Indoors, the choice is driven less by drilling speed than by what the space can tolerate: water, dust, or neither.

Quick decision

Situation	Method
Occupied building, dust-sensitive	Wet with containment
No water available, sealed floor	Dry with HEPA extraction
Overhead or wall above equipment	Dry with extraction, or wet with a catch collar
Large diameter, deep core	Wet; dry overheats the segment
Electrical or data room work	Dry with HEPA, wet not acceptable

Wet coring: what it needs

• Water supply at 3-6 bar with a flow the bit actually needs; a garden hose tee is not a supply.
• A vacuum ring or collar on the bit for slurry capture, plus a wet vacuum downstream.
• Slurry dam and floor protection, especially on finished surfaces.
• Water off before the bit exits, or the last 20 mm washes out the hole edge.

Dry coring: what it needs

• A dedicated HEPA extractor sized to the bit, not a shop vac with a bag.
• A dust shroud that actually seals; most dry complaints are shroud leakage, not the bit.
• Segment temperature discipline: pull the bit every 20-25 mm and let it cool, or the weld fails.
• Air monitoring in occupied buildings, with the work area sealed.

Speed and cost

Wet coring is typically 20-40% faster in reinforced concrete and extends bit life. Dry coring is faster to mobilise, needs no water containment and leaves no slurry to dispose of, which often wins on small jobs in finished buildings.

Compromises that work

Wet coring with a vacuum collar gives near-dry results on walls. Dry coring with a water mist on the segment (not the hole) reduces heat without producing slurry. Both are common on refurbishment work where neither pure method fits the site.

Wet coring indoors: containment is the whole job

Wet coring is faster, gives longer bit life and leaves a cleaner hole, but indoors the water becomes the risk. Forty litres of slurry on a finished floor, a data centre or a hospital corridor is a bigger problem than a slow hole, and the containment plan should be written before the rig is positioned.

Item	What good looks like	What fails
Water supply	Regulated feed with a shut-off at the rig	Garden hose taped to a tap, no control at the hole
Slurry collection	Ring dam plus wet vacuum running continuously	Towels and a bucket, changed after the floor floods
Floor protection	Plastic sheet taped with a lip, masking on adjacent finishes	A single sheet with no lip, water runs underneath
Disposal	Settling tank or filter bag before drain	Slurry into a storm drain, which is illegal in most jurisdictions
Air and dust	Mist suppression plus extraction at the collar	Water only at the bit, dust plume from the vacuum

The ring dam is the piece most crews skip and the reason most wet jobs fail. A 50 mm dam of sealant or putty around the hole, with the vacuum nozzle inside it, keeps water where it belongs and turns a flood into a puddle. Building the dam takes four minutes; drying a flooded corridor takes a day and a complaint.

Dry coring: heat, bit choice and dust

• Use a bit designed for dry cutting, with a segment or crown that clears dust rather than relying on water to flush it.
• Run lower rpm and lighter feed than wet coring. Heat, not hardness, is what kills a dry bit, and a glazed segment stops cutting quietly.
• Pull the bit every 25-40 mm to clear dust. A dry hole that is not cleared loads the crown and starts to wander.
• Extract at the collar with a shroud, not at the floor. Dust released at head height is the reason dry coring is banned in occupied healthcare and food areas.
• Watch for smoke or a colour change on the crown. Both mean the segment is overheating and the hole is about to go off-line.

Dry coring is the right choice where water cannot be controlled, where the finish cannot be wetted, or where the slab is cold and wet coring would freeze the rig. It is the wrong choice for deep large-diameter holes in hard aggregate, where the heat build-up makes bit life uneconomical.

Deciding by material, depth and what is under the floor

Material drives the decision more than the room does. Hard, dense aggregate and deep holes favour wet; soft block, tile-faced walls and shallow fixings favour dry. Reinforcement changes it again: a rebar strike in a dry hole produces a hot, blunt segment and a wandering hole, while the same strike wet is usually just a slower cut.

• Above 100 mm diameter and 300 mm depth, plan for wet unless containment is impossible.
• Through tile, terrazzo or a sealed finish, dry with a shroud and tape the finish first.
• Near live services or in a ceiling, dry with a vacuum and a fire watch, because water and electrics are a worse combination than dust.
• In a cleanroom or operating theatre, dry with HEPA extraction and a sealed work zone; wet is not permitted regardless of speed.

Never run a wet core in an area with live electrical equipment below, and never run dry in a sealed room without air monitoring. The method decision is a safety decision first.