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4 Different Concrete Forms and Their Uses

01 Dec 2018, Posted by F.A. in Concrete Forms

Formwork is used by manufacturing molds made out of certain materials onto which concrete is poured. There are a number of different types of concrete forms used in construction, and the method for choosing one usually relies on the project specifications.

Formwork is used by builders and contractors as a tool to help complete projects quickly, offering a reliable way to cast and construct the vital components of the structure, such as the roof and the floors.

Usually, once poured, the concrete is left to harden in the structure after which the formwork is stripped. However, with the advent of stay-in-place formwork techniques, it is often left as part of the structure.

Wood Forms for Concrete Slabs

Wood forms are the most basic and oldest of concrete formwork slabs and are still heavily used when constructing smaller structures.

Wood forms consist of wooden boards, usually plywood, that may be screwed or nailed together to additional stakes, which are usually made of wood and steel. When using wood formwork, the stakes are driven into a prepared sub base, and the forming boards are set to a proper level or slope, using leveling devices.

Leveling devices include hand levels, laser levels, and string lines. Additionally, to secure areas where one board butts up against another, contractors use additional boards.

Thinner and slimmer cross-section boards are used when the need for rounded edges, turns, or even free-form arises. Concrete can often stick to wood and to counter this issue, wooden planks are regularly coated with a low-grade oil or a particular form-release agent.

Preventing concrete from sticking to the wood is critical for two reasons. Not only does it keep the formwork clean, but it also allows contractors to use them multiple times before they are discarded.

Concrete Wall Forms

Pre-manufactured concrete wall forms are used for pouring walls or larger structures – such as when building piers or building foundations. Pre-manufactured wall systems are generally made out of engineered wood and reinforced with a metal frame, or consist of an entirely metal body.

These systems sometimes referred to as gang forming systems,  are designed to attach and form a uniform structure using a system of latches or pins. Additionally, pre-manufactured wall systems also make use of a tie when holding reinforcing bars in place inside the wall form, and in order to secure one section to another when walls are being poured.

Pre-manufactured wall forms are available in a wide variety of shapes and sizes, with most manufacturers willing to produce custom sizes for specific projects.

Insulated Concrete Forms (ICFs)

An insulated concrete form system consists of a hollow block of insulating materials that fit together and is filled with concrete, and further reinforced with steel.

ICF systems are constructed using a foundation slab, and the system remains in place to become the foundation and the exterior wall system. Once the block of insulating materials is placed, a network of metal reinforced bars are placed inside the block wall structure – and lastly, water-mixed or ‘high slump’ concrete is poured in the block wall structure.

ICFs are extremely energy efficient, and the foam-concrete sandwich is highly durable – making it suitable to be used as walls, roofs, and even floors!

Foam and Decorative Concrete Forms

Concrete has gone from being a construction component to being used inside the house, in fancy concrete countertops, and other decorative precast products. The growth in popularity of such items has led to new, innovative methods of concrete forming.

These non-traditional and unconventional concrete forming methods are generally used to create negative spaces or inverted forms, where the concrete piece is usually pored upside down to achieve the desired fancy effect or texture finish.

Decorative concrete foams are generally made of materials such as melamine, laminated board, acrylic glass, or screw mounted to a large board. The inside of the forms is often attached with particular inserts that provide decorative edging or artistic relief.

There has been a sharp rise in the use of decorative form liners, owing to the rise in municipalities and states looking to add to their concrete construction projects. The inside of the forming system is attached with plastic sheets with a relief of tile, stone, or artistic designs – which leads to the concrete assuming the shape of the design, and eventually a decorative concrete surface.