Concrete Repair
in St. Louis.

The Four-Front Attack on St. Louis Concrete

Freeze-thaw cycling is the most visible force. Water infiltrates concrete through surface cracks and the capillary pores of the paste matrix, freezes and expands, then thaws and contracts. Each cycle in a St. Louis winter slightly widens the crack and drives moisture deeper. A slab that was poured without cracks in 1985 in Tower Grove South or Kirkwood has been through forty Missouri winters since then. The crack patterns you see now are the result of all of them.

Road salt is the chemical force. MoDOT's deicing program on the major interstate routes and St. Louis County and city road crews on surface streets deposit sodium chloride and calcium chloride on garage floors across the metro every winter. Chloride ions migrate into the surface paste, accelerate concrete carbonation, and break down the binder that holds the aggregate together. The spalling and surface crumbling that results is a chemical degradation process, not just surface wear.

Summer vapor pressure is a factor unique to the St. Louis river valley location. High ambient humidity and moisture in the subgrade combine to drive moisture vapor upward through slabs from below, especially in older homes on native grade in the river bottom areas. A coating applied over a slab under active vapor pressure without addressing that pressure will delaminate from below as the vapor pushes against the coating-concrete interface.

Clay soil movement is the foundation variable. St. Louis's older residential neighborhoods sit on expansive clay subsoil that swells with spring moisture and contracts in summer drought. That seasonal differential movement has been working on residential slabs for decades in neighborhoods like the Hill, Dogtown, and Carondelet, producing diagonal cracking and in some cases measurable differential settlement across the slab plane.

Crack Assessment and Injection in St. Louis Slabs

The first step in concrete repair is accurate diagnosis. Not every crack is the same. A hairline crack in the surface paste layer that does not penetrate the full slab depth is a different repair from a structural crack that runs through a four-inch pour. Diagonal cracks from soil movement have different implications from shrinkage cracks from the original cure. We walk every inch of the floor, probe cracks, and evaluate the pattern before determining the repair approach.

Structural cracks that penetrate the slab depth are repaired by injection. We drill ports into the crack at intervals, then inject low-viscosity epoxy or polyurethane material under pressure from the deepest point up. The material fills the void, displaces any residual moisture, and bonds to both faces of the crack. When cured, the injected section is typically stronger in tension than the surrounding concrete. A surface filler applied over the same crack would mask it temporarily but would not prevent water infiltration or provide structural repair.

Spalling Repair and Salt Damage Restoration

Spalling repair starts with removing the degraded material. Concrete that has been chemically broken down by chloride exposure does not provide a sound bonding surface for a repair mortar. Applying mortar to friable, salt-damaged concrete is like painting over rust: the surface looks better temporarily but the bond fails at the degraded interface.

We use diamond grinding and, in deeper spalling cases, scarifying equipment to remove the degraded surface down to clean, structurally sound concrete. Once clean material is exposed, we apply repair mortars engineered to match the thermal expansion coefficient of standard residential concrete. A mismatched mortar that expands and contracts at a different rate from the surrounding slab will crack at its perimeter inside the first thermal cycle. Product compatibility is a specification decision, not a convenience choice.

After repair, the surface is re-profiled across the full floor area to create a consistent substrate for the coating. The finished prep surface behaves as a single continuous slab rather than a patchwork of original concrete, repair material, and injection fills.

Diamond Grinding and the Surface Profile Standard

Diamond grinding is not optional prep. It is the mechanical foundation that determines whether a coating stays or lifts. Concrete as it cures produces laitance on the surface, a thin layer of calcium carbonate paste with low tensile strength that is the most common point of early coating failure when prep is skipped or abbreviated. Diamond grinding removes laitance completely, opens the concrete pores for chemical adhesion, and creates the surface profile that gives the epoxy basecoat its mechanical grip.

For St. Louis slabs with prior sealers, oil contamination from vehicle parking, or deteriorated paint from previous coating attempts, diamond grinding is also the primary mechanism for removing those surface contaminants and reaching clean, bondable concrete beneath. Chemical strippers are often inadequate for heavily contaminated surfaces. The grinder reaches clean material regardless.

The surface profile produced by grinding is measured against ICRI standards. For standard residential applications, we target CSP-3, which provides the mechanical profile specified by the epoxy basecoat manufacturer for adhesion under residential thermal cycling. Matching the coating specification to the surface profile is not a detail, it is the engineering basis for the warranty we provide.

Free Concrete Assessment in St. Louis: What to Expect

The free assessment is a genuine evaluation of your concrete condition by a member of the local crew who has assessed dozens of St. Louis slabs in similar neighborhoods. We look at crack pattern and depth, spalling extent, surface contamination, moisture indicators, and any evidence of soil movement beneath the slab. We give you an honest account of what we find, including the rare cases where a floor has conditions that a surface coating cannot adequately address.

Most St. Louis slabs, even those with significant cracking and spalling, are good candidates for our system when proper repair and prep are executed. The assessment determines the repair scope and how it integrates with the coating project. Contact us to schedule your free concrete repair and assessment for your St. Louis, MO home. We serve both the city and county, from Soulard and Kirkwood to Chesterfield and O'Fallon.