What should you decide before your builder starts?
Budgets often suffer months before work commences on-site. An incomplete specification results in the builder making “allowances” in the contract which are often subject to variation once the full details are presented. By this stage, the additional work isn’t subject to competitive tendering, and delays caused can add to costs.
Certain decisions can wait until further information is known, such as post-demolition discoveries (and with older homes there is always something hiding), but there are certain items that are harder and more expensive to change once work has commenced.
It’s cheaper to change a line than a wall
A paper change can be a few hours, even days of work to complete. On-site, changing a wall, adjusting the plumbing, installing a new beam can add weeks, add material costs, and require the removal of freshly installed works.
Under the Home Building Act 1989 (NSW), variations of the building works, plans and specifications must be in writing and signed by or on behalf of each party. Most builders quote legitimately at this stage, but there is definitely less competition in this pricing.
Certain modifications and changes need changes to the original planning consent, which can mean changes to plans, specifications, engineering, BASIX, acoustics, glazing details and Council approvals. All of this may be possible, but it can add significant time and money to the budget.
We just want to knock out a wall and open it up
A very common brief, normally super achievable. But please, don’t just go ahead this weekend and do it with your mates.
There may be structural considerations at a minimum. But further to this, I often see the aftermath of a previous “simple job”, which means a better result for the property has been lost.
Good practice is to ask a designer first, work out whether it does need an approved consent (it may be exempt development), and get the advice of an engineer. This will incur fee costs, but it provides certainty AND safety.
Kitchens, bathrooms and laundries – down to the toilet roll holder
These areas soak up cash like nowhere else and decisions to modify are generally more expensive. Waterproofing, setdowns, pipe placement, falls to drains, electrical terminations, supports for that wall set cistern – all expensive to move. Is that floor area strong enough for a bathtub instead of the planned shower???
Does the toilet roll holder match the towel rail? Don’t find out the answer to this question on the day it is to be installed.
Joinery, appliances, integrated items, boiling water tap, built-in oven vs freestanding range: 600, 900 or 1200mm wide. Did I mention everything needs to be clad in marble as well? In my guide to extension costs I mention the $80,000 oven. There is no problem with you having this item, it just helps to know about it before the building starts, how it needs to be installed, whether it needs electrical connection only or gas as well and that there is a space in the joinery to fit it.
Glazing: windows, doors and skylights
An increasing area of cost with more areas being affected by noise, as well as climate resilience considerations, requiring a higher specification.
Heritage buildings may require timber-framed windows only – not aluminium. BASIX considerations may require us to have argon-filled double glazing with thermally broken frames of a medium colour. Then there are lintel and jamb details. If added windows and doors further impact on your neighbours’ privacy, Council may not be happy approving them.
“Does the toilet roll holder match the towel rail? Don’t find out the answer to this question on the day it is to be installed.”
Everything electrical
The number of home appliances now requiring electrical connection has ballooned. The selection of light switches and power points with USB-C charging, mesh Wi-Fi to get through masonry walls, air-conditioning placement and ceiling fans all need accounting for.
An electrical plan is a great starting point, but we find the electrician will then offer suggestions of how to wire the switching together more effectively. Placement of an accessible service board is an easy “on-plan” consideration that is expensive to fix later – I have seen plenty of boards poorly positioned right next to the front door. It happens when nobody plans for it. Solar is the same: I’ve seen inverters fixed to the front wall of a house when a metre further around the corner would have kept them out of sight.
Finishes can cost anything
If you have a modest specification for a kitchen, for example simple Laminex-fronted MDF cabinets, glass splashback, standard stainless sink and a piece of sintered stone for the island – that is one price.
When you go shopping however, and fall in love with gold-plated tapware, Bianco Carrara marble, artisanal tile splashbacks and fluted timber panelling, the additional costs can detonate your budget. Selecting these earlier on allows for competitive tendering from your joiner for a start.
Dial it in
Get everything, as much as possible, selected and agreed to before finalising quotes. Assist your designer by telling them what you want and what you don’t want early on. “I’m not sure what I like but I know it when I see it” isn’t much of a guide. Instagram, Pinterest and TikTok may be a potential rabbit hole of conflicting ideas, but can be useful. Come up with half a dozen images you like for each part of the house.
Then, the plans need to be approved and a final direction approved and documented.
Often, it is easier and cheaper to change something at the end of the project work as it doesn’t interfere with the program instead of creating the turmoil of a variation. By then, too, that window you wanted added, that your designer said you didn’t need, no longer makes sense to the design as a whole.
Even with all this, older homes can still throw up surprises. If you have already stretched your budget due to added costs you may be in a predicament when you discover the pile of asbestos sheet hidden under the 1980s extension. Leaving a contingency can save a lot of this stress.
Design fees: do they count?
Sure, everything is expensive when you build. Often, at the end of the project, my clients think fondly of my modest by comparison invoices.
But fee amounts and the mechanics of how they are charged differ.
Modifying documents once they are complete can also be time-consuming and this will be an additional cost to consider.
“I have always preferred to charge a fixed fee as that way it mitigates potential conflicts of interest if the budget needs to be kept tight.”
As a Building Designer, my industry peers sometimes charge based on a percentage of construction costs, but generally favour a fixed fee arrangement based on the project scope and complexity, which in my experience roughly equates to somewhere between 3 and 7 per cent of the construction cost.
Architects, however, generally favour a percentage of construction cost, based on their industry cost guides, which in my experience come to between 10 and 15 per cent. If the final construction costs exceed the initial cost guide estimate then the amount of their fee payable is still the same percentage, but it is a larger total amount.
I have always preferred to charge a fixed fee as that way it mitigates potential conflicts of interest if the budget needs to be kept tight.
If you significantly change your scope, brief and level of detail required once work has commenced however, you must expect to be charged more in fees.
Common questions
Variations: how do they affect a building contract?
These are generally changes to the contract after building has commenced. Often, they are in response to an unforeseen or indeterminate condition, such as a foundation discovery after demolition. Other times they are the substitution of one specified item for another. Other times they are “while we are doing this” add-ons.
Under the Home Building Act 1989 (NSW), variations of the building works, plans and specifications must be in writing and signed by or on behalf of each party.
Can I alter the design after council approval?
Some small internal changes, or construction details to comply with the conditions of the consent, may not need approval, but best to ask your designer or certifier.
More significant changes will generally require a modification to be assessed, approved and construction details updated. “Easier to ask forgiveness instead of approval” is not always the best wisdom.
What are prime cost items and provisional sums?
Both are allowances in the builder’s quote for something loosely decided upon. A prime cost item is for supplying a particular thing that hasn’t been chosen yet – a toilet, say, allowed at $1,000 until you pick one. A provisional sum is for work that can’t be priced exactly until it starts, like excavating rock. If the final cost is higher (rarely lower), you pay the difference with the builder’s margin added. This is where a lot of budgets get off track. The good quality bathroom taps are replaced with taps that are priced more like jewellery, and clients are left wondering what happened to the budget.
Contingency: how much is enough for a renovation?
A contingency is generally allowed for in the budget to make sure there is money for cost overruns. This is especially important with renovations, as unwelcome discoveries are often made. It can be as high as 10–15 per cent of the build cost for work on an older house. The phrase “they don’t make them like they used to” is not necessarily a compliment.
Sources
- Bark, How much does an architect cost (updated 27 March 2026) – architect and building designer fees
- ArchiPro, What is a building designer (24 September 2024) – building designer fees
- NSW Fair Trading – home building contracts and variations
- NSW Planning Portal – BASIX
- NSW Planning Portal – modifying a development consent