How to Choose a Suitable Formwork for Your Home Project
Formworks are usually temporary structures and as such are not part of the final design. However, they are indispensable when it comes to building concrete structures, including residential homes. Formworks are used as molds to create the house slabs, columns, and other concrete sections. They support the weight of the freshly poured concrete until it hardens and has enough strength to support itself.
Photo by Brett Jordan
What are the different types of formwork frames and facing panels?
Frames:
1. Timber
Timber is the most common material used for formwork frames. It is also suitable for most small construction projects due to its low cost, flexibility, and availability.
However, it has several disadvantages, including:
Susceptibility to termites
Tendency to absorb moisture
Warping
Swelling
Shrinking
Shorter lifespan compared to other formwork materials
Furthermore, timber cannot hold a significant amount of fresh concrete pressure and is also often discarded after a single project.
2. Aluminum
Aluminum does not absorb moisture so there will be no issues with warping or shrinking. It also has numerous advantages, such as:
Scratch-resistant surfaces, resulting in less concrete adhesion and easier cleaning
Due to the welded-in nuts, it is convenient to assemble and disassemble
The aluminum frames can be repaired and refurbished
Although aluminum is usually more expensive than timber, the additional costs can be offset by reusing it multiple times.
3. Steel
Steel formwork comprises thin steel plates with hollow profiles, and is secured by locks or bolts and nuts. Although the initial costs are significant, they can be reused and thus provide long-term financial savings and returns. Steel has the same advantages as aluminum, except that it is tougher and easier to modify.
4. Plastic
This type of formwork consists of plastic panels or modular systems designed for concrete pouring. Like aluminum, it is easy to carry. However, it will hold less fresh concrete than steel formwork. Plastic formwork also requires more connections and alignments, thereby increasing the labor costs.
Nevertheless, plastic has several unique advantages:
Easy to prepare if you need formwork quickly for complex-shaped concrete structures
Lightweight but resistant to water
Reusable, and you can recycle the damaged sheets and create new ones
Facing Panels
1. Plywood
Plywood facing is often used with timber formwork and is available in various thicknesses and sizes. It is easy to handle and one of the cheapest materials on the market. In addition, as long as the plywood does not absorb moisture and therefore swell or warp, it can be reused.
2. Steel
Steel facing is suitable for circular or curved concrete sections. You can reuse it several times to offset the high initial cost.
3. Plastic
This material is durable and lightweight. It is also sustainable as it can be repaired and reused. Although plastic facing is rigid, it is still flexible enough to bend and shape. If handled properly, you can reuse it many times.
Which formworks are required for specific concrete structures?
The unique formwork system you need will depend on the type of concrete structure you are building.
1. Foundation
As with any concrete structure, a home construction project will entail building a strong foundation. When designing a foundation formwork, you must consider the number of columns and walls required as well as the size and shape of the footing.
2. Slab
Once the foundation is in place, the next step is to design the slab formwork. Depending on the type of structure you are building, you can choose either a conventional slab formwork or a modular slab formwork.
Conventional
Due to its design flexibility, conventional slab formwork is suitable for most concrete layouts. This formwork system will require the use of
Facings
Crossings
Girder stringers on props or shoring towers
Modular
Modular slab formwork systems will enable you to cut the cost of the materials by almost half and also speed up your construction time. The panels include integrated
Facings
Primary and secondary beams
Props with drop heads
3. Column
For circular formworks, steel is suitable as it is economical, reusable, and available in various dimensions. If you only intend to use the formwork once, previously used or discarded formworks will be perfectly adequate.
Meanwhile, for rectangular columns, there are three formwork options:
Timber girders secured by steel walers and plywood facing are suitable for multiple columns of a particular size or shape.
Windmill systems composed of columns or multi-purpose panels are used for standard-sized columns.
Foldable column formwork is used for high columns. This system can enable you to make significant savings on labor, time, and construction costs as all the essential components are integrated into a single platform.
4. Wall
There are several types of wall formwork.
Conventional
This is a flexible wall formwork system as it uses squared timber and boards or sheets. However, the conventional system has some disadvantages. Each component needs to be assembled on-site and according to exact specifications. This can result in a longer construction time and also significant construction costs.
Girder
Girders are much better than their conventional counterparts. This formwork system has girders with two chords and one web. The panels are also standardized and ready for use.
Frame
Using frames can reduce your building time as a single panel contains all the essential components.
Single-sided / two-sided
Single-sided formworks are often used when you need to pour the concrete against an existing structure, hill, or soil. Meanwhile, the two-sided system is installed on both sides of the wall.
Prefabricated
This system comprises two prefabricated concrete panels assembled and transported in advance. Once it has been set up, it can be quickly filled with concrete. Builders prefer prefab formworks as they help reduce labor time and costs. However, you must ensure that the formwork is transported safely and on time in order to avoid costs and delays.
There are also other special types of formwork, including circular systems for septic tanks and climbing systems for high-rise residential buildings.
What qualities should you look out for in a formwork system?
You need to consider the following factors when choosing a suitable formwork material and system for your house construction.
Load Capacity
The form should be able to withstand:
Deadweight – this refers to the total weight of the concrete structure, including permanent loads
Live weight – the maximum possible weight of the occupants, traffic, equipment, and other temporary loads
Shape retention
The formwork construction must be able to retain its shape and be supported by the necessary props and braces.
Lightweight and reusable
Formworks that are easy to handle, transport, and assemble will reduce your time and labor costs. Meanwhile, reusable and easy-to-repair forms are excellent investments and are also environmentally friendly.
Furthermore, a high-quality formwork will not leave any concrete damage once it has been removed.
Conclusion
Residential construction work will always require the use of reliable formwork systems. Depending on your specific requirements, you can choose between timber, aluminum, steel, and plastic formwork. The various sections of your concrete structure, including the foundation, slabs, columns, and walls, will require specific systems. Ideally, the formwork you choose will be reasonably priced, durable, reusable, and cost-effective.
Author: Anna Alforque
