What's the Difference Between Concrete Cutting and Concrete Breaking?

Both remove concrete. That is where the similarity ends. Breaking is percussive. A hydraulic or pneumatic tool puts impact energy into the slab until it fractures. Cutting is abrasive and continuous. A diamond blade or wire grinds out a narrow kerf and puts almost no impact energy into anything around it. Everything else follows from that. Concrete fails where it is weakest, not where you aimed, so a breaker takes material beyond your line. A saw leaves the line where you put it.

At Shepherd and Sons the choice between the two comes up on nearly every job, on airfields, live carriageway, ports and occupied buildings alike. It is usually settled before anyone reaches site, because it decides the plant, the programme and who has to sign it off. This article covers what that energy difference actually decides. Whether the surrounding slab survives, whether you can work near live services, what the building next door has to put up with, and what each method costs. It also covers stitch drilling, which is the answer when breaking is banned and a saw cannot reach.

A breaker drives a chisel into the concrete at high frequency. Each blow sends a stress wave through the material. The concrete then fails in tension at its weakest plane, and that plane can sit a long way from the chisel point. Micro-cracking runs further again, and it is invisible. That is the part people miss. Visible spalling stops somewhere. The damaged zone carries on past it.

A diamond blade hits nothing. The segments abrade a narrow kerf, cooled and flushed by a continuous water feed. How narrow depends on the blade, from around 3mm on a fine one up to about 12mm on a wide blade meant for fast bulk cutting. The energy goes into removing the material inside the kerf, and into the water. Very little of it travels sideways. That makes concrete cutting a geometry decision rather than a demolition one. You choose a line and the cut arrives on it. The methods themselves, and which one suits which cut, are set out in what is concrete cutting.

This is the difference that costs the most money, and it is nearly always found late. Take a failed bay in an industrial floor or on port hardstanding. Industrial slabs usually run 150mm to 250mm thick. Port hardstanding is more like 250mm to 400mm. The specification says replace one bay.

Break the perimeter out and look at what you are left with. The edge is ragged, undercut in places, and cracked back into the concrete you meant to keep. New concrete then has nothing square to bond against. Feathered edges and shaken arrises fail first, and they fail at the joint line, which is exactly where the wheel loads land. A full depth saw cut gives a vertical face through the whole slab instead. The retained concrete stays sound right up to it.

In our experience the commercial consequence is blunt. A bay taken out with a breaker turns a one bay repair into a two or three bay repair, because the neighbours have been loosened and nobody will reinstate against a damaged edge. That cost is decided in the method statement, weeks before anyone reaches site.

The second question is whether percussive energy is permitted at all. Often it is not, and no amount of programme pressure changes that.

Alongside a live high pressure aviation fuel main, a breaker is simply out of the question. Buried ducts, high voltage cable, gas, water and post-tensioning tendons sit in the same category. A tendon is worse than most, because it is stressed. Shock it or cut it and that energy comes out, with somebody standing next to it. Reinforcement matters too, though for a different reason. A breaker will bend and drag bar, and dragged bar tears the concrete it is cast into.

Load is the other constraint. A slab or a deck still carrying load is not a lump of material, it is a structural element. Impact energy into a member under load changes what that member is doing while somebody works on it. Bridge decks typically run 200mm to 400mm, highway concrete 200mm to 350mm, airfield taxiways and aprons 300mm to 500mm. Those are structural thicknesses, and they are that thick for a reason.

Occupied buildings are the everyday version of the same problem. A hospital, a data centre, an office above a car park, a laboratory with sensitive kit on the floor below. Breaking sends structure borne vibration through columns and slabs for a surprising distance. It gets felt several floors away. The airborne noise carries as well, and a breaker cannot be turned down.

Diamond sawing is quieter, and the noise it makes is continuous rather than percussive. Continuous noise is easier to live with, easier to explain to a tenant, and easier to programme around. Vibration into the structure is far lower, and that is often the difference between work being permitted in an occupied building and not being permitted at all. Where sensitive equipment is involved it still gets monitored against whatever limit the building owner has set.

Dust separates the two methods cleanly. Breaking runs dry unless suppression is fitted, and dry breaking liberates respirable crystalline silica right where the operative is standing. Water suppression or on-tool extraction is what controls it, and on a breaker that is a bolt-on rather than something built into the method. HSE guidance on construction dust treats that as a health risk to be controlled at source. Diamond cutting is wet by design. The water suppresses dust as it is made, and produces slurry instead. Slurry has to be contained, which is a real cost. The gain is that the dust is caught as it is made rather than left airborne at the operative's face. It still has to be managed, and the slurry is cleared before it dries and is walked back into the air.

Breaking is faster and cheaper, and pretending otherwise helps nobody. A breaker on the back of an excavator moves through a slab quickly and costs very little per cubic metre. Cutting is slower and dearer. Blades are a consumable, rigs and wire are specialist plant, and both water and slurry have to be managed.

So where the concrete is coming out in its entirety, no edge is being kept, and nothing sensitive is nearby, breaking is the right answer. Specifying diamond cutting for a straightforward demolition is money spent for nothing. Any contractor telling you otherwise is selling their own plant.

The comparison changes the moment an edge is being retained. Then the price of the saw is set against the extra material broken, the extra concrete poured back, and the repair that has to be done twice. On a scheme with traffic management or a possession behind it, the return visit is usually the biggest number on the page. Over enough jobs we've found the arithmetic turns there, not in the rate per linear metre.

There is a programme argument as well. Cutting is predictable. You can state how long a given run of 300mm cut will take and then hit it. Breaking out an unknown quantity of extra material is not predictable at all. On the M20 between junctions 8 and 9 our possession ran from 10pm to 3:30am, twenty nights running, with the carriageway open behind us each morning. A method whose duration you cannot state is no use in that window.

There is a case neither method covers. Breaking is banned outright, and a saw cannot reach the line or cannot get through it. A blade only cuts on a straight line from one face. It will not turn a corner, and it cannot finish an internal corner without over-running past it.

Stitch drilling is the answer there. A row of overlapping cores is drilled along the cut line, each one intersecting the last, so the line is formed by holes rather than by a blade. The thin webs left between them are broken out, and the section is lifted clear, normally by vacuum plant so nothing is dropped. Core drilling puts no percussive energy into the structure, runs water through the barrel, and can be set out around an obstruction a saw would never negotiate.

It is slower than cutting and far slower than breaking, and it is the dearest of the three by some way. It is also the only method available in certain places, which is the whole point of it. We use it on airside work where fuel mains run under the line. The same diamond drilling plant does precision work of a different sort too. At Stansted we cored 150 airfield ground lighting seating pots across ten weeks of restricted overnight possessions.

The decision is not really a matter of preference. It falls out of the site if you work through it in this order.

• Is any concrete being retained? If an edge stays, and anything is going to bond to it later, that edge has to be cut.
• What is embedded, and what is live? Services, tendons and reinforcement settle the method before any other consideration does.
• Is the element still carrying load? If it is, percussive work needs a structural opinion rather than a site decision.
• Who is above, below and next door? In an occupied building, vibration and noise limits are usually the binding constraint.
• Can the saw physically reach the line? If it cannot, the honest answer is stitch drilling, not a compromised cut.
• How deep is the cut? A floor saw reaches 420mm, and depth follows blade diameter rather than engine power. A wall saw reaches a little under half its blade diameter, around 730mm from one face on the largest in common use. Past that it is wire sawing.
• What happens after the cut? A slot that will be sealed has to be cut to the sealing specification, not to whatever a breaker happened to leave.

The last one gets forgotten more than the rest of them put together. Where the cut feeds joint sealing, the geometry of the slot is a cutting specification, not a sealing one. Sealant needs sound, near vertical faces to bond to. A broken edge cannot be sealed as it stands. It has to be sawn back to sound, near vertical faces first, which is joint widening, so the sealing gang inherits a problem the cutting method created.

Worth saying plainly, because it saves arguments on site. On anything structural, the choice of method belongs to the structural engineer or the asset owner. It does not belong to the contractor holding the saw.

An airport operator states what percussive work is permitted airside, and when. A highway authority states it for a bridge deck or a concrete carriageway. A building owner with a tenant upstairs will have vibration limits written into the contract. Those are conditions, not opinions, and a contractor who overrides one has made a decision that was never theirs.

What a competent contractor owes you is different. Tell you what each method will do to the structure. Price both honestly. Say out loud when breaking is the sensible choice and cutting is not worth your money. If nobody has issued a method for sensitive work, ask who is going to, and get it in writing before mobilisation. Competence sits alongside that: NVQ Level 2 in cutting and drilling, CSCS cards, and Drilling and Sawing Association training behind the operatives doing it.

We are a family run firm at Little Westerhill Farm in Linton, near Maidstone, with more than 40 years in this work. SafeContractor and CHAS accredited, members of the Extruded Sealant Association, and sole contractor to the British Airport Authority since 2008 across all seven former BAA airports. Kent, London, Sussex and Essex are covered from our own yard, and longer programmes are mobilised UK wide.

If you have a slab that needs part of it out and the rest kept, tell us what is embedded in it and what sits above it. That normally settles the method inside one conversation, and it settles the price with it. For the service rather than the explanation, we are concrete cutting contractors in Kent. To talk a scheme through, get in touch with our team.