Pickleball Court Paint Peeling and Blistering: What Is Causing It and What to Test Before You Recoat in Negros Oriental

A flake lifted with a screwdriver tells you more than the colour does: look at the underside. Illustrative photo.

Short answer: in AEDO's experience, a failing court coating is usually a slab, preparation or weather problem more often than a bad-paint problem (that is our observation, not a survey). The data sheets we read put the same conditions on the slab and the day: moisture limit, cure time, surface finish, temperature and humidity. In our judgement, round blisters point first at moisture moving up through the slab. Peeling in strips points at a coat that never bonded: a smooth or sealed concrete face, laitance left on, or the wrong product. Chalky dust points at the texture coat. Puddles are a levels problem, and rust-coloured stains can mean corroding steel, which is structural. Before you pay for another coat, tick what you see in the checker below. It ranks the likely causes, names the test to run next, and gives one verdict: test before you recoat, repair then recoat, or slab problem: get it assessed.

This one is written for owners in Negros Oriental, from a barangay or LGU court in Bais or Tanjay to a resort, school or private club in Dumaguete, Sibulan or Manjuyod, who either have a court that is already failing or are about to paint a basketball slab or a new pad. One honest limit first: AEDO builds only in Negros Oriental. Everywhere else in the Philippines we design, seal, review remotely and check milestones of a contractor you hire. We name no climate figures here; the sequence and weather side is in our court painting schedule guide, and the layers and quantities in our court paint types guide.

1. Read the Symptom

Start with what the failure looks like, because each pattern has a short list of usual suspects and a test that separates them. The last column says where the statement comes from, so you can tell sourced facts from AEDO judgement.

2. Moisture From Below and the Vapour Barrier

Concrete on the ground is never perfectly dry. Water from the subgrade, from a high water table or from a flooded pad moves up as vapour, and a coating film that does not let it out gets pushed off the slab. The American Concrete Institute's guide on slabs that receive moisture-sensitive coverings, ACI PRC-302.2-22 (first printed February 2023, replacing ACI 302.2R-06), says moisture-related problems with floor covering materials include blistering and delamination, and its scope names epoxy coatings and athletic flooring among the materials covered. It is written for floor coverings on slabs, mostly interior work, not for open-air court paint, so we use it for the mechanism and not as a court specification. We read the free preview of that guide (scope, contents and Chapter 1), not the paid body. What the preview does say is worth quoting in spirit: reaching a target moisture reading should not be the only test of a slab, because flatness, texture, cracking, curling, structural capacity, joints and whether the slab will stay dry matter too.

What the manufacturers set as the moisture limit

There is no single number. Each coating states its own limit, and the limits differ because the products differ. These are the ones we read:

Read the middle column twice. Two Nippon products from the same company differ (below 6% and below 4%), Sika asks below 4% by weight, and a damp-proof primer still insists on a slab free from rising damp. The takeaway is practical: ask the coating supplier for the moisture limit and the test method in writing before the slab is poured, because a barrier can only be laid before the pour. One more line from the Sika court sheet: its concrete-court preparation opens with "all concrete courts must have waterproof membrane" before the 28 days and the finish, and it adds an acrylic primer coat before the colour coats. It does not say what kind of membrane, so ask. Those four documents are all from outside the Philippines; we did not find a Philippine data sheet for a pickleball coating with these limits, and whether a given product is sold here is for the supplier to say.

The tests, and what each can and cannot tell you

• Plastic-sheet method, ASTM D4263. The ASTM page gives the scope as indicating the presence of capillary moisture in concrete before coating. Tnemec describes the 2005 edition as an 18 by 18 inch (457 by 457 mm) sheet taped down for at least 24 hours, then looking for darkening or moisture. KTA-Tator and DeFelsko describe the same 18 by 18 inch sheet left for a minimum of 16 hours (KTA-Tator adds that 22 to 26 hours, morning to morning, is ideal). Tnemec says the test does not quantify moisture and only picks up the upper part of the slab. Sika's primer data sheet asks for no rising moisture on a polyethylene-sheet test "according to ASTM" and gives no number. Sherwin-Williams describes a different protocol, a 2 by 2 foot sheet for 48 hours. So the sheet size and time vary with the document, from 16 to 48 hours: use the one your coating maker names.
• In-slab relative humidity probe, ASTM F2170. The ASTM page gives the scope as the quantitative determination of percent relative humidity in concrete slabs; Tnemec says the probe goes in at 40 percent of the slab depth. It measures the same quantity as the "85% RH" lines above, but Nippon's sheets cite BS 8204 for that figure, which we did not read, so do not assume the two methods give the same number.
• Calcium chloride test, ASTM F1869. The ASTM scope covers the rate of moisture vapour emitted from bare concrete floors, expressed as pounds over 1,000 square feet in 24 hours, and it says the result reflects the floor at the time of the test. It is written around floor coverings, and its scope says it is not to be used to evaluate moisture emissions over coatings on concrete.

We read the ASTM store pages (scope and summary only) and the three secondary descriptions; the standards themselves are paid, so the current edition's own wording on size and time is not confirmed. AEDO's "16 to 24 hours" sits inside that range (16 hours minimum per KTA-Tator and DeFelsko, 24 per Tnemec). Its 450 mm square is close to the 457 mm (18 in) sheet those pages give. We suggest the longer end, overnight, unless your coating maker names a time.

The vapour barrier under a new slab

The ASBA and USA Pickleball manual describes the barrier for post-tensioned concrete courts: a vapour retarder generally of a minimum of two layers of 6 mil polyethylene, laid in opposite directions, lapped and taped, taking care not to puncture it. It points to ASTM E1745 (a standard on water vapour retarders under slabs) and ACI 302.2R for more. The manual does not give a barrier spec for a reinforced slab. AEDO's Manjuyod slab is reinforced, and the job plan uses one 6 mil sheet on the gravel with the steel on wide-base plastic chairs (never rebar offcuts, which puncture it), 150 mm laps taped, turned up at the wall, and every hole patched before the pour. That is a design choice for that slab. For yours it is the designer's call, and it is a call made before the pour, not after the first blister.

AEDO's plan also says to pour straight onto the barrier with no sand blotter layer over it, citing ACI 302.2R. We could not confirm that from what we read (the free abstract, the contents and Chapter 1 only), and 302.2R-06 has since been replaced by PRC-302.2-22. We report it as AEDO practice and name what we did not read.

On an existing slab you cannot add one. The options are to stop the water at its source (fix the levels, drainage and fill: see our lot filling guide), to let the slab dry and prove it by test, or to ask the coating maker what moisture-tolerant system it supports. Sika's primer data sheet says that if moisture is above 4 percent by weight a cementitious system can go on as a temporary moisture barrier; Nippon's damp-proof primer is described as moisture-tolerant during application but still wants a slab free from rising damp. Those are product decisions with their own limits, not a repair you can improvise. If the real problem is water entering the wall or the base, see our damp wall and peeling paint guide, which says the same thing about walls: repainting over an active moisture source often peels again within a rainy season, in our experience. Our waterproofing guide prices flat roofs and exposed roof slabs, decks, gutters, tanks and pools, not ground-bearing court slabs, so do not read its rates across.

3. Too Early and Too Alkaline

The 28-day figure. Nippon's sport floor finish data sheet says new concrete must have cured at least 28 days, with a porous light-broom finish. Sika's Courtkote acrylic court coating data sheet says to allow new concrete to cure for 28 days. Those are the two sports-court documents we read, and AEDO's job plan uses the same figure, "28 days minimum". The manual gives a different shape for a post-tensioned slab: keep it moist for about seven days, then allow a further 21 to 38 days. Our concrete mix ratio guide asks for at least seven days of continuous curing, which agrees with the first part.

Time is not dryness. The manual's indoor chapter says concrete cures two ways, strength curing between 21 and 45 days and moisture curing that depends on conditions and is hard to gauge, so it is usually determined by testing. For indoor sports floors it asks for concrete in place at least 60 days and tested below the manufacturer's limit. That is an indoor-floor rule, not an outdoor acrylic one, but it shows why a calendar alone does not clear a slab. A slab on well-drained ground and a pad built up on fill over a wet site are not the same slab on day 28.

Alkalinity. Fresh cement is strongly alkaline. A resin supplier's leaflet (Synthomer) says Portland cement mixed with water reaches pH 13 to 14 and causes alkali burn and discolouration when painted. A Sherwin-Williams article on peeling concrete floors aims for a pH of 7.0 to 10.0 after cleaning and lists oil-based coats on bare, unetched, uncured concrete among seven causes of peeling. The manual's indoor chapter lists alkali among the bond-breakers a slab must be free of before a resilient athletic floor goes on, and the ACI preview lists a chapter on concrete pH testing, but we read no pH figure from either. AEDO's job plan says new concrete pH 12 to 13; we could not match that exact range to a source, so treat all of these as showing the direction, not as a limit. The limit that counts is the one on your coating's data sheet.

4. Slab Finish, Preparation and Sealers

This is where most "peeling in strips" starts. The data sheets are specific:

• Laitance and profile. Both epoxy primer data sheets ask for a clean substrate free of laitance (the weak cement-rich skin), prepared by blasting, scarifying or grinding, with a minimum compressive strength of 25 N/mm2 and a pull-off strength of 1.5 N/mm2. The surface profile guideline used to specify this, ICRI 310.2R, grades roughness from CSP 1 (nearly flat) to CSP 10; we read only its scope and the CSP description on DeFelsko's page, and the guideline is paid.
• Finish. Nippon's acrylic wants a porous light-broom finish (the manual says medium-broom below, so the roughness asked for differs by document), with the surface etched using a high-pressure water blaster and a hydrochloric acid solution (1 part acid to 10 parts water, at least 15 minutes) and rinsed. Sika's Courtkote says a wood float or broom finish and that under no circumstances should a steel trowel be used. The manual strongly recommends a medium-broom finish for the adhesion of an acrylic surface on the post-tensioned concrete it describes.
• Hardeners and curing compounds. Nippon says no curing membranes, hardeners, dryers or calcium chloride accelerators (its line is worded about the concrete mix). Sika's Courtkote says the concrete should be additive-free with no curing membrane. The manual says liquid curing agents are not recommended and only if compatible with the colour coat and the manufacturer's recommendations; its indoor chapter adds that sealers should not be used under a resilient athletic floor. Sika's epoxy primer asks for a substrate clean of coatings and surface treatments. Sherwin-Williams lists poor adhesion, which it says often occurs when hardeners are added to concrete, among its causes of peeling. None of the pages we read names a densifier by that word.

What that means for a polished slab. Our surface guide prices the system AEDO used in Manjuyod: a machine-troweled and polished slab, then an epoxy primer and rubberized top coats. A troweled or polished face is the opposite of the broom finish the acrylic data sheets ask for, and the primer data sheets ask for mechanical preparation. AEDO's own job plan says so too: tell the polishing subcontractor not to apply a densifier or hardener, because a densified surface will not take the primer, and either leave a lightly abraded finish or budget a light diamond grind before priming. Whether a polished face is acceptable for a given product is the coating maker's decision, so get it in writing for your product before you polish.

5. Weather on the Day

Each data sheet sets a window. Outside it you can get a sticky film, a film that blisters, or a coat that never bonds.

Two points follow from those lines. First, a slab sitting in strong sun can be well over the air temperature, and Nippon sets a 35 degrees C limit on the concrete, not the air. Second, the pin-hole note explains a blister that is not moisture from below at all: a primer put on while the slab warms up can trap air and blister the coat above it. Both are things an applicator can plan around with a thermometer and a hygrometer, and both are things you can ask to see in a daily log.

For a court in Negros Oriental the practical consequence is simple: the painting date is a weather decision, and the right contractor can tell you the limits for their product and what they do when it rains mid-coat. We deliberately print no rainfall or climate figures here. How the cure and recoat holds fit into a real programme, with PAGASA data, is in our painting schedule guide.

6. Wrong Product and Dusting

Wrong product. Sherwin-Williams puts unsuitable coating selection for the floor's wear and exposure at the top of its seven causes of peeling concrete. A sports-court product is made and tested for it: Nippon's sport floor finish says it is designed for sport courts and claims resistance to ponding water for 48 hours; Sika's Courtkote is sold as a hardcourt sports surfacing system. AEDO's own list of failure causes includes a wall or roof elastomeric used on a trafficked court. No standard we read says that, so treat it as AEDO field judgement. The same logic shows up in walls: our painting cost guide notes Boysen publishes its masonry putty for interior use only, and that using it outside is a common reason exterior repaints peel in sheets. The test is simple: read the can, then the data sheet's application areas. If neither says sports court or trafficked floor, ask why that product is on your slab.

Dusting. AEDO's Manjuyod plan says silica sand only in the final coat, over a smooth substrate, is the usual cause of first-season dusting, and says to consider a lighter silica loading in the first top coat as well as the working loading in the second. That is AEDO practice, not a published finding. For comparison, Nippon's Malaysian professional page describes its anti-slip epoxy hybrid system as applied with non-skid sand in the intermediate coat. If your court sheds sand, ask the applicator which coat carries it and how much, and compare against the supplier's sample board.

7. Cracks, Puddles, Rust, Salts and Fading

• Cracks. The manual says all courts will crack eventually, that fine cracks may be covered by recoating but most need a court contractor, that driveway crack fillers are not recommended, and that a repaired crack will eventually reappear. Nippon's sport finish data sheet says the same of hairline cracks: the finish hides them at first and they may reappear, and the coating will not solve expansion and contraction cracking. A crack with a height step, or one that keeps growing, is a slab question. See the cracks section of our surface guide and our crack repair cost guide.
• Puddles. The manual wants a hard-court fall of 0.83 percent (1:120) to 1.00 percent (1:100) and says less than 0.83 percent risks excessive water after rain. It defines a birdbath as standing water at least 1/16 inch deep after flooding and says to string-line it, then patch and level real low spots. Nippon claims 48-hour ponding resistance for its acrylic, so a puddle that lasts days is a levels problem a coat cannot fix.
• Rust. The manual warns that portable net metal can rust and stain the court. Rust stains that bleed from a crack, along the line of steel, or with spalling concrete point to corroding rebar, which is structural. Read our warning signs guide before anyone paints over it.
• White salts. The Concrete Masonry and Hardscapes Association, writing about masonry walls rather than slabs, says three things must be present: soluble salts, moisture to carry them to the surface, and a force such as evaporation or hydrostatic pressure to move it; remove one and it does not happen. It says most efflorescence comes off by dry brushing then flushing. If you see it, water is moving through that concrete, so the next coat would sit on a wet source.
• Fading and wear. The manual says all courts fade, wear shows first in the high-traffic areas, minor blemishes can be patched but lead to a speckled look, and a stain left in place can bleach the colour with no way to correct it. Patching a faded court over time leaves a patchy look; that is cosmetic, not a failure.

8. The Repair Route and Prevention

The order that saves money. Repainting over an unfixed cause repeats the spend. For scale, AEDO's Manjuyod contract paint line was PHP 78,158 on a 352.63 sqm pad, PHP 221.64 per sqm (already public in our surface guide). That is a contract line, not a recoat price, and we do not publish a repair price for failed courts; it only shows the size of money that is thrown away each time a coat goes over a cause nobody fixed.

1. Stop and read the failure. Photograph the worst patches and the underside of a lifted flake: wet, white, chalky, rusty or clean?
2. Test the slab, not the paint. Plastic-sheet test first, then RH or calcium chloride only if your coating data sheet sets that limit. A failed test sends you back to the water source, not to the painter.
3. Fix the cause. Levels and drainage for puddles; the slab and its supports for rust and settlement; mechanical preparation for bond failures.
4. Remove the failed film back to sound edges. The data sheets we read prepare by blasting, scarifying or grinding, not by painting over a loose film.
5. Patch and level. Flood-test the clean court again; patch compounds and crack fillers must suit your coating.
6. Recoat inside the weather window of your data sheet, with the log kept, and protect the cure from rain.

For a new court, close each cause before it happens. This list mixes sourced items with AEDO practice, marked as such:

1. Get the coating data sheet before the slab design is final, because the moisture limit and finish it asks for decide what happens before the pour (sourced: data sheets).
2. Decide the vapour barrier before the pour and protect it from punctures (manual for post-tensioned slabs; AEDO practice for reinforced).
3. Cure moist for about seven days with no curing compound unless the coating maker approves it (manual; Nippon; Sika).
4. Ask for a broom or other profile finish per the maker, and no densifier or hardener (data sheets; AEDO plan).
5. Wait at least 28 days and then prove dryness by the test the maker names (data sheets; days alone are not proof).
6. Fix the fall at 0.83 to 1.00 percent before the forms go in (manual).
7. Require a daily log of temperature, humidity, dew point and rain, and a sample board on your own slab (data sheets; AEDO practice).

9. AEDO's Manjuyod Rules: Sourced or Not

AEDO's job plan for a 2-court open court in Manjuyod, Negros Oriental, has its own list of working rules for the coating. We are not asking you to take them on trust. Here is each one against what we could read this session:

That job's coating results are not part of this article. The finish lines (slab, polish and paint) and their rates are in the surface guide.

10. Painting or Building in Negros Oriental

An open-air court takes sun and rain, so every point above is live: the barrier and the cure plan belong in the design, the weather limits belong in the contract, and the test belongs before the first coat. If you are in Dumaguete, Bais, Sibulan, Tanjay, Manjuyod or a neighbouring town and want one firm to take the court from slab to lines, that is what design-build is for, and construction from your plans covers a court you have already designed. Our Dumaguete and Bais pages describe the area. Our construction page lists a pickleball court in Manjuyod as work currently on site.

On the checking side, a Single Milestone Check from PHP 7,500 per visit is one site visit tied to a critical stage; for a court the stages that matter are before the pour (barrier laid and undamaged, chairs, levels) and before final payment (coating log, sample board). Our PHP 5,000 structural assessment lists foundation and settlement, columns, beams and slabs, and crack pattern and width in its scope, and the report is a structural finding. It does not list coating chemistry or moisture testing, so for a court slab we would confirm that a visit fits before you book. Outside Negros Oriental we design, seal and check remotely; we do not build there. See also what a structural assessment report contains and structural engineer fees.

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