Whether you’re building a concrete patio or a skyscraper, you’re going to need concrete forms to get the job done. Without concrete forms, your concrete won’t hold its shape and will be at risk of cracking and losing its strength. Concrete forms go hand-in-hand with other concrete placing techniques to ensure your concrete remains strong and durable. So to guarantee your concrete construction projects go smoothly, order enough concrete products for the job and make sure you use concrete forms.
Keep on reading and learn how to use formwork, the principles behind it, and why it is so helpful on the job site.
Formwork, also known as concrete forms, is a temporary or permanent mould used to create concrete slabs and structures. It’s a barrier that holds the fresh concrete in place and helps with shaping the concrete until the concrete is strong enough to hold its own weight and shape.
To work effectively at supporting the concrete’s weight and shape, concrete forms must:
Formwork is usually made from timber and plywood. But it can also be made from other materials, such as metals, ceramic, or glass fibre reinforced plastics.
Plywood formwork is also called shuttering. Shuttering is the most popular type of formwork and is created on-site using water-resistant plywood and timber.
When on the job site, concrete contractors will erect plywood, steel, or aluminium formwork to create the moulds of concrete slabs, walls, and other structures.
Concrete formwork includes the following components:
The formwork that comes in direct contact with concrete is called the formwork sheeting, or the formwork shell. This sheeting will mould the shape of the concrete and have the most influence on the finished concrete surface.
The formwork bearers, which are usually made of timber or steel beams and clamps, support the formwork sheeting. These distribute the concrete forces through the falsework, supporting structures, formwork ties, and soil.
Formwork ties are usually made of steel wire and are used to tie two formwork faces together to support horizontal pressure from vertical formwork.
The steel wire is slung around the formwork bearers, guided through boreholes in the formwork sheeting, and tightened by twisting the wire.
Once the formwork is constructed, concrete contractors will place rebar inside the formwork to reinforce the concrete.
Next, contractors will pour concrete inside the forms. Once the concrete hardens, they will remove (strip) the forms from the concrete structure if using temporary formwork.
To prevent damage to the concrete and difficulties when removing formwork, it’s important to consider the placement of formwork and the sequence in which the framework will be stripped.
Avoid using too many nails and supports (falsework) when building formwork, as this will be too difficult to strip later on. Only use as much as necessary to maintain the support of the formwork.
Temporary concrete forms should be left to support the concrete until the concrete has thoroughly dried and reached an ideal strength to support its shape. This usually takes about two days after pouring the concrete.
If you remove the formwork too soon, the concrete might begin to sag, crack, and collapse. Remember to be patient and let your concrete thoroughly dry before removing formwork.
Formwork is used for holding the shape of concrete while it dries. It is commonly used for building concrete for:
The type of formwork you use will depend on your project needs. A simple temporary plywood formwork, such as plank shuttering, is suitable for moulding concrete paths and driveways.
But if you’re building a concrete foundation for a home, you will want to use more sophisticated formwork, such as permanent insulated concrete forms.
Unlike traditional concrete forms, insulating concrete forms (ICF) are not removed once the concrete hardens. Instead, ICFs remain as permanent parts of the concrete structure.
While concrete creates the structure, the ICFs insulate the structure. Homes and buildings with ICF foundations are soundproof, airtight, and comfortable in all seasons. This insulation helps homeowners save on energy costs for heating and cooling throughout the year.
ICFs are often made from a combination of insulating materials, such as plastic foam beads and cement, or wood fibre and cement.
Another popular material for ICFs is expanded or extruded polystyrene. Expanded polystyrene is made by expanding plastic beads in a mould, similar to Styrofoam coffee cups.
Extruded polystyrene is made by expanding plastic resin and extruding through a die, similar to meat trays from grocery stores.
ICFs typically come in blocks or planks. ICF block systems are pre-formed with foam and metal or plastic ties. They are ready to stack and interlock when they arrive on site.
Plank ICFs are individual panels or planks of foam requiring assembly on site with ties.
Block ICFs save you time and labour costs, while plank ICFs save on shipping costs since they are more compact to ship.
These concrete forms usually provide at least two inches of insulation on both sides of a concrete wall.
ICFs are not only faster to place, but they also provide significantly better insulation compared to wood or steel frames. So if you’re planning to build a new home, consider using ICFs for a well-insulated foundation.
Formwork is necessary when there is no soil or other structural components to support freshly poured concrete and hold it in the desired shape.
Formwork is necessary for the construction of concrete and reinforced concrete structures, such as:
Vertical formwork is necessary for building concrete foundations, walls, and columns. Tie wires or tie rods are also used with this formwork to support the lateral pressure of concrete.
Vertical formwork must also be anchored to the subsoil to prevent lifting from buoyant forces in the concrete.
Horizontal formwork is necessary for constructing concrete ceilings and beams. This formwork must be supported against vertical and horizontal loads, using formwork load-bearers and columns, braces and struts, or a rigid connection to existing structures, such as walls and columns.
Concrete forms are an essential part of building sound concrete structures. When constructed correctly, formwork moulds concrete into the desired shape and supports the weight of concrete while it’s drying.
And most importantly, concrete forms allow concrete to reach its optimal strength and durability without sagging or cracking.
Unlike traditional formwork, engineered formwork is made of metal. They are prefabricated, not built on-site as the conventional ones. Engineered formwork consists of steel or aluminium, and since it is prefabricated using a more durable material, this option is often more cost-efficient and can be reused – up to 3 000 times! It is also more durable and reliable since a change in environment or temperature will not change its performance. Since you don’t have to spend time on setting up like the conventional ones, it makes the whole process faster, too.
It is clear that concrete forms are necessary for ensuring the concrete setting properly during a construction project, whatever the size of it. Even though timber is usually used for maintaining the form of concrete, there are different materials and types of formwork that can be used. However, prefabricated formwork is more useful for contractors, but you can easily sell them after finishing the project. A.L. Blair can help you with any project you have in mind, so don’t hesitate to reach out.
Poured concrete is a viscous solution that can take up to 48 hours to properly set. During the setting time, the concrete needs to be contained in a concrete form. Concrete forms or formwork are the supporting materials or molds that are used when working with concrete. They also determine the final shape of the concrete, because liquid takes on the shape of its container.
However, not just any material can be used as a concrete form, as formwork needs to be able to hold the concrete’s weight and shape. For the formwork to be useful, it should have strong joints to prevent leaks, a rigid structure so that it doesn’t bend or break under the weight of the concrete, and it should also be able to be used with horizontal and vertical bracing. Keep reading for more details and important information about how to use concrete forms.
Photo: istockphoto.comConcrete is used regularly in construction projects. For example, it can be poured to create supports for a fence or gate or as a foundation for a new shed. However, when concrete is initially mixed, it isn’t a stiff compound that will hold a shape without help. It is a thick, viscous liquid that is difficult to mix, and it’s hard to manage without using concrete forms.
A concrete form or formwork is a support or mold that the concrete is poured into. Temporary or permanent, the formwork is built into the shape that the user wants the concrete to take when the liquid concrete begins to dry.
Photo: istockphoto.comThere are several different materials that are used to make formwork, but the most commonly used material is timber. This is because timber is cost-effective, lightweight, durable, and flexible, allowing the concrete to shift while it sets without pieces breaking off or putting strain on the formwork.
For the best results, invest in timber formwork that is easy to work with, lightweight, and dried thoroughly. Also, make sure the timber doesn’t have any loose knots that could pop out and allow the wet concrete to seep through the hole. While there is the chance that wood formwork will warp if it absorbs the water from the concrete, this effect can be limited by treating the timber forms with a sealant.
Photo: istockphoto.comIn addition to timber, there are a few other common materials used to make concrete forms. Steel is regularly used in heavy civil construction to create thin steel plates, which can be held together with clamps or with fasteners to support broad concrete projects. This durable material is more expensive than timber, but it’s also stronger and can be reused or sold.
Another type of material used to make formwork is resin-bonded plywood. These sheets of plywood will typically be attached to timber frames to create large, inexpensive concrete forms. However, plywood is less durable and rarely reusable. Fiberglass concrete forms are best for projects with curved surfaces, though they are expensive and often need to be custom ordered.
Photo: istockphoto.comIn order for a concrete formwork to be suitable for a construction project, it needs to be strong enough to hold the weight of the concrete without slipping, cracking, or bending. Any significant damage to the formwork will allow the concrete to pour out, or it may just ruin the intended shape if the concrete is partially cured.
However, the concrete forms also can be made with a lightweight material that are used without significant physical effort on the part of the user. Timber and plywood are great examples of material that is strong, flexible, and relatively lightweight, yet rigid enough that the concrete forms will keep the same shape, allowing the concrete to set in the desired form.
Photo: istockphoto.comMany people either don’t know about concrete forms or they don’t want to have to pay for timber or plywood to set up formwork because the extra cost is too high. Unfortunately, without the use of formwork, it’s all too easy for construction projects to go awry, leaving the concrete slab for the new shed or workshop uneven and difficult to use as support. So, while it’s a bad idea to go without concrete forms, there are ways that can help save on the cost of these materials.
Plan out the project carefully so that pieces of the formwork can be reused for multiple sections and it’s also a good idea to limit the number of slender sections to avoid wasting small pieces of timber or plywood. By reducing the number of cuts that need to be made in the concrete forms, there is less timber or plywood needed in total. However, users should keep in mind that while formwork typically costs about $1.10 per square foot of the concrete area, a rounded or contoured framework is generally more expensive.
Photo: istockphoto.comThe initial cost and skill required to make steel concrete forms are higher than what’s needed for timber or plywood. Due to the impressive strength, durability, and resilience of steel, the steel concrete forms can be used on multiple projects without damage. For companies or independent professionals that regularly work with concrete, this is a way to cut costs on a project.
DIYers also can benefit from the long-lasting strength and flexibility of steel concrete forms by using this formwork on more than one project. If the steel formwork is just sitting in storage in the garage, consider selling it to another avid DIYer. A professional also may be interested in a bargain price for used concrete forms to help reduce the total cost of a project.
Photo: istockphoto.comThere are many different construction projects that utilize concrete and most of them require some type of formwork to ensure that the concrete sets according to plan. Goals can range from making a few simple steps to lead up to the porch to pouring a complex foundation to make insulating concrete forms for the home. Insulating concrete forms are essentially concrete walls that are poured between two layers of insulating material to create a strong and insulated foundation.
Other common uses for concrete forms include pouring a simple concrete slab to act as the foundation for a shed or workshop, securing the posts of a fence or a gate in the ground with a concrete base, or making simple paving stones for the yard with a shallow formwork mold.