Stopping Concrete Cracks in Boston with Sika Injection
Cracks in concrete slabs, foundations, and walls demand different repair strategies depending on whether they're actively leaking or structurally compromised. Sika offers two injection chemistries: polyurethane for wet, moving cracks and epoxy for dry, load-bearing damage. We diagnose the crack, select the right Sika product, and inject to full depth. No guesswork, no failed repairs.
The most common mistake in crack injection is using the wrong chemistry. Polyurethane is hydrophilic; it reacts with water and expands to fill the crack, making it the only choice for active leaks where moisture is present during injection. Epoxy is a structural adhesive; it bonds the two sides of a crack permanently, restoring monolithic strength. Epoxy fails in wet conditions because water prevents proper cure and adhesion.
We begin every job by classifying the crack: Is water present? Is the crack moving or stable? Does it carry structural load? Once we know the answers, the chemistry choice is clear. Sika manufactures both in injection-grade formulations with the ports and equipment needed for controlled, full-depth delivery.
We examine the crack for water presence, movement, depth, and structural role. This assessment determines whether polyurethane or epoxy is the right choice and informs port spacing and injection pressure.
Prepare the crack surface
The crack is cleaned of loose material and debris. Injection ports are installed at engineered intervals along the crack length, and the surface between ports is sealed with paste to contain the injection material.
Inject the Sika product
Polyurethane or epoxy is injected through each port in sequence at controlled pressure, allowing the material to flow to full depth before advancing to the next port. Pressure is monitored to ensure complete fill.
Cure and finish
The material cures (polyurethane fast, epoxy over several days). Ports are removed, the surface is sealed with matching paste, and the repair is tested for proper fill and structural integrity.
For active leaks
Why Polyurethane Injection Stops Wet Cracks
A basement wall or foundation slab that is actively leaking cannot be repaired with epoxy. The water in the crack prevents epoxy from curing and bonding properly. Polyurethane, by contrast, is designed to react with water. The moisture in the crack triggers the polyurethane to expand and harden, filling the crack and stopping the leak. This is why polyurethane is the standard for any active water intrusion.
After polyurethane injection stops the leak, we can assess whether additional Sika waterproofing is needed for the broader wall or slab. For residential basements, see our basement waterproofing options. Coordinate with Sika repair mortars if surface restoration is needed after injection.
Polyurethane vs epoxy, active leaks, port spacing and structural restoration.
Polyurethane for active wet cracks (it reacts with water to expand and bond), epoxy for dormant dry cracks that need structural restoration (it bonds the crack sides permanently). The wrong chemistry fails immediately.
Yes, polyurethane is specifically designed for this. The water in the crack triggers the polyurethane reaction, the material expands to fill the crack, and the leak stops.
Yes, with epoxy. Properly injected epoxy restores the two sides of the crack to monolithic strength. The crack itself becomes structurally stronger than the surrounding concrete in many cases.
Based on crack width, depth, and the chosen chemistry's flow characteristics. Sika specifies port spacing per product; we follow the spec so material reaches full-depth without gaps.
Most residential crack injections are a single-visit job, a few hours from port install through cure. Large structural projects with many cracks stretch over days. The schedule is in the quote.
Polyurethane injection on an actively leaking basement crack. Water stopped during injection, dry for two years since. The right chemistry made the difference.
Q. Y5
Property Owner, Boston
★★★★★
Epoxy injection for structural restoration on a foundation crack. Test cores after cure showed the crack zone stronger than surrounding concrete. Real structural repair.
Y. Y5
Engineer, Cambridge
★★★★★
Multiple cracks across a structure, each classified properly and injected with the right chemistry. The discipline of product-per-crack-condition is rare and showed in the result.
Z. Y5
GC, Somerville
★★★★★
They diagnosed an injection that another contractor had failed on. Used the right Sika polyurethane this time; held through three winters. Crack chemistry matters.
X. Y5
Builder, Quincy
From the blog
Concrete Guides & Articles
Practical reading on planning, finishes and caring for concrete in Boston.
Describe the crack location and condition (active or dormant, wet or dry, structural or cosmetic), and we will recommend the matched Sika product and provide a written quote.
