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Pre-stressed Hollowcore Flooring

Pre-stressed Hollowcore Floor Slabs

Hollowcore flooring comes in 1200mm wide sections. Our slabs are pre-stressed. There is steel strand at the bottom of the slab which is stretched and held in place until it forms a bond with the concrete in the slab. Once this occurs the strands are released. The tension in the strands pulls the slab together, causing the slab to act upwards creating a slight camber (bow). This strengthens the slab against the downward service loads which act on the floor once it is in place.

The slabs come in a range of depths;

  • 150mm
  •  175mm
  • 200mm
  • 225mm
  • 250mm


Smart Design System

Mc Grath precast can design a concrete slab for all domestic / industrial projects, regardless of span, loading or fire rating.

Fire Resistance

Our slabs provide 1 hour fire protection as standard.

Reduced Weight

Our slabs are poured with a polystyrene infill which greatly reduces the overall weight of the slab. The reduced weight of the Hollowcore Slab results in decreased loads being transferred to bearing walls; hence the loads being transferred to the foundation are also reduced.

No Voids – Solid Ends

Our slabs have solid ends unlike our competitors who have open cores in their slabs. (Fig. B) There are a lot of advantages to this;

  • Rain water or other contaminants will enter open cored slabs causing rotting/dampness.
  • When using “pumped insulation” open cored slabs will have to be closed as insulation beads will end up filling the cores, thus adding extra cost for the added insulation needed. (eg. 150mm Hollowcore slab will require an extra 8m of insulation per 130m of flooring.)
  • Solid ended Hollowcore Slabs will transfer roof and upper blockwork loadings directly to the foundations. No risk of core collapse with excessive loading.
  • End Detail of Slabs: All our slabs have 90 degree / right angled ends. Unlike our competitors who have 75 degrees or less. Therefore there is no added expense of end shuttering all slabs to ensure correct structural bedding for blocks. (Fig. B)

Reduction in Airborne and Impact Sound

Mc Grath’s Pre-stressed Hollowcore Floor Slabs offer excellent sound insulation. The polystyrene present in the hollowcore slab acts as an ideal sound barrier. Reduces noises travelling between storeys.

Safe Working Platform

Once the slabs are placed, they will provide a safe working platform for the subsequent follow on trades straight away. No waiting for a structural screed to cure.

Millimeter Perfection

All our precast is made to measure. Unlike our competitors who manufacture slabs to incremental lengths (50mm increments), thus leaving slabs either too long or too short. We guarantee our slabs will sit 100mm on the internal leaf (Fig. A).

Underfloor Heating

Our slabs can be used as a finished slab when using underfloor heating. (Fig. A) Insulation can be placed directly onto the slab surface, and then heating pipes and screed placed directly onto the insulation. No added expense as there is no requirement for a structural screed to be poured and cured.

Increased Thermal Properties

McGrath’s Pre-stressed Hollowcore Floor Slabs have better thermal properties than slabs with open cores, due to the fact that the cores are completely closed & filled with polystyrene offering the slab added insulation.

Grouting for joints between Hollowcore Slabs

Joints between the slabs are to be grouted after installation and before screeds are placed. A minimum 30N/10 grout/concrete with 3 parts sand to 1 part cement is to be used.