A bathroom renovation can look relatively straightforward on paper.

New tiles. A new vanity. Updated tapware. Maybe a walk-in shower and some better lighting.

But once demolition starts, bathrooms have a habit of revealing problems that were impossible to see beforehand.

That doesn’t mean bathroom renovations are unpredictable or that your budget is destined to blow out. It means a good renovation budget needs to account for what might be hiding behind the walls, underneath the floor and inside the existing plumbing.

Here are some of the most common hidden costs Brisbane homeowners should understand before renovating a bathroom.

1. Water Damage You Can’t See Yet

One of the biggest risks in an older bathroom is moisture damage.

A shower might appear perfectly functional while water has slowly been getting through failed grout, silicone, waterproofing or plumbing connections for years.

Once tiles, shower screens and wall linings are removed, we sometimes find:

  • Damaged timber framing
  • Swollen flooring
  • Mould growth
  • Deteriorated wall sheeting
  • Water damage around shower bases
  • Corrosion around plumbing fittings

The extent of the problem usually cannot be confirmed until demolition begins.

Minor repairs might only add a relatively small amount to the renovation. Structural timber or extensive moisture damage can require considerably more work.

This is one reason it can be dangerous to compare bathroom renovation quotes purely by the number at the bottom of the page. The cheapest quote may simply allow very little contingency for what happens once the room is opened up.

2. Old Plumbing That Needs More Than a New Tap

Replacing a vanity or shower does not necessarily mean the existing plumbing can simply stay where it is.

Older Brisbane homes can contain ageing pipes, unusual previous repairs or plumbing layouts that no longer suit the new bathroom design.

Problems might include:

  • Corroded pipework
  • Inadequate drainage
  • Leaking connections
  • Poorly positioned waste pipes
  • Older plumbing that should be replaced while it is accessible

Moving fixtures can add further cost.

If the toilet, shower, bath and vanity remain in roughly their existing locations, plumbing is generally simpler.

Move everything around the room and plumbers may need to relocate water supplies and drainage beneath the floor or inside walls.

That doesn’t mean you shouldn’t change the layout. Sometimes moving fixtures dramatically improves how the bathroom works.

It just needs to be included in the budget from the beginning.

3. Waterproofing

Waterproofing is one of the least exciting parts of a bathroom renovation.

It is also one of the most important.

You won’t see the waterproofing membrane once your bathroom is finished, but failure underneath the tiles can cause expensive damage throughout the home.

During a renovation, demolition may also reveal that the previous waterproofing system was poorly installed or has failed.

Trying to save money on waterproofing can become extremely expensive later.

A well-built bathroom is not just about what you can see when the project is finished. What sits underneath the tiles matters just as much.

4. Floor Preparation and Levelling

Once existing tiles are removed, the floor underneath isn’t always ready for new tiles.

The substrate may be:

  • Uneven
  • Cracked
  • Damaged by moisture
  • Poorly prepared during an earlier renovation
  • Unsuitable for the new tile format

Large-format tiles in particular require a good surface underneath them.

Additional preparation, levelling or repair work might therefore be necessary before waterproofing and tiling can begin.

It is another job homeowners rarely think about because it completely disappears underneath the finished bathroom.

5. Electrical Upgrades

Modern bathrooms often contain considerably more electrical equipment than older bathrooms.

You might want:

  • LED lighting
  • Illuminated mirrors
  • Additional power points
  • Exhaust fans
  • Heated towel rails
  • Underfloor heating
  • Upgraded ventilation

An electrician may also discover that existing wiring, switches or electrical equipment should be upgraded while the room is being renovated.

Individually these items might not look significant, but several electrical additions can quickly increase the overall project cost.

Planning them before construction begins is far cheaper and easier than deciding you want another power point or light after the tiling has been completed.

6. Ventilation

Poor ventilation is one of the reasons bathrooms develop mould and moisture problems in the first place.

Installing a powerful exhaust fan sounds simple, but its effectiveness depends on how the air is actually removed from the bathroom.

Depending on the property, additional ducting or ceiling work may be required.

A beautiful bathroom that remains damp for hours after every shower is not a particularly successful renovation.

Good ventilation helps protect the renovation you’re investing in.

7. Asbestos and Older Brisbane Homes

Older homes require another consideration: asbestos-containing building materials.

It can be present in various areas of older properties and may not be obvious until renovation work begins.

If suspected materials are discovered, work may need to stop while they are appropriately assessed and, if necessary, professionally removed.

This isn’t something a renovation company should simply work around.

If you’re renovating an older Brisbane home, particularly one that hasn’t had significant work completed for decades, it is worth considering this possibility when establishing your renovation budget.

8. Changing Your Mind During Construction

Some hidden costs aren’t hidden inside the building.

They’re hidden inside the renovation process.

One of the easiest ways to increase the cost of a bathroom renovation is making major changes after construction has started.

For example, deciding to move a vanity to another wall might sound simple.

In reality, that change could involve plumbing, drainage, electrical work, waterproofing, wall preparation, tiling and cabinetry.

Another common issue is changing tile selections after quantities have already been calculated or materials ordered.

The earlier decisions are made, the easier it is to control the budget.

9. Fixtures That Need Other Fixtures

That freestanding bath you love might need different plumbing.

The wall-mounted vanity might require additional framing.

The oversized mirror might need electrical work.

The concealed-cistern toilet might require substantial wall preparation.

The premium shower head may need different plumbing or water-pressure considerations.

The cost of the fixture itself is only part of the equation.

When selecting bathroom products, it is important to consider what is required to actually install them properly.

So How Much Contingency Should You Allow?

Every bathroom and every property is different, but it is sensible to keep part of your budget available for unexpected work rather than spending every dollar on visible finishes.

The risk is generally higher when you’re dealing with:

  • Older properties
  • Previous DIY renovations
  • Known water leaks
  • Major layout changes
  • Substantial plumbing relocation
  • Bathrooms that have not been renovated for decades

If nothing unexpected is discovered, fantastic.

If something is found, you have the ability to fix it properly rather than compromising the renovation because the entire budget has already been allocated.

A Bathroom Renovation Should Fix the Room, Not Just Make It Look New

There is a big difference between making an old bathroom look modern and genuinely rebuilding it properly.

A quality bathroom renovation considers the plumbing, waterproofing, drainage, ventilation, electrical work, structure and finishes as one complete system.

That’s particularly important with bathrooms because mistakes underneath the finished surface can be extremely expensive to correct later.

At Briswest Renovations, we renovate bathrooms throughout Brisbane’s western suburbs and help homeowners understand the project before construction begins.

If you’re planning a bathroom renovation in Indooroopilly, The Gap, Bardon, Kenmore, Chapel Hill or surrounding Brisbane suburbs, talk to Briswest Renovations about what’s possible, what needs to be considered and how to establish a realistic renovation budget.

Planning a bathroom renovation? Contact Briswest Renovations to discuss your project and arrange an initial consultation.