In Queensland, a primer seal (primerseal) is bitumen sprayed onto a new road base and covered with small stone. It waterproofs the base and can carry controlled construction traffic until the asphalt goes on. A tack coat has no stone. It is a thin film of bitumen emulsion sprayed just before paving so the asphalt bonds to the layer below.
Updated 25 September 2026.
Staging the roads on a new estate? Send your plans for a quote. Based in Cooroy, working across the Sunshine Coast, Noosa and Gympie, plus Brisbane north, Moreton Bay, the Fraser Coast, Bundaberg, the North and South Burnett, Toowoomba and the Western Downs. See our service areas.
A primer seal is bitumen sprayed onto a new road base and covered with small stone. It sticks to and waterproofs the base and gives traffic a temporary running surface until the asphalt is laid. A tack coat has no stone. It is a thin spray of bitumen emulsion that bonds new asphalt to the surface beneath.
Names vary. Council documents still say primer seal (Western Downs, for example, calls for an “AMC4 7mm Primerseal” under asphalt on industrial streets), and TMR’s emulsion specification MRTS12 lists primerseals. TMR’s MRTS11 (July 2025) and Austroads Part 4K (2026) call a seal sprayed straight onto an unprimed base an initial seal, so search a specification for both terms.
| Prime | Primer seal (primerseal) | Tack coat | Seal coat (US usage) | |
|---|---|---|---|---|
| What it is | A primer sprayed onto the prepared base that soaks in and fills the surface pores | A sprayed bitumen seal covered with small stone, on a base that has not been primed | A thin spray of bitumen emulsion | A liquid coating spread over existing asphalt |
| Stone cover | No, unless the specification calls for prime cover material so traffic can use it | Yes | No | No |
| Goes onto | A new granular or stabilised base | A new base that has not been primed | A primer seal, an existing seal or asphalt, or between asphalt layers | Existing asphalt on car parks and driveways |
| Main job | Fills the surface pores of the base and gives the next layer something to bond to | Waterproofs the base and gives a temporary running surface | Bonds the new asphalt to the layer below | Protects old asphalt and improves its look |
| Carries traffic? | Not public traffic; only once dry, and its life under traffic is brief | Yes, controlled traffic, until the final surface | Not public traffic; only the paving trucks and equipment during paving | Used mainly on car parks and driveways, rarely on public roads (US) |
| When it goes down | Before a seal or asphalt | Can go down well before the asphalt on a staged estate | Just before paving; the emulsion must break before the asphalt is laid | As upkeep of old asphalt |
| Usually applied by | A bitumen sprayer | A bitumen sprayer | Usually part of the asphalt work | n/a: a North American commercial product |
| Rules to check | TMR MRTS11 (non-emulsion) or MRTS12 (emulsion); Austroads AGPT Part 4K | TMR MRTS11 or MRTS12; Austroads AGPT Part 4K | TMR MRTS30, clauses 7.1.9 and 8.9 | None for the US product; in Australian documents a seal coat usually means a sprayed seal layer |
Sources: TMR MRTS11 (July 2025), MRTS12 (November 2018) and MRTS30 (March 2024); Austroads Guide to Pavement Technology Part 4K (2026); Fraser Coast Regional Council’s development works policy for the Australian use of seal coat; U.S. Geological Survey for the US meaning of sealcoat (background only). Checked 25 September 2026.
A prime is a primer sprayed onto the prepared base, usually with no stone, that soaks in and fills the surface pores so the seal or asphalt above can bond. It is a preliminary treatment, not a finished road surface. A tack coat goes on later, just before paving, onto the primer seal, seal or asphalt, to bond the new asphalt layer to what is underneath. How a prime compares with a primer seal is covered on our page about primer seals.
From the bottom up: subgrade, sub-base and base course, then a prime or primer seal that waterproofs the base. Just before the asphalt, the surface is repaired, swept and tack coated. A tack coat also goes between asphalt layers, unless the lower one was laid that day or the day before, is clean and has carried only the paving train.
Fraser Coast Regional Council’s development works policy puts the core of it in one line: asphalt pavements “must be primed as for bitumen seals and tack coated immediately prior to laying asphalt”. The full stack, from the bottom:
For the sprayed step itself, see how a road or driveway is spray sealed.
TMR and Austroads both class a prime and an initial seal as the “initial treatments” for a new base, so the specification names one or the other. On TMR work, an unbound pavement to be surfaced with asphalt typically gets a single/single sprayed seal first to waterproof it. For which one suits a site, see our page on primer seals.
Under TMR’s asphalt specification, MRTS30, the tack coat goes onto a clean, dry surface free of loose material and must break and be dry to touch before paving. MRTS30 does not require it where the asphalt goes over asphalt or a sprayed seal that:
A primer seal that has carried construction traffic through an estate build does not meet those conditions, so expect a tack coat. Under open graded asphalt, TMR typically places a sprayed seal instead of a tack coat to waterproof the pavement. Project and council specifications can differ, so check the one for your job.
TMR expects the tack coat to give a strong bond both to the pavement below and between asphalt layers. Asphalt used only by the paving train can be lightly trafficked without a fresh tack coat, but a layer that has been open to general traffic or wider construction access would typically need one. So if an estate street gets its asphalt base course early and the wearing course later, allow for a second tack coat.
No. In North America, sealcoat is a black liquid coating spread over existing asphalt car parks and driveways to protect them and improve their look. A tack coat is a bonding film sprayed under new asphalt. In Queensland, a seal is a thin layer of sprayed bitumen with stone worked into it, laid as a running surface.
| Term | What it means |
|---|---|
| Tack coat | A thin spray of bitumen emulsion that bonds new asphalt to the layer below (TMR MRTS30) |
| Seal, or sprayed seal | Binder sprayed and then covered with a layer of stone; New Zealand calls it chipseal (Austroads Part 4K) |
| Seal coat, in an Australian document | Usually a sprayed seal layer (a coat of the seal): Fraser Coast’s policy describes a bitumen seal as “a prime coat and two seal coats”, and Austroads refers to “seal coat binder” |
| Sealcoat, in North America | A liquid coating over existing asphalt, sold mainly for car parks and driveways and rarely used on public roads (USGS) |
So a Queensland specification that mentions a seal or a seal coat is usually talking about a sprayed seal, not a US-style coating, and neither does a tack coat’s job. Sprayed seals as a finished surface are covered under bitumen spray sealing.
Without a tack coat, or with a patchy one, new asphalt may not bond properly to the surface below. ARRB research for Main Roads Western Australia notes that poor bond between layers can significantly reduce a pavement’s ability to carry traffic and shorten its life. Main Roads WA also worries that poor bond between deeper layers may mean costly rehabilitation.
The bond depends on the surface texture and condition, trafficking, the tack coat type and rate, the asphalt mix, temperature, emulsion curing time and contamination. The mistakes to watch for:
A primer seal can go down once the road base passes inspection (Fraser Coast, for example, requires a pre-prime inspection). It waterproofs the base and can carry controlled construction traffic, including traffic for later stages, while the asphalt waits. Before the asphalt, it is inspected, repaired, swept and tack coated. The council conditions and the specification set the hold points.
Austroads and TMR point to four reasons an initial seal suits a staged job:
The Sunshine Coast development works policy plans for staged traffic too: it requires the pavement design to allow for construction traffic from later stages that will use roads built in earlier stages, or the road to be rebuilt before the works are accepted off maintenance.
How long a primer seal must cure before it is covered depends on the binder and its cutter oil content, the weather, the traffic and the stone size. Our primer seals page covers the treatment itself.
| Stage | Usually done by |
|---|---|
| Base construction, compaction and testing | As the development contract sets out, with council inspections before priming and paving |
| Prime or primer seal | A bitumen spraying contractor. Cuzkell’s part: primes and primer seals |
| Construction-traffic period and repairs to the primer seal | As the contract and council conditions set out |
| Sweep and tack coat | Usually part of the asphalt work |
| Asphalt base course and wearing course | The asphalt contractor |
| Two-coat sprayed seal instead of asphalt, where the council accepts it | A bitumen spraying contractor |
The MRTS30 weather rule for the tack coat can hold up the asphalt stage even when the primer seal is ready: no tack coat or asphalt on a wet surface or when rain is imminent. Spraying has its own limits; see weather limits for spray sealing.
The councils checked here set road surfacing for new estates in their planning scheme policies, and the rules differ. Several call for a prime or primer seal under the asphalt; some accept a two-coat sprayed seal on rural or residential streets. Read the current document for your council area before pricing or programming the work.
| Council area | Document | What it says |
|---|---|---|
| South East Queensland (ShapingSEQ 2023) | ||
| Sunshine Coast Council | Sunshine Coast Planning Scheme 2014, SC6.14 Planning scheme policy for development works (a new scheme is being prepared) | Asphalt streets and roads underlaid with a 7 mm single seal (C170); sprayed seals only to match existing rural works; pavement design allows for construction traffic across stages |
| Noosa Shire Council | Noosa Plan 2020, SC6.7 PSP6 Engineering Design Standards | Asphalt surfacing required in urban areas; testing, supply and laying to TMR specifications |
| City of Moreton Bay | MBRC Planning Scheme, Planning scheme policy: Integrated design, Appendix A (Streets, Roads & Utilities) | Surfacing clause not checked; the council resolved in January 2026 to replace the scheme |
| Brisbane City Council (north side) | Brisbane City Plan 2014: Infrastructure design planning scheme policy; Brisbane Standard Drawings; Reference specifications for engineering work | Surfacing clauses not checked |
| Toowoomba Regional Council (urban extent only in SEQ) | Toowoomba Regional Planning Scheme, SC6.2 PSP No. 2 Engineering Standards, Roads and Drainage Infrastructure | No asphalt until the RPEQ and council have inspected the base; primed with AMC4 and 10 mm cover aggregate before asphalt; two coats of seal on rural roads |
| Outside South East Queensland | ||
| Gympie Regional Council | Gympie Regional Council Planning Scheme 2013 (Version 4.0), SC6.1 PSP 1 Development Standards | Residential pavements fully primed before at least 30 mm of TMR-specification asphalt; rural and rural residential two-coat chip sealed; spray sheets in the as-constructed documents |
| Fraser Coast Regional Council | Fraser Coast Planning Scheme 2014, SC6.3 Planning scheme policy for development works | Asphalt pavements primed as for bitumen seals and tack coated immediately before the asphalt; a bitumen seal is a prime and two seal coats; pre-prime inspection |
| Bundaberg Regional Council | Bundaberg Regional Council Planning Scheme 2015, Schedule 6.3 Planning scheme policy for development works | Surfacing clause not checked |
| South Burnett Regional Council | South Burnett Regional Council Planning Scheme 2017 (Version 2.0), SC6.2 PSP1 Design and Construction Standards | Surfacing clause not checked |
| Western Downs Regional Council | Western Downs Planning Scheme, SC6.2 Planning scheme policy 1, Design and construction standards | Urban and rural residential streets: “Prime & 2 coat seal or Primer Seal & Seal”; industrial streets (access and collector): asphalt over an AMC4 7 mm primerseal |
| All areas | ||
| IPWEA | IPWEA standard drawings, where a council calls them up | Noosa and South Burnett refer to them for some items; no IPWEA surfacing rule is stated here |
| TMR | Estate road works on a state-controlled road | TMR approval is needed as well as the council’s, and the works are built to TMR standards |
Checked 25 September 2026; confirm the current version at design time. Regions follow ShapingSEQ 2023, Map 3.
Councils differ. The Sunshine Coast, Noosa and Gympie documents put asphalt on urban or residential streets, and the Sunshine Coast, Toowoomba, Gympie and Fraser Coast documents call for a seal or prime under the asphalt. A sprayed seal as the finished surface appears mainly on rural roads: two-coat chip seals in Gympie’s rural and rural residential areas, two coats of seal on Toowoomba’s rural roads, and a two-coat seal on Fraser Coast major rural roads with council approval. Western Downs goes further and specifies spray-sealed urban and rural residential streets.
Send the civil drawings, the pavement and surfacing specification, the council conditions, the areas and staging dates, and site access details. For sprayed seals generally, Austroads points to two cost drivers: the treatment and binder specified, and traffic management. This guide gives no prices.
The quote will also ask for the other details on the list above, such as the area in each stage and when each base will be ready. To send plans, contact us or email admin@cuzkell.com.au.
Not with public traffic. On TMR works a tack-coated surface is not opened to public traffic, and the tack coat must be intact when paving starts. The trucks and paving equipment do run over it during paving, which is why MRTS30 asks for an emulsion grade with minimal pick-up on truck tyres and paving equipment. If a road has to carry traffic before the asphalt, that is a job for primer seals.
There is no fixed figure. TMR says the time between spraying the tack coat and laying the asphalt varies with the weather and the grade of emulsion. The test is its condition: the emulsion must break and be dry to touch before paving. TMR also rules out tack coat on a wet surface or when rain is imminent. For where the tack coat fits in an estate program, see how surfacing is staged on a new estate road.
On a staged estate, usually yes. TMR’s MRTS30 does not require it over asphalt or a sprayed seal placed that day or the day before, untrafficked and clean. A primer seal that has carried construction traffic does not qualify, and Fraser Coast’s policy asks for pavements to be tack coated immediately before the asphalt. See what happens if you don’t use a tack coat.
Not in Australian sprayed seal terms. Austroads uses “bond coat” for the bitumen sprayed onto a pavement to hold the fabric in a geotextile reinforced seal. TMR’s asphalt specification, MRTS30, calls the bonding layer under asphalt a tack coat. If a document you are working to says “bond coat”, check which layer it means. A geotextile reinforced seal is a type of sprayed seal (Austroads Part 4K). For other terms that get mixed up, see is seal coat the same as tack coat.
The project specification sets it. For TMR works, MRTS30 clause 8.9 sets 0.10 to 0.30 L/m² of residual binder at 15°C, doubled at joints, with the low end over new asphalt and the high end over oxidised or milled surfaces; the contractor nominates the emulsion grade and rate in its quality plan. Council and project specifications can set other figures. The primer seal underneath has its own spray rates, which Fraser Coast, for example, approves before priming; see our page on primer seals.
A prime coat is a primer sprayed onto a new base, usually without stone, that soaks in and fills the surface pores. A tack coat is a thin spray of bitumen emulsion that bonds new asphalt to the surface below. “Seal coat” means a coating over old asphalt in North America, but in an Australian specification it usually means a sprayed seal layer, as in Fraser Coast’s “a prime coat and two seal coats”. See the comparison table above.
Several council documents call for a sprayed seal or prime under the asphalt. The Sunshine Coast requires a 7 mm single seal under asphalt streets; Toowoomba, a prime with 10 mm cover aggregate; Gympie and Fraser Coast, a primed pavement. Western Downs’ standards, by contrast, specify spray-sealed urban residential streets. Check the current document for your council area, and see our service areas for where we work.
All checked 25 September 2026.
About this guide
Prepared by Cuzkell Pty Ltd, a bitumen spray sealing contractor based in Cooroy that provides primes and primer seals. The rules quoted come from TMR, Austroads and council documents; your project’s specification and council conditions govern.
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