Two Perth builder quotes for the same floor plan can differ for reasons that have nothing to do with the house: one includes the site works your block actually needs, and the other leaves them as an allowance to be settled later. Comparing the totals tells you very little until both quotes are describing the same job.
The short version, if that is all you need:
- Give every builder the same brief: the same plans, the same block, the same specification level.
- Split each quote into the same buckets: base house, site works, allowances, upgrades and items outside the contract.
- List what each quote leaves out, in writing.
- Check the site costs against your actual block, not a typical one.
- Compare the contract terms, not just the price.
- Check the builder as well as the quote.
The rest of this page goes through each step, with the questions that get you a straight answer.
Step 1: Give every builder the same brief
Most uneven comparisons start before a single quote is written. One builder prices their standard version of a plan, a second prices a version with the upgrades you mentioned in passing, and a third prices a similar plan from their own range. Three quotes, three different houses.
Send every builder the same pack:
- The floor plan and elevations you want priced, or the plan you have chosen from one builder’s range with a note asking the others to price the nearest equivalent.
- The block address and lot number, so each builder can look at the same land.
- The contour survey and soil report if you have them. If you do not, ask each builder whether their price assumes a site classification and what it is.
- The estate’s design guidelines, if the block is in a new estate. Many Perth estates set rules on façades, roofing, fencing and front landscaping, and those rules cost money.
- The bushfire attack level (BAL) for the block, if it sits in a mapped bushfire prone area.
- The specification level you expect: standard, the builder’s mid-range package, or a list of specific inclusions you want.
Ask each builder to confirm, in writing, which drawings and which specification their price is based on. That one line saves arguments later.
Step 2: Split each quote into the same buckets
Builders lay their quotes out differently, and some layouts make a price look lower than it is. Before comparing totals, rewrite each quote into the same five buckets.
| Bucket | What goes in it | What to ask the builder |
|---|---|---|
| Base house | The home itself at the stated specification | Which plan revision and which specification is this based on? |
| Site works | Earthworks, sand, retaining, footing and slab upgrades, service connections | Is this a fixed amount for my block, or an allowance? |
| Allowances | Provisional sums and prime cost items | What happens if the real cost is higher than the allowance? |
| Upgrades and promotions | Anything above standard, including “free” promotional packs | What exactly is in the promotion, and does it replace anything standard? |
| Outside the contract | Items you will pay someone else for | What will I still need to buy or arrange after handover? |
Two of those buckets deserve a closer look.
Allowances. A provisional sum is an amount the builder sets aside for work whose cost is not known yet, such as excavating rock. A prime cost item is an amount set aside for something you have not chosen yet, such as tapware or a cooktop. Both are estimates. If the real cost comes in higher, you usually pay the difference. A quote with low allowances will look cheaper on paper and can finish more expensive.
Promotions. A promotional upgrade pack is worth exactly what it adds over the standard specification, which is not always what the brochure implies. Ask for the standard inclusions list and the promotion list side by side.
Step 3: List what each quote leaves out
The quickest way to find the gap between two quotes is to ask each builder for a written list of exclusions. These are the items that most often sit outside a new-home quote in Perth:
- Driveway, paths and crossover
- Front and rear landscaping, and any landscaping the estate requires
- Fencing, including side and rear boundary fences
- Window treatments such as blinds and curtains
- Floor coverings in some or all rooms
- Clothesline, letterbox and TV antenna
- Air conditioning, or anything beyond a basic system
- Council and estate approval fees, if the builder passes them through
- Retaining walls beyond what the slab needs
If one quote includes landscaping and fencing and another does not, the cheaper total may simply be the smaller job. Our guide to fixed-price and cost-plus building contracts covers what usually sits outside a fixed-price contract in more detail.
Step 4: Check the site costs against your actual block
Site works are where Perth quotes move the most, because they depend on the land rather than the house.
- Soil. Much of Perth’s coastal plain is sand. Blocks in parts of the south-east and the hills can carry clay, which changes the footing and slab design. Ask what site classification each builder assumed, and whether that came from a soil test on your lot or from a typical figure for the area.
- Slope. A sloping block may need cut and fill, retaining walls or a stepped slab. Ask whether retaining is included and how much of it.
- Bushfire rating. A higher BAL means extra construction requirements for windows, doors, cladding and roofing. A quote that ignores the rating is incomplete.
- Services. Power, water, sewer and NBN connections are sometimes included and sometimes left as allowances.
- Access. Narrow lots, rear-loaded lots and tight estates can need smaller machinery or extra handling.
If a builder has not seen the block, their site costs are a guess. Our page on how to evaluate a land release walks through what to check on a block before you commit to it, which is also what a builder needs to price it properly.
Step 5: Compare the contract terms, not just the price
Two quotes with the same total can carry very different risk. Look at:
- Contract type. Fixed price, or cost-plus? On a fixed-price contract the builder carries most of the cost risk on the items it fixes. On cost-plus, you do.
- How long the price holds. Ask how long each quote is valid for, and whether the price can change between signing and starting work.
- Timeframes. When construction is expected to start, and how long the build period is in the contract.
- Variations. How changes are requested, priced and approved, and what each builder charges to process one.
- Payment stages. When each progress payment falls due and what has to be finished before it does.
- Insurance. Ask to see the home indemnity insurance for your job before work starts.
None of this shows up in a headline price, and all of it affects what the build actually costs you.
Step 6: Check the builder, not just the quote
A sharp quote from a builder who handles the job badly is not a good deal.
- Confirm the builder is registered with the WA building regulator using the government’s registered building service provider search.
- Read recent reviews, and look for how the builder responds when something goes wrong, not only the five-star ones.
- Ask how long their current builds are taking from slab to handover.
- Ask who your contact will be during construction, and how often you will hear from them.
A simple way to lay the quotes side by side
Once each quote is split into the same buckets, a single table makes the comparison honest:
| Builder A | Builder B | Builder C | |
|---|---|---|---|
| Base house at agreed specification | |||
| Site works: fixed or allowance? | |||
| Total provisional sums | |||
| Total prime cost items | |||
| Upgrades you actually want | |||
| Exclusions you will pay for separately | |||
| Price valid until | |||
| Contract type | |||
| Expected build time |
Fill in every cell before you look at the totals. An empty cell is a question to send back to the builder, not a zero.
Red flags in a builder quote
- A site works line that says “allowance” on a block the builder has not looked at.
- Prime cost allowances that seem low for the finishes shown in the display home.
- A quote based on a different plan revision from the one you sent.
- A promotion with an expiry date that leaves you no time to compare.
- Reluctance to put exclusions in writing.
- A price that only holds if you sign a deposit agreement this week.
When to get a second pair of eyes
Lining up three quotes properly takes time, and the expensive mistakes tend to sit in the small print rather than the headline. Part of what our consultants do for every client is exactly this work: checking that the working drawings match what was promised, that fixtures, fittings and finishes are what you were shown, that site works and allowances make sense for the block, and that the contract and the plan say the same thing. You can see how that review works on our plan and contract review page.
We do it at no cost to you. House & Land Co is a building broker, paid by the builder you choose from our panel rather than by you, and how we get paid is set out in full if you want to check that for yourself.
Common questions
How many builder quotes should I get in Perth?
In our experience three is enough to see a pattern. Beyond five, the extra quotes tend to add noise rather than clarity, especially once the briefs drift apart. What matters more than the number is that every builder priced the same house on the same block.
Why are site costs so different between Perth builders?
Because they depend on assumptions about your land: the soil, the slope, the bushfire rating and the service connections. A builder who has seen a soil report and contour survey for your lot can price site works with some confidence. A builder working from a typical figure for the suburb is estimating, and the difference often turns up later as a variation.
Is the cheapest quote usually the cheapest build?
Not reliably. A quote can be lower because it leaves out items another builder included, because its allowances are low, or because its site costs are placeholders. Compare the buckets, not the totals, and the cheapest build is usually obvious.
Can I ask a builder to requote using another builder’s inclusions?
Yes, and it is a fair request. Send the inclusions list you want priced and ask them to quote against it, noting anything they cannot match. In our experience builders would rather requote than lose a job on a misunderstanding.
Does House & Land Co charge to help compare quotes?
No. We are paid by the builder a client chooses from our panel, from the builder’s side, and nothing is added to your contract. If you would like us to go through your quotes, get in touch with our team.
General information only, not financial or legal advice. Contract terms, insurance requirements and site conditions vary. Check the details of your own contract with the builder and, if you need it, a legal adviser before you sign.
