One of the most common questions after pool removal is: “Can I build over where the pool was?” The answer depends on whether it was a full removal or a partial fill-in, the quality of the compaction, the soil conditions, and what you want to build. This guide explains what’s structurally required, what you can and can’t build over different types of pool removal sites, and what documentation you need.
The Fundamental Difference: Full Removal vs Partial Fill-In
The distinction between full removal and partial fill-in is critical for future building:
Full removal: The entire pool shell — base, walls, and all shell material — is excavated and removed from site. The void is backfilled with specified fill material and mechanically compacted in layers. The finished site has no buried structure.
Partial fill-in: The pool is drained, drainage holes are punched through the base, the upper walls are demolished to a depth below surface level, and the void is filled and compacted. The lower portion of the pool shell (base and lower walls) remains in the ground permanently.
Building Over a Full Removal Site
With full removal and documented compaction to specification, you can generally build on the site — subject to:
- Compaction test results meeting the specification required for the intended structure
- Engineer’s assessment and sign-off on compaction records
- Normal building permit processes for whatever you’re constructing
Building Over a Partial Fill-In Site
Building over a partial fill-in site is more complex. The buried pool shell creates:
- A zone of different stiffness from the surrounding soil (the shell is rigid; the fill inside it is compacted but may behave differently from undisturbed soil)
- A drainage channel that can affect moisture distribution in the soil
- A structural unknown that your engineer needs to address
Building structures directly over a partial fill-in typically requires:
- Engineer’s site investigation (may include boreholes or dynamic cone penetrometer testing)
- Specific structural engineering design for the footing/slab (possibly a stiffened raft slab or pier-and-beam system)
- Geotechnical reporting on the fill and buried structure
- Potentially additional remediation work (further compaction or additional fill) before building
Some engineers will simply refuse to certify a residential building slab directly over a partial fill-in without full removal of the buried structure — in which case, you’re back to doing the full removal anyway, at additional cost.
What Can You Build Over a Full Removal Site?
| Structure | Requirements | Notes |
|---|---|---|
| Lawn or garden | None — just topsoil and planting | Fully suitable after compaction |
| Paving (tiles, pavers, concrete slab) | Good compaction; may need sand bed | Suitable for most well-compacted sites |
| Timber or composite deck | Footings must be designed for compacted fill | Check with builder; engineer may need to inspect |
| Carport or light structure | Footings designed for fill site; compaction test documentation | Standard engineering process |
| Garage (concrete slab) | 95%+ compaction standard; geotech report; engineer sign-off | Standard commercial practice |
| Residential addition (slab or footings) | 95–100% compaction standard; geotech report; structural engineer; BCA compliance | Full removal required before full BCA-standard structure |
| New pool | Not over old pool site without full re-excavation | Need to excavate old fill to establish new pool |
Compaction Specifications for Different Uses
Compaction is expressed as a percentage of maximum dry density (MDD) achieved by the Modified Proctor compaction test. The required percentage depends on the intended use:
| Intended Use | Minimum Compaction Standard | Testing Method |
|---|---|---|
| Lawn/garden | 90% MDD | Not typically tested |
| Paths and paving | 90–92% MDD | Nuclear density gauge or sand replacement |
| Light structures (deck, carport) | 92–95% MDD | Nuclear density gauge |
| Concrete slab (shed, patio) | 95% MDD | Nuclear density gauge |
| Residential building slab | 95–100% MDD | Nuclear density gauge + cone penetrometer |
| Commercial or engineered structure | Per engineer specification | Comprehensive geotech testing |
These standards are indicative. Your structural engineer or building certifier will specify the exact requirement for your project.
Getting Compaction Documentation From Your Pool Removal Job
If you want to build over the pool removal site in future — even if you’re not planning it now — request compaction testing documentation at the time of the removal job. This costs approximately $300–$600 as an add-on and provides:
- Nuclear density gauge test results at multiple points across the filled area
- A report confirming achieved compaction percentage
- Documentation to present to your engineer or building certifier
Getting this documentation at the time of the job is much cheaper than:
- Coming back years later and trying to demonstrate the compaction quality from an old job
- Paying for borehole investigation or intrusive testing to determine fill quality after the fact
We include compaction test documentation in any pool removal job where the customer requests it. Advise us at booking if you want this.
The Engineering Process for Building Over a Pool Removal Site
When you engage a builder or structural engineer for work over a pool removal site, the typical process is:
- Advise your engineer that the proposed building location is over a filled pool void
- Provide the compaction documentation from the pool removal job
- Engineer assesses the compaction results against the required specification for your proposed structure
- If compaction documentation satisfies the requirement: Engineer designs the structure with any appropriate additional measures (e.g., a stiffened raft slab rather than strip footings)
- If compaction documentation is insufficient: Engineer may require further testing (dynamic cone penetrometer, borehole investigation) to assess fill quality
- If fill quality is inadequate: Engineer may specify remediation (further compaction, replacement of fill) before proceeding
The critical point is that your engineer needs information to work with. Good compaction documentation from the removal job gives them that information. Without it, they have to investigate — at additional cost.
The Southern Highlands Clay Soil Factor
Clay soils — common in the western Highlands plateau (Moss Vale, Sutton Forest, Exeter) and parts of Bowral — add complexity to the “building over removed pool” question for several reasons:
Reactive clay classification. Clay soils are classified by reactivity (Low, Moderate, High, Extreme) based on their potential for volume change with moisture. Wingecarribee Shire has areas of High and Extreme reactivity clay (Class H1, H2, E under AS 2870). Building on reactive clay — regardless of pool removal — requires site classification and appropriate slab design.
Implications for pool fill sites: On highly reactive clay sites, the fill material specified for the pool void needs to be carefully chosen to be compatible with the surrounding clay’s movement behaviour. Inappropriate fill can create differential settlement between the fill zone and surrounding soil.
We discuss soil type at the site inspection and specify fill material accordingly.
The Simple Rule of Thumb
For lawn, garden or paving with no future building plans: A partial fill-in or full removal with standard compaction is fine.
For any structure — from a simple deck to a house extension: You need full removal (not partial fill-in) and documented compaction to specification, followed by an engineer’s assessment before building starts.
If there’s any possibility you’ll want to build on the site in the future — even years from now — choose full removal and get the compaction documentation. The extra cost of doing this properly now is far less than the cost of doing it wrong and having to remediate later.
Frequently Asked Questions — Building Over Pool Removal
Can I build a house extension over where my pool was? With full removal and documented compaction, this is possible subject to engineer’s sign-off. The engineer will need to see the compaction test results and may specify particular footing designs. See your structural engineer early in the planning process.
My contractor didn’t do compaction testing when they removed my pool 5 years ago. Can I still build over the site? Yes, but you’ll need to commission geotechnical investigation (boreholes, testing) to assess the fill quality before your engineer can design the structure. This costs $1,500–$5,000 depending on the extent of testing. Get advice from a geotechnical engineer.
Can I build a carport over a partial fill-in? Possibly, but it requires engineering assessment. A carport has lower structural demands than a dwelling, but the presence of the buried pool shell still needs to be factored into the footing design. Engage a structural engineer before starting.
How deep is the fill in a typical Southern Highlands pool removal? A typical inground pool void is 1.5–2.5m deep. After full removal, this entire depth is backfilled with compacted fill. After a partial fill-in, the lower 0.5–1.5m of the old pool shell remains in place.
Does the presence of a previous pool affect a property’s building envelope? The council’s building envelope is not affected by a previous pool removal as such. The practical constraint is the soil bearing capacity and compaction of the filled site, which is an engineering (not planning) issue.
Planning to build over your removed pool site? Get the compaction documentation right from the start — ask us about testing at booking.