Concrete slabs in buildings
Contents |
[edit] Introduction
A slab is a structural element, made of concrete, that is used to create flat horizontal surfaces such as floors, roof decks, and ceilings. A slab is generally several inches thick and supported by beams, columns, walls, or the ground.
Concrete slabs can be prefabricated off-site and lowered into place or maybe poured in-situ using formwork. If reinforcement is required, slabs can be pre-stressed or the concrete can be poured over rebar positioned within the formwork.
There are several different types of slabs, including:
[edit] Flat slab
This is typically a reinforced slab supported directly by columns or caps, without the use of beams. This type of slab is generally easy to construct and requires little formwork.
[edit] Conventional slab
This type of slab is supported with beams and columns, with the load transferred to those elements. A conventional slab is classified as either:
- One-way: Supported by beams on two opposite sides, carrying the load in one direction.
- Two-way: Supported by beams on all four sides, carrying the load along with both directions.
[edit] Hollow-core ribbed slab
The hollow core concrete slab has tubular voids that run the entire length of the slab, typically with a diameter equal to 2/3-3/4 of the slab's thickness, which decreases the weight of the slab, as well as the amount of concrete required. They can also function as service ducts. This type of slab is generally reinforced with longitudinal rebar and can achieve long spans, making it suitable for office buildings, multi-story car parks, and so on.
[edit] Waffle slab
This type of slab contains square grids with deep sides, resembling a waffle shape, often used where large spans are required without the interference of columns. Waffle slabs can be capable of supporting a greater load than conventional slabs.
[edit] Solid slab raft
This is a type of shallow foundation, typically formed by a reinforced concrete slab that covers a wide area, often the entire footprint of a building. It spreads the load imposed by a number of columns, walls, and so on, over a large area, and can be considered to ‘float’ on the ground in a similar way to a raft floating on water. It is often used for lightly-loaded buildings on weak or expansive soils such as clays or peat.
For more information, see Types of raft foundation.
[edit] Composite slab
Composite slabs are typically constructed from reinforced concrete cast on top of profiled steel decking, (re-entrant or trapezoidal). Slabs are most commonly made of concrete because of its mass and stiffness which can be used to reduce the floor's deflections and vibrations, and achieve the necessary fire protection and thermal storage. Steel is often used as the supporting system underneath the slab due to its superior strength-weight and stiffness-weight ratio and ease of handling.
For more information, see Composite slab.
[edit] Related articles on Designing Buildings
- Building foundations.
- Cast-in-place concrete.
- Cellular raft foundation.
- Concrete.
- Concrete floor.
- Domestic floors: Part 1: Construction, insulation, and damp proofing.
- Floating floors in buildings.
- Floor slab.
- Floor void.
- Footings.
- Pad foundation.
- Strip foundation.
- Types of the floor.
- Types of raft foundations.
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.