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Flat Slabs

Load Path: Here
Information to provide in scheme design:
  • Constant thickness of flat slab
  • Thickness of drop panels, if required. These drop panels serve as thickened section surrounding columns to provide additional shear strength at the ends of the columns.
  • Clear floor height
Reasons to use this slab type:
Capabilities
  • Support directly by and transfer loads directly to columns
  • Provides higher headroom due to unobstructed ceilings and lack of beams
  • Lack of beams that can otherwise interfere with light and air flow
  • Provides robustness
  • Provides space for partition wall placement
  • Flat soffit decreases concrete spalling, decreasing maintenance cost
  • Accommodates voids for service installation and distribution
  • Absent of sharp corners which increases fire resistance and safety protection
  • Adequate for resistance to heat, sound, vibration, and acoustics
Construction
  • Structural design provides repetitive construction sequence of components which speeds up schedule and decreases cost of construction
  • Uses standardized and simple formworks, reinforcement placement, and shuttering methods that speed up construction
Advantages over other slabs:
Flat Slab vs Beam Slab
  • Flat slabs provide a more aesthetic appearance due to unobstructed ceilings and lack of beams which show beam underside
  • Beam slabs require more labor for shuttering and complicated reinforcement positioning
  • In Beam Slabs, the penetrations through downstand beams may affect the strength of the beams. The size and location of slab openings will also be limited due to limited openings for services and floor to floor openings.
Disadvantages 
  • Need to design to suit concentrated loads and partitions
  • Less flexibility for openings. Trimming beams are needed around openings for support of slab.
  • Flat slabs are larger in thickness so the structure will be heavier. This will incur a higher cost for the amount of concrete and steel reinforcement needed for the foundation.
  • Not a lot of stiffness provided for wind resistance If there are no core walls
  • Can only utilize a limited span range
In your Detail Designed Calculations, you will need to put more emphasize on calculations and check on punching shear and deflection, if flat slabs are used.

Beam Slabs

Load Path: Here
Information to provide in scheme design:
  • Thickness of slab spanning in one direction
  • Size of secondary and primary beams
  • Clear floor height
Reasons to use this slab type:
Capabilities
  • Flexible for future additional and alteration designs
  • Accommodates heavy utility systems and other loading
  • Not a lot of maintenance cost needed
  • Accommodates slab openings for services installation and distribution
  • Strong resistance to sound, fire, vibration, and heat
  • Flat soffit decreases concrete spalling
  • Provides robustness
  • Accommodates design for irregular grid lines and different shapes of buildings
Construction
  • Repetitive construction of components, which decreases the learning curve, construction cost, and construction schedule
  • Local experience of construction of beam slabs
Advantages over other slabs:
Beam Slab vs Flat Slab
  • Beam slabs are more common, making them more cost and time efficient
  • Beam slabs can provide longer spans
  • Beams slabs can accommodate slab openings and future alteration in design
  • Beam slabs can be designed for irregular grid lines and different shapes of buildings
  • The structures in flat slabs are heavier than those of beam slabs, so beam slabs are less expensive due to less cost in materials used for foundation
  • In Flat Slabs, not a lot of stiffness provided for wind resistance if there are no core walls
Beam Slab vs Ribbed Slab and Waffle Slab
  • Beam slabs uses a more common formwork that that of ribbed/waffle slabs, which saves time and cost
Disadvantages 
  • Less flexibility with size and location of slab openings due to limitations on penetrations
  • Larger structural depth which requires construction of a heavy foundation at times
  • More labor needed for complicated reinforcement positioning for downstand beams
  • Penetrations through beams will affect beam strength and clash and placement issues with reinforcement in beams

Wall Slabs

Load Path: Here
Information to provide in scheme design:
  • Thickness of slab
  • Thickness of load bearing walls that support slab
  • Distance between load bearing walls
  • Clear floor height
Reasons to use this slab type:
Capabilities
  • Uses partition walls as structural elements not columns, which makes structure more economical due to less materials used
  • Higher headroom are then produced from this wall type since space for beams are not needed
  • Good lateral action in both directions provided by core walls
  • Flat soffit of slabs reduces concrete spalling so not a lot of need for maintenance
  • No concern for the reduction of beam strengths since beams are not needed
  • Not a lot of maintenance cost needed
  • Suitable for irregular grids and structural shapes
  • Provides limits to deflection
  • Provides robustness
  • Accommodates slab openings for service routing
Construction
  • Uses standardized formworks, the simplest method of reinforcement placement, and shuttering
  • Repetition of component construction
Advantages over other slabs:
Wall Slab vs Ribbed Slab or Waffle Slab
  • Wall slabs use standardized formworks, the simplest method of reinforcement placement, and shuttering to reduce construction time and effort
  • More contractor experience in building wall slabs so not a lot of technical issues will occur
Wall Slab vs Flat Slab
  • More contractor experience in building wall slabs
  • Wall slabs accommodate more slab openings for installation of services and for floor to floor openings
  • Wall slabs offer minimum thicknesses that are suitable for large ceiling voids for service installation and routing
  • Wall slabs provide more lateral wind resistance due to its rigid walls
  • Walls provide better sound and vibration insulation than columns
  • Flat slabs need heavy reinforcement, which can increase material cost and congest reinforcement placement.
Wall Slab vs Beam Slab
  • Wall slabs provide higher headroom since space for beams are not needed.
  • Wall slabs provide more lateral wind resistance due to its rigid walls
  • It is more economical to use partition walls as structural elements.
  • Wall slabs use standardized formworks to reduce construction time and to increase simplicity of construction processes
  • In Beam Slabs, beam strengths will reduce due to penetrations through downstand beams for service installations and there will be clashes in reinforcement placements
  • Because of the beams in the Beam Slab structure, construction will be more complicated and time consuming because more reinforcement arrangement design and labor force would be needed.
Disadvantages 
  • Construction is only inexpensive for regular spaced walls
  • Wall slabs are not flexible for large span concentrated loads
  • Structural walls are not as accommodating for service installations
  • Walls need to be a certain thickness for efficient reinforcement placement
  • The fixed layout for structural walls do not give a lot of flexibility for architectural design and planning purposes

Ribbed Slabs

Load Path: Here
Information to provide in scheme design:
  • Statement that the design is a one way ribbed slab
  • Thickness of topping on top of slab
  • Depth of ribs, which are small downstand beams, and distance from center to center
  • Size of flat beams
  • Clear floor height
Reasons to use this slab type:
Capabilities
  • Aesthetically pleasing due to regular patterns induced by ribbed slab and ceiling shape on the underside
  • Accommodates for floor penetrations, service installations, and high headrooms in one direction
  • Decreases the overall self weight of slabs, but at the same time, has strength and stiffness to limit deflection
  • Provides robustness
  • Standardized fabric glass formworks or lightweight formers on formworks can be used to decrease construction time and effort
  • Parallel spans can accommodate for good service routing arrangements
  • Appropriate for long spans
Disadvantages:
  • Difficult to design and construct partition walls underneath ribbed slabs
  • Difficult to detail and position reinforcements in ribbed slabs
  • Not suitable for heavy and concentrated loads due to small shear capacity of ribs
  • Difficult to construct structures with irregular shapes
  • More finishes work required for large surface area of the structure
  • Service penetrations through ribbed beams decreases beam strength and will lead to reinforcement congestion
  • Long construction time for formwork construction due to void formers
  • Standard formwork used is expensive for low-rise structures

Waffle Slabs

Load Path: Here
Waffle Slabs consist of coffers, or shaped voids, in soffits of slabs.
Information to provide in scheme design:
  • 2-way waffle slab
  • Thickness of topping
  • Depth of ribs and distance of ribs from center to center
  • Size of flat beams
  • Clear floor height
Reasons to use this slab type:
Capabilities
  • Suitable for long spans
  • Voids can reduce the self-weight of slab
  • Accommodates space for services installation and distribution through slab openings
  • Flat beams can provide lateral resistance for wind loads
  • Provides robustness
  • Provides limited deflections
  • General aesthetics
  • Standardized formworks can be used to reduce construction time and effort
Disadvantages 
  • Aesthetics of underside of slabs is dependent on workmanship
  • Service penetrations through rib beams will decrease their inherent strength and stiffness and can lead to reinforcement congestion within the beams
  • Long construction time needed to construct void formers and reinforcement placement
  • No stiffness or lateral system to resist lateral wind loads when there are no core walls in the design
  • Standard formworks used can be quite expensive for low-rise structures
  • More finishes work required for structures of large surface areas