Waffle Formwork
In today’s construction industry, the use of modern structural systems to reduce costs, improve the quality of architectural plans, and enhance the seismic performance of buildings has become more important than ever. To select a suitable structural system, it is initially necessary to have a structural floor with diaphragm performance according to Standard 2800, among which one can consider beam-slab floors, two-way waffle slabs, and one-way waffle slabs. Of course, with proper implementation of joist-light form floors and the ability to model this type of floor in relevant software, it is possible to achieve a floor with appropriate performance.
When did Beton Baspar Sanat Company start producing waffle formwork?
Accordingly, Beton Baspar Sanat Company, considering the country’s needs and the increasing progress of construction engineering in our beloved country, initiated the production of two-way and one-way waffle formwork. Around the year 2011 (1390 in the Iranian calendar), when the first waffle floors were designed and constructed in Tehran, Beton Baspar Sanat, in collaboration with structural and architectural designers, including Mr. Farzad Deliri, began producing two-way waffle formwork measuring 60×60 cm with a height of 30 cm, and 90×90 cm waffle formwork with heights of 30 and 40 cm. In Chapter 9 of the National Building Regulations, a section is dedicated to slabs and floors with two-way joist performance, which must be considered when producing two-way waffle formwork.
The most important point in this regulation is that the free distance between two waffle joists should not exceed 75 cm, which has not been observed in some types of waffle formwork produced in the market.
Why should waffle slabs be used? What is the role of waffle formwork in waffle slabs?
Waffle slabs, as a modern and efficient system with two-way load distribution and two-way performance, have gained a special place in construction projects. Due to their grid-like and honeycomb appearance, two-way load transfer capability, and reduction of dead load, waffle slabs have become an attractive and widely used option among structural designers.
According to various international codes such as ACI 318 and Eurocode 2, waffle slabs, in addition to increasing structural stiffness, significantly save concrete and steel compared to beam-slab systems of the same thickness. This feature has made the waffle slab system, together with appropriate waffle formwork, applicable in large international projects as well as in various medium- and small-scale urban buildings.
Top view of 90×90 cm waffle formwork with 40 cm height and 20 cm joist width before placing rebar
Top view of 90×90 cm waffle formwork with 40 cm height
Bottom view of 80×80 cm waffle formwork with 28 cm height for a 12-meter span
The price of each 80×80 cm waffle formwork with 28 cm height is approximately 580,000 Toman.
Execution detail of 80×80 cm waffle formwork with 28 cm height
Execution detail of 80×80 cm waffle formwork with 28 cm height
History of Waffle Slabs
The idea of designing grid slabs (waffle slabs) first emerged in the 1950s in Europe and the United States. The main goal was to achieve a system capable of covering longer spans (column-to-column distances of around 10 meters or more) without the need for heavy beams. The first projects using waffle formwork and waffle slabs included multi-story parking structures and commercial buildings, which faced limitations with traditional beam sizes defined by regulations.
With the advancement of formwork technology and the introduction of lightweight plastic and fiberglass forms, various waffle formworks such as 60×60, 75×75, 80×80, and 90×90 cm with different heights for various span lengths were rapidly adopted in large projects such as airports, shopping centers, sports halls, and high-rise buildings. In Iran, waffle slabs have been introduced over the past two decades and are now widely used in modern construction projects, including office complexes, cultural centers, and luxury residential buildings.
What is a Waffle Slab? (Waffle Slab Definition)
A waffle slab, or two-way ribbed slab, consists of a series of intersecting joists arranged regularly in two perpendicular directions. The voids between the joists are formed by temporary waffle formwork, which can have various dimensions. Today in Iran, there is high demand for 80×80 cm waffle formwork with a height of 28 cm and 60×60 cm waffle formwork with heights of 25 and 30 cm. The spacing between waffle forms usually ranges from 10 to 20 cm and is selected based on the span and column-to-column distances in the architectural plan.
Designing waffle slabs using waffle formwork allows:
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Reduction of slab weight
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Transfer of loads in two directions
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Increased flexural stiffness and overall system strength
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Easier passage for mechanical and electrical installations
Advantages of Waffle Slabs
Material Savings:
By removing concrete in non-essential areas (tensile regions of the waffle slab), the volume of concrete used is reduced, and construction costs are approximately 20–30% lower than flat slabs. This feature not only contributes to economic savings but also results in a lighter slab with a lighter foundation.
Long Span Coverage:
This system can cover spans of up to 15 meters or more without large suspended beams, while flat slabs typically cover only 6–8 meters. This capability is crucial for commercial and industrial projects requiring open, column-free spaces.
Dead Load Reduction:
Removing excess concrete lightens the slab and improves the building’s seismic performance, which is particularly important in earthquake-prone areas.
Architectural Beauty and Exposed Ceilings:
The underside of the slab is a regular grid, which in many projects serves as the final ceiling without additional finishing. This feature is highly valued in the design of auditoriums, cultural centers, and modern commercial buildings.
Ease of Installation for Services:
The voids between joists provide a suitable path for pipes, cables, and other utilities, reducing the need for separate channels or additional openings.
Durability and Longevity:
With proper design and execution, waffle slabs can remain functional for decades with minimal maintenance.
Disadvantages of Waffle Slabs and Waffle Formwork
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Requires precise formwork and substructure
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Relatively longer construction time compared to flat slabs
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Needs skilled personnel for correct reinforcement placement between waffle forms and proper positioning of shear studs
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Initial cost of waffle formwork is higher, but it is compensated by reusability, with over 20 uses possible
Applications of Waffle Slabs and Waffle Formwork
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Office and commercial buildings with wide spans greater than 10 meters and vibrations/frequencies above 5 Hz
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Multi-story parking structures where finishing of the ceiling is unnecessary using the waffle formwork surface
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Multipurpose halls and cultural/educational centers
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Architectural projects requiring modern exposed ceilings
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High-rise and industrial projects requiring long spans, high strength, and reduced dead load
International examples include airports, shopping centers, and luxury residential projects with minimum column-to-column distances of 10 meters. In Iran, commercial complexes, convention halls, and high-rise projects have also utilized waffle slabs and waffle formwork.
Steps for Waffle Slab Construction
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Preparation and Formwork Substructure:
Install temporary shoring and scaffolding to support the weight of the formwork and fresh concrete. -
Placement of Waffle Formwork:
Forms are placed regularly according to the designed spacing. -
Reinforcement Between Waffle Forms:
Top and bottom rebar grids and column perimeter reinforcement are installed. -
Concrete Pouring:
Concrete with appropriate slump (10–12) is poured and fully vibrated to remove air bubbles. -
Curing:
Maintain sufficient moisture to prevent cracking and ensure final strength. -
Removal of Waffle Formwork:
After achieving the required strength, waffle forms are removed and can be reused for the next project. On average, one set of waffle forms can be used to construct three 8-story buildings.
Designing Waffle Slabs According to Codes
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ACI 318-19: Slab thickness 80–120 mm, void dimensions 60×60 to 90×90 cm, deflection control, and punching shear around columns
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Eurocode 2 and Chapter 9 of the National Building Regulations (Design of Reinforced Concrete Buildings): Similar provisions for deformation control and reinforcement design
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Additional details include two-way load analysis, deflection control for long spans, and design of joists and reinforcement grids
Comparison of Waffle Slabs with Other Structural Floor Systems
Features
| Feature | Flat Slab | Prestressed Slab | Cobiax Slab | Waffle Slab |
|---|---|---|---|---|
| Concrete Consumption | High | Medium | Lower | Lower |
| Span Coverage | 6–8 m | 10–12 m | 10–12 m | 12–15 m |
| Architectural Appearance | Simple | Simple | Medium | Modern / Exposed |
| Structural Weight | Heavy | Medium | Light | Light |
| Construction Cost | Lower | Higher | Higher | Balanced |
Economic Review of Waffle Slabs
Despite the initial cost of waffle formwork, savings in concrete and steel, reusability of the waffle formwork, and reduced labor and construction time make this system completely economical for medium and large projects. In fact, the cost of the waffle formwork is usually recovered in the first project.
Environmental Role and Sustainability
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Reduction in material consumption and transportation energy
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Use of recycled and new materials in the production of waffle formwork
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Reduction of construction waste and increased lifespan of the formwork
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Compatibility with green and sustainable building projects
Raw Materials and Products of Beton Baspar Sanat Company
What are the raw materials of waffle formwork? What is the difference between white and black waffle formwork?
Beton Baspar Sanat uses high-quality and durable raw materials to produce various types of waffle formwork. These waffle forms are primarily made of polypropylene (PP) and polyethylene (PE), which offer the following features:
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High mechanical strength
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Lightweight and easy to transport
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Long lifespan and durability
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Reusable in multiple projects
Waffle formwork materials can be either virgin petrochemical or processed recycled materials, which, in addition to reducing cost, contribute to environmental protection and sustainable construction.
Different Sizes of Waffle Formwork Produced by Beton Baspar Sanat
The company manufactures waffle formwork in various dimensions and heights to meet the needs of different projects:
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60×60 cm Waffle Formwork
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Height: 19, 25, and 30 cm
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Joist Width: 10 cm
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Suitable for medium buildings and projects with short to medium spans
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75×75 cm Waffle Formwork
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Height: 28 cm
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Joist Width: 10 cm
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Suitable for projects with larger spans and higher stiffness requirements
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80×80 cm Waffle Formwork
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Height: 28 cm
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Joist Width: 12 cm
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Suitable for heavier projects and medium-long spans
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83×83 cm Waffle Formwork (Height 40 cm)
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Height: 40 cm (one of the few available 40 cm high waffle forms in the market)
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Joist Width: 13 cm
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Ideal for high-rise projects and spans longer than 10 meters
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90×90 cm Sky Dome (Sky Dome Waffle Formwork)
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Dimensions: 90×90 cm
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Height: 30 and 40 cm
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Joist Width: 20 cm
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Suitable for very large spans up to 15 meters and special architectural projects
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Half Waffle 80×40 cm (Half Waffle Formwork)
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Same as the regular waffle form, but one dimension is halved
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Example: 80×80 becomes 80×40
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Use: Projects with smaller spans or specific architectural spaces
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Conclusion on Waffle Formwork and Waffle Slabs
The waffle slab is a modern, strong, and economical system that, with its numerous advantages such as reducing structural weight and dead load, saving materials, providing architectural beauty, and allowing long-span execution, has gained a prominent place in the construction industry.
Beton Baspar Sanat, with technical knowledge, experience, and high-quality waffle formwork, is ready to provide innovative solutions for the execution of waffle slabs and production of various waffle forms for different construction and civil projects. The company’s products, produced according to international standards and using high-quality materials, guarantee the durability and quality of your project. Premium white waffle formwork, top-grade black waffle formwork, and second-grade black waffle formwork are available. A one-year warranty for breakage of premium white and black waffle forms with new molds is offered only by this company, demonstrating its commitment to delivering high-quality products to clients.