Ten Renovation Mistakes, Ranked by What They Actually Cost
Every list of renovation mistakes gives you the same ten items with the same weight. Poor planning sits next to picking the wrong tapware as though the two were comparable. They are not. Some of these you fix on a Tuesday afternoon. Two of them can put a stop-work order on your house and leave you paying to put back what you have already thrown in a skip.
Ranked below by damage, worst first, with a straight answer on each about whether you can still undo it.
TL;DR
- Renovation mistakes are not equal. Two can force you to put back what you removed. The other eight cost money.
- Check heritage and character controls before you spend a dollar on design. Demolition cannot be undone.
- Assume asbestos in anything built before 1990 and inspect before demolition, not after.
- Price the structure early. Double brick or single skin decides what open plan really costs.
- Read the contract against WA's deposit and progress payment rules, and see the insurance certificate before you pay anything.
- Services, contingency and late changes take the budget. Late selections and DIY on the critical path take the programme.
What can and cannot be undone
1. Starting work in a character retention area without checking
Perth has whole pockets where the front of your house is not entirely yours to change. Mount Lawley, Menora, Highgate, parts of Bassendean and Victoria Park have heritage or character controls that can limit what you can alter. For heritage-listed properties, the City of Vincent requires development approval for changes such as partial demolition, alterations and additions.
Demolish first and ask later, and you may be required to reinstate what was removed. Tuck-pointed brickwork, a jarrah verandah or a terracotta roof can be expensive to recreate, and a replica will never be the original.
Check the planning controls before spending money on design. Contact your local council to confirm whether the property is heritage listed or within a character retention area, and ask for the advice in writing.
2. Assuming there is no asbestos
If your house was built before 1990, treat asbestos as a possibility until it has been checked. It can be found in eaves, bathroom and laundry linings, fencing, flooring underlay and other building materials, particularly in Perth's older homes.
Once renovation work starts, asbestos needs to be managed under WA workplace safety rules. If asbestos needs to be removed, the licensing requirements depend on the type and amount involved. Removal of friable asbestos must be carried out by a licensed asbestos removalist, while licensed removal is also required for non-friable asbestos above the relevant threshold.
Finding out after demolition has started is the expensive version. Work stops, the area is sealed, a removalist is booked at short notice, and every trade behind it gets pushed. A pre-start inspection takes a morning and costs a fraction of that.
3. Designing a plan the structure will not give you
Most Perth homes from the 1950s onward are double brick, while many older cottages are single skin. That construction can have a bigger impact on an open-plan renovation than anything on a mood board.
Removing a double-brick internal wall can involve a structural engineer, a steel beam sized to support the load above, temporary propping during removal, and suitable piers or footings for the beam to bear on. In a single-skin cottage, there may be little or no footing beneath what appears to be a simple partition, potentially making the work more complex.
An open-plan layout may still be possible. The key is to assess the structural implications early, while the design can still respond to the findings, rather than after you have already paid for a design the existing structure cannot accommodate.
4. Signing a contract that does not meet WA requirements
WA sets rules for residential building contracts and most owners sign without checking a single one of them.
A builder can only take a deposit up to the amount allowed under WA law, and progress payments must generally relate to work completed or materials supplied. If you are asked to pay significantly ahead of the work, check that the payment schedule complies with the contract and WA requirements. These rules help limit the amount of money you have at risk if a project does not proceed as planned.
Home indemnity insurance is another important check. For eligible residential building work above the relevant contract value and requiring a building permit, the builder must arrange and pay for the cover. You should receive the certificate before work starts or make the relevant payment. The insurance can provide protection if the builder dies, becomes insolvent, disappears or has their registration cancelled, subject to the policy's terms and conditions.
5. Budgeting the finishes and forgetting the services
The parts of a renovation you can see are rarely the only things that affect the budget. In older Perth homes, kitchen and bathroom renovation surprises often start behind the plaster.
An older house may have an electrical system that needs upgrading to accommodate new appliances and additional circuits. Existing drainage may also limit where you can place new fixtures, particularly when relocating a bathroom. Sewer connection points and existing pipework can make moving wet areas more complex than the floor plan suggests.
Much of this only becomes obvious once walls and floors are opened up. The cost of the work itself may be manageable; the bigger problem is discovering it after the new linings or finishes are installed and having to open them up again.
When pricing a kitchen or bathroom renovation, ask what needs to change to the power, water and waste before you start choosing the benchtop.
6. Taking the cheapest quote without reading the scope
A wide gap between three renovation quotes often means you are looking at three different scopes, not three prices for the same job.
Look at what the cheapest quote leaves out. Provisional sums may be unrealistically low, asbestos removal may not be allowed for, structural work may be priced as though a wall is a simple stud partition, and there may be no allowance for approvals, making good or other necessary work. A bathroom quote may also exclude items such as waterproofing and certification.
You may have to pay for these things either way. The question is whether you account for them upfront, when you can compare quotes properly, or later as variations, when you have less room to negotiate and changing builders is no longer practical.
7. Running with no contingency
Contingency is often treated as padding, which is why it is one of the first things to get cut. In an older home, it is better thought of as money set aside for decisions you cannot make until the building is opened up.
Demolition can reveal issues that were not visible during the initial inspection, such as timber damage, inadequate waterproofing or movement in the structure. With a contingency allowance, you can address these issues without immediately putting the rest of the project under financial pressure.
Without one, you may have to choose between compromising on the repair or finding additional funds while the project is already underway.
Ask your builder what contingency they would recommend for a home of your age and what unexpected issues they have encountered on similar renovation projects. Their recent experience can give you a more useful starting point than a generic percentage.
8. Changing your mind after lock-up
A change at the concept stage is usually a redraw. The same change once the roof is on and trades are booked can become a variation, with costs for both the change itself and any work that needs to be undone or rearranged around it.
Move a doorway after the walls are lined, for example, and you may need to revisit framing, plastering, electrical work, cornices and painting. It can also disrupt the schedule, potentially pushing other trades back and creating further costs.
It is one of the more avoidable sources of additional cost during a renovation. Settle the layout and key decisions while they are still on paper, before construction makes changes more expensive.
9. Leaving selections until the trade is on site
Tiles, tapware, cabinetry hardware and appliances can feel like the fun part of a renovation, which makes them easy to leave until later. The problem is that lead times can affect the construction schedule.
If the tiles are not available when the tiler is due to start, the work may need to be rescheduled. A late cabinetry order can also delay the benchtop template, which can then affect plumbing and other finishing work.
Make key selections before construction starts and order items with longer lead times early. If something takes six weeks to arrive, you want to know that during the planning stage, not the week it is needed on site.
10. Taking on DIY that sits on the critical path
Painting a bedroom yourself at the end of a renovation can save money without holding up other work. Taking on a task that sits in the critical path can have the opposite effect.
Anything that will be covered by later work, requires certification or has another trade waiting on it is worth leaving to the appropriate professional. Waterproofing is a good example. If it fails after the tiles are installed, fixing the problem can mean removing the tiles and other finished work to access the underlying area.
Keep your own DIY work towards the end of the sequence, where a slower pace is more likely to cost you time rather than delay the rest of the project.
Three checks worth making now
If you are mid-design or comparing quotes, three of these checks are worth making now. Confirm whether the property is in a character retention area or on a heritage list. Arrange an asbestos inspection before any demolition. Read the contract carefully, including the deposit limit, progress payment requirements and home indemnity insurance.
The other seven can cost money, sometimes a lot of it. These three can affect what you are allowed to do, how the work can proceed and whether unexpected costs arise. With heritage properties in particular, changes made without the right approvals can be difficult and expensive to reverse. If you are unsure where your property stands, a [contact with MJD Projects (contact page internal link)] can help you work through the renovation requirements before design progresses.
Most Perth home renovations are shaped by decisions made before anyone picks up a tool. If you are planning work on an older home, it is worth resolving the structural, safety and approval questions before the design goes any further. If you are comparing builders, understanding what to look for in [Perth renovation builders (locations internal link)] can also help you assess the scope and process before committing.
Frequently asked questions
What is the most costly renovation mistake?
Unapproved work on a character or heritage property can be among the most costly mistakes. Unlike many unexpected renovation costs, unauthorised changes may have to be reversed or reinstated, depending on the property's planning controls and council requirements. Structural surprises and service upgrades can also add significant costs, but they can usually be addressed as part of the renovation. Reinstating a demolished facade can become a project of its own, using money that was intended for the rest of the renovation.
Which renovation mistakes can't be fixed later?
Demolition. Original brickwork, joinery, roof tiles and leadlight cannot be put back once they are gone, only reproduced. Everything else on this list is reversible with enough money.
How much contingency should I allow on a Perth renovation?
There is no single contingency percentage that suits every Perth renovation. A 1920s cottage can carry different risks from a 1990s brick home, particularly where the existing structure, services or materials are difficult to assess before work begins.
Rather than relying on a generic percentage, ask your builder what contingency they would recommend for a home like yours and what unexpected costs they have encountered on similar recent projects. A clear answer based on experience is more useful than a number with no context.
What happens if I renovate without approval in a character retention area?
The council can direct you to stop work and, in some cases, reinstate what was altered or removed. You may also need a retrospective development application, which can be refused. Requirements vary between local governments, so check with yours before work starts.
What do I do if asbestos is found after work has started?
Stop work in the affected area and do not disturb the material. Your builder should isolate the area and arrange for the material to be assessed before work continues. If removal is required, a licensed asbestos removalist must be engaged.
How can I tell if a renovation quote is too cheap?
Compare the scopes, not just the totals. Look for provisional sums that seem unusually low, missing allowances for asbestos, approvals or making good, and structural work priced without the necessary engineering input.
A significantly cheaper quote is not necessarily a better deal. Check what each builder has included and excluded before comparing the prices. A lower total can simply mean some of the work has been left for variations later.
Can I change the design once the build has started?
Yes, but changes generally become more expensive once construction is underway. Before work reaches lock-up, many changes can still be incorporated with relatively little disruption. Later in the build, a single change can affect several trades, finished work and the construction programme.
If you are unsure about a design decision, it is usually cheaper to resolve it during the design stage than to change it once work is underway.
What should I check before signing a renovation contract in WA?
Confirm the builder's registration is current, the deposit sits within the cap, progress payments are tied to completed work, and home indemnity insurance is in place where the contract value requires it. Read the scope for exclusions and check the variation process before you sign, not after.
