How to Estimate a Knockdown Rebuild
Estimating a knockdown rebuild means pricing two linked jobs against one address: demolishing and clearing the existing house, then building the new home from a cleared, serviced site. Start with the demolition scope — waste classification, an asbestos allowance where the home is older, and service disconnection — then measure the new-home Bill of Quantities across every trade from slab through to fit-out, and add the costs that are unique to knockdown rebuilds, such as reconnection works and a temporary accommodation allowance for the client while building is underway.
Key takeaways
- A knockdown rebuild estimate has two linked scopes — demolition and site preparation, and a full new-home build — and both need to be measured and priced in the one document.
- Demolition cost turns on waste classification more than size alone; homes built or renovated before around 1990 commonly need an asbestos survey before any demolition work starts.
- Once the site is cleared, the new home is measured like any other new build — slab, frame, lock-up, fit-out — across every trade, with no shortcuts because it is a rebuild.
- Service disconnection and reconnection, site clearing, and a temporary accommodation allowance for the client are costs specific to knockdown rebuilds that do not appear on a vacant-block build.
- Automated takeoff from the new home’s plans, an editable rates library, and a structured Bill of Quantities and tender let My Trade Hub turn a knockdown rebuild scope into a priced tender up to 60–75% faster than doing it manually.
What counts in a knockdown rebuild estimate
A knockdown rebuild (KDR) estimate has to cover everything from demolishing the existing dwelling through to a completed new home, so it needs two connected scopes priced against the one address — the demolition and site preparation works, and the new-home build itself.
The usual order of work is a pre-demolition check (including an asbestos assessment where relevant), disconnection of existing services, demolition of the structure, waste removal and site clearing, then the new build proceeds in its normal stages — civil and slab, frame, lock-up, fit-out — before services are reconnected and the home is handed over.
Because it is one continuous project for the client, both scopes belong in a single tender or Bill of Quantities. Pricing the demolition separately from the new build, or treating the old house coming down as an afterthought, is where knockdown rebuild estimates most often miss cost.
- Demolition and site preparation — existing structure down, waste removed, site cleared
- The full new-home build — slab through to fit-out, every trade measured and priced
- Costs unique to knockdown rebuilds that do not appear on a vacant-block build — service works, allowances, staging
Demolition, waste classification and disposal
Demolition pricing turns on how the waste from the existing house is classified, because general demolition waste, contaminated waste and asbestos-contaminated waste are transported and disposed of differently — and disposal fees follow the classification, not just the tonnage or floor area.
A licensed demolition contractor typically measures the structure — footprint, storey height and construction type, such as brick veneer, double brick or fibro sheeting — then estimates the waste volume and classifies it before quoting removal and tip fees.
Council conditions also affect cost. A demolition permit or development approval may carry tree protection, heritage overlay or asset protection conditions that change the method of work and the price, so these should be checked before the demolition line is priced.
- Structure demolition — labour, plant, temporary fencing and hoarding
- Waste classification and cartage to the appropriate facility
- Tipping and disposal fees at a licensed facility
- Any salvage or recycling credit where materials are reused rather than disposed of
Asbestos allowance for older homes
Homes built or renovated before around 1990 commonly contain asbestos in sheeting, eaves, flues or floor coverings, so an estimate for these properties should carry a defined allowance for a pre-demolition asbestos survey and removal — priced as its own line item rather than folded into general demolition.
The usual sequence is a licensed assessor surveys the property and issues a report, a licensed asbestos removalist quotes removal based on that report, and general demolition then proceeds once clearance is issued. Pricing this as a separate allowance line keeps it visible in the tender rather than hidden inside a lump-sum demolition figure.
Not a substitute for licensed advice
This is a costing consideration, not safety or compliance advice. Asbestos identification, removal and disposal in Australia must be carried out by a licensed asbestos removalist in line with state work health and safety requirements. My Trade Hub lets you carry this as an editable allowance line in your estimate — it does not assess, manage or clear asbestos works itself.
Service disconnection, reconnection and site clearing
Before demolition can start, the existing power, gas, water, sewer and any NBN or telecommunications connections at the property generally need to be formally disconnected by the relevant utility or a licensed contractor, and once the new home is built those same services need reconnecting — or replacing with new connections sized for the new dwelling.
Because the block already has established connections and, in most cases, an existing driveway or crossover, some early civil costs on a knockdown rebuild can come in lower than on a vacant-block build. That saving sits alongside the demolition, disconnection and reconnection costs, though, so the two scenarios are not directly comparable until both are fully priced.
- Disconnection request and inspection fees with each utility before demolition
- Temporary capping or making safe of services during demolition and site works
- Site clearing and levelling once the structure and waste are removed
- Reinstatement or upgrade of connections sized for the new home’s design and load
Building the new-home Bill of Quantities: slab to fit-out
Once the site is cleared, the new home on a knockdown rebuild is measured and priced exactly like any other new build — a full Bill of Quantities broken into stages, with every trade’s quantities and rates included, because from this point the site is effectively a vacant, serviced block.
The stages follow the usual pattern: slab (site works, footings and slab), frame (structural frame and roof trusses), lock-up (roof covering, external walls or cladding, windows and doors), then fit-out (electrical, plumbing, insulation, linings, kitchen and bathroom joinery, painting, flooring, plus driveway and landscaping).
Every trade needs its own measured quantities and its own rate, with the same rigour as any new-home Bill of Quantities. Treating the new-build scope as simpler because “it’s just a rebuild” is a common way real costs get missed further down the job.
| Stage | Typical scope | Illustrative rate basis (example only) |
|---|---|---|
| Demolition and site prep | Structure demolition, waste classification and disposal, asbestos allowance if applicable, site clearing | Example: priced per m² of building footprint, plus a separate asbestos allowance where identified |
| Service works | Disconnection before demolition, reconnection or upgrade for the new home | Example: priced per connection type, as quoted by each utility or contractor |
| Slab | Site works, footings and slab on the cleared block | Example: priced per m² of slab area, by soil class and slab type |
| Frame | Structural frame and roof trusses | Example: priced per m² of floor area, by frame material |
| Lock-up | Roof covering, external walls or cladding, windows and doors | Example: priced per m² of external envelope |
| Fit-out | Electrical, plumbing, insulation, linings, kitchen and bathroom joinery, painting, flooring | Example: priced per room or area, or as a fixed fit-out allowance per trade |
Extra costs unique to a knockdown rebuild
A knockdown rebuild carries several costs that simply do not appear on a vacant-block new build, and missing them is the most common way a knockdown rebuild estimate falls short of the final job.
Some of these sit inside the construction scope and belong in the Bill of Quantities. Others, like where the client lives during the build, sit outside the construction contract but still belong in the estimate documentation as context for the client’s overall budget.
- Demolition, waste disposal and any asbestos allowance
- Service disconnection before demolition and reconnection or upgrade after
- Temporary fencing, hoarding and traffic management on an established street
- Any tree protection, retaining wall or party-wall conditions attached to the council approval
- A temporary accommodation allowance for the client — most families need to arrange rental or interim housing for the build period, which is a real cost to their overall budget even though it sits outside the construction contract itself
How My Trade Hub speeds up knockdown rebuild estimating
My Trade Hub speeds up knockdown rebuild estimating by measuring the new home’s quantities automatically from the uploaded plans and applying your own editable rates library to the demolition, service and build stages, then assembling the whole scope into one structured Bill of Quantities and tender.
Upload the new home’s plans and drawings, and the automated quantity takeoff measures the new-build items across slab, frame, lock-up and fit-out and lists them against your rates library. You add allowance lines for demolition, any asbestos survey and removal, and service disconnection or reconnection, so the entire knockdown rebuild scope sits in one place rather than across separate quotes. Every rate stays editable — nothing is guessed, and you are always working from your own figures.
Because a knockdown rebuild has more moving parts than a standard new build, teams using My Trade Hub prepare a fully priced tender for the whole scope up to 60–75% faster than doing it manually. See the pricing page for plan details, since estimating and takeoff sit on paid plans rather than the free account tier.
- Automated quantity takeoff from the new home’s plans
- Editable rates library applied to every measured item
- Structured Bill of Quantities covering demolition and service allowances through to fit-out
- One tender document for the whole knockdown rebuild scope
Frequently asked questions
How do you estimate a knockdown rebuild?
Treat it as two linked scopes priced against one address: demolition and site preparation (waste classification, any asbestos allowance, service disconnection, site clearing), then a full new-home Bill of Quantities across every trade from slab through to fit-out. Add the costs unique to knockdown rebuilds, such as reconnection works, on top.
What does it cost to demolish a house in Australia?
Demolition cost depends mainly on how the waste is classified, not just the size of the house. General waste, contaminated waste and asbestos-contaminated waste are handled and disposed of differently, and council conditions such as tree protection can also affect the price. A licensed demolition contractor prices this against the actual structure rather than a rule of thumb.
Do you need an asbestos survey before demolishing an old house?
Homes built or renovated before around 1990 commonly contain asbestos, so a survey by a licensed assessor is standard practice before demolition, with removal carried out by a licensed asbestos removalist. This is a costing consideration, not legal advice — check the specific requirements in your state before demolition begins.
Is a knockdown rebuild cheaper than building on a vacant block?
Not necessarily. An established block may have lower early civil costs because services and a driveway already exist, but demolition, waste disposal, service disconnection and reconnection add cost on top. Both scopes need to be priced before the two options can be compared.
What is included in a knockdown rebuild Bill of Quantities?
Both scopes — the demolition and site preparation scope (structure demolition, waste disposal, any asbestos allowance, service disconnection and site clearing) and the full new-home Bill of Quantities across every trade, from slab and frame through to lock-up and fit-out.
Where do you stay during a knockdown rebuild?
Most clients arrange rental accommodation or stay with family for the build period, since the existing home is demolished before the new one is built. This sits outside the construction contract itself, but it is worth noting as a temporary accommodation allowance in the estimate documentation for the client’s overall budget.
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