We can renovate on a concrete slab

Renovating a bathroom on a concrete slab

renovating on a concrete slab in Sydney

Believe it or not, we often get asked whether it is possible to renovate a bathroom that has been built on a concrete slab. Passion Built is a renovation contractor that can work on practically any type of site including homes built on piers or ones that are on a slab.

Renovating a structure that has timber floor boards with joists and bearers is normally easier, but a lot depends on the crawl space available under the building. If there is enough space it makes it relatively easy to access the plumbing through the floor to move a toilet, relocate a tap or change the layout of a bathroom.

You can do the same things on a concrete slab, the difference comes down to the approach that has to be taken, labour involved & the costs as it is typically more complex to deal with because it might require wet saw cutting into the slab.

It is mainly newer homes that have been built on slabs and of course, units, apartments, villas or townhouses as well. In fact most homes across Sydney are sitting on a concrete slab of some shape or form.

Therefore, it isn’t so much a question of ‘can you renovate on a concrete slab’ it is more relevant to consider what you would like to achieve and then the various costs associated with those ideas.

concrete slab bathroom demolition

Demolishing a bathroom on a concrete slab

If you have decided to renovate your bathroom the first decision to make is whether you are doing a simple refresh with some new paint, taps and fixtures or will you do a complete renovation starting with demolishing the old bathroom?

The benefit of stripping everything back to the bare framework of the room is that you can build exactly what you want either using the current placement of toilet, shower, vanity and lighting or creating a new floor plan.

By demolishing the room, even on a concrete slab, your renovation contractor can get access to every electrical wire, water supply point, sewage waste pipes and the wall frames. From that stage things can be moved, new items added or new channels cut into the concrete for new plumbing.

By being able to access the structure of the property you can make nearly infinite renovation changes to your bathroom that are not as easily done if you leave the existing tiling or waterproofing in place.

The other big benefit is that everything is built from scratch and together rather than in sections or areas of the room. This can help with the longevity of the room including managing water leaks.


Complete ensuite bathroom renovation on a concrete slab with bath and shower

Does it cost more to renovate a bathroom on a concrete slab?

The main factors that effect the cost of renovating doesn’t necessarily relate to being on a concrete slab or not. The biggest factors that lead to huge variations in the cost of renovating are;

  • Complexity; if all the existing services are being re-used then the cost to renovate on a slab vs other foundations are fairly similar as the work required is about the same. If you have to move a toilet or shower then doing so on a concrete slab might cost more vs a timber floor if lots of cutting has to be done to fit the new plumbing needed.
  • Time of year; like any product or service, pricing may change based on availability or time of year. So renovating at Christmas or school holidays may cost more vs other times of the year. Or during summer may cost more than winter because of industry demands.
  • Materials; you can buy a tap from Bunnings for $10 or choose a designer item for $1,000. That’s how quickly the cost of materials can vary and this applies to tiling, bathtubs, shower heads, vanities etc. So a fit out may cost you $5,000 or $15,000 depending on what you select to install in the new bathroom.
  • Access; if you live on a property with easy parking access, lots of space to move, on a single level then the cost of labour or time required to complete a renovation will be shorter vs trying to renovate a room on the top floor of an apartment block in the middle of Bondi Junction. Every tradesperson has to get in and out easily to complete the job quickly.
  • Size of the room; a bathroom that is 1×2 metres in size will be cheaper to renovate vs a 3×3 metre room because it will take longer, need more materials & may even need more trades. A smaller room might be expensive it only one tradesperson can fit into the room at a time to complete any work. So size does matter.
  • Labour; with any skilled labour there will always be industry average rates that you can research and compare. In some instances based on experience, reviews or industry standing a tradesperson may charge slightly more. The thing to be careful of is super cheap labour costs as typically this could be sub-contracted staff who are not extremely experienced or capable.


small bathroom renovated in a unit on a concrete slab with new sink taps

Is it hard to renovate a bathroom in a unit or apartment block with concrete floors?

The most common request we are fielding for renovations is for units or apartments with concrete floors. These are a bit more difficult to work with because of the shared walls, floors and ceilings with adjoining properties – but not impossible.

The simplest way is to plan your unit bathroom layout to have the toilet, shower and vanity remain in the same locations as the existing fixtures. That way you can concentrate on remodelling the room without worrying about plumbing or cutting into the concrete to move things around.

In most cases you will have to get strata approvals anyway, so being able to demonstrate you will use the existing services will make that process much easier to manage.

bathroom renovated on a concrete slab with bath and shower

Can you add a bathroom on a slab without cutting the concrete?

Let’s say you want to build a new bathroom on concrete but not sure if you need to cut holes or new channels, what can you do? You call a plumber for an estimate, and they will tell you they have to break through the floor or drill through the concrete to install a drain line for the plumbing — a messy and time-consuming job with a high price tag.

Some plumbers might suggest a sewage ejector system. Still, this would mean doing jackhammer or wet saw cutting to dig up the floor while not knowing what’s beneath. There are several possible hazards, such as not knowing how thick the floor is, unforeseen rocks or pipes. Plus, any time you disturb the concrete floor, there’s a chance of water from the outside seeping through.

The alternative is to consider electric products like a modern macerator pump. This is an innovative technology that allows you to add your septic plumbing into wall cavities and through the roof. This means that you do not even need to cut or boar into concrete at all. 

Instead of routing flush water through below-floor drainage lines to sewage access or a sewage ejector, the wastewater from the fixture drains through gravity into a macerator. The term “macerate” means to soften or break up. The macerator pump uses a stainless steel fast-rotating cutting blade to convert solids and fluids into a fine slurry that is discharged under pressure through small-diameter piping (¾-inch or 1-inch) and expelled into the sewage line or septic tank.

This means it can be installed on top of any floor in the home. This allows you to place a new bathroom wherever you want really and without costly excavation of the floor to install plumbing. 

Walls and floors remain intact, and installation is performed quickly and economically with minimal disturbance to room layout. 

This electronic system can be installed behind the toilet or in the wall. Once everything is broken down it can be pumped through a narrow pipe until it reaches the septic point. It means you could build a new bathroom in a garage, outdoor shed, external laundry or even in a second storey room.

Can you bypass the existing plumbing?

If your new bathroom is close to an exterior wall, another option might be to core drill into the concrete and then bore underground to that point.

Special care needs to be taken to make sure the structural integrity of the house is not compromised. This is because boring a new pathway underneath the footings may be up to a metre deep. This method allows you to install new sewage lines that run around the slab to a sewer point outside.

You have to use the ‘Dial Before You Dig’ service to make sure you are not going to hit any underground infrastructure. Sewage pipes in Australia need to be buried below ground level, so a trench would need to be dug all the way around until it meets with the sewerage point.

DO you need council approval to build a bathroom on a concrete slab?

For most people trying to renovate internal rooms you do not require planning permission to add something like a new bathroom unless it will change the structure of your home or is part of an extension.  

Read our Free guide about getting renovation approvals in Sydney.


Free site inspection, consultation & quote

It’s really easy to find out the cost to renovate. We offer an obligation free site inspection, consultation & written price quote so that you can work out all the costs before you commit to renovating.

Bathroom renovation before and after examples

We explain some of the renovation work we have completed for different projects in Sydney.

Absolutely you can renovate a bathroom on a concrete slab in Sydney – house, unit, townhouse, villa or apartment. Most modern housing structures are built on concrete slabs. Even though all the plumbing is set into the slab during construction you can create new pathways by cutting holes into the existing slab and joining new plumbing connections.

The cost to achieve these types of bathroom renovations will vary based on complexity, size of room, access and materials chosen.

Absolutely you can move a toilet or shower on a concrete slab in Sydney – house, unit, townhouse, villa or apartment.

The cost to move these fixtures will depend on how far you want them moved & what access to the slab is like or how far plumbing has to be adjusted. 

Passion Built are renovation contractors in Sydney that can provide a fixed price quote and site inspection.