Knockdown Rebuild: What Happens If Old Footings, Buried Debris or Suspected Contaminated Soil Are Found After Demolition?
You arranged demolition separately. The site looks cleared, the new builder starts excavation, and then concrete, buried debris or questionable soil appears. The immediate worry is both practical and financial: what has been found, what needs to happen and who is being asked to pay?
Start with evidence and the actual scopes. A visibly cleared surface does not establish everything beneath it. Equally, discovering buried material does not automatically make every additional charge the owner’s responsibility. The demolition agreement, building contract, foundation information and circumstances need to be read together.
ClearScope can discuss a separately scoped visual inspection of accessible conditions. Send the stage and main question, without assuming a building inspection will classify contamination, design a footing solution or decide contractual liability.
Ask for an accurate description before accepting a broad label
“Bad soil” or “rubbish underground” can describe very different conditions. Ask what was encountered, where it is, how it was exposed and what evidence supports the description. Keep ordinary rubble, unsuitable foundation material and suspected contamination as separate questions.
Photographs and a marked-up plan can help locate the discovery. They do not establish the full underground extent or identify chemical contamination. Ask whether the stated quantity is measured, estimated or still unknown.
If suspected asbestos or another hazardous material is involved, the response needs appropriate professional controls. Do not collect a sample, break fragments or try to identify it yourself. The commercial discussion should not delay making the affected work area safe.
A cleared surface and a cleared subsurface are different
Demolition completion may leave an open block that looks ready to build. What that means contractually depends on the agreed demolition scope and records. It may not demonstrate that every old footing, service, tank or buried item has been removed.
Read the actual inclusions, exclusions and any agreed excavation depth or nominated structures. Ask what evidence was provided at completion and whether concealed conditions were specifically addressed. Do not infer a universal removal depth from the word “demolition”.
If you are still planning the project, agree the interface before the contractors start. Ask the new builder what site condition and documentation they require, and ask the demolition contractor what they will deliver. An undefined handover between the two can leave important assumptions unresolved.
Gather the demolition documents
Keep the signed scope, quote, variations, relevant permits, completion correspondence, invoices and disposal records available. Identify who arranged service disconnections and any specialist removal work. Request missing records through the appropriate contractor rather than guessing what happened.
Compare the discovered material with the actual scope. Was removal of existing foundations included? Was a particular structure excluded? Was additional work discussed but never authorised? These questions help define the issue; they do not settle responsibility without considering the rest of the evidence.
Avoid asking the builder to remove everything immediately and sort out the price later unless you understand the consequences and required process. If urgent safety action is necessary, distinguish that action from the broader disputed scope and obtain prompt professional advice.
Foundation information is central to the building-price question
Consumer Affairs Victoria’s foundation guidance says builders must obtain foundation data before the contract and be satisfied it is accurate. It also explains that owners should not have to pay extra for problems the builder should have identified from that information.
The guidance says the contract price should include removing existing foundations and other listed structures. That is a reason to review the actual contract and data carefully, rather than assume a new charge is payable merely because the concrete was found after demolition.
Ask which report, investigation and site information informed the price. What did it identify, what assumptions were made and how does the discovery differ? A generic statement that ground conditions are always the owner’s risk does not answer those questions.
A soil classification report is not automatically a contamination assessment
Foundation and site-classification information addresses a different purpose from environmental assessment. Read the report’s scope, investigation locations, findings and limitations. Do not assume a soil classification label means the soil has been tested for contamination.
A geotechnical professional may need to assess unsuitable fill or advise on foundation conditions. A structural engineer may need to review the proposed footing response. An environmental professional may be needed where contamination status or waste classification is uncertain.
Ask the author of an existing report what it establishes. A visual building inspection cannot fill a laboratory or specialist-investigation gap. The correct next step depends on the question, not simply on whether a document is called a soil report.
Keep engineering suitability and waste classification separate
Concrete or mixed fill may affect excavation and foundation preparation without proving chemical contamination. Conversely, soil that looks ordinary may require environmental investigation. Appearance alone does not settle either question.
EPA Victoria’s waste-soil guidance explains classification and management obligations, including use of an authorised receiving place. Ask the contractor or environmental adviser what classification is needed and what evidence supports the proposed disposal route.
Do not approve a disposal price solely from a photograph or an unexplained description such as “contaminated load”. Ask for the professional assessment, quantity basis, receiving facility and relevant records. This is a request for substantiation, not an instruction to handle or sample the material yourself.
Suspected asbestos needs a controlled professional response
Tell the builder immediately if suspected material has been encountered and ask how the affected work will be managed. Keep away from the area and do not disturb the material to obtain a better image or sample.
WorkSafe Victoria’s asbestos-in-soil guidance explains why specialist assessment and appropriate controls matter. The necessary expertise can include an occupational hygienist and appropriately licensed asbestos professionals, depending on the circumstances.
Ask what assessment, removal and clearance documentation is appropriate for the actual work. A previous demolition or asbestos-removal document should be read for its scope; it is not automatically proof that every later excavation is free of suspect material. Avoid assigning a hazard category through appearance alone.
Request a proposed work scope with a quantity basis
Ask the builder to separate investigation, removal, replacement material, engineering, testing, transport, disposal and making good. Identify what is included in the original contract and what is claimed as additional.
For quantities, ask whether the proposal uses excavation volume, truck capacity, measured weight or another basis. Request unit rates, assumptions, allowances and how final quantities will be reconciled. A capped estimate and an uncapped rate schedule create different cost exposure.
Ask about programme effects and whether the proposed work changes permits, design or inspection requirements. Keep the technical reason for the work separate from the question of who owes its cost. Necessary work and a valid additional-price claim are related but not identical matters.
Do not treat every discovery as an automatic variation
Consumer Affairs Victoria’s payments and variations guidance describes written variation requirements and exceptions. Ask for the contractual basis, proposed price and time effect, and obtain advice before agreeing to a disputed change.
The owner, demolition contractor and builder do not automatically pay solely because of their role. Responsibility may depend on agreed scopes, what was reasonably foreseeable, available information and the applicable contract and law.
If the claim is contested, give your building lawyer or adviser the complete documents, not just the latest invoice. Do not rely on this article to authorise withholding a contractual payment or instruct work contrary to a contract. Get advice on the specific issue and preserve the evidence.
Close the loop before the next construction stage
Keep location photographs, professional advice, approved work scope, quantity records, disposal documentation and any relevant repair or replacement records together. Ask who confirms the affected area is ready for the next activity and what inspections remain required.
If drains or services were affected, ask the relevant licensed trade about follow-up. Our pre-slab CCTV guide explains a separate internal drain-condition question. It does not replace ground assessment or foundation approval.
For nearby properties, a before-works condition record may also be relevant, with scope and timing agreed separately through the dilapidation inspection service. Neither that record nor an inspection photograph establishes contamination status beneath the development site.
Keep the commercial and technical decisions connected
Use a written sequence: discovery recorded, appropriate assessment obtained, work scope proposed, contractual position reviewed and completion evidence retained. The steps may need urgent coordination, but they should not disappear into one unexplained additional invoice. Ask who owns each outstanding action before the site proceeds.
Ask ClearScope about the visual question
Explore inspection services and report examples to understand the reporting role. If you need accessible conditions documented, tell us the address, what has been found, the current stage and what will be concealed next.
Contact ClearScope to discuss a scoped visual inspection. We can help clarify what a visual record can contribute, while geotechnical, engineering, environmental, asbestos and contractual questions go to the appropriate specialists. The useful outcome is an evidenced scope and a clear next step before the project moves on.