Hollowcore Floors

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Our manufacturing technology of pre-stressed hollowcore floor slabs gives many advantages unachievable in traditional manufacturing process.

  • Better Sound Resistance – Concrete slabs between ground and first floor level greatly reduce the sound transfer throughout the home.
  • Improved Thermal Efficiency – Concrete will absorb heat and contributes to providing an overall warmer home.
  • Flexibility in Design
  • Structural Efficiency
  • Fire Resistance – Concrete is a natural fire repellant. Unlike other materials it will not burn, rust or rot.
  • Financially Sound – Concrete floors will hold its value over time.
  • Design – Our team can advise and draw slab detail for customers, architects and engineers.

Unlike extruded units, O’Reilly Concrete flooring slabs have solid closed ends. This eliminates the risk of water and other contamination in cores and improves the shear capacity at bearing.

Pre-stressed hollowcore floors have many advantages over beam block system.

  • much faster erection on site results in great savings on labour
  • structurally stronger slabs cover longer spans
  • unusual floor shapes can be easily covered without cutting on site using hollowcore slabs manufactured exactly to site dimensions
  • service opes can be factory formed reducing number of additional hungers
  • excellent fire resistance
  • better thermal properties
  • excellent acoustic performance
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Benefits & Details

Speed of Erection – O’Reilly hollowcore floors can be installed up to 500 square metres per day, saving time on site and reducing overall program of works

Reduced Weight – O’Reilly hollowcore floors have polystyrene infill reducing overall weight of floors; this means­­ reduced loads transferred to the foundations and smaller foundation size is required

No Open Voids – O’Reilly hollowcore floors have solid ends; this eliminates the risk of water or other contamination in cores

No Additional Work on site is required to close open cores
no drilling and cutting – all service openings can be easily formed in hollowcore floor slabs at production stage; slabs are manufactured up to exact site dimensions

O’Reilly pre-stressed Hollowcore floor units have better thermal properties than slabs with open hollow voids due to completely closed cores filled with polystyrene. The air movement in traditional hollowcore slabs reduces their thermal performance.

Here is a comparison of U-value between our standard Hollowcore slabs and the same slabs with open voids; lover U-value means better thermal insulation:

Slab Depth U-value U-value
for O’Reilly standard Hollowcore slab for the same slab with open voids
150 mm Hollowcore 1.719 2.449
200 mm Hollowcore 1.481 2.003
250 mm Hollowcore 1.317 1.722
300 mm Hollowcore 1.192 1.522

The thermal performance of standard O’Reilly Hollowcore floor slabs is 25% better in average comparing to the same slabs with open voids

  • Standard O’Reilly Concrete pre-stressed hollowcore floor units have a minimum fire rating of 1 hour
  • Unlike extruded units, our units have solid concrete ends which further improves fire retardation
  • the use of high strength concrete and pre-stressed steel offers better span to depth ratio and strengths far greater than the traditional floor systems
  • improved shear resistance gives additional safety at construction phase and in use
  • part of slab can be manufactured as solid to allow for point loads
  • additional top reinforcement can be cast in slabs for cantilevered action
  • effective shear key designed up to BS EN 1168:2005 ensures composite action between Hollowcore slabs and transverse load distribution
  • Hollowcore planks can be used to form a diaphragm to resist horizontal forces
  • Hollowcore planks can accommodate all specific tying details for progressive collapse requirements
  • O’Reilly Concrete hollowcore floor units have a high resistance to both airborne noises and impact sounds
  • Because our cores are made using polystyrene formers, our units are also the perfect acoustic barrier between floors such as in apartment buildings
The minimum cement content is 420 kg/m3
The maximum water cement ratio is 0.43
The minimum 28 day concrete cube strength is 50N

150 mm deep Hollowcore slab

Self weight of precast unit (without structural screed):  2.59 kN/m2
Concrete strength at service (28 days):  50 N/mm2
Concrete strength at transfer:  30 N/mm2
Prestressing strands: 7 wire 9.3 mm strand
Prestressing: 70% fpu
Maximum number of strands: 14
Cover to strand: 25 mm
Fire resistance (BS8110: Part 1:1997; Table 4.9): 1 hour
Minimum required effective bearing width (BS8110: Part 1:1997; Clause 5.2):
On concrete: 55 mm
On structural steel: 40 mm
On masonry: 65 mm:
150 mm deep Hollowcore slab

Self weight of precast unit (without structural screed):  2.59 kN/m2
Concrete strength at service (28 days):  50 N/mm2
Concrete strength at transfer:  30 N/mm2
Prestressing strands: 7 wire 9.3 mm strand
Prestressing: 70% fpu
Maximum number of strands: 14
Cover to strand: 25 mm
Fire resistance (BS8110: Part 1:1997; Table 4.9): 1 hour
Minimum required effective bearing width (BS8110: Part 1:1997; Clause 5.2):
On concrete: 55 mm
On structural steel: 40 mm
On masonry: 65 mm:
250 mm deep Hollowcore slab

Self weight of precast unit (without structural screed): 3.59 kN/m2
Concrete strength at service (28 days):  50 N/mm2
Concrete strength at transfer: 30 N/mm2
Prestressing strands: 7 wire 9.3 mm strand fpu = 1700 N/mm2
Prestressing: 70% fpu
Maximum number of strands: 14
Cover to strand: 25 mm
Fire resistance (BS8110: Part 1:1997; Table 4.9): 1 hour
Minimum required effective bearing width (BS8110: Part 1:1997; Clause 5.2):
On concrete: 55 mm
On structural steel:  40 mm
On masonry: 65 mm
300 mm deep Hollowcore slab

Self weight of precast unit (without structural screed): 4.09 kN/m2
Concrete strength at service (28 days): 50 N/mm2
Concrete strength at transfer: 30 N/mm2
Prestressing strands: 7 wire 9.3 mm strand fpu = 1700 N/mm2
Prestressing: 70% fpu
Maximum number of strands: 14
Cover to strand: 25 mm
Fire resistance (BS8110: Part 1:1997; Table 4.9): 1 hour
Minimum required effective bearing width (BS8110 Part 1:1997; Clause 5.2):
On concrete: 55 mm
On structural steel: 40 mm
On masonry: 65 mm