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Hole Design for Concrete

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Concrete breaks differently depending on thickness, rebar, and access for drilling. Use the diagrams below as starting points — then confirm spacing with our hole-design guide for your specific slab or wall.

Breaking concrete — layout guide

d 32 - 35 mm
1½ " - 1¾ "
L 40 - 60 cm
1´ 4" - 2´
D 70% of Height
...
When vertical access is limited, bore horizontal holes with a slight downward angle.

Reinforced concrete

d 35 mm 38 - 44 mm
1 3/8" 1 ½" - 1 ¾"
L 20 - 25 cm 30 - 40 cm
8" - 10" 1'-1'4"
D 90% of Height
...
Hole diameter and depth depend on rebar density and layout.

Thin sections and walls

(1) SQUARE ARRANGEMENT
d 32 - 38 mm
1 ¼" - 1 ½"
L 25 - 30 cm
10" - 1'
D Almost Wall Thickness
...
The leading row opens a wider gap than rows behind it.
(2) AVOIDING DIAGONAL CRACKING
d 32 - 38 mm 25 mm 32 - 38 mm
1 ¼"-1 ½" 1" 1 ¼" - 1 ½"
L 25 - 30 cm 10 cm 10 - 15 cm
10" - 1' 4" 4"-6"
...
Keep corner radius R above 15 cm (6 in) to limit diagonal cracking.
(3) SPLITTING OF WALLS
d 38 - 44 mm
1 ¼" - 1 ½"
L 25 - 30 cm
10" - 1'
...
 
(4) SPLITTING OF SLABS
d 38 - 44 mm
1 ½" - 1 ¾"
L 25 - 30 cm
10" - 1'
...
 
...
 
(5) ESTABLISHING FREE SURFACES
d 38 - 44 mm
1 ½" - 1 ¾"
L 25 - 30 cm
10" - 1'
...
Where a burn cut isn't practical, cross-drill to create a free face on walls.

Large mass pours

  Concrete Reinforced Concrete
d 38 - 51 mm 38 - 44 mm
1 ½" - 2" 1 ½" - 1 ¾"
L 50 - 90 cm 40 - 60 cm
1'8" - 3' 1'4" - 2'
...

Pile foundations

d 38 - 44 mm
1 ½"-1 ¾"
L1 20 cm
8"
L2 20 - 25 cm
8" - 10"
...

Thick retaining walls

d 38 - 44 mm
1 ½" - 1 ¾"
L 30 - 60 cm
1' - 2'
...
Fractures tend to follow the wall face.

When you need cracks running into the wall face:

...
(1) Add a relief hole, spaced 10–20 cm (4–8 in) apart. (2) Use a larger bit where needed.

Bridges, piers, and footings

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...
...
 

Drill layout depends on structure shape and site access.

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(1) Large-block removal; finish with a hydraulic breaker
...
(2) Small-piece removal; drill from one side only.
...
(3) Tall wall — vertical drilling may not be feasible.
...
(4) Thick footing — use a hydraulic breaker for secondary breaking.

Partial / zone demolition

(1) STAGGERED ARRANGEMENT (PILLAR)
d 38 - 44 mm
1 ½" - 1 ¾"
L 30 - 40 cm
1' - 1'4"
D 90% of Width or Height
...
 
(2) X FIGURE ARRANGEMENT (PILLAR, WALL)
d 38 - 44 mm
1 ½" - 1 ¾"
L 30 - 40 cm
1' - 1'4"
D 90% of Width or Height
...
 
(3) CROSS DRILLING (BEAM)
d 38 - 44 mm
1 ½" - 1 ¾"
L 30 - 40 cm
1' - 1'4"
D 90% of Width or Height
...
 

Staged filling (delayed pours)

Fill set (1) first, then set (2) after a suitable delay.
Staggered filling helps steer crack direction (see below).

...
 
FIGURE 1: SPLITTING OF LARGE BOULDER
d 32 - 35 mm 44 - 51 mm
1 ¼" - 1 3/8" 1 ¾" - 2"
L 30 - 40 cm 60 - 90 cm
1' - 1'4" 2' - 3'
D 70% of Height
...
FIGURE 2: TRENCHING AND TUNNELING OF ROCK
d 38 - 51 mm
1 ½" - 2"
L 30 - 60 cm
1' - 2'
D 1 - 1.8 m
3' - 6'
⊖ 45°-60°
...
Add relief holes when trench depth is high
...
Repeat the same relief-hole pattern for greater depth
FIGURE 3: MASS CONCRETE
  Concrete Reinforced Concrete
d 38 - 51 mm 38 - 44 mm
1 ½" - 2" 1 ½" - 1 ¾"
L 50 - 90 cm 40 - 60 cm
1'8" - 3' 1'4" - 2'
...