TOPIC 4

FLOOR SLAB Recap BC1

TOPIC CONTENT: FLOOR SLAB
4.1 REINFORCED CONCRETE SLAB 4.1.1 RC Ground Slab 4.1.2 RC Suspended Floor Slab 4.1.3 Work Procedures for RC Floor Slab4.2 TIMBER SLAB4.3 FLOOR FINISHES 4.3.1 Floor Tiles 4.3.2 Natural Stone Flooring 4.3.3 Raised / Cavity Flooring

4.1 REINFORCED CONCRETE SLAB

Slab is a flat, two-dimensional planar structural component of building having a very small thickness compared to its other two dimensions. It provides a covering shelter or working flat surface in buildings. Its primary function is to support load and transfer the load by bending in one or two directions, then transferring the load to the beam, column and footing.
Slab becomes either the floor, ceiling or roof in a building. Slabs that does not have direct contact with the ground is called a suspended slab.

ADVANTAGES OF REINFORCED CONCRETE SLAB:

Strength and Durability: high compressive strength, allowing them to withstand heavy loads and resist deformation over time.
Versatility: can be customized to suit different architectural designs and construction requirements, in various shapes and sizes, enabling flexibility in building layouts.
Fire Resistance: added layer of safety and protection in case of fire incidents.
Thermal Comfort: ability to store and release heat slowly, contributing to better thermal comfort within buildings, helping regulate indoor temperatures and reduces energy consumption for heating or cooling.
Sound Insulation: effective sound insulation due to its mass and density, reducing noise transmission between floors and creating a quieter living or working environment.

4.1.1 RC GROUND SLAB

The slab which is casted on the surface of the earth is known as Ground slab. It is used in the Basement floor or at plinth level. It is suitable for a well-compacted stable ground rock or confined sand which is not influenced by moisture, and soils that does not undergo even slight movement due to moisture. When placed over soil of low bearing capacity or over highly compressible or expansive soils or filled by soil, a concrete ground slab must be designed as a mat or raft foundation

1. HARDCODEa heap of solid materials, generally broken down bits of concrete, stones and bricks – which do not deteriorate or absorb water to create a base for heavy load-bearing stone and concrete floors.

2. SAND BLINDINGa layer of sand placed above a hardcore fill, typically made from building aggregates, to create a level working surface. It also prevents sharp stones and gravel in the aggregate mixture from coming into contact with the damp proof course and tearing the membrane.

3. DAMP-PROOF MEMBRANE (DPM) / VAPOUR BARRIERmembrane material is used to prevent dampness from occurring through capillary action. It is often used underneath a concrete floor to stop it from gaining moisture. Materials usually used as DPM include Nylon, Mastic Asphalt or Bitumen Sheets.

4. UNDERSLAB INSULATIONany type of insulation that is used below a concrete slab on grade (a concrete floor directly on the ground). Common examples of under slab insulation include extruded polystyrene (XPS) and expanded polystyrene (EPS). This is important for region with cold climate, to increase thermal mass in floor and prevent heat loss from space

5. CONCRETE BEDat least 100mm thick of fresh concrete with our without reinforcement. Can be fitted with heating pipes for certain climatic condition

6. CEMENT SCREEDto give a smooth and level floor on which to lay your chosen floor finish. The thickness of the screed allows it to take up normal variations in flatness and levelness of the base on which it is laid.

General guideline for Concrete Slab Thickness

4.1.2 RC SUSPENDED FLOOR SLAB

DEFINITION OF SUSPENDED SLAB:Suspended slabs sit above the ground and have no contact with the earth, yet provide the same feeling underfoot as a slab on ground. They can be deployed to create floors for upper stories, or used on top of supporting walls to form a ground floor (common on sloping sites)
There are occasions where due to the ground conditions that a suspended floor is needed rather than a ground bearing slab. These instances include:

When soil has a low bearing capacity
On sloping sites
On soils containing aggressive chemicals and
On soils with high water levels.

TYPES OF SUSPENDED CONCRETE FLOOR SLAB:

One Way Slab
Two-Way Slab and Beam
One Way Joist Slab
Two-Way Waffle Slab
Two-Way Flat Plate
Two Way Flat Slab
Composite Slab
Pre-Cast/Pre-stressed RC Slab

Each type of floor system has its own advantages in application depending upon the following considerations:

Spacing of the column
The magnitude of the loads to be supported
The length of the span
Cost of construction

CONVENTIONAL SLABS

ADVANTAGE OF CONVENTIONAL SLAB:

Simplicity, flexibility in design and cost-effectiveness
Requires less framework
Suitable for small to medium-sized buildings
Designed to meet specific load requirement and can be modified to accommodate future changes in the building
Used in relatively short span, medium loading building, particularly where the floor-to-ceiling height is limited.

DISADVANTAGE OF CONVENTIONAL SLAB:

Limited span
Not suitable for large span or heavy load
Prone to cracking and shrinkage

NON-CONVENTIONAL SLABS

Pre-cast/Prestressed Concrete Joists

ADVANTAGE OF JOIST SLAB:

High-load carrying capacity, allowing longer span and fewer columns
Joist or ribs provide better structural system for resisting lateral loads such as wind and earthquake
Quicker to construct due to pre-fabricated components casted off-site
More economical due to lesser use of concrete, reinforcement and formwork

DISADVANTAGE OF JOIST SLAB:

Limited ability to accommodate heavy load
Parallel ribs make it difficult to install mechanical and electrical system within slab
Have lesser aesthetic appeal compared to waffle slab

Waffle Mould & Formwork

ADVANTAGE OF WAFFLE SLAB:

High-load carrying capacity but lightweight due to the voids, allowing longer span and fewer columns
Voids created by the grid beams can be used for utilities, reducing the need for suspended ceiling
More resistant to vibration and deflection due to their high stiffness and shear capacity
Provides unique architectural features to the building's interior
Used in shopping malls, warehouses, office, airport terminals for large spanning area with high load

DISADVANTAGE OF WAFFLE SLAB:

Complexity in design and construction
Increased cost and time in construction
Voids created can pose challenges when fixing lightings or other architectural features

ADVANTAGE OF FLAT PLATE:

Simplicity in design, reducing construction time and cost
Flexibility in layout allowing larger open spaces
Provide a smooth level surface
Useful in buildings with repetitive floor plans like hotel, offices and apartment. Ideal for building with low headroom requirement like parking or mezzanine floor.

DISADVANTAGE OF FLAT PLATE:

Not suitable for long span or heavy load
Requires more concrete and reinforcement
More susceptible to vibration and deflection, leading to cracking and other structural problems.

Drop Panel Formwork

ADVANTAGE OF FLAT SLAB:

Simplicity in design, reducing construction time and cost
Flexibility in layout allowing larger open spaces
Provide a smooth level surface
Higher load capacity compared to flat plate
Can span longer distances without the help of beams or girders.
The drop panel or column capital increases shear capacity
Useful in buildings with repetitive floor plans like hotel, offices and apartment. Ideal for building with low headroom requirement like parking or industrial spaces

DISADVANTAGE OF FLAT SLAB:

Greater weight and thickness requiring more concrete and reinforcement
More susceptible to cracking due to high rigidity and lack of ductility

COMPOSITE SLAB
typically constructed from reinforced concrete cast on top of profiled steel decking. 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.
ADVANTAGES:

Versatility; they can be adapted to many practical cases and a multitude of solutions.
Resistance/Weight ratio; greater resistance with less weight, thus enabling a global reduction of the structure’s weight. The minimum slab edge measures a mere 12 cm.
Quick installation; the absence of props means that more than one floor can be concreted at the same time, thus reducing construction time per floor.
Cost reduction; both in terms of labour costs and prices, as there is no need for props, and in terms of materials, as less concrete is used, which in turn means a lighter structure and less waste.

PRE-CAST/PRE-STRESSED RC SLAB
casted and cured in manufacturing plants, and then delivered at site for erection. The biggest advantage of precast concrete slab is that, as they are manufactured in plants, their efficiency is increased and higher quality control is achieved over the on-site concrete slabs. Cost is reduced by almost 25% as formwork is not needed and duration of construction is also reduced, due to no concrete curing time.

Normal precast/pre-stressed RC Slab

Hollow core precast/pre-stressed RC Slab

4.1.3 WORK PROCEDURES FOR RC FLOOR SLAB

1. PREPARE THE SITE-Includes site clearing, excavation, levelling etc. Please refer to Site Preparation lecture
2. ERECT FORMWORK- Type of framework will depend on the location of the slab, either on ground or suspended
3. PREPARE SLAB BEDDING- Layering and compacting of hardcore and sand blinding; and the layering of Damp-proof Membrane. This step may be limited or not required for suspended floor slab due to no contact with the ground
4. INSTALLATION OF SERVICE PIPES - This may include heating element, water supply etc. that is to be imbedded in the concrete bed
5. INSTALLATION OF REINFORCEMENT BAR- Reinforcement bars, spacers and ties are installed in accordance with the approved building plans.
6. CONCRETE POURING- Fresh concrete of specific ratio is prepared and continuously poured over the prepared bed.
7. CONCRETE COMPACTION- Vibration method is being used to consolidate the concrete and remove all air bubbles within the concrete mix
8. CURING OF CONCRETE- involves the application of water over an approximate 7 day period. Applying moisture to the concrete helps it to seal. Spraying twice daily is ideal – use light mist sprays with complete coverage.
9. REMOVAL OF FORMWORK- it is recommended to remove formworks after 14 days.

Construction of Ground Floor RC Slab

Construction of Suspended RC Slab

4.2 TIMBER SLAB

Slab using timber as structural components have to be built suspended as timber is more susceptible to damage from ground moisture. Continuous ventilation within the suspended void area is the key characteristics any timber structural slab design.
The preparation of the ground is similar to those of concrete slab - the layering of Hardcore bedding, sand blinding and damp-proof membrane. However, a sleeper wall made of bricks will be used to raise the entire slab to a minimum of 150mm to completely separate the ground from the timber material.
Timber joists are arranged paralel to each other to form the primary support of the slab before the floor covering is placed to later take on the final finish of the floor surface.

Due to the ventilation requirement, the bricks for the sleeper wall have to be arranged in a honeycombed pattern to allow air flow from the exterior wall into the void beneath the suspended slab.

Air Bricks are being used on the external wall to allow ventilation within the void space underneath the suspended timber slab

4.3 FLOOR FINISHES

4.3.1 MANUFACTURED FLOOR TILES

DEFINITION:hard, modular surface covering used to cover floors in homes, commercial buildings, and other structures. They are typically made in relatively small, repeating units, from materials like ceramic and porcelain, and come in a variety of shapes, sizes, colours, and designs.
ADVANTAGES:

Durability. They are made from materials such as ceramic and porcelain making them resistant to scratches, dents, and other types of damage. This can make them a good choice for high traffic areas such as entrances, kitchens, and bathrooms.
Low maintenance, requiring only occasional wiping down with a damp cloth or swept.
They can be arranged in different patterns and designs to create unique and eye-catching designs.
They can be a cost-effective option, are long lasting, and can be installed quickly and easily

Types of Manufactured Floor Tiles:

Ceramic tiles are made from clay that has been fired at high temperature, making them durable and long-lasting.
Porcelain tiles are a type of ceramic tile that is denser and more water-resistant than standard ceramic tiles. They are often used in bathrooms and other areas where water is present, such as shower enclosures.
Glass tiles come in a variety of colours and shapes. They are often used as accent tiles in bathrooms or other areas.
Vinyl tiles can be a cost-effective flooring option that is easy to install and maintain. They come in a variety of colours and patterns, and some are designed to look like natural stone or wood. They can be indented or have raised profiles to increase grip and to introduce variety.
Cement tiles are a type of handmade tile made from cement, sand, and pigments. They are often used in kitchens and bathrooms.

Ceramic Tile

Porcelain tiles

Vinyl Tiles

Glass Tiles

CERAMIC TILE INSTALLATION
1.Preparation of Concrete Sub Floor- clean the concrete surface off dust and debris using either a shop vacuum or a broom, followed with a robust detergent solution to ensure that the floor is clean to standards.
2.Levelling Sub Floor- Check on the level, smoothen the compound against the adjoining concrete with a trowel and give it a break to dry.
3. Establishing the Layout of the Tile Floor- This is to ensure all edges of the space will be covered in the right pattern arrangement
4. Mortar Application- Using a Smooth trowel, apply the mortar on the concrete sub floor. Then, using a notched trowel comb the thin-set and ensure your lines runs horizontally throughout the surface. This combed mortar surface provide grip to the tile pieces
5. Tile Placement- Install the tile by pushing it slightly into the mortar bed
6. Tile Spacing & Levelling- Use spacer bars to ensure each tile have consistent gap between each other, and to provide sufficient grout space in between the tiles. Use a level to ensure that the tiles are placed according to the desired degree.
7. Grouting- Fill the grout space with grout mix and wipe the excess grout with damp cloth/mop
8. Water Proofing- Apply sealant where needed especially in bathroom and kitchen area, to increase water resistance.

4.3.2 NATURAL STONE TILES

DEFINITION:Natural stone tile is tile cut directly from stone blocks formed over millions of years as opposed to man-made tile that is manufactured by combining various substances and chemicals such as porcelain or ceramic tile.
These stone tiles are cut into specific size according to manufacturer's details and the installation process is similar to those of factory-made tiles
TYPES OF FINISHES:

Polished - glossy and reflective surface. to helps the color and pattern of the stone to appear more saturated. It also show dust, smudges and wear more quickly than other finishes. Can also be more slippery, especially when wet.
Honed - satin-smooth surface. Colors and patterns appear more earthy and less shiny. Often used in bathrooms and kitchen floors because it gives more traction when wet.
Tumbled - similar to the honed, but leaves more of the stone’s natural texture. The floor won’t be completely flat and smooth but will have a more chiseled look.
Flamed - involves a hot torch flame to create a non-slip finish with a semi-rough surface. Used outdoors or in any room that needs a less slippery surface.
Brushed - brushed with wire wheels and brushes to obtain a brushed finish. The result is a smooth-to-the-touch stone that looks casually worn

TYPE OF NATURAL STONE FLOORING

MARBLEa softer calcium-based stone prone to scratching and etching from acidic foods and drinks that dull the finish

GRANITEmost durable of all stone flooring, not easily scratched, etched or scorched

TRAVERTINEformed by hot spring water that bubbles through limestone. prone to scratching and etching

SANDSTONEa sedimentary rock composed mainly of cemented silicates, quartz, feldspar, clays, and silt. soft and relatively porous, so it can scratch and stain easily

SLATEcharacterized by its fine grain and unique cleft texture. comes in multiple colors such as green, red, purple, black, and brown, determined by the type and amount of iron and other organic material it contains.

LIMESTONEmade of calcium carbonate in the form of mineral calcite like marble. Since it forms in shallow marine water, fossilized creatures, corals, shells, and algae can be seen in the pattern.

ADVANTAGES:

solid and durable, with long life span
good heat retention, suitable for colder climate area
Natural feel to the building due to its organic colors and patterns
Repairable by repolishing & refinishing to look like new.
Easy maintenance.

DISADVANTAGES:

Expensive compared to ceramic or porcelain tile
lesser durable stones can easily scratch, etch and scorch.
traces of iron in the natural stones, manifested as bright red or amber hues on the surface of the stone, can oxidize or rust, degenerating the tile over time
natural stone is quite porous and needs to be treated with a sealing agent periodically to protect its surfaces.

4.3.3 RAISED / CAVITY FLOORING

DEFINITION:An elevated flooring system that creates a void between the structural floor and the floor covering, supported by pedestals or stringers.

FUNCTION:

The void allows for the concealed installation of various utilities, such as electrical wiring, data cables, and HVAC systems.
The pedestals where the floors are mounted, are adjustable, allowing for precise leveling of the floor surface
The flooring panels used in raised access flooring systems are removable (or via Hatch Panels), providing easy access to the underlying infrastructure when needed.
cavity floor can be fitted with floor heating or air-conditioning.
cavity floor system can be used with a wide variety of surfaces like e.g. elastic or textile surfaces, parquet, laminate, or stone.
commonly used in commercial buildings, data centers, server rooms, control rooms, and other spaces where efficient cable management and flexibility are crucial.

ADVANTAGES:

Dry laying or installation as moisture component is not required, thus reducing screed cost and speeding completion.
Enhanced Flexibility and Adaptability for easy reconfiguration of the floor layout, accommodating changes in technology or office space requirements.
Easy Access to Utilities, providing neat and organized appearance and easing maintenance of underfloor services
Improved Airflow and Cooling Efficiency due to the void space created by the raised access floor, especially crucial in sensitive areas requiring proper ventilation and temperature control such as data centers
Reduced Maintenance Costs as damaged panels can be individually replaced without affecting the entire floor, minimizing both downtime and expenses.

DISADVANTAGES:

Lack of moisture-resistant property, leading to potential damp issue underneath floor surface.
Increased Installation Complexity as expertise and precision are required to properly level the pedestals, place the stringers and fitting the panels to ensure stable and even floor surface.
Height and Space Considerations as it adds height to a room, which can be a limiting factor in spaces with low ceilings. Careful initial design must account for the cavity space below the floor
Potential Noise and Vibration, particularly relevant in environments where noise reduction is crucial, such as offices or libraries. Proper acoustic insulation measures should be implemented to mitigate potential disturbances.
Limited Load Capacity may not be suitable for heavy equipment or machinery.
Higher Initial Cost including materials, installation, and additional considerations such as cable management and finishing. However, it is important to weigh this upfront expense against the long-term benefits and the potential cost savings in maintenance and adaptability.

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