Concrete Resurfacing ACT - Cost and Suitability Guide

What Concrete Resurfacing Costs in the ACT

Resurfacing means bonding a new surface to an existing concrete slab rather than removing it. The systems range from a spray on textured coating a couple of millimetres thick at $45 to $85 a square metre, through plain cementitious overlays at $55 to $95, to stencilled and stamped toppings at $70 to $130. All of them depend on the slab underneath, which is the point most quotes skate over.

The comparison that makes resurfacing attractive is against removal and replacement at $113 to $210 a square metre all up. On a 45 square metre Canberra driveway that is $2,475 to $5,850 for an overlay against $5,085 to $9,450 for a replacement, with the work finished in days rather than weeks. Where the slab is sound, that is a genuine saving rather than a compromise.

Where the slab is not sound, an overlay is money thrown after a problem. A topping is a few millimetres of material bonded to a surface, and it has no structural capacity of its own. It follows the slab. A crack that is still moving reappears through the new surface within a season. A section still settling continues to settle. A surface already delaminating carries the overlay away with it when it goes. Concrete driveway repairs in the ACT deal with those causes, and the order of operations matters.

The ACT position on approval works in resurfacing favour, which not everybody realises. A like for like replacement in plain or asphaltic concrete is generally exempt from driveway layout approval, and resurfacing that leaves the size, shape, location and surface type unchanged generally sits outside it too. Where a decorative topping changes the surface type on the verge portion, that is a different matter and the City Services application applies with a minimum of 15 working days.

Resurfacing Costs by System

Resurfacing systems differ mainly in thickness, and thickness is what decides both the price and how much the overlay can hide. A spray on textured coating is a couple of millimetres thick at $45 to $85 a square metre and conceals almost nothing. A plain cementitious overlay at $55 to $95 runs three to six millimetres and evens out minor surface variation. A stamped overlay at $85 to $130 runs eight to ten millimetres and can accommodate a little more. Even then the tolerance is a few millimetres rather than a level correction.

None of them has structural capacity, and that is the single fact to hold onto. A topping is bonded to the slab and behaves as part of its surface, so it inherits every movement, every crack and every void underneath. Thicker systems hide more surface imperfection and none of them bridge movement. Thickness buys concealment rather than strength. That distinction decides most resurfacing outcomes.

Preparation is the figure that moves a resurfacing quote from attractive to marginal and it is where the honest quotes separate from the optimistic ones. Grinding at $22 to $48 a square metre, crack preparation at $28 to $65 a lineal metre, stitching at $95 to $180 and patching of spalling, which is concrete flaking away from the surface, at $85 to $190 a square metre can together exceed the overlay itself. Ask for preparation as a separate line rather than folded into a rate. A rate with preparation inside it cannot be checked. Ask for the two separated.

Testing Whether the Slab Suits

Four checks decide whether resurfacing is sensible and none of them need a contractor. Tap across the surface with a hammer or the handle of a screwdriver and listen for a change in note, because a hollow sound means the top layer has already separated from the slab. Anything hollow has to come off rather than be covered. Covering it simply delays the failure. The hollow area then takes the new topping with it.

Look at the cracks with a coin for scale. Hairlines under about two millimetres with both sides level are shrinkage and are routed and filled before the overlay. Anything wider, or with one side sitting higher, means movement, and that has to be resolved first or it reappears through the new surface. Usually inside a single season. One Canberra winter is normally enough.

Check for settlement by sighting along the slab from a low angle or laying a long straight edge across it. A section that has dropped needs lifting at $120 to $280 a square metre before anything goes on top, because an overlay follows the level it finds rather than correcting it. That is the single most misunderstood thing about toppings. People expect a topping to correct what it is laid over. It does the opposite and reproduces it.

Look for oil, sealer and curing compound. Contamination prevents a bond, and a slab that has been sealed at some point in its life needs that sealer removed by grinding. In a garage, oil staining is the usual obstacle and it frequently goes deeper into the concrete than the surface suggests. A building inspection in the ACT is worth commissioning where several of these show up at once. At that point the slab itself is what needs assessing rather than the surface.

Where the checks raise doubts, the Territory framework offers two useful references. WorkSafe ACT publishes the work health and safety material covering the grinding and dust controls that preparation involves, and Access Canberra holds the licence register for the trades that are licensed in the ACT, which on a Canberra resurfacing job means the plumber or electrician rather than the applicator. Access Canberra cannot answer whether a slab suits, which remains a question of testing it.

Bond, Preparation and Why Overlays Lift

When a resurfacing job fails, the overlay lifts off the slab rather than cracking, and the cause is almost always bond. A topping has nothing holding it except its adhesion to the surface beneath, so that surface has to be clean, sound and mechanically keyed. All three, not two of the three. Any one missing and the bond is compromised. Preparation is where resurfacing jobs are won or lost.

Mechanical preparation means grinding or shot blasting at $22 to $48 a square metre to open the surface and give the topping something to grip. A smooth trowelled or burnished slab offers almost nothing to bond to. Laitance, which is the weak layer of fines that rises during finishing, has to be removed as part of that process.

Chemical contamination is the other half. Oil, grease, sealer, curing compound and sometimes old paint all prevent adhesion, and none of them are removed by a hose. Degreasing at $18 to $42 a square metre handles oil, and grinding handles sealer, but a slab that has been sealed repeatedly over decades may need more material taken off than expected. That shows up as a higher grinding figure. Old sealed slabs are the usual culprits.

The Canberra climate then tests whatever bond has been achieved. A marginal bond survives a mild autumn and fails over the first winter, because freeze and thaw cycling at the interface between the topping and the slab prises them apart. That is why a bond test at $280 to $650 before committing is proportionate rather than excessive on any sizeable job. The test costs a fraction of the overlay. It is also the only objective evidence available.

Cracks Under an Overlay

Every crack under a proposed overlay needs a decision, and the decision turns on whether it is still moving. A settled crack is routed out to a clean profile and filled with a flexible material at $28 to $65 a lineal metre, and the overlay goes over it with a reasonable chance of the line never reappearing. Routing gives the filler something to hold onto. A filler smeared over an unrouted crack holds nothing. Routing takes time and is not optional.

A moving crack is different and no overlay will hide it. Stitching at $95 to $180 a lineal metre sets bars across the crack to tie the two sides together, and where that succeeds in stopping the movement the overlay can proceed. Where the movement comes from ground conditions rather than from the slab, stitching treats a symptom.

On the reactive clay that covers much of the ACT, ground movement is the common cause rather than the unusual one. Sites are classified under AS 2870 from class A for stable sand and rock through S, M, H1, H2 and E for increasing clay reactivity to P for problem sites, and a slab on a reactive Canberra site moves seasonally with the soil beneath it. No surface treatment changes that. The movement comes from below rather than within. Engineering advice is the right next step.

The practical approach on a slab with a straight line crack running through several bays is to accept that the line will show through any overlay, and to decide whether that is tolerable. Where it is, an overlay with a control joint cut along the crack line turns an uncontrolled crack into a deliberate joint. Where it is not, replacement with a proper joint layout is the answer. A new slab is the only chance to fix the joint spacing. Spacing follows the site class under AS 2870.

Settlement and Levelling First

An overlay follows the level it finds. A slab with a section that has dropped twenty millimetres gets an overlay with a section that has dropped twenty millimetres, which is rarely what the owner had in mind. Levelling comes first or not at all. There is no third option. A thicker topping is not a levelling method.

Slab jacking at $120 to $280 a square metre lifts a sunken section by injecting material into the void beneath it, and polyurethane foam cures in minutes so the work does not hold up the programme. Where the void came from a finished event the lift is permanent. Where water is still running along the same path, the void returns and the overlay goes with it. Fix the water before the surface. Drainage correction runs $650 to $2,400.

A thicker overlay is sometimes proposed as a way to level a slab, and on small variations of a few millimetres that works. On real settlement it does not, because the topping would need to be thick enough to become a slab in its own right, and a thick unreinforced topping over a void cracks under vehicle load. Thickness is not a substitute for support. A topping is not a slab regardless of depth. Reinforcement is what makes a slab a slab.

Where settlement is extensive the arithmetic turns. Jacking at $120 to $280 a square metre plus an overlay at $55 to $130 approaches or exceeds removal and replacement at $113 to $210, with less certainty about the outcome. Concrete driveway repairs in the ACT and resurfacing are frequently quoted together for that reason, so the comparison can be made properly. Two quotes side by side is the useful arrangement.

Overlay Systems Compared

Most overlay products are proprietary systems rather than generic mixes, and that matters because the preparation, the primer, the application and the curing are specified by the manufacturer rather than by convention. A system applied outside its own instructions has no warranty behind it and often no performance either. Ask which system the quote assumes. The name is the answer, not a description.

Polymer modified cementitious overlays are the mainstream choice for driveways in the Territory. They go on at three to ten millimetres depending on the finish, take colour, and can be stencilled, stamped or trowelled smooth. They are also the systems with the most established track record in Canberra conditions. Track record matters in a freezing climate.

Micro toppings and skim coats are thinner again at one to three millimetres and suit interior or covered areas rather than a driveway that freezes. Polyurethane and epoxy coatings are a different category altogether, suited to garages and covered alfresco areas and not to exposed surfaces that see ultraviolet light all summer. Ultraviolet exposure breaks those products down. Keep them under cover.

Ask which system a quote uses by manufacturer name and whether the applicator is trained or accredited in it. Most manufacturers run accreditation and most will confirm it on a phone call. That one question separates a crew that applies a system as specified from one improvising with whatever is on the shelf. Accreditation is the distinguishing question.

Stencilled and Stamped Toppings

Stencilled concrete is the most common decorative resurfacing finish on Canberra driveways and it works differently from stamping. A paper or adhesive stencil is laid on the prepared slab, a coloured topping is sprayed or trowelled over it, and the stencil is lifted to leave the base colour showing through as the joint lines. At $70 to $120 a square metre it reads as paving at a fraction of the cost. It is the most popular decorative resurfacing finish here.

A stamped overlay at $85 to $130 presses a pattern into a thicker topping while it is still plastic, which gives genuine texture rather than a flat pattern. It carries the same timing constraint as stamping fresh concrete, since the topping has its own working window, and it needs the same specialist crew. Crew size decides how much area can be covered. Ask how many will be on site.

Both inherit the slab beneath them, and on a decorative finish that matters more because a reappearing crack is visible against a pattern in a way it is not on plain grey. Setting out the pattern so the joint lines relate to existing control joints is the detail that distinguishes a considered job, and it means any movement follows a line the pattern already contains. That turns a future crack into a joint. Set out beats hope on a decorative surface.

Sealing is part of both systems rather than an extra. The colour in a stencilled or stamped topping sits in the top few millimetres and the sealer is what holds it, so the Canberra resealing cycle of every two to three years applies in full. Stamped concrete in the ACT covers the same pattern question on a fresh slab. The pattern decisions are identical.

Spray On Coatings

A spray on textured coating is the thinnest and cheapest resurfacing option at $45 to $85 a square metre. A polymer modified cementitious material is sprayed on in two or three coats to a couple of millimetres, giving a uniform textured surface that takes colour and can be patterned with a stencil. It is the fastest of the systems to apply. Two or three coats and the job is done.

Its strengths are speed, cost and adding almost no height, which on a driveway with a tight garage threshold or a fixed verge level is a genuine advantage. A 45 square metre Canberra driveway can be sprayed in a day or two. Vehicle access returns within days rather than weeks. On a single crossing that is the deciding factor.

Its weakness is that two millimetres hides nothing. Every surface variation, every patched area and every crack line shows through, and the thinness means it is more vulnerable to freeze cycling than a thicker topping. In a Territory winter a spray coating on a driveway is working harder than the same product would in Sydney.

The practical application for a spray coating in Canberra is a sound slab with a tired surface where the owner wants a colour and texture change rather than a repair. On a slab with real defects it is the wrong product, and a quote proposing it over cracks and patches is proposing a short lived result. Two millimetres covers nothing structural. Every line underneath shows through.

Thickness, Levels and the Verge

Every overlay raises the surface and three places have to be checked before committing. The garage threshold is the first, because a door that cleared the old slab by eight millimetres does not clear a ten millimetre topping. The junction with a path or a step is the second. The verge is the third and it is the one with no flexibility at all.

Verge levels in the ACT are set to the City Services driveway standard and cannot be altered to suit a resurfacing job, so an overlay that carries across the boundary has to still meet the kerb and the footpath correctly. A lip at the footpath is both a trip hazard and a problem at the next inspection. Verge geometry is fixed rather than negotiable. City Services sets those levels.

The usual answer is to terminate the overlay at the property boundary with a neat edge at the existing control joint, which is also where the surface type changes in approval terms. That reads as a deliberate line rather than an interruption, and it keeps the verge in its original condition. That also sidesteps the approval question entirely. One decision solves two problems.

Where the whole crossing genuinely needs resurfacing, the thinner systems become more attractive for level reasons alone. A two to three millimetre spray coating affects the verge transition far less than a ten millimetre stamped topping, which is a design constraint rather than a preference. Thinner systems win on level grounds alone. Two millimetres against ten is a real difference at a threshold.

The City Services Exemption Position

The approval position works in resurfacing favour and repays a close reading. A like for like replacement in plain or asphaltic concrete is generally exempt from driveway layout approval, which is administered by ACT City Services as part of the driveway standard. Resurfacing that leaves the size, shape, location and surface type unchanged generally sits in the same position. Confirm rather than assume where the verge is involved.

Where the question arises is on surface type. A plain overlay on a plain concrete crossing does not change the surface type in any meaningful sense. A stencilled or stamped topping that makes the crossing read as paving may well do, and a prudent approach is to confirm the position rather than assume it. The application runs a minimum of 15 working days if it is required.

The simplest way to avoid the question entirely is to terminate the decorative finish at the property boundary, which is also the sensible answer on level grounds. The private portion carries whatever finish the owner wants and the verge stays as it is. Two surfaces, one boundary joint.

Where a crossing is being resurfaced across the verge, the other verge conditions still apply. Concrete work on the verge meets 32 MPa and a formwork clearance is a hold point before any pour, although a bonded topping rather than a new pour changes how that applies in practice. Confirming it with City Services before starting is a short conversation that prevents a long one. City Services will answer the question.

Licensing sits alongside the approval question in the Territory. Access Canberra administers construction occupation licences in the ACT and concreting is not among them, so on a Canberra resurfacing job there is no licence to verify. The occupations needing a licence are builder including owner builder, electrician, plumber, drainer and gasfitter, building surveyor, building assessor, gas appliance worker, works assessor and plumbing plan certifier. That leaves the ABN, the insurance, the system accreditation and completed work as the available evidence.

Freeze Cycling on a Thin Topping

Canberra is the coldest Australian capital and a thin overlay feels that more acutely than the slab beneath it. The airport records a July mean minimum of 0.1 degrees, a June minimum of 0.9 and an August minimum of 1.2, so freeze and thaw cycling runs across three months of each year. No other Australian capital does that to a driveway.

A topping has two vulnerable places. The surface itself, where water in the top millimetre or two freezes and lifts material away, and the bond line between the topping and the slab, where water that has worked its way in freezes and prises the two apart. The second is what causes an overlay to lift in sheets rather than erode gradually. The bond line is the real vulnerability.

Sealing addresses both and the interval in the Territory is every two to three years at $12 to $28 a square metre. The sealer keeps water out of the topping and therefore out of the bond line. A resurfaced driveway that is sealed on schedule lasts; one that is not goes through a pattern of surface loss and then lifting within five to eight years. Both stages are avoidable with sealing.

De icing salt is worth avoiding on any resurfaced Canberra driveway. Salt and some ice melt products attack cementitious surfaces and a two to ten millimetre topping has far less material to lose than a 100 millimetre slab. Sand gives grip without doing any of that. Keep a bucket by the door through winter.

Slip Resistance on a Resurfaced Driveway

Resurfacing changes the slip characteristics of a driveway and the change is not always in the right direction. A textured spray coating is generally better than the worn slab it replaced. A smooth trowelled overlay under a glossy sealer is generally worse, and on a sloping Canberra driveway that matters on a frosty morning. Slope, moisture and a smooth sealer together are the problem.

AS 4586 sets out the slip resistance classification for new pedestrian surface materials, which is the reference to quote. The practical measure on a resurfacing job is the anti slip additive mixed into the sealer at $3 to $8 a square metre, which should be specified at the outset on any driveway with a slope. Retrofitting costs roughly ten times as much.

Where a surface is already finished and too smooth, chemical treatment or a grit coating runs $35 to $85 a square metre. Non slip coatings and anti slip strips in the ACT cover that work, and it is a retrofit rather than a repair. Prevention at the first seal is far cheaper.

Sealing and the Maintenance Cycle

An overlay has to be sealed and the sealing is doing more work than it does on a plain slab. On plain concrete a sealer protects the surface. On a topping it also protects the bond line between the topping and the slab, which is the interface that determines whether the overlay stays attached. That makes the sealing cycle more important than on plain concrete.

The first application runs $12 to $28 a square metre and resealing runs the same, with a Canberra cycle of every two to three years. That interval is shorter than many manufacturers quote because their figures assume a milder climate, and treating the manufacturer number as an upper bound rather than a target is the sensible approach in the Territory. Manufacturer intervals assume a milder climate.

Budget the cycle into the original decision. On a 45 square metre driveway, resealing at $12 to $28 a square metre every two to three years is $540 to $1,260 a cycle. Across fifteen years that is $2,700 to $7,500, which is comparable to the saving resurfacing produced over replacement and is the figure most often left out of the comparison. Ask for it to be stated at quote stage.

Cleaning before each reseal is part of the cost at $6 to $14 a square metre and it is not optional, because sealing over a dirty surface traps the dirt permanently. Concrete and paver cleaning in the ACT and driveway cleaning and sealing are the services that keep a resurfaced driveway in condition. Both are cheaper than redoing the overlay.

When Replacement Is the Honest Answer

There is a point where resurfacing stops making sense and the signals are consistent. The slab has broken into independent pieces. Cracking is widespread and still moving. More than about a quarter of the surface sounds hollow. Settlement affects multiple areas. Or the required preparation is approaching the cost of replacement on its own.

That last one is the test that catches most borderline cases. Grinding at $22 to $48 a square metre, crack stitching at $95 to $180 a lineal metre, jacking at $120 to $280 a square metre and spall patching at $85 to $190 add up quickly, and once preparation plus overlay approaches $113 to $210 a square metre the comparison with replacement is no longer favourable. Price both totals rather than the rates.

Replacement also resets the things that cannot be fixed from above. A new slab gets the right thickness, the right strength, proper reinforcement, a sensible joint layout for the site class and a fall that drains. On a reactive Canberra site those five decisions determine how long it lasts, and an overlay inherits whatever the original had. Five decisions, none of which can be fixed from above.

The exemption position makes replacement less painful than it would be elsewhere. A like for like replacement in plain or asphaltic concrete is generally exempt from driveway layout approval, so choosing replacement over a marginal overlay does not add an approval delay unless something is also being changed. That makes replacement less painful here than elsewhere.

Timelines and the Canberra Window

Resurfacing is quick compared with replacement and the stages are short. Preparation and grinding take a day or two. Crack and spall repairs take another day with cure time. The overlay itself goes on in a day for most driveway sized areas. Sealing follows once the topping has cured, commonly a few days rather than the 28 a new slab needs.

Light foot traffic is usually possible within 24 hours of the topping going down and vehicle traffic within three to seven days depending on the system. That is substantially faster than the 28 days a new slab requires, and on a Canberra property with a single crossing it is one of the strongest practical arguments for resurfacing. Four weeks without a driveway is a long time.

The Territory climate constrains the window more than it does for a thick slab. Most overlay systems have minimum application temperatures around five to ten degrees and will not cure correctly below them, and a Canberra winter morning sits under that well past dawn. Frost on the slab rules out the day. October to November and March to April are the reliable months.

Rain is the other constraint and it is sharper on a topping than on a slab. A fresh overlay caught by rain before it has set is damaged rather than delayed, so a settled forecast matters. A crew that postpones on a doubtful day is protecting a result that cannot be repaired invisibly. A rained on topping is damaged rather than delayed.

Canberra District Pricing and Slab Age

Resurfacing viability across the ACT tracks the age and original quality of the slab far more than the suburb. A 1970s crossing poured thin and unmeshed is a poor candidate regardless of where it sits. A 1990s slab in sound condition is a good one. Age is a proxy for the original specification.

The districts fall into a pattern that is useful for budgeting. Inner Canberra brings the oldest slabs, routinely thin and often with tree root damage, where replacement is more often the answer. Woden Valley and Weston Creek bring sloping sites where drainage has eroded bases along the edges. Belconnen and Tuggeranong bring 1970s to 1990s slabs where resurfacing regularly does suit. Gungahlin and the Molonglo Valley bring current stock where a surface problem is more likely cosmetic than structural.

Access moves the figure at the margins across the ACT rather than at the centre. Grinding equipment and material have to reach the slab, so a narrow inner Canberra block or a steep Woden Valley site adds time. Rubbish removal across the Territory is a smaller item on resurfacing than on replacement, which is one of its quieter advantages, since grinding dust and packaging are the only waste rather than tonnes of broken concrete. That also means a smaller bin and a shorter job.

Silica and Dust Controls on Preparation

Grinding a slab back to a key is the most dust intensive operation in resurfacing and it releases respirable crystalline silica. The workplace exposure standard is an eight hour time weighted average of 0.05 milligrams per cubic metre, which is low enough that a short period of uncontrolled grinding exceeds it. The limit is a workplace standard rather than guidance.

The Work Health and Safety Regulation bans uncontrolled dry cutting of crystalline silica materials, and concrete falls inside that along with stone, masonry, brick and mortar. The order runs elimination first, then continuous water flow, then wet suppression with a second control, then on tool extraction with a second control, with respiratory protection last. A respirator backs up the controls instead of standing in for them.

On resurfacing there is a practical complication to weigh. Wet grinding produces slurry, and a slurry that is not contained reaches the Territory stormwater system from a Canberra driveway. On tool extraction with a vacuum avoids the slurry entirely and is the method most Canberra applicators use on a driveway for that reason. Work health and safety duties are administered by WorkSafe ACT and environmental protection through the ACT environment directorate.

The exposure prevention course has been mandatory since July 2023, monitoring falls due at least once a year and again on any change of control, and records stay on file for three decades. Monitoring measures exposure rather than reducing it. A homeowner can reasonably ask what the arrangement will be before grinding starts, since the equipment is visible from the kerb. Nobody needs technical knowledge to check it.

What to Look for in Resurfacing Quotes

A resurfacing quote that can be compared with another separates six items. The system, named by manufacturer with the thickness stated. The mechanical preparation method and area. Crack, spall and settlement preparation as separate figures with rates. The level implications at the threshold, path and verge. The sealing with the product and interval. And whether a bond test is included.

The system name is the item that reveals most. Overlay products are proprietary, with the preparation, primer and curing specified by the manufacturer, so a quote that says textured overlay without naming a product has committed to nothing. Ask whether the applicator is accredited in that system, since most manufacturers run accreditation and will confirm it. It is the single most useful question on this job.

Preparation belongs as provisional items with rates rather than as a fixed sum, because nobody can price it accurately before the slab has been tested and ground back. A quote with no preparation line at all has assumed a perfect slab, which on a Canberra driveway old enough to need resurfacing is an optimistic assumption.

Getting the Best Value from Resurfacing

The decision that determines whether resurfacing was good value is made before any product is chosen: honestly assessing the slab. Fifteen minutes with a hammer, a straight edge and a coin establishes whether the slab is a candidate, and a bond test at $280 to $650 settles it on anything sizeable. Resurfacing a sound slab is excellent value and resurfacing a failing one is money spent twice. The test is what tells you which situation you are in.

The second is addressing water before surface. Where drainage has eroded a base along one edge, redirecting the water at $280 to $850 costs a fraction of the overlay and determines whether it lasts. Landscaping in the ACT is often where a grading problem gets solved rather than in the concrete. Water first, surface second.

Budgeting the sealing honestly is third. At $12 to $28 a square metre every two to three years, a 45 square metre Canberra driveway costs $540 to $1,260 a cycle and $2,700 to $7,500 across fifteen years. That is comparable to the saving against replacement, so the two should be compared on whole of life rather than on install price. Fifteen years of resealing is a real number.

Bundling pays where a crew is coming anyway. Resurfacing a driveway, a path and a patio in one visit shares the preparation setup, the grinding equipment and the material order, and it guarantees the colour matches across all three. Patio and verandah work in the ACT commonly sits in the same programme. One setup across three areas beats three setups.

One last Territory specific point. Where a slab is genuinely finished, a like for like replacement in plain or asphaltic concrete is generally exempt from City Services driveway layout approval, so replacement is quicker in Canberra than the 15 working day approval path suggests. Concreting driveways in the ACT and driveway installation both operate under that exemption, which means choosing replacement over a marginal overlay costs time only where something is also being changed. That is worth knowing before settling for a marginal overlay.