Slots and recesses

The proper setup of slots in KLB masonry

If the limit values listed in the following table are adhered to, a special static proof is not required. If masonry is slit afterwards, you should omit uncontrolled chiselling or hitting as the structure of the mostly still fresh masonry is damaged, and the maximum slot depths and widths can also not be complied with.

Scouring machines with replaceable scouring heads create the respective slot depths and widths in a single work process. The slots are then precise and sharp-edged. Slots and/or recesses must be completely closed after the appropriate processing with suitable mortar. Empty receptacles for electrical installation must be plastered enclosing on all sides

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Wide butt joints ≥ 5 mm must be closed with the masonry mortar used on both sides. The mortar has to be given enough time to dry before plastering.

Permitted recesses and slots in load-bearing or stretching walls

Slots created afterwards
Slots in masonry bond

Wall thickness	Horizontal and slanted slots¹)		Vertical Slots and Recesses
	Slot length		Slot depth⁴))	Individual slot width⁵)	Distance from openings
mm	unlimited slot depth	≤ 1,25 m²) slot depth
≥ 115	-	-	≤ 10	≤ 100	≥ 115
≥ 175	0	≤ 25	≤ 30	≤ 100	≥ 115
≥ 240	≤ 15	≤ 25	≤ 30	≤ 150	≥ 115
≥ 300	≤ 20	≤ 30	≤ 30	≤ 200	≥ 115
≥ 365	≤ 20	≤ 30	≤ 30	≤ 200	≥ 115

Wall thickness	Vertical Slots and Recesses
	Slot width⁵)	Remaining wall thickness	Minimum distance
mm			from openings	from each other
≥ 115	-	-	≥ 2 slot width ≥ 240	≥ slot width
≥ 175	≤ 260	≥ 115
≥ 240	≤ 385	≥ 115
≥ 300	≤ 385	≥ 175
≥ 365	≤ 385	≥ 240

Table explanations

Horizontal and slanted slots are only permitted in an area ≤ 0.4 m above or below the raw ceiling as well as respectively on a side of a wall. They are not permitted for horizontal coring bricks.
Minimum distance in the direction of length of openings 490 mm, from the next horizontal slot twofold length of slot.
The depth may be increased by 10 mm if tools are used that allow the depth to be precisely maintained. When using such tools slots opposite walls ≥ 240 mm may also be executed with a respective depth of 10 mm.
Slots that reach up to a maximum of 1 m above the floor may be executed up to a depth of 80 mm and width of 120 mm for wall thicknesses ≥ 240 mm.
The overall width of slots according to column 5 (Tab. 1) and column 2 (Tab. 2) must not exceed the dimensions in column 7 per 2 m wall length. For wall lengths less than 2 m the values in column 7 must be reduced proportionally to the wall length.