The best roof for fteel frameworks

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September 19, 2024
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What is the best roof for a metal frame? The framework of most buildings is made of metal, and roofs are an inseparable part of these structures. An appropriate roof should be insulated against moisture, wind, and rain, preventing moisture from penetrating the building. It must also have high resistance to storms and wind. To ensure that a roof functions effectively, high-quality materials must be used in its construction. In this article, we intend to introduce the best roofs for metal frame buildings and provide information about their advantages. So if you’re wondering which roof is better for a metal frame, stay with us until the end of the article.

What you will read!

Types of Roofs for Metal Frames

The roofs we mention are suitable for bolted metal frames. Which one is better depends on various factors. Among these roofs, we can name chromate roofs, composite roofs, steel deck roofs, and block-and-beam roofs. When engineers intend to select a roof, they first consider the following factors and then make their choice:

Building plan
Roof load
Underside appearance of the roof
Flooring method
Roof location
Desired lateral resistance
Desired thickness for the roofs
Fire resistance
Sound wave transmission
Total weight of the roofs and building
Installation method of utility systems
Building usage
Construction budget

Now, we will introduce each of the types of roofs suitable for metal frames separately:

➕ Chromate or Steel Beam Roofs

Steel roofs are constructed with open web joists and steel beams. The bottom chord of this roof is made with a strap, and its web is constructed using bent rebar. The fixed formwork is made of polystyrene and concrete blocks, while the temporary and infill formwork is made of lightweight composite materials that fill the empty spaces between the beams. The distance between the beams ranges from 73 to 100 centimeters, depending on the model of the formwork.

The roof is covered with 4 to 10 centimeters of concrete. The exterior appearance of the roof is very similar to that of a conventional block beam, but with the difference that the joists used in the chromate roof are different, as steel joists are used for this roof. Before installing the joists, it is necessary to ensure that there are no defects in them. This roof has high and integrated resistance due to the use of steel in its framework, and it offers more advantages compared to other roofs.

Read More: Understanding Metal frame connections

Types of Chromate Roofs

Chromate roofs are divided into three models:

Polymer Chromate Roof: This roof uses polystyrene blocks and utilizes less steel and joists. Simpler plastering is done underneath the roof.
Chromate Joist Roof: This roof is simpler than the conventional joist roof.
Composite Chromate Roof: In this roof, fewer joists are used. Instead of using I-beams or honeycombs, open web steel joists are applied. The open web joists are filled with concrete and covered with a concrete slab.

✔ Advantages of Chromate Roofs

Chromate roofs have many advantages, including:

The execution of this roof is done quickly and easily; so that after 48 hours of pouring concrete, it can be walked on.
The joists are well welded to the framework, and after the concrete of the framework and roof is solidified, they become integrated.
This roof does not require shoring; therefore, multiple roofs can be prepared simultaneously, and concrete pouring can be performed on them at the same time. This is especially beneficial for buildings with small footprints and many stories, saving time and costs.
Due to the lower level of the blocks compared to the joists in chromate roofs, the coverage of soil and plaster underneath the joists is greater than in other areas of the roof, resulting in less absorption of suspended particles.
This roof does not require shoring; therefore, multiple roofs can be prepared simultaneously, and concrete pouring can be performed on them at the same time. This is especially beneficial for buildings with small footprints and many stories, saving time and costs.
Since the joists can bear the weight of wet concrete, blocks, etc., before pouring, the stress created in the concrete is very low.
Shoring can be eliminated when executing this roof, resulting in a more uniform underside and reduced steel consumption.
There is the possibility to design and execute roofs with long spans and specific load-bearing capabilities.
Due to the large spacing of the joists, there is no need to cut them extra. Thus, the installation of ducts for chimneys, ventilation pipes, etc., is easily feasible.
It has high ductility and good resistance.

➕ Composite Ceilings or Mixed Ceilings

One of the best ceilings for a metal frame is composite ceilings. Its components include secondary beams, shear connectors, concrete slabs, and thermal rebar grids. These ceilings are constructed using steel and concrete, and to create a cohesive structure, angles or shear connectors are utilized so that the angle and concrete engage with each other. In this ceiling, the upper flange of the beam, along with the shear connector, supports the pressure on the ceiling, while the lower flange of the beam withstands the tensile forces.

Composite ceilings are made from a combination of materials to withstand natural elements. These materials include asphalt or asbestos shingles, wood, slate, etc. When these materials are mixed, a combination is formed that can serve as the best ceiling for metal frames. Additionally, the mix of different materials results in diversity in composite shingles. Composite shingles come with a warranty of 30 to 50 years, while other roofing shingles may have a warranty of 15 to 20 years. This is due to the greater durability of composite shingles compared to other types.

The features of composite shingles include their availability with additives for protection against algae, moss, UV radiation degradation, and more. Other characteristics include resistance to cracking and splitting, not delaminating, and not warping. Eco-friendly shingles are made from recyclable materials such as industrial plastics, jute fibers, and materials from demolished roofs. Various types of composite ceilings are available in different colors, shapes, and sizes, and they are reasonably priced.

✔ Advantages of Composite Ceilings

Now that we have introduced composite ceilings, let’s discuss their advantages:

They are constructed quickly.
They are lighter than other ceilings.
They do not require shoring.
They save on concrete consumption.
Due to their combination with concrete, the size of the ceiling beams is reduced.
They create a rigid diaphragm.
They eliminate the effects of steel underneath the ceiling.
They provide a unique cohesion between the ceiling and the frame.
They have high resistance.

➕ Steel Deck or Metal Deck Ceilings

Steel deck, or metal deck, is another type of ceiling that is used in the construction of metal frame buildings. This ceiling is very similar to composite ceilings. It is constructed using corrugated galvanized sheets. The installation of this ceiling is cheaper and easier compared to other types of ceilings. There is no need for shoring when installing these ceilings, allowing multiple ceilings to be executed simultaneously. Additionally, the formwork stage is eliminated in its construction. This ceiling consumes less concrete, has a low thickness and lightweight, and boasts high durability and longevity, making it suitable for use in all climatic conditions.

✔ Advantages of Steel Deck Ceilings

The advantages of steel deck ceilings include:

Multiple steel deck ceilings and concrete pouring can be executed simultaneously in a short time.
Tension rebars and secondary beams are eliminated.
Span lengths of up to 4 meters can be achieved without the need for shoring.
Sheets are welded to the beam using shear connectors.
Human error is minimized.
They are resistant to fire and earthquakes.
They form a rigid diaphragm in the ceiling.
Sound transmission is reduced.

➕ Block and Beam Ceilings

This ceiling is constructed using cast concrete. Beams and blocks are manufactured in a factory or workshop, and blocks are used at regular intervals in the design and execution of the ceiling. To establish connections between each section of the block, beams are utilized. According to the design and supervision of the structural engineer, the beams and blocks are positioned on top of the load-bearing walls. Instead of hollow concrete blocks for lightweight insulating slabs, polystyrene blocks are used to help keep buildings warmer in winter and cooler in summer.

✔ Advantages of Block and Beam Ceilings

Block and beam ceilings have many advantages, making them quite popular. Some of these advantages include:

They have high resistance to lateral forces due to the creation of a rigid diaphragm.
Loads are better distributed, preventing ceiling vibrations.
Due to the hollow nature of the blocks, they provide good thermal and acoustic insulation.
Less steel or reinforcement is used compared to the load-bearing capacity of the ceiling.
Since concrete is eliminated in the tensile area and replaced with blocks, concrete consumption is reduced.
There is a saving in formwork costs compared to concrete slabs.
As beams and blocks are produced in a factory or workshop, less manpower is required for ceiling installation.

Conclusion

Today, metal frame roofs have become highly regarded and are constructed with great precision. Considering the information above, there are various criteria for selecting the best roof for a metal frame structure. After reviewing different models, you can choose the suitable roof for your metal frame. Our colleagues at Saman Dezh can also provide guidance in this regard. If you have any questions or uncertainties about these roofs, our experts are ready to assist you and clarify any doubts you may have.

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