Hollowcore Plank Technical Details

Design

All Hollowcore planks are designed to the requirements of BS 8110. Standard Hollowcore planks have a minimum fire resistance of 1 hour. Units are manufactured to the following nominal depths 150mm, 200mm, 250mm, 300mm, 400mm and 500mm. Hollowcore planks are ideal for use in upper floors, being lightweight and easy to install.

Drawings

Longley Concrete will provide layout drawings for the Hollowcore plank details prior to manufacture. These drawings show the structure supporting the precast units, position of service entries etc., typical sections and the loads for which the floor is designed.

Quality

Quality is the prime concern of designers, developers, builders and ultimately homeowners. The robustness of a concrete floor adds to the quality of a house. Concrete floors act as a thermal store, this can reduce heating costs especially when under-floor heating systems are used.

LOAD/SPAN TABLE – Non Composite Floor

Overall Structural Depth (mm) Fire Resistance (hours) Self Weight (kN/m²) Spans indicated below allow for characteristic service load, self weight of units and 2.0kN/m² for finishes
Characteristic service loads (kN/m²)
1.50 2.00 2.50 3.00 4.00 5.00 7.50 10.00 12.50
Effective Span (m) to include 100mm bearing both ends
150 1 2.25 7.0 6.9 6.8 6.7 6.5 6.3 5.9 5.3 4.9
150HD 1 3.00 7.0 6.9 6.8 6.7 6.6 6.4 5.7 5.2 4.8
200 1½ 2.63 9.0 8.8 8.7 8.6 8.3 8.1 7.5 6.8 6.2
200HD 1½ 3.00 9.0 8.9 8.8 8.6 8.4 8.2 7.3 6.7 6.1
250 2 3.33 11.0 10.9 10.7 10.6 10.3 10.1 9.2 8.3 7.7
320 2 3.78 13.2 13.0 12.8 12.7 12.4 12.2 10.9 9.2 7.9
400 2 4.32 15.7 15.5 15.3 15.1 14.8 14.3 12.9 11.7 10.7

This hollowcore plank span table is to be used for preliminary purposes only. Other factors may affect slab performance.

Maximum spans may improve with the addition of a structural screed.

Considerations:

i) Propping may be required for composite floors

ii) Camber needs to be considered when allowing a structural screed

iii) Penetrations must be considered when using the above table