Floor slab
[edit] Introduction
The term ‘floor slab’ usually refers to a floor that has been formed using concrete (and generally steel reinforcement) and may form part of the structure of a building. It may form the floor of a basement, at ground level or at upper levels. It will be typically reinforced, either by rebar or steel fibres, and can be either formed on site or prefabricated. A floor that is made of timber or other material is not referred to as a floor slab.
Concrete slabs that form the ground floor of a building may be either supported on beams (called a suspended slab) or supported directly on the subsoil, (via hardcore, for example) called a ‘ground-bearing slab'.
When a concrete slab forms part of the roof construction of a building, it is normally referred to as the 'roof slab'.
[edit] Types of floor slab
The term 'floor slab' refers to the finished result, but the ways of achieving it are numerous, which means there are different types of floor slab construction. The important point is that it may be referred to as a 'floor slab' irrespective of its formation and its inclusion of other materials.
A floor slab may be:
- A horizontal, flat thickness of concrete (usually 100mm minimal thickness), supported on two or more sides by concrete or steel beams. The underside of the set concrete (if an upper floor) will be visible when viewed from the floor below and may bear the marks of the formwork (or shuttering) that was used to provide temporary support.
- A horizontal, flat thickness of concrete that is supported by profiled steel-ribbed sheeting (decking). The steel provides reinforcement and both temporary and permanent support for the concrete. When viewed from the underside, a steel ceiling (or soffit) is observed which may have recesses for hangars to support ducts and other services. Such slabs are often referred to as ‘composite’, where the resulting structural efficiency of the floor slab is greater than the sum efficiency of the steel and concrete.
- A waffle slab is formed when the concrete is poured over a series of plastic formers to result in an egg-crate-style (like a waffle) formation on the slab’s underside. Although such constructions may typically have thicknesses of 500mm or more, the hollow areas make the construction lighter, more economical and more structurally efficient
- A horizontal, flat thickness of concrete topping that has been poured in-situ over a beam and block substructure or a hollow-rib arrangement that incorporates rebar.
- A pre-cast concrete slab supported by a steel frame (especially in a high-rise building).
For further information on the various floor slab types, read the article on concrete slabs in buildings.
[edit] Related articles on Designing Buildings Wiki
- Building foundations.
- Cast-in-place concrete.
- Cellular raft foundation.
- Concrete.
- Concrete slabs in buildings.
- Deck.
- Domestic floors: Part 1: Construction, insulation and damp proofing.
- Finished floor level.
- Floating floors in buildings.
- Footings.
- Pad foundation.
- Resilient flooring.
- Rubber flooring.
- Strip foundation.
- Subfloor.
- Types of floor.
- Types of raft foundation.
Featured articles and news
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
CIOB Construction Manager of the Year 2025
Just one of the winners at the CIOB Awards 2025.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.
Construction Products Reform Green Paper and Consultation
Still time to respond as consultation closes on 21 May 2025.
Resilient façade systems for smog reduction in Shanghai
A technical approach using computer simulation and analysis of solar radiation, wind patterns, and ventilation.