Concrete spalling is what happens when the surface layer of a concrete slab breaks away in flakes, chips, or larger sections, leaving a rough, pitted, or cratered surface behind. It's one of the most common concrete problems in Las Vegas and one of the most misunderstood in terms of what causes it and what actually fixes it.
A lot of homeowners see spalled concrete and reach for a bag of concrete patch from the hardware store. Sometimes that works. Often it doesn't, and a failed repair is more noticeable than the original spalling was. Understanding why spalling happens and what a proper repair involves makes the difference between a fix that holds and one that fails within a season.
What Causes Concrete Spalling
Spalling doesn't happen randomly. It has causes and understanding them matters because in some cases the cause is still active and needs to be addressed before any repair can be expected to hold.
Freeze-thaw damage is the most common cause nationally but less relevant in Las Vegas where hard freezes are rare. When it does occur here, it typically affects surfaces that stayed wet for extended periods during the occasional cold spell.
Corrosion of embedded rebar is a serious spalling cause that homeowners often don't recognize. When moisture penetrates to rebar that has inadequate concrete cover, the rebar corrodes and the expanding rust pushes outward against the surrounding concrete. The concrete breaks away in a pattern that follows the rebar layout. Spalling from rebar corrosion is structural in nature and a sign that the concrete itself may be compromised. Patching the surface without addressing the corroding rebar underneath does not fix the problem.
Poor curing during original placement produces a surface layer that's weaker than the concrete below. In Las Vegas summer conditions where rapid surface drying is a constant challenge, poorly cured concrete develops a surface layer that's prone to flaking and scaling. This is one of the more common spalling causes in the Las Vegas market.
Delamination of the surface layer from the concrete below can produce spalling-like symptoms. This happens when the concrete was finished while bleed water was still present on the surface, sealing the surface layer and trapping moisture below. The weakened bond between the surface layer and the slab below eventually allows the surface to break away.
Chemical attack from pool chemicals, fertilizers, de-icing salts, and similar substances can degrade the concrete surface over time. Pool deck spalling near the waterline is sometimes related to pool chemical exposure accelerating surface deterioration.
Age and weathering eventually affect any concrete surface. Las Vegas UV exposure, temperature cycling, and occasional moisture events accelerate normal aging. Older concrete that has never been sealed or maintained eventually reaches the point where the surface layer has weathered beyond the point of simple maintenance.
Assessing the Damage Before You Start
Not all spalling is the same and not all of it calls for the same repair approach. Taking the time to honestly assess the damage before starting saves the frustration of applying a repair that isn't matched to the actual problem.
Depth of damage. Surface spalling that's limited to the top quarter inch or so is typically addressed with surface repair products and overlays. Deeper damage that extends an inch or more into the slab may require more substantial repair approaches.
Extent of damage. A few isolated spalled areas on an otherwise sound slab can be spot-repaired. A slab where a significant percentage of the surface is spalled or at risk of spalling is a candidate for full surface overlay rather than multiple spot repairs.
Active rebar corrosion. If the spalling pattern follows a grid or linear pattern that could indicate rebar below, or if you can see rust staining in the spalled area, rebar corrosion may be the cause. Probe the damaged area carefully. If the rebar is exposed and actively corroding, the repair needs to include treating the rebar and providing adequate cover in the repaired section, not just filling the cavity.
Structural integrity of surrounding concrete. Tap the concrete around the spalled area with a hard object. A solid sound indicates sound concrete. A hollow sound indicates delamination — the surface layer has separated from the slab below even if it hasn't broken away yet. Delaminated areas need to be removed before repair, not patched over.
Cause identification. If the cause is still active — ongoing moisture intrusion, continuing rebar corrosion, chemical exposure — the repair needs to address the cause as well as the surface damage. A cosmetic repair over an active cause will fail.
Choosing the Right Repair Approach
Based on the assessment, here are the main repair approaches and when each is appropriate.
Spot Repair with Repair Mortar
For isolated areas of spalling that are limited to the surface layer, a polymer-modified repair mortar is the standard approach. These products are specifically formulated to bond to existing concrete, accommodate some differential movement between the patch and the surrounding slab, and accept finishing and sealing.
The critical steps for a successful spot repair:
Remove all loose, delaminated, and unsound material from the damaged area. Don't just fill over the top of loose material — it needs to come out. Use a cold chisel, angle grinder, or rotary hammer to remove concrete until you reach sound material.
Saw-cut or grind a defined edge around the repair area rather than feathering it to zero thickness at the edges. Repair products need a minimum thickness to bond and cure correctly. A saw-cut edge creates a defined boundary and ensures adequate thickness at the perimeter of the patch.
Clean the repair area thoroughly. Remove all dust and debris. The repair mortar needs to bond to clean, sound concrete.
Apply a bonding agent or primer appropriate for the repair product being used. This step is often skipped and its omission is a frequent cause of patch delamination.
Mix and apply the repair mortar according to the manufacturer's instructions. Work it firmly into the repair area and finish it to match the surrounding surface texture as closely as possible.
Allow to cure fully before applying sealer or returning the surface to use.
Full Surface Overlay
When spot repairs would cover a significant portion of the surface area, when the existing surface has widespread deterioration, or when the goal is a uniform finished appearance that spot repairs can't achieve, a full surface overlay is the more practical approach.
An overlay applied over a properly prepared surface covers all of the damage uniformly and creates a fresh surface that can be finished, stained, or sealed to any desired specification. The result looks better than a surface with multiple visible spot repairs and in many cases is a more economical solution when the scope of damage is widespread.
The preparation requirements for an overlay are the same as for a new overlay application on any surface: remove all loose and failing material, profile the surface mechanically, repair any significant cracks or deep damage before the overlay goes down, and prime correctly.
See our overlay and repair products here.
Resurfacing Systems
For pool decks and exterior surfaces where the goal is both repair and decorative improvement, a full resurfacing system that includes crack repair, surface preparation, overlay application, and sealing addresses both the repair need and the appearance goal in a single project.
This is often the most cost-effective approach for a Las Vegas pool deck that has scattered spalling, surface wear, and an outdated appearance. Doing the repair and the upgrade at the same time, with products specifically formulated for the application, produces a result that's better than either a repair alone or a cosmetic overlay over inadequate surface preparation.
Application in Las Vegas Conditions
Repair work in Las Vegas heat has the same timing considerations as any other concrete product application. Most repair mortars and overlay products have upper application temperature limits. Applying them to a surface that's been in direct sun in summer means working with a substrate that can exceed those limits.
Early morning application, shading the work area if possible, and pre-cooling the substrate with water are all practical steps for repair work in Las Vegas summer conditions. Allow the surface to dry after any wetting before applying repair products — most require a dry substrate.
Working time is shorter than the product label suggests in hot conditions. Mix only what can be placed and finished within the working time adjusted for actual temperature. A batch of repair mortar that sets up before it's placed is wasted material and a delay.
Sealing After Repair
A repaired concrete surface needs sealing. The repair area has fresh concrete surfaces that are more porous than the surrounding weathered concrete and will accept moisture more readily if left unsealed.
Sealing the repair area along with the surrounding surface creates a uniform protective barrier. If you're doing a spot repair on a surface that already has a sealer, the entire surface will likely need to be resealed to avoid a visible difference between the new sealer over the patch and the existing sealer on the surrounding concrete.
Choose a sealer appropriate for the environment and the surface type. For Las Vegas outdoor concrete, UV-stable sealer is not optional.
See our sealer selection here.
When to Call a Professional
DIY concrete repair is appropriate for isolated, surface-level spalling on a structurally sound slab. It's not appropriate when:
The cause of the spalling is active rebar corrosion that needs structural assessment. The scope of damage is extensive enough that a full resurfacing project is warranted. The surface is on an elevated deck or other location where structural integrity questions are real. The repair needs to be essentially invisible and the surrounding surface is decorative.
In those situations, a professional assessment and repair is the right approach. The cost of doing it correctly is always less than the cost of doing it incorrectly and having to address the failure.
If you're not sure which category your repair falls into, bring photos to either DCS location. We'll look at what you've got and give you a straight answer about what the repair actually requires.
South Las Vegas: 4125 Wagon Trail Ave, Las Vegas, NV 89118
North Las Vegas: 4601 E Cheyenne Ave Ste 107, Las Vegas, NV 89115
Phone: (702) 749-6318
Or reach out through our contact page and we'll get back to you.
Jose Argueta
Owner of Decorative Concrete Supply. US Marine Corps veteran with 30+ years in the decorative concrete industry in Las Vegas, NV.