Floor Levelling Sydney: Why Sand Is Broadcast Over Moisture Barriers

In some manufacturer-approved floor levelling systems, clean, dry sand is broadcast into a wet epoxy moisture barrier to create a mechanical bonding surface for the levelling compound. This is relevant to Sydney concrete subfloors requiring moisture management. Sand broadcast is not a universal requirement or a substitute for every primer. A preparation quote should specify the barrier, sand application, curing, cleaning and compatible levelling product.

ELYMENT Insights | Flooring & Renovation Operations | Sydney, NSW | 11 November 2026

The Sand Is Not the Moisture Barrier. It Is the Connection Above It.

There is an unusual stage in some Sydney floor preparation projects when a newly coated concrete slab is deliberately covered with sand.

To an observer, it can look like the installer has contaminated a surface that was only just prepared.

The explanation is more technical. Certain epoxy moisture-barrier systems need a textured bonding interface before a cementitious levelling compound can be installed above them.

The epoxy helps manage moisture transmission from the concrete. The sand, embedded into the resin while it remains wet, provides a mechanical key for the next layer.

Without the specified interface, the levelling compound may not bond reliably to the resin-coated surface.

That distinction matters because floor preparation is increasingly divided between specialist contractors. One team may remove the existing flooring, another prepares the concrete, a third applies moisture mitigation and levelling, and a flooring installer arrives to complete the finish.

The performance of the final installation depends on the compatibility of every layer, not simply whether the concrete looks smooth.

For Sydney property owners, builders and strata managers, the commercial question is therefore straightforward: has the contractor allowed for the complete manufacturer-approved system, including any required sand broadcast, or only the visible moisture coating and levelling pour?

What the ARDEX Technical Bulletin Actually Specifies

ARDEX Australia provides a useful example in Technical Bulletin TB170, Epoxy Priming Systems for ARDEX Levelling Compounds, dated 31 January 2025.

The bulletin describes epoxy-based priming systems for nominated levelling compounds where internal concrete floors require moisture management or a more robust bonding system.

For its specified damp-floor system using ARDEX WPM300 HydrEpoxy, the bulletin describes the following sequence:

1. Prepare the concrete. Establish a sound substrate using the specified mechanical preparation method. Shot blasting is identified as the preferred approach in this system.
2. Apply the first epoxy coat. ARDEX specifies an application rate of 3 m² per litre and an initial curing period of approximately two hours in the bulletin.
3. Apply the second coat. The second application is also specified at 3 m² per litre.
4. Broadcast the sand while the second coat remains wet. The bulletin identifies clean, dry sand of approximately 0.5 mm particle size at around 700 g/m².
5. Allow curing and remove excess sand. TB170 describes overnight curing, followed by brooming and vacuuming before applying the smoothing cement.

These figures illustrate one published ARDEX system. They should not be copied into a specification for an unrelated resin, primer or levelling compound.

Importantly, the ARDEX WPM300 product data sheet specifies a minimum 24-hour cure for the sand-seeded system before excess sand is removed and subsequent subflooring work proceeds. Actual curing depends on site conditions.

Project teams should follow the current product data sheet, applicable technical bulletin and manufacturer confirmation rather than treating an indicative curing period as permission to start the next trade.

ARDEX also expressly warns in TB170 that omitting broadcast sand from the relevant epoxy systems can cause the levelling compound to debond.

This is the critical distinction: the sand is not being scattered for convenience or appearance. In these specified applications, it forms part of the designed bonding mechanism.

Why a Smooth Epoxy Surface Can Become a Bonding Problem

Concrete and cured epoxy present different surfaces to a cement-based levelling compound.

Mechanically prepared concrete can provide a suitable mineral substrate when matched with the correct preparation system. A cured epoxy moisture barrier is comparatively dense and non-absorbent.

Where the levelling product is not approved for direct application over that resin, the installer needs an alternative bonding method.

Sand broadcasting creates a granular interface through a controlled sequence:

• The resin wets and retains the specified sand particles.
• The particles remain partially exposed after the resin has cured.
• The next approved cementitious layer engages with that textured surface.
• Excess, unbonded particles are removed so they do not become a loose separating layer.

The quality of this interface depends on more than the presence of sand.

Material cleanliness, grading, resin coverage, broadcast timing, adhesion and subsequent cleaning all influence whether the surface matches the selected system.

Too little sand can leave inadequately textured areas. Sand added after the epoxy has already cured may not become properly embedded. Excess loose particles left behind can interfere with the next bond.

A floor that appears evenly sandy is therefore not automatically compliant with the manufacturer's specification.

Sand Broadcast, Separate Primer and Aggregate Extension Are Different Operations

One source of confusion is that the word sand appears in several unrelated floor preparation methods.

A specified sand broadcast should not be confused with mixing aggregate into a deep levelling pour or applying a conventional primer to porous concrete.

Sand broadcast into wet epoxy

• Principal function: Creates a mechanical bonding interface above an approved resin system.
• When it may be appropriate: Where the selected epoxy and levelling specification requires sand seeding.

Separate floor primer

• Principal function: Prepares or regulates the bonding surface according to the substrate and product chemistry.
• When it may be appropriate: Where the manufacturer specifies a compatible primer for the relevant substrate or membrane.

Aggregate extension

• Principal function: Changes the composition of a levelling mix for permitted deeper applications.
• When it may be appropriate: Only where the levelling product expressly allows the specified aggregate and mixing ratio.

In some systems, the epoxy acts as both a moisture-control layer and a specialist priming system, with the sand providing the necessary mechanical key.

Other manufacturers may specify a separate compatible primer or another approved bonding treatment. A sand broadcast is not automatically required merely because a floor has received moisture mitigation.

ARDEX's Technical Bulletin TB140 illustrates the distinction by identifying ARDEX P51 as a primer for standard absorbent concrete in its relevant dry-floor applications, while describing a sand-broadcast epoxy approach for damp-floor applications.

ELYMENT's earlier analysis of primer selection for concrete, timber and old adhesive floors explains why the underlying substrate determines the starting point.

A separate article examines adding sand or aggregate directly to floor levelling compound. That process serves a different purpose and must not be confused with broadcasting sand onto wet resin.

The practical rule is to specify the entire material system, rather than selecting individual products because they have worked on other projects.

The Handover Problem on Sydney Renovation Sites

The risk becomes more significant when moisture mitigation and floor levelling are performed under separate work orders.

Consider an illustrative Sydney apartment refurbishment where old vinyl flooring has been removed, concrete grinding has exposed the original slab and moisture testing indicates that the proposed flooring system requires additional moisture control.

The preparation contractor installs an approved epoxy barrier. A levelling team is scheduled to return before engineered timber or vinyl installation.

At first glance, the project appears ready to proceed.

But several questions remain:

• Was the moisture-control system approved for the recorded substrate conditions?
• Was the specified sand broadcast completed while the relevant resin coat was wet?
• Has the required curing period elapsed?
• Has loose sand been removed using the approved cleaning method?
• Is the selected levelling compound compatible with the completed interface?
• Who has inspected and accepted the surface before it becomes concealed?

If these matters are unresolved when the levelling crew arrives, the problem is no longer only technical.

It can affect booked installers, deliveries, strata access arrangements, subsequent joinery work and the overall renovation programme.

A missing bonding operation may be inexpensive compared with the cost of removing a failed levelling layer after the finishing contractor has commenced work.

For multi-trade projects, a documented inspection point between moisture-barrier installation and levelling is a practical safeguard.

The Inspection Point That Should Happen Before the Pour

The most useful time to assess a sand-broadcast interface is after the manufacturer-required curing and cleaning process, but before the levelling material conceals it.

A practical inspection record should establish:

1. Product identity. Record the moisture barrier, sand and proposed levelling compound, including the applicable technical documentation.
2. Substrate suitability. Confirm that preparation and relevant moisture testing were completed before the coating was applied.
3. Application record. Identify the number of coats, approximate coverage and broadcast procedure required by the specification.
4. Surface condition. Check for obvious missed areas, contamination, coating damage and loose particles.
5. Curing and cleaning. Confirm that the required curing interval and removal of excess sand have been completed.
6. Release for levelling. Record acceptance by the responsible contractor or suitably qualified project representative, with manufacturer technical advice where necessary.

Photographs taken during application can provide evidence of steps that cannot be verified reliably once the epoxy has cured.

However, photographs and visual inspection do not establish every performance characteristic. Where product compatibility, adhesion or substrate strength remains uncertain, the responsible team should obtain the necessary technical verification before proceeding.

Similarly, the sand interface does not establish that the concrete's moisture condition has been resolved for every possible final floor covering.

ELYMENT's related article on why concrete moisture readings do not replace pH testing explains the importance of assessing different substrate conditions separately.

What a Sydney Floor Preparation Quote Should Actually Itemise

A quotation that states only "moisture barrier and self-levelling compound" may conceal significant differences in methodology.

Where sand broadcasting is part of the selected system, the scope should make the operation identifiable, even if the contractor prices several related activities together.

Substrate preparation

• What the buyer should confirm: Required grinding or shot blasting, cleaning, repairs and preparation area.

Testing and assessment

• What the buyer should confirm: Moisture-test method, results, responsibility and any further technical review.

Moisture-barrier system

• What the buyer should confirm: Product name, application area, specified number of coats and coverage.

Sand broadcast

• What the buyer should confirm: Whether required, approved sand grading, application method and specified coverage.

Curing and protection

• What the buyer should confirm: Required waiting period, site conditions and protection against traffic or contamination.

Excess-sand removal

• What the buyer should confirm: Cleaning method, responsibility and readiness checks before levelling.

Levelling application

• What the buyer should confirm: Named product, measured area, depth allowance, compatibility and required finished tolerance.

Handover and exclusions

• What the buyer should confirm: Inspection records, outstanding repairs, assumptions, possible variations and flooring handover responsibility.

A quote that is more expensive because it includes the required coating sequence, material preparation and curing allowance may not be commercially comparable with one that assumes a simple primer-and-pour operation.

Equally, buyers should not be charged for unnecessary sand broadcasting when the chosen system permits a different approved approach.

The objective is to establish precisely what is required, rather than treating the longest materials list as evidence of better workmanship.

Why the Extra Preparation Stage Can Affect Project Costs

Sand itself may be a relatively modest material expense. The operational costs surrounding a specified broadcast system can be more substantial.

Project teams may need to account for:

• Additional site attendance for successive resin applications.
• Controlled material handling and coverage across the nominated floor area.
• Protection of the freshly coated floor during curing.
• Cleaning and removal of excess sand before levelling.
• Reinspection if another trade damages or contaminates the surface.
• Building access restrictions that prevent consecutive work stages from occurring on the same day.
• Rescheduling of levelling, adhesive installation and finished-floor works.

These considerations are particularly relevant to Sydney strata apartments, where lift bookings, noisy-work hours, common-property protection and delivery access can restrict how work is organised.

A staged commercial refurbishment can present similar constraints when a tenancy must remain partially accessible while adjoining floor areas are prepared.

The quotation should therefore distinguish material application from project sequencing. A curing interval is not merely an administrative gap that can always be removed by booking more labour.

When Sand Broadcasting Should Not Be Assumed

The existence of a sand-broadcast method in an ARDEX technical bulletin does not make the method applicable to every Sydney renovation.

Several situations require a different assessment.

1. The chosen system uses a different approved primer

Some products are designed to achieve compatibility through a nominated primer or alternative interface. Adding sand without manufacturer approval may introduce an unnecessary or incompatible layer.

2. The floor does not require moisture mitigation

Sound, suitably prepared concrete that satisfies the selected flooring system's requirements may be able to receive an appropriate conventional primer and levelling compound.

There is no reason to specify an epoxy moisture barrier solely because the contractor routinely uses one elsewhere.

3. The substrate is not included in the manufacturer's guidance

Old tiles, weak screeds, timber and mixed substrates cannot automatically be treated as standard concrete.

For example, ARDEX TB170 expressly excludes sand-cement screeds from its stated recommendations and identifies tile removal as preferable to levelling over existing tiled floors in the circumstances it addresses.

4. There is active water ingress

A moisture-control coating should not be assumed to repair a plumbing leak, uncontrolled seepage or hydrostatic pressure problem.

The underlying source of water must be investigated and the proposed system assessed for the actual exposure conditions.

5. The final floor has additional requirements

Engineered timber, resilient vinyl, carpet, epoxy and other finishes can have different requirements for moisture, surface strength, flatness and adhesive compatibility.

Approval of the moisture barrier and levelling interface does not automatically constitute approval of the complete finished-floor installation.

NSW Compliance: Document the Method Before It Becomes a Variation

In NSW, floor preparation is not simply a matter of product preference. The work may sit within a residential renovation contract, strata approval conditions or commercial construction documentation.

The NSW Government's guidance on residential building contracts sets out when written contracts are required and how variations to covered contracts must be documented.

If unexpected slab moisture leads to a revised system after the existing flooring has been removed, the contractor and owner should establish the additional scope, price and programme consequences before proceeding.

The change may involve more than adding a moisture-barrier product. Depending on the approved specification, it can alter substrate preparation, sand broadcasting, curing, cleaning and the date on which the levelling team can return.

There is also a work health and safety consideration.

Concrete grinding and handling certain silica-containing materials can expose workers to respirable crystalline silica if dust is generated and not adequately controlled.

SafeWork NSW guidance on crystalline silica outlines the importance of controlling dust-generating work and using appropriate work methods and equipment.

Sand-broadcast operations should therefore be planned with suitable material handling, housekeeping and dust controls, particularly during excess-sand removal.

The manufacturer's instruction to remove loose sand does not justify uncontrolled dry sweeping that creates airborne dust.

Four Questions Worth Asking Before Accepting the Quote

For owners, builders and property managers, the most useful questions are technical enough to expose an incomplete scope but straightforward enough to obtain clear written answers.

1. Which complete manufacturer-approved system is being installed? Ask for the moisture barrier, primer or bonding interface, levelling compound and applicable product documentation.
2. Is sand broadcasting required for this particular system? If yes, confirm the specified sand, application stage and cleaning requirements. If no, establish the approved alternative.
3. Who is responsible for approving the surface before levelling? Confirm whether the barrier contractor, levelling contractor or another appointed party will inspect and release the work.
4. Which stages are included in the price and programme? Check preparation, coatings, sand application, curing, cleaning, levelling and any anticipated return visits.

A competent quotation should make these matters understandable without requiring the buyer to become a flooring chemist.

Where a contractor proposes a different installation method from the published specification, written manufacturer guidance should support that decision.

The Real Risk Is an Unverified Interface Hidden Under a Perfect-Looking Floor

The sand broadcast used in some floor levelling systems is a small operation with a disproportionately important function.

It can determine whether the cementitious levelling layer receives the mechanical bonding surface required above a particular epoxy resin.

But it is not a universal procedure, and it should not be added, omitted or substituted without reference to the actual manufacturer-approved system.

For Sydney renovation projects, the strongest approach is to identify the substrate condition, select a compatible moisture-management and levelling system, specify every necessary interface and establish a documented handover before the pour.

The finished surface may eventually conceal the sand entirely. The decision to use it, and the evidence that it was installed correctly, should remain visible in the project records.

FLOOR PREPARATION | PROJECT DELIVERY | SYDNEY

Review the Preparation System Before the Pour

Planning flooring removal, concrete grinding, moisture management or floor levelling in Sydney? ELYMENT can help review preparation requirements, coordinate renovation stages and clarify the scope before installation begins.

Discuss Your Project

Technical Sources and Further Reading

• ARDEX Australia: Technical Bulletin TB170, Epoxy Priming Systems for ARDEX Levelling Compounds, 31 January 2025.
• ARDEX Australia: WPM300 HydrEpoxy Product Data Sheet.
• ARDEX Australia: Flooring Systems Technical Bulletin Library.
• NSW Government: Contracts for Residential Building Work.
• SafeWork NSW: Crystalline Silica Safety Guidance.

Related ELYMENT Articles

• Self-Levelling Compound Primer Guide: Concrete, Timber and Old Adhesive Floors Compared
• Can You Add Sand to Floor Levelling Compound? The Shortcut Sydney Owners Should Question
• Floor Levelling Sydney: Why a Moisture Reading Does Not Replace a Concrete pH Test

Technical note: Product specifications, substrate acceptance criteria and curing requirements can change. Confirm the current manufacturer documentation and suitability for the specific site before commencing work.