Almost every structural slab, wall and column has steel in it, and that steel is what makes drilling reinforced concrete a different job from drilling plain mass concrete. The barrel will cut through rebar, but the decision of whether it should, and where, is the part that needs thinking about before anything spins.
This covers what the reinforcement means for a core, why scanning comes first, and how a clean core is achieved through steel.
Why rebar changes the job
Reinforcement is there to carry tension the concrete cannot. Cut the wrong bar in the wrong place and you weaken the very thing the slab or beam relies on. In a lightly loaded position, catching a stray bar with a core is a routine occurrence and the diamond segments deal with it. In a heavily stressed zone, over a support or in a post-tensioned member, the steel is not something to cut through casually.
So drilling reinforced concrete is really two questions. Can the barrel physically get through the steel here, and should the design allow steel to be cut in this position at all. The first is a matter of the right barrel and feed. The second is a structural question that belongs with the engineer, not the drill operator.
Concrete scanning before the barrel
You cannot see steel through concrete, so you find it first. Concrete scanning maps the reinforcement, along with conduit, drainage and any live services, before a barrel touches the face. The scan gives cover depth and bar spacing, which is enough to see whether a core can slip between bars or whether it will have to pass through them.
Where a core can be nudged a few centimetres to clear a main bar, the setting out is adjusted to suit. Where it cannot move, the scan is the evidence you take back to the engineer to agree whether cutting that steel is acceptable. Scanning first is far cheaper than a service strike or a structural bar cut nobody signed off. It is the same first step for drilling as for sawing, and it underpins the whole overview of the types of diamond drilling.
How a clean core is cut through steel
A clean core through reinforced concrete comes down to the barrel, the water and the feed. Barrels for reinforced work carry segments matched to cutting steel as well as aggregate, because a segment set for soft concrete will glaze and stop cutting the moment it hits a bar.
Water does the rest. It cools the segments as they work through the steel, flushes the swarf and slurry out of the cut, and binds the fines so respirable silica is not thrown into the air. Running through rebar dry is hard on the barrel and worse for dust, which is the balance set out in our guide to wet vs dry core drilling. Feed matters too: hit a bar and the sensible move is to ease the feed and let the segments do the work rather than force it, which is how you keep the bore true and the barrel alive.
When density decides diameter
In a heavily reinforced slab, the amount of steel can shape the diameter as much as the service does. A large single core through a dense mat of bars may cut more steel than the design will allow, in which case a formed opening with smaller overlapping cores can be kinder to the reinforcement. Getting the finished size right against the services and the fire-stopping is covered in choosing core drill diameters, and in reinforced concrete that choice and the rebar layout have to be read together.
Why diamond suits reinforced concrete
The reason diamond drilling is the method for reinforced concrete is that it is non-percussive. There is no hammering to shake the structure, crack a slab edge or disturb the bond between concrete and steel around the hole. The barrel grinds a smooth, round, square-edged bore straight through concrete and any rebar in its path, and the finish needs almost no making good.
That control is exactly why it works in occupied buildings, near slab edges and in thin sections where a breaker would risk real damage. Steel does not stop the method. It just decides where the hole is allowed to go.
Getting a reinforced core right
Drilling reinforced concrete well is a sequence: scan the position, agree with the engineer where steel can and cannot be cut, set out to clear the critical bars, then core wet with the right barrel and a steady feed. Skip the scan and you are drilling blind through something you cannot afford to get wrong.
If you have got cores to cut through a reinforced slab or wall and you want them scanned, agreed and cut clean, that is everyday diamond drilling Essex work for us. Send the drawings and the positions and we will scan before anything spins.