Pre-Purchase Block Due Diligence: What to Check Before You Buy Land

Some of the most expensive building projects in the Southwest didn't go wrong during construction. They went wrong the day the block was purchased, when nobody checked what the land could accommodate. This checklist exists so that doesn't happen to you.

A conveyancer handles the legal transfer of land. A surveyor confirms title boundaries. What neither of those professionals routinely covers is what you can build on the block, and what it will cost. That's the gap this checklist addresses.

1. Planning and zoning

•      R-Code density — determines the minimum lot size per dwelling and therefore the development potential. Check the City or Shire's zoning map, don't rely on the agent's description.

•      Local Planning Policies — check the council website for any LPPs that apply to the area. In Busselton and Augusta-Margaret River particularly, design guidelines and vegetation policies can significantly affect what's buildable.

•      Special control areas — coastal erosion setbacks (common near the Leeuwin-Naturaliste ridge and Geographe Bay foreshore), flood risk areas (relevant near the Vasse, Collie, and Harvey Rivers), and airport noise zones all appear as overlays on local planning scheme maps.

•      Heritage listings — towns including Bridgetown, Manjimup, and Bunbury CBD surrounds have heritage precincts where even minor works may require heritage assessment.

2. Bushfire risk

•      Bushfire-prone area mapping — check the DFES online mapping. A block in a declared bushfire-prone area will require a BAL assessment before a building permit can be issued.

•      Likely BAL rating — a preliminary BAL assessment costs $300–$600 from an accredited assessor and can be completed before purchase. At BAL-29 and above, construction cost premiums are significant — BAL-FZ adds $30,000–$80,000+ to a standard home.

•      Asset protection zone — in high-BAL areas, an APZ must be maintained on the property. On a small lot, the APZ requirement can effectively sterilise a large portion of usable land area.

3. Site constraints

•      Slope and topography — check Landgate contour data before inspecting. A 2m fall across a 20m lot is manageable; a 5m fall can add $20,000–$50,000 in cut, fill, and retaining.

•      Orientation — a block where the street frontage faces due south means the house faces south — the worst passive solar orientation. This is not a reason not to buy, but it affects design approach and potentially energy performance compliance cost.

•      Significant trees — the Shire of Busselton and Shire of Augusta-Margaret River both have tree protection provisions. Significant Peppermint, Tuarts, Marris, and Jarrah standing on private land can restrict building placement. Walk the site and note any substantial trees.

•      Lateritic soil profiles — common around Donnybrook, Harvey, and parts of the Busselton hinterland. Laterite can be highly variable in bearing capacity — a soil test before purchase on sites with obvious laterite surface exposure is worthwhile.

4. Services

•      Deep sewer — check Water Corporation's online mapping. Lots without sewer connection require an on-site wastewater system — allow $8,000–$15,000 for a conventional septic or $15,000–$25,000 for an AWTS, plus annual servicing costs.

•      Water supply — scheme water is available across most of the Southwest, but rural blocks may require bore or rainwater supply. Check Water Corporation's served area mapping.

•      Power connection — for rural lots, confirm grid connection distance with Western Power. Remote connections can cost $20,000–$60,000+ depending on distance and terrain.

•      High groundwater — areas near the Vasse wetlands, Ludlow tuart forest, and some coastal areas around Dunsborough have shallow water tables that affect both wastewater system siting and slab design. Council environmental health officers can advise.

5. Title and encumbrances

•      Easements — drainage, access, and service easements restrict where you can build. They appear on the Certificate of Title and the Deposited Plan. A 3m wide drainage easement through the middle of a small lot can make a compliant design impossible.

•      Restrictive covenants — some estate lots carry covenants restricting materials, colours, or design style. These appear as notifications on the title under Section 129 of the Transfer of Land Act.

•      Registered building envelopes — common in premium subdivisions around Dunsborough, Margaret River, and Yallingup. The registered envelope may be significantly more restrictive than the standard setback envelope — check the title carefully.

•      Rights of way — particularly relevant on rural lots. A right of way or access easement for a neighbour's benefit can restrict where structures can be placed.

6. Flood and drainage

•      Flood risk — check council flood mapping and the state's flood risk system. Properties near the Harvey, Collie, Vasse, and Donnelly rivers in the Southwest carry genuine flood exposure that affects insurance, design, and floor level requirements.

•      Natural drainage paths — on sloped rural blocks, understanding where overland flow travels in a 1-in-100-year event affects where a house should be positioned and how drainage is designed.

Key principle: The purchase price of land is only one component of the total cost of building on it. A cheaper block with complex constraints can easily be more expensive overall than a straightforward block at a higher price. Run the numbers on both.

Frequently Asked Questions

How do I check if a block is in a bushfire-prone area in WA?

DFES publishes bushfire-prone area mapping on its website. The mapping is publicly available and searchable by address or lot number. If the block appears in a designated bushfire-prone area, a BAL assessment will be required before a building permit is issued.

What is a pre-lodgement meeting with council and should I ask for one?

A pre-lodgement meeting is an informal consultation with council planning staff before submitting a development application. It's available at most Southwest councils and is strongly recommended for any non-standard or complex project. The council cannot make binding decisions at a pre-lodgement meeting, but they can identify likely issues, saving you from submitting a DA that will be refused or heavily conditioned.

Can I commission a soil test before I purchase a block?

Yes, and with the seller's permission it's a worthwhile investment. A standard residential soil test costs $400–$800 and takes 5–14 business days to return results. If you're purchasing subject to finance, building approval, or other conditions, you can often add a condition allowing you to commission a soil test. Knowing the soil class before purchase lets you model realistic slab and site cost estimates.

Book a pre-purchase site assessment before you sign a contract of sale, it's one of the most cost-effective decisions you can make: fastlane.drafting@gmail.com