By: Kathy Midence on August 28th, 2020
Types Of Concrete For Metal Decking: Structural Vs. Non-Structural Insulating
Do you have a project that is specifying metal deck and you know that it is going to have concrete poured over it?
You may already know that some types of metal decking come in composite and non-composite forms such as b-deck. But, did you know that there are also different types of concrete for different types of metal deck?
If you are trying to figure out what type of metal decking to use, knowing which type of concrete is being poured on top can be a key to figuring it out. The two basic types of concrete used with metal decking are: structural and non-structural insulating.
Just by the names, the purpose of each type is pretty straightforward. One is used structurally and the other as insulation and roof fill. Structural concrete is used mostly on composite and non-composite floor decking. Insulating concrete is used more often on roof decking as a part of the insulation system.
At Western Metal Deck, we talk to customers daily that aren’t sure whether they need composite or non-composite metal deck.
One way we try to help them narrow it down is by asking them “are you pouring concrete over the metal deck?” In some cases, we need to take it a step further and ask them what specific type of concrete is being poured. This has saved customers countless times from ordering and installing the wrong type of decking on their project.
In this article, we will cover both types and help you identify the different types of concrete for the different types of metal deck. We will cover the following:
- What is Structural Concrete?
- Types of Structural Concrete
- What Types Of Metal Deck Do I Use with Structural Concrete?
- What is Insulating Concrete?
- What Types of Metal Deck Do I Use with Insulating Concrete?
What Is Structural Concrete?
Structural concrete is a special type of concrete made from a mixture of aggregates, cement, and water. It is designed to withstand different levels of pressure, normally around 4,000 pounds per square inch. Structural concrete adds strength to the structure. The concrete works with the structural steel to withstand different stresses such as movements from earthquakes, wind, and other forces, and it does this over long span conditions.
Types Of Structural Concrete
There are two types of structural concrete used with metal deck: normal and lightweight. As mentioned above, concrete is a mix of aggregates, cement, and water. The type of aggregate used is what differentiates the two types of structural concrete.
An aggregate is a type of material used to mix with the cement. It is commonly a type of rock, clay, or even sand.
Normal Weight Concrete
Normal weight concrete typically weighs between 145 - 155 pounds per cubic foot. The type of aggregate used in this type of mix is normally crushed stone.
Lightweight concrete typically weighs 110 pounds per cubic foot. The type of aggregate used in this mix is normally slate, clay, or shale.
What Types Of Metal Deck Should I Use with Structural Concrete?
The most common type of metal decking used with structural concrete is composite metal deck. Composite metal deck comes in 1 ½”, 2”, and 3” depths, in a variety of gauges and finishes.
Structural concrete is used with composite metal deck because this type of concrete bonds with the metal deck. Once the concrete cures, the strength of the composite product is greater than the sum of the individual parts (concrete & metal deck).
To learn more about composite metal deck, check out our this article: What Is Composite Floor Decking & How Does It Work?
Another type of metal decking used with structural concrete is form deck, or non-composite floor deck. In this case, the metal deck does not add strength to the final product. The form deck is simply used to hold the concrete in place during the concrete pour and while the concrete cures.
To learn more about floor deck, you'll find this article valuable: Metal Deck For Concrete Types: Types & Uses Of Composite And Form Decking
What is Insulating Concrete?
Non-Structural insulating concrete is a product that is used as insulation over the metal deck. It is concrete that is mixed with insulating properties such as vermiculite or zonocel. It is lightweight, weighing approximately 28 pounds per cubic foot.
Prior to the introduction of rigid board insulation, insulating concrete was used alone as an insulation product. However, now it’s used together with the rigid board insulation.
Insulating concrete is poured over the metal deck and is then covered up with rigid board insulation. After that, another layer of insulating concrete is poured over the rigid board insulation. The concrete helps bond the products together.
Types of Insulating Concrete include:
- Zonolite- made with a vermiculite aggregate
- Perlite - made with a perlite aggregate
- Elastizell - this is a foam concrete
What Types Of Metal Deck Do I Use with Insulating Concrete?
The vast majority of insulating concrete is used on non-composite decking. As previously mentioned, insulating concrete is placed on top of the metal roof deck, then covered up with rigid board insulation, then another layer of insulating concrete is added. It then gets covered with built-up roofing. The metal roof deck comes in different profiles, in depths ranging from 1 ½” to 3” deep.
To learn more about roof deck, here's an article you might be interested in: What Is Metal Roof Decking? Why Is It Used On Buildings?
How To Choose The Right Metal Deck?
If you are pouring concrete over your metal deck, you want to make sure you choose the right metal deck. Whether you are using structural or insulating concrete you don’t want to find yourself in a position where you poured concrete over the wrong type of metal deck.
So how do you make sure you pick the right type of metal deck?
Well on most metal deck jobs, plans have gone through engineering. The engineer will have specified everything from the type of metal deck, type of concrete, accessories, to how everything gets attached to the framing. This is because of the different properties that each offers, including how far the decking will be capable of spanning, to how heavy a load it can carry, and even what types of stresses it can withstand.
If the engineer has specified a certain metal deck type and certain concrete type, it is important to purchase and install what has been specified. It is especially important to understand the differences between composite and non-composite metal deck. Some profiles are identical, however, the only thing that separates them are embossments on the vertical legs. Those simple embossments enable the structural concrete to bind to the metal deck and create a stronger system.
At Western Metal Deck we stock metal decking for concrete both structural and non-structural. We carry different types in different profiles, gauges, and lengths. Our sales reps have years of experience working with metal deck and can assist you today.