Can You Resurface a Cracked Pool Deck? Which Cracks a Coating Can Handle

Almost every pool deck in the Valley has cracks. Concrete shrinks as it cures, the ground under it shifts, and a slab that bakes in July sun and cools off on a January night is always moving a little. The real question is which kind of crack you have.

We install cool deck coatings and decorative overlays over existing concrete, and crack repair is part of nearly every job. This is how we sort cracks on an estimate and where a coating stops being the right answer, with the concrete industry’s published guidance linked in place.

The four kinds of cracks on a Phoenix pool deck

The American Concrete Institute’s crack report, ACI PRC-224.1, works in three steps: cause, evaluation, then repair. On a pool deck, the sorting comes down to four patterns.

1. Hairline and shrinkage cracks

These are the fine lines and spider-web patterns most decks have. Concrete loses water as it cures and shrinks, and a slab without enough control joints cracks on its own schedule; Concrete Network’s crack repair guide lists a lack of control joints as a common cause of cracking in slabs. Both sides of the crack sit level, and the crack is usually narrow. On a sound slab these are the cracks resurfacing handles best.

2. Joint cracks

Control joints are the straight saw-cut or tooled lines in the deck. They make the slab crack inside the joint instead of across a section, so a crack running down a joint is usually the joint doing its job. Many pool decks also have a joint where the deck meets the coping, so the pool shell and the deck can move separately. Fill a working joint solid and coat over it, and the movement it was absorbing tears through the new coating. On an estimate we look at whether cracks follow the joints or run across them, because cracking across the joints usually points to the slab, not the coating.

3. Widening cracks

A widening crack is one that is still moving. It gets longer or wider from season to season, usually across a section rather than along a joint. Common causes are soil settling under the slab, water from irrigation, a downspout, or a leak, and tree roots. Concrete Network notes that slabs can crack from subgrade settlement caused by poor compaction or soil erosion. Ground movement is also real at a larger scale here: the Arizona Geological Survey reports that subsidence and earth fissures affect more than 3,000 square miles of Arizona, including expanding areas of Phoenix. Most deck cracks are far more local, but a crack driven by moving ground keeps moving until the ground stops.

4. Offset cracks and heave

When one side of a crack sits higher than the other, the slab has already moved vertically: one section heaved up, or one sank. You can feel the lip with a bare foot. Offset cracks are trip hazards first, and the clearest sign that a coating alone is the wrong fix. Concrete Network’s resurfacing guide puts it plainly: “It is not feasible to resurface concrete that is heaving, has severe cracks, or is damaged due to freeze/thaw damage.”

A crack test you can do at home

You can sort most cracks yourself with a pencil, a credit card, a coin, and a phone camera.

Also watch where water goes after a storm: a section that holds a puddle beside a crack is telling you about the slab. Our monsoon drainage guide shows how to read it, and the five signs your pool deck needs resurfacing covers the surface problems that travel with cracks.

How cracks are repaired before a coating goes on

A coating hides a crack only as well as the crack was repaired underneath it. Here is the sequence from our resurfacing process.

• Diagnose first. At the estimate we sound the deck for hollow spots and check crack width and pattern. ACI’s field guide to crack repair (RAP-2) starts the same way: “Before any concrete is repaired, the cause of the damage must be assessed and the objective of the repair must be understood.”
• Open, clean, fill. Cracks are opened, cleaned, filled with a flexible repair compound, and feathered so they do not telegraph through the texture.
• Strip what is loose. Hollow and delaminated areas come off back to solid concrete. Coating over a hollow spot just moves the failure up a layer.
• Patch and level. Spalls and pits at the coping and skimmer are patched and leveled, and low spots are corrected where the slab allows.
• Coat the whole deck. Primer, texture, color, and sealer go over everything, so repairs disappear into one surface.

Why flexible? ACI’s RAP-2 bulletin is direct about the limits of a rigid fill: its gravity-fed resin method is meant “to seal cracks that are not moving—for example, shrinkage cracks, and settlement cracks that have stabilized,” and it is “not effective for repairing moving cracks.” For those, the bulletin says, “it is most often necessary to rout and seal the crack to create a joint capable of movement.” Concrete Network’s resurfacing guide makes the same point from the coating side: active cracks get filled “so they don’t mirror through to the overlay,” while small plastic-shrinkage and crazing cracks can be covered by the polymer prime coat and base coat.

If your deck has Keystone Kool Deck, or you want it, the rules are stricter. Genuine Kool Deck bonds only to bare, sound concrete. Mortex’s instructions for existing concrete call for removing existing toppings, and say: “Any major repairs of structural damage in the deck or cracks should be done well in advance of the PTA and topping application.” That is why already-coated decks usually get a texture coating instead. Our cool deck repair page covers what that looks like on a worn, cracked deck.

Why cracks can reappear through a new coating

This is the part a sales pitch skips. A coating is a few layers of coating on top of the concrete, not structure. If the slab under a repaired crack keeps moving, the crack can come back through the coating, from any contractor and with any product. The usual reasons:

• The ground is still moving. Settling soil, water, and roots do not stop because the surface looks new.
• A working joint was filled and coated over. The slab still moves at that joint, and the coating cracks along it.
• The crack was skimmed, not repaired. Filler over a dirty, unopened crack has nothing to bond to.
• Daily heat cycling. Concrete grows and shrinks with temperature. A fine line can show again at a repaired crack even when the slab is stable; that is usually cosmetic, and the crack can be filled and touched up.

A good repair keeps a stable crack hidden. It cannot hold a moving slab together, which is why, when we see signs of movement, we write it into your estimate instead of promising the crack is gone for good.

When to replace a section instead

Coating over a slab problem is money spent twice. Consider cutting out and repouring a section, or a full replacement instead of a resurface, when you see any of these:

• An offset at a crack that you can feel underfoot, or a lip a coin catches on.
• A section that rocks, sounds hollow underneath, or has broken into loose pieces.
• A section that has sunk or heaved so water now runs toward the house or pools against it.
• A crack your pencil marks show is still growing after the cause has been found and fixed.

Replacing one section is often far less work than a full tear-out. The section is saw-cut out, the cause underneath is dealt with, and new concrete is poured to grade; once it is ready, the whole deck can be coated so the new section does not stand out. Ask your coating installer how long the new concrete needs to cure before their system goes on; for genuine Kool Deck, Mortex’s existing-concrete instructions say the surface should preferably be 28 days old.

What the warranty covers on a cracked deck

Read any coating warranty for the word “crack.” Ours, in full, is on our warranty page and in Section 6 of our Terms of Service. In short:

• Term: two years, on all pool deck resurfacing and coating installation projects.
• Covered: defects in materials and workmanship under normal use and conditions, including peeling, flaking, or delamination of the coating we applied caused by material defects or workmanship errors.
• Not covered: structural movement, settling, or cracking of the concrete underneath, including cracks we flagged in your estimate.

Put simply: the warranty covers the coating we applied, not the slab under it. Hairline and surface cracks are routed and filled before we coat, and when we see signs of movement, we write it into the estimate. If a crack reopens because the slab moved, that is outside the warranty, and any repair is quoted like any other job: free, in writing, and measured from the actual surface. Be wary of any bid that promises cracks will never come back.

Ask every bidder which cracks they will repair and how, which they think are moving, and what their warranty says about cracks. Our guide to choosing a pool deck contractor in Phoenix has the full list. When you are ready, here is how we approach pool deck resurfacing in Phoenix.

Frequently asked questions

More answers in our full FAQ, or see cool deck repair.

Keystone Kool Deck is a trademark of Mortex Manufacturing Co., named here only to identify its published instructions. Master Pool Decks is independent and is not affiliated with, endorsed by, or a dealer for Mortex or any coating brand.