

What to check: Confirm this allowance with your plumber. If you have thicker pipes, unusual angles, or specific requirements, let us know in your order form and we can alter the design to suit.

3. Drawer Waste Clearance

Our Standard: 150mm space to accommodate waste pipes.

If your basin sits above a drawer, we need to create space for the waste to pass through. We do this in one of two ways:

Central cavity between two drawers – when your basin is centred between two drawers, we create an open space between them to house the plumbing. The drawer fronts will be the whole way accross hiding the cavity. This cavity is the whole height of the vanity.
U-shaped cutout in a single drawer – for layouts with a basin above a drawer, we create a 150mm recess in the centre of the drawer. This cutout is in the top drawer only. You will need to inform us if you require cutouts in all drawers.

What to check: Your basin and plumbing layout will affect which option is best. We can guide you on this, or you can check with your builder or plumber before finalising your order.

Can I Customise These Allowances?

Absolutely. If your bathroom has specific requirements, we can adapt any of our allowances, whether it’s increasing the side at the reer of the drawers, modifying the size waste cutout or amending the whole internal structures to accomodate a semi-inset or undermount basin.

Customisation may add a small fee depending on complexity and the extent of changes to the origional design.

Who Should You Speak To?

To get it right the first time, we recommend speaking with your:

Plumber – to confirm waste pipe placement, dimensions and if our allowances will be suitable.
Builder or cabinet installer – to ensure the vanity fits correctly with other elements
Basin supplier – for access to specification sheets and cutout requirements

We’re also happy to liaise directly with your trades if needed. Our goal is to make your experience smooth from design through to installation.

Have more questions?

If you're unsure if our allowances are right for your space, or you'd like help tailoring your design to suit your plumbing layout, we're here to support you. You can book a design consultation to speak with one of our team, or simply send through your questions via our enquiry form.

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View our range of timber vanites

At Bombora, we take pride in building wooden vanities that are not only visually stunning but also genuinely functional. Every piece is crafted by experienced furniture makers in our solar-powered workshop on the Victorian Surf Coast and made to suit your space, both in form and in function.

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