Formwork
Types of formwork and scaffolding in construction. El-Eman Office provides reinforced concrete works with engineering supervision.
Criteria for choosing the type of formwork
Choosing between timber and metal formwork is not based on price alone. The first question is how many times the formwork will be reused. A project with repeated, similar floors benefits from reusable metal formwork that can be used dozens of times. A unique building with irregular shapes is better served by timber, which is more flexible and cheaper to shape. The surface quality required also matters, since exposed concrete needs smooth boards with precise joints. Available labour and time play a role too: ready-made systems cut erection and stripping time but need planning and training.
What to check before pouring
Pouring is a point of no return, and any error that shows afterwards becomes demolition or repair. The formwork is therefore reviewed against a written checklist.
- Beam, column and slab dimensions match the drawings.
- Column verticality and straight sides, checked with a plumb bob or laser.
- Soffit and edge levels and the required slab falls.
- Stable props bearing on firm ground that will not settle under load.
- Tight joints to prevent cement paste leaking.
- Sound reinforcement, concrete cover and spacers.
- Formwork free of timber scraps and debris.
Safety and formwork collapse
Formwork usually collapses for recurring reasons: weak or leaning props, an unsuitable base for them, fast unbalanced pouring, and stripping too early before the concrete has gained the required strength. Overloading from piled materials, workers or equipment adds to the risk. Formwork must therefore be designed for the expected loads and not judged by eye, the timing of stripping set by member type and weather conditions, and scaffolding, guardrails and safety harnesses provided for those working at height.
- Approve the formwork and propping drawing before erection.
- Check levels and verticality with instruments before handing over for pouring.
- Pour in a balanced sequence and do not overload one part.
- Do not remove props before the supervising engineer approves.
Planning for reuse and storage
How formwork is handled between pours affects its life and the quality of the concrete. Panels are cleaned as soon as they are stripped and coated with a suitable release agent before the next use, to ease stripping and improve the surface. They are stored away from damp and warping, laid flat and in order. With timber formwork, sound boards are sorted from cracked ones so the latter are not reused in important members. A schedule setting out the formwork cycle between floors helps reduce the quantity needed and save cost without sacrificing the time concrete needs to gain strength.
Frequently asked questions
Does formwork affect the final look of the concrete?
Yes. Concrete takes the shape of the surface it is cast against, so precise formwork gives smoother surfaces and reduces plastering work.
When is formwork stripped?
When the concrete has reached sufficient strength. The time varies with the type of element and the temperature range, and the responsible engineer decides.
What causes concrete to leak from the formwork?
Usually open joints or damaged boards. It is dealt with by sealing joints, cleaning surfaces and not reusing a damaged board.
