Concrete coring leaves a hole—and that hole needs proper sealing or epoxy work to restore structural integrity and prevent water intrusion. Understanding what contractors should include in their scope protects both the concrete surface and your property from costly damage down the road.
What Happens After the Core is Cut
When a concrete coring contractor removes a cylindrical section—whether for plumbing, electrical, HVAC, or structural access—they're creating a void that exposes the interior concrete and rebar. This opening becomes a pathway for water, debris, and corrosive materials if left unsealed. The contractor's responsibility doesn't end at the saw; proper post-coring work is essential to protect your investment.
The depth and diameter of the core determines which sealing method makes sense. A 2-inch hole for a conduit might only need epoxy filler, while a large-diameter core for a mechanical sleeve often requires a structural epoxy or polyurethane system plus finishing work.
Epoxy vs. Polyurethane: Knowing the Difference
Epoxy is the standard choice for most coring jobs. It bonds well to concrete, cures hard, resists moisture, and typically costs $150–$400 per hole depending on diameter and depth. Two-part epoxy systems require proper mixing, surface prep, and cure time (usually 24–48 hours). Contractors mix resin and hardener on-site and inject or trowel it into the hole.
Polyurethane is tougher and more flexible—better for cores in high-movement areas or where vibration is present. It costs 20–30% more than epoxy but handles thermal cycling better and is less brittle. Some contractors prefer it near joints or in areas exposed to freeze-thaw cycles.
Both require a clean, dry hole. Contractors should blow out dust, remove loose concrete, and sometimes etch the surface for better adhesion. Skip this prep and the epoxy won't bond properly, leading to premature failure.
Contractor Scope: What to Require
Your coring contractor should include these steps in their quote:
- Hole cleaning: Remove all saw dust, loose concrete, and debris using compressed air and brushing
- Moisture check: Ensure the hole is dry (not freshly wet from cooling water used during the cut)
- Surface preparation: Light etching or scarification if specified by epoxy manufacturer
- Epoxy application: Mix and apply per manufacturer specs; some holes need multiple coats for deep cores
- Finishing: Trowel smooth, sand if needed, and match surrounding concrete color if aesthetic match is required
- Cure time: Contractor should note when the hole reaches full strength (typically 24–72 hours)
If the core involves rebar or structural elements, ask if the contractor is reinforcing the epoxy with fiberglass strands or rebar dowels. This is common for larger holes and adds $50–$150 per core.
Hidden Costs to Discuss Upfront
Contractors sometimes exclude sealing from the base coring price. Always confirm whether epoxy is included or bid separately. Typical breakdowns:
- Cutting only: $100–$250 per hole
- Cutting + standard epoxy sealing: $300–$500 per hole
- Cutting + structural epoxy reinforcement: $400–$700 per hole
Prices vary by region, concrete strength, and access. Thick industrial slabs cost more than standard walls. Multiple nearby cores are cheaper per hole since setup costs are shared.
Water intrusion or staining after coring often means the sealant failed—and who pays to fix it? Get this in writing. A reputable contractor stands behind their sealing work with a 2–5 year warranty.
Timeline Realities
Coring takes 1–3 hours per hole. Epoxy application adds 30–60 minutes per core. The curing period (24–72 hours minimum) means the hole can't handle load or water exposure immediately. Plan accordingly if the core is supporting equipment or in a wet area.
Finding the Right Contractor
Compare contractors on sealing scope, not just cutting price. A $150 savings on the cut means nothing if you're paying $500 to fix water damage a year later. Platforms like Mercoly make it easy to compare concrete cutting and coring providers side-by-side, review their sealing practices, and check warranties before booking.
Ask contractors for photos of previous sealed cores and ask how they handle aesthetic matching on exposed interior walls.
Frequently Asked Questions
Q: Can I seal a concrete core myself? A: Small diameter holes under 2 inches can be DIY with two-part epoxy and basic tools, but professional application ensures proper bonding and structural reliability, especially for larger holes or load-bearing areas.
Q: How long before the sealed core can hold weight or get wet? A: Most epoxy systems require 24–48 hours to cure fully, though initial set happens in 4–8 hours; check your contractor's specific product datasheet for exact timelines.
Q: Will epoxy sealing match my concrete color? A: Standard epoxy is gray or clear; ask your contractor about color-matched epoxy or tinted options if visual appearance matters on exposed surfaces.
Compare trusted concrete cutting contractors in your area and get detailed sealing quotes today.