Go to any multi level car parking in Dubai and check upwards. The ceiling is quite open with just a few columns visible; the most likely form of this ceiling is double tee slabs. They are the structural workhorses that span across floors for large distances without the forest of the columns that are found in older systems, and being the preferred choice for developers and structural engineers across the UAE’s fast-moving and quality conscious construction sector, they have become a preferred choice.
This guide will discuss what double tee slabs are, how they function, the various sizes and types of slabs, where they are used throughout the UAE and what steps are required for getting Dubai Municipality (DM) approval when purchasing precast concrete.
Precast Concrete Double Tee Slabs: What are they?
A double tee beam, or double tee, is two T-beams connected together to form one load bearing unit. There is a good bonding between the flange (horizontal deck) and the two vertical webs under the deck, providing high load capacity for the slab over long spans.
Imagine the Greek letter π cut in half – the broad flat surface above two stems that are pointing downwards. Simple yet it will work great in load. Double tees are produced at the factory as precast elements, greatly reducing the time required for onsite production of cast-in-place double tees. Their amazing strength to weight ratio is due to prestressing, where high strength steel strands are stretched before the concrete is placed around them.
Standard dimension for Double Tee Slabs are listed below:
Sizing is important for the procurement of precast products for any project. Double tee slabs are available in flange widths up to about 15 feet (4.6m), web depths up to about 5 feet (1.5m) and spans as long as 80 feet (24m) or greater for larger installations. Common widths are generally from 8-12 feet wide, and the overall depths are usually 18-36 inches depending on the load and span requirements. Generally the stems are widest at the top and narrow to 4 inches at the bottom.
For larger or more specialized projects, custom configurations can always be made, and the manufacturer can make such adjustments for unique structural requirements. Generally, project drawings in UAE are in metric measurements and your precast manufacturer will convert the standard dimensions to millimetres during the shop drawing process.
There are two types of Double Tee Slabs.Double Tee Slabs come in two types
Not all double tee slabs are created equal. The right type can vary based on loading requirements, finish and the overall design of the project.
Standard double tee units (not topped) are delivered as a unit and then topped with a structure on site. This is frequently incorporated into the flange and is used to add composite strength, especially with parking structures.
An advantage of pre-topped units is that the topping is already in place before leaving the factory, minimizing on-site assembly time.
Compared to conventional double tee slabs, lightweight double tee slabs have a lower overall dead load due to the use of lightweight aggregate concrete, and are appropriate for projects that require minimizing foundation loading or for projects where weight reduction is an important factor in seismic performance.
Wide flange double tee units are designed for those projects where longer spans per joint and fewer joints are desired, such as a roof installation.
Inverted double tee slabs are less frequently used but there are some bridge and elevated structure projects in which the geometry is appropriate for the structural scheme.
Article on uses of Double Tee Slabs in UAE
Double tee slabs satisfy the requirements of the UAE’s growing skyscrapers and expanding industrial infrastructure, achieving a perfect blend between efficiency and sustainability.With Dubai’s skyline constantly rising and Abu Dhabi’s industrial base expanding, double tee slabs are well-suited for the region’s need for efficient and large span precast flooring systems that are environmentally friendly.
Double tees are inexpensive and reliable, and are a popular choice for parking structure designers and are great choice to use for flooring or roofing in other buildings when spans are limited to approximately 75 feet. The key applications are multi-level car parks in commercial and mixed use developments, large span industrial warehouse and logistics centres, airport infrastructure and cargo handling areas, sports halls and indoor arenas, and retail podium structures, which demand open floor plates throughout the UAE. Precast double tees have also been installed in parking structures throughout Abu Dhabi, where they offer the structural benefits and quickness of erection that make them an ideal choice for any type of parking structure application, including those that are underground and elevated.
The advantages of Precast Double Tee Slabs are highlighted here:
For many reasons, double tees are often the preferred option over cast in place slabs for engineers.
The biggest benefit is speed. Double tees can be installed in a matter of hours, and can be part of a fast turnaround that can mean the difference between profit and loss on a tight construction schedule.
Structural efficiency is a further attraction. The key reasons precast concrete parking structures appeal to owners and developers include the generally lower total cost, quicker construction time and the uniformity of product quality.
The design incorporates fire resistance, and usually a double tees will provide a minimum 2-hour rating, which is the minimum code standard for buildings if they are not otherwise protected.
The benefits continue with ease to integrate with other precast parts – double tees can be used in conjunction with precast wall panels, columns and beams to create a full precast building system. They are also easy to maintain throughout the lifecycle of the building and this is significant in the UAE geographical context where the coastal climate increases corrosion in exposed steel structures with high salt content in the air.
OEMs must obtain the approval of Dubai Municipality (DM) for precast concrete manufacturing
This is where sourcing precast concrete in Dubai begets specifics and a lot of it, if you’re sourcing precast concrete products in Dubai.
Dubai Municipality has issued the Administrative Decision No. (316) of 2012 governing Ready Mix Concrete Plant, Precast Concrete Plants and Central Batching Units to ensure that the manufacturers adhere to the approved quality regulations and specifications. This isn’t optional. In compliance with the regulations of Dubai Municipality, every precast concrete factory working under the jurisdiction of DM is required to have a Certificate of Conformity obtained from the Dubai Central Laboratory’s Certification and Quality Control of Products Section (DCLD-CQPS). DCLD-CQPS has recently published Technical Guide TG-02 outlining the operational requirements that are required to be met for precast concrete factories to maintain that certification.
In other words, if a precast company in Dubai is not registered under DM, then their products cannot legally be utilized for the construction projects that are subject to regulation in the emirate. In addition to factory-level certification, the building system must be approved and it will be the responsibility of the contractors and consultants to verify that the systems designed for the specific project are approved by Dubai Municipality. The Dubai Building Permits System (Dubai BPS) can be used to submit applications digitally for building systems approval.
Always ask your supplier to provide you with their current DM Certificate of Conformity when you are sourcing for Dubai project work and if you need to check, do so directly with Dubai Central Laboratory. A good manufacturer will be able to do this without reservations — if not, it’s a red flag.
What to Look For in a Double Tee Slab Manufacturer in the UAE
The UAE precast sector has a long history and is a well-established sector with skilled manufacturers in Dubai, Abu Dhabi and Sharjah. When considering a supplier, it’s important to note a few key points:
In particular, Dubai projects are highly sensitive to DM approval and certification, and are good quality indicators across all Emirates.
The maximum unit length a manufacturer can produce is determined by its production capacity and the length of its pretensioning bed, so it is advisable to verify against the span requirement for your project, before you place your order.
Close attention should be paid to quality control and the mix design due to the UAE marine environment for which concrete needs to be designed to withstand the effects of sulphates and chlorides. Request lab test reports from suppliers that verify durability performance and that list the admixtures used.
Specialist delivery equipment is needed for large precast items. Before committing, verify that the manufacturer will be able to accommodate your site’s access needs.
Strength is the difference between good suppliers and bad: Technical support and Shop drawings. A good precast partner is an integral part of your engineering team in determining connection details, camber allowances and erection sequencing, not just a supplier and stand aside.
Installation and Connection Details
Installing a double tee is not hard to do for an experienced precast contractor, but the structural connections must be carefully taken care of. Units are usually supported on precast beams or cast in place ledges at each end. Adjacent double tees are typically joined by embedded weld plates and steel connectors, which are welded on-site by certified welders ‘flange to flange’.
An evolving parking structure floor system concept is that precast double tee beams flange to flange with embedded connectors to form an integral multi-beam floor system. Typically, installation is completed with a structural topping layer applied on the precast flange to enhance the composite action and increase the load capacity of the completed installation, if specified.
Considerations for Costs in the UAE Market
Precast double tee slabs are a cost effective alternative, especially if the entire construction timeline is taken into consideration. In general, a factory produced product has fewer defects, less rework and more predictable delivery schedules than cast in place.
The price of concrete in the UAE varies depending on the quantity of units, the grade of concrete, the need for prestress, and the logistics for each site. While general pricing information is available online, it’s best to ask a DM approved manufacturer for a quote for the project for accurate project cost planning, construction budgets don’t have a lot of room for guesswork.
Final Thoughts on Precast Concrete Double Tee Slabs in the UAE
Precast concrete Double Tees are one of the most extensively tested structural floor systems today. They are suitable for use in parking garages, warehouses, and large commercial buildings across the UAE, as they are quick to assemble, long-lasting, and compliant with DM’s regulations.
When ordering sourcing double tee slabs for a project in UAE, key points are to check the manufacturer’s approval from Dubai Municipality, check the certificate with Dubai Municipality, check the shop drawing by a licensed structural engineer and check whether Dubai BPS has approval for the building system in which the project is being dealt with by Dubai Municipality.
Do the steps correctly, and that unique π-shaped slab will reliably carry your next project for decades.
Contact reference: Dubai Municipality (dm.gov.ae) Administrative Decision No. (316) of 2012, Ready Mix/Precast Concrete certification requirements and internal contact page of KKK Precast (original source content).
Some notes: The double tee origin/history section was omitted as names and dates could not be confirmed and added no value to the UAE anyway. I also combined the four confusing size ranges from the original into one unified range, instead of having it as its own, contradictory data point; if KKK’s own product spec sheet for double tees contains the exact numbers, send it over and I’ll replace the general industry range with those numbers.