14 October 2026 Uncategorized 0

Cut a Concrete Recess in Australia Without Missing Dust or SWMS Rules

Yes, you can cut a recess in a concrete slab to create a flush shower entry or a seated fixture, and it’s one of the most reliable ways to get a true curbless result compatible with in-slab heating. Typical recess depth runs about 1.5 to 2 inches, enough room for slope, a waterproofing membrane, and the tile bed. The alternative, building up the surrounding floor instead, skips the cutting but leaves a transition step at the door.

TL;DR:

A curbless shower recess typically needs 1.5 to 2 inches for the slope, waterproofing membrane, and mortar or tile bed.

Scan the slab for reinforcement and services before cutting; post tensioned or heavily reinforced slabs may require an engineer’s approval.

WorkSafe Victoria requires water suppression at the tool or extraction connected to a Dust Class H vacuum, plus a SWMS before high risk cutting.

Building up the surrounding floor avoids cutting but leaves a doorway step; recessing adds removal, drain, waterproofing, and tile costs, and drain changes may require permits.

Vicsawing

vicsawing.com.au

Plan a Cleaner Concrete Recess

Vic Sawing & Drilling provides concrete cutting services across Melbourne and Victoria for residential and commercial projects.

Explore concrete cutting services

Steps to recess a concrete slab the right way
Which tools and methods fit your recess job?
Cutting technique that avoids rework and damage
What dust control and paperwork does this job require?
Should you recess the slab or build up the floor instead?
How Vic Sawing & Drilling approaches a recess cutting job
Where most recess cutting advice gets it wrong
Getting a quote for your recess cutting project
FAQ
Sources

Steps to recess a concrete slab the right way

Getting a clean, code-ready recess comes down to sequence. Skip a step and you’ll likely redo work later, especially around drains and slope.

Measure and mark the recess footprint on the slab, then scan for rebar, conduit, or plumbing lines before anything touches the surface.
Confirm drain position and slope so you know exactly how deep to cut. Most curbless showers need 1.5 to 2 inches of depth to fit a 1/4 inch per foot slope, a waterproofing membrane, and the mortar or tile bed on top.
Cut the perimeter with a saw fitted with a diamond blade matched to the slab’s aggregate, using step cutting (several shallow passes) rather than one deep plunge.
Remove the interior concrete with a rotary hammer or jackhammer once the perimeter is scored to full depth, then clear debris and check the base is flat and sound.
Prepare the base for a mortar bed or a pre-sloped shower pan, confirming the subsurface can support the finished assembly.
Install waterproofing, let it cure per the manufacturer’s instructions, then test the slope toward the drain with a straightedge and a small amount of water before you commit to tile.

Trade how-to references describe this same core sequence: score the perimeter, break out the interior, and prep the base before setting a pre-sloped pan or mortar bed. For a worked example of slab cutting on a real project, our guide to cutting balcony concrete walks through a similar depth-and-removal sequence outdoors.

Which tools and methods fit your recess job?

Tool choice depends on the shape of the recess, the depth you need, and how much dust control the site demands.

A 230 mm (9 inch) angle grinder fitted with a recess disc or a wheel-bearing guide works well for circular cuts, especially puddle flange recesses around a shower drain.
A walk-behind or larger floor saw suits long, straight perimeter cuts or deeper recesses where a handheld grinder would take too many passes.
A rotary hammer or jackhammer handles bulk removal once the perimeter is scored, breaking out the interior concrete without disturbing the finished edge.
Dedicated recess kits, built from diamond discs, shrouds, and extraction ports, cut a full flange recess in one pass. 200 mm puddle flange recess kits sold in Australia pair a centering bearing with a dust shroud for consistent, repeatable results.
Pair any of these tools with on-tool water suppression or dust extraction rather than cutting dry.

Pro Tip: For repeat jobs like multiple bathroom renovations, a dedicated puddle flange kit saves far more time than freehand grinding and gives you a more consistent edge every time.

Our guide to concrete sawing breaks down blade and saw selection in more depth if you’re choosing equipment for the first time.

Cutting technique that avoids rework and damage

The depth of your cut matters as much as the tool you use to get there.

Cut in shallow passes of about 0.5 inch (12 to 13 mm) each, working down to full depth rather than forcing a single deep plunge.
Choose a continuous rim blade for clean, chip-free edges or a turbo or segmented blade when speed matters more than finish.
Let the saw run at its rated speed. Forcing it causes blade burn, binding, and a rougher cut that needs more cleanup.
Score a clean perimeter first and back-chisel stubborn edges by hand to prevent spalling at the cut line.
Dry-fit the drain flange or fixture several times before the final trim so you’re not cutting corrections into finished waterproofing later.

What dust control and paperwork does this job require?

Cutting concrete releases respirable crystalline silica, and the controls aren’t optional. WorkSafe Victoria’s industry standard requires engineering controls, either on-tool water suppression or on-tool extraction connected to a Dust Class H vacuum, along with a Safe Work Method Statement (SWMS) for high-risk cutting work.

Choose wet or extracted cutting every time. WorkSafe guidance confirms that cutting, grinding, or drilling silica-containing materials generates airborne dust that needs on-tool controls to manage.
Write a SWMS before starting and coordinate the timing with any plumber or electrician working nearby. Our SWMS guide for concrete cutting covers what the document needs to include.
Contain wet-cutting slurry so it doesn’t dry out and become airborne dust again; wet and dry vacuums handle this cleanup efficiently.
Set up PPE and an exclusion zone: respirators, eye and ear protection, and attention to electrical safety if you’re running a petrol saw versus an electric one indoors.
Stop work if you hit rebar or post-tensioning cables you weren’t expecting, and get a structural engineer or a licensed cutter to assess before continuing.

Dust control compliance is not a guideline you can skip. WorkSafe Victoria’s standard makes on-tool suppression or extraction a mandatory control for concrete cutting, not an optional precaution. Our breakdown of wet versus dry cutting shows how much dust wet methods remove compared with dry grinding.

Should you recess the slab or build up the floor instead?

Both paths get you a usable shower or fixture base, but they carry different structural and budget consequences.

Weigh the structural impact. Recessing gives the cleanest flush result; building up the surrounding floor avoids cutting into the slab but creates a step at the doorway.
Check the slab type first. ACI 360R-10 outlines how reinforcement and slab design affect what you can safely cut into, and a post-tensioned or heavily reinforced slab usually needs an engineer’s sign-off before any cutting starts.
Budget for the full scope, not just the cutting: site access, concrete removal and disposal, a plumber for drain relocation, waterproofing, and tile labor all add to the total.
Confirm permit requirements with your local building authority if the job involves relocating a drain or altering waterproofing membranes.
Prepare a short checklist for your contractor or quote form: slab thickness, drain location, site access, and your target timeline.

How Vic Sawing & Drilling approaches a recess cutting job

Recess cutting is routine work for licensed operators experienced in this field. On a typical job, the slab is scanned for reinforcement and services, a SWMS is prepared, and wet cutting or on-tool extraction is set up before the first cut goes in.

Equipment is sized to the job, whether a handheld recess disc for a single bathroom or a walk-behind saw for a larger commercial fit-out, and removal and disposal are managed so the site is left clean. If you’d like to see the techniques in practice, our page on the benefits of hiring a concrete cutting crew covers what a licensed crew adds over DIY attempts on load-bearing slabs.

Where most recess cutting advice gets it wrong

Most guides treat recess cutting as a tool selection problem: pick the right grinder, get the right blade, and the job falls into place. That’s backwards. The variable that actually determines whether a curbless shower works long-term is the sequencing of depth, slope, and waterproofing, not the hardware.

A recess cut to the wrong depth, even by a quarter inch, forces a compromise somewhere downstream: a thinner mortar bed that cracks, a membrane that gets stretched too thin at the drain, or a slope that never quite reaches code. The step-cutting discipline and the repeated dry-fitting of the drain flange matter more than which brand of diamond disc you buy.

We’d also push back on treating dust control as a site-safety afterthought tacked onto the end of the job. Under Victoria’s industry standard, it’s a planning input that shapes which tool you can even use. Readers who plan dust control and slope together, before the first cut, end up with fewer surprises than readers who plan the cut first and retrofit compliance later.

— MYBMC

Getting a quote for your recess cutting project

A fast, accurate quote starts with a few details: photos of the area, the slab thickness if you know it, the drain or fixture location, site access, and your preferred timing. Send those through and we can scope the job without a back-and-forth.

On the first visit, we scan the slab, prepare the SWMS, recommend the right dust controls for your site, and leave you with a written quote before any cutting starts.

We confirm slab reinforcement and services before quoting, not after.
We recommend wet cutting or on-tool extraction based on your site conditions.
We provide a written scope and price so there are no surprises mid-job.

Request a quote through our concrete cutting services page or ask about scheduling a free site assessment if you’d like a closer look before committing.

FAQ

How do you cut a groove in concrete?

Score the groove’s perimeter with a diamond-blade saw, cutting in shallow passes rather than one deep plunge, then clean out the material with a chisel or small breaker. For deeper grooves, step cutting in passes of about 0.5 inch keeps the blade from binding or overheating.

What is poor man’s concrete?

The term usually refers to compacted gravel, crushed rock, or a simple sand-cement mix used as a low-cost substitute for a full concrete pour, often for informal paths or temporary surfaces. It isn’t a recognized structural material and isn’t suitable for load-bearing slabs or recess cutting applications.

What groove cutting depth does a concrete recess need?

For a curbless shower, plan for about 1.5 to 2 inches of depth to fit the slope, waterproofing membrane, and tile or mortar bed. Smaller grooves for conduit or drainage lines are typically cut to match the specific pipe or cable diameter plus clearance, so the depth varies by project.

What is the 4 2 1 rule for concrete?

This isn’t an established concrete standard, and we haven’t found a recognized definition tied to slab cutting or design in primary technical references. If you’ve seen it referenced for a specific application, check the original source, since definitions circulating online vary and aren’t consistent with guidance like ACI 360R-10.

Do I need a permit to cut a recess for a shower drain?

Permit requirements depend on whether the work involves relocating a drain or altering plumbing, which typically falls under your local building authority’s rules. Check with your local council or building surveyor before cutting if the drain position is changing.