What Is Concrete Topping | Topping Slab Definition | Types of Topping Slab | Advantages & Disadvantage of Topping Slab

Topping Slab

What Is Concrete Topping?

A Concrete topping is a process of laying out a layer of high strength concrete on the old worn-out layer of the concrete. It is nothing but placing a layer of concrete over the existing slab in order to give a finished floor surface on the old layer of concrete.

Concrete topping slabs are usually applied on top of the structural floors in order to provide a finished floor surface.

Concrete Topping

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Topping Slab Definition

A  topping slab is defined as the overlay which is designed in order to provide a dense, abrasion-resistant, and finished floor surface for multiple purpose use such as providing a wearing course to support traffic loads in parking facilities.

Providing a level surface for interior floors in our home, providing a special base for the electrical and mechanical equipment, and to resurface worn or damaged floors.

In this article, you will get to know all about topping slab its types, purpose, Construction, and advantages and Construction process.

Purpose of Topping Slab

  1. The use of the topping slab is to provide waterproofing.
  2. It provides abrasion resistance to the underlying slab.
  3. It provides a wearing course to support the loads coming on it.
  4. It provides a level surface to the floor.
  5. Topping slab helps to develop additional superimposed load-bearing capacity.

Also, read: What Is Plumbing | Systems of Plumbing | Difference Between One pipe, Two Pipe, Single Stack, and Single Stack Partially Ventilated | How to Choose of Plumbing System.

Need for Construction of Topping Slab

Warehouses and factories are considered as the hottest sector for concrete Construction.

Nowadays Topping slab is widely used in Re-development and Construction projects because it is cost-effective and aesthetically pleasing as compared to other slabs.

Topping slab is more sustainable and high-performing. They provide finer finish, healthy indoor air quality, and stronger foundation that’s it is widely accepted and recommend in the construction.

Tooping Slab

Also, read: What Is Self Compact Concrete | What Is J-ring Test | Equipment of J-ring Test | Procedure of the J-Ring Test

Types of Topping Slab

The Concrete Topping Slab is mainly categorized into two types, Bonded Topping Slab, and Unbonded topping slab.

  • Unbonded Topping Slab.
  • Bonded Concrete Slab.

1. Unbonded Topping Slab

In this type, the Topping Slab is not bonded with the underlying existing concrete slab. There is no bond between both slabs.

The Concrete topping slab is not mechanically adhered to or bonded to the underlying structural floor. Unbonded systems are provided when it is desired that the two slab courses move independently or to permit easy replacement of the topping slab at a later period of time.

Unbonded construction with a minimum thickness of 100mm is preferred.

If there are any cracks in the base slab or if a good bond is only partially attainable or totally lacking.

A slab thickness of 127 mm provides a better serviceable life.

Unbonded topping slab allows for the introduction of a radiant system for heating and cooling or ice melting applications. Radiant systems are an integral part of Sustainable building construction.

2. Bonded Concrete Slab

In this type of slab, the concrete topping is adhered to or bonded with the underlying concrete slab. Bonded slabs are usually used for both structural and functional purposes.

The Bonded concrete slab can be used for both light duty as well as heavy-duty slabs.

The minimum thickness of the bonded concrete slab is 1 to 2 in. (25 to 50 mm).

Also, read: What Is Self Compact Concrete | What Is Slump Flow Test | Equipment for Slump Flow Test | Procedure of Slump Flow Test

Steel Reinforcement in Topping Slab


Reinforcement such as deformed bars and welded wires are used in the construction of the topping slab in order to reduce its shrinkage and avoid crack formation.

The addition of reinforcement will minimize the potential crack width.

Advantages of Topping slab

  1. It is used to strengthen the weak and fragile concrete surface.
  2. It helps to provide a finished surface to the floor and increase its thickness.
  3. It helps to provide specific slopes to the post Construction drainage.
  4. It reduces the Repair cost for finished Construction.
  5. It increases the load-bearing capacity of the slab.

Disadvantages of Topping Slab

  1. There may be chances of crack formation due to lack of bonding between new and old slab.
  2. Laying concrete layer on existing one increase the dead load of the structure.
  3. Concrete topping raise the level of the existing slab.

Also, read: What Is Self Compact Concrete | What Is Slump Flow Test | Equipment for Slump Flow Test | Procedure of Slump Flow Test

What Is Sand Topping Mix?

Sand Topping Mix is a uniformly blended mixture of portland cement, graded sand and other ingredients.

This mix is ideal for repairing and topping damaged concrete surfaces that are less than 2 in. thickness.

It can be applied to a 1/2 in. The thickness and will maintain the strength which is required for traffic areas.

  • Sand topping mix is used for repairing the damaged concrete having less thickness.
  • It is used as a base for laying bricks.
  • Used for patching and leveling steps.
  • It is also used for repairing the cracks.

What Is Micro-Topping?

Micro topping is a cement product that is widely used for repairing cracks in concrete components like beams, columns, and walls.

It is used in RCC jacketing to increase the strength of the concrete structures. Micro topping is suitable for a modern environment and gives a classic look to the surface.

Also, read: What Is Concrete | 31 Different Types of Concrete

Construction Process of Laying Concrete Topping

  • Assessment of Base Concrete.
  • Preparation of Base Concrete.
  • Placing of Topping Concrete.
  • Finishing.
  • Curing.

Construction Process of Laying Concrete Topping

1. Assessment of Base Concrete

The existing concrete on which the topping should be done should be free from cracks. The existing concrete should be hard and strong. It is not preferred Tu to construct concrete topping on a slab having a weak base.

2. Preparation of Base Concrete

It is one of the important steps before starting the construction of concrete topping. The surface on which the topping will be laid should be uniform and free from dust particles.

3. Placing of Topping Concrete

Before placing the topping concrete on the surface, it should be checked properly. The surface should be kept wet so that it cannot absorb water from the topping concrete.

4. Finishing

The surface of the topping concrete should be well finished. The finishing of topping concrete depends upon the place and its utility. The surface of the topping concrete should be smooth finish so that it looks aesthetically pleasing.

5. Curing

Proper curing should be done of topping concrete. It should be cured at least for seven days. Effective curing helps to achieve maximum strength and resistance to abrasion. It also helps to avoid shrinkage cracks on the surface of the concrete.

Short Note

Concrete Topping Slabs

Concrete topping slab is an overlay designed to provide a dense, abrasion-resistant, and finished floor surface for multiple purposes such as providing a wearing course to support traffic loads in parking facilities and bus terminals, providing a level surface for interior floors, providing a special base for electrical and mechanical equipment, and to resurface worn or damaged floors.

Minimum Thickness of Concrete Topping Slab

The minimum recommended thickness is 1 to 2 in. (25 to 50 mm) for a fully bonded concrete overlay placed on a base slab that is practically free of cracks and in which the concrete is sound, clean, and of good quality.

What Is Concrete Topping?

Topping concrete is defined as a layer of high strength concrete placed on an old, worn out concrete surface to provide a dense, abrasion-resistant surface, to increase structural depth and strength of the base concrete.

Topping Slab Definition

topping slab is a concrete slab poured over an existing subfloor, generally made of concrete or plywood. A topping slab is often intended to be purely decorative but nevertheless it has to maintain structural integrity. In order to do so, the minimum thickness needs to be 2″ (2-1/4″ on hydronic heat systems).

Types of Topping Slab

There are two major types of concrete topping slab namely bonded and unbonded toppings. Both are suitable for heavy duty and light duty concrete slab. The former generally includes residential, office, institutional, and light commercial uses.

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