High-Rise Concrete: Thickness and Core Choices for Formwork
In high-rise concrete work, a formwork plywood panel faces two loads simultaneously: outward pressure from wet concrete and increasing hydrostatic force as the pour height rises. Dongstar Wood quotes 18 mm for heavy formwork and 21 mm or more for bridge decks and high-load platforms, across cores of birch, eucalyptus, acacia, white hardwood, rubber and combi. The right panel is the one whose thickness and core match the load path of the structure.
Key takeaways
- 18 mm is the quoted thickness for heavy formwork and the overall standard choice across the range.
- Thicker panels at 21 mm or above suit bridge decks and high-load platforms where both span and load increase.
- The product page lists six core options — birch, eucalyptus, acacia, white hardwood, rubber and combi — each offering a different strength-to-weight profile.
- High-grade panels are quoted for reuse up to 10–20 times in concrete pouring projects, which changes the cost per pour.
Reading the thickness guidance for high-rise work
The category page treats thickness as a functional choice rather than a number to memorise. Eighteen millimetres appears as the quoted thickness for heavy formwork and is described as the overall standard choice, which makes it the default for wall and column panels on a typical floor cycle. Twenty-one millimetres and above is the guidance for bridges and high-load platforms, where the panel spans a greater distance and carries workers, equipment and wet concrete at the same time.
The distinction matters more on a high-rise than on a low building, because the pour pressure at the bottom of a tall formwork panel is higher than at the top, and the panel has to survive that pressure cycle after cycle. A panel that is flat, well edged and correctly thick for the job will hold its dimensions across the reuse range; a panel that is merely cheap will not, and the cost arrives as re-pour work rather than as a lower unit price.
Core options and what each brings
Six core options appear on the product page, each described by the structural role it serves. Acacia carries the density-and-life role: a hardwood of high strength, exceptional density, strong load-bearing capacity and a long service life. Eucalyptus is described as maximum strength with high compression resistance and bending performance in a dense hardwood. White hardwood, covering species like bodhi and mixed light hardwoods, is described as stability, balanced mechanical strength and cost-performance.
Combi cores combine eucalyptus with acacia, or hardwood with softwood, balancing strength, weight and cost in one panel. Rubber cores appear where weight and handling matter. For a high-rise programme the usual logic is simple: the highest-load positions take the densest hardwood core, the standard wall panels take the balanced option, and the positions where crews lift panels all day take the lighter one. The core choice is a load decision wearing a materials costume.
Film surfaces: dark brown, black and anti-slip
The product page lists three film finishes: dark brown, black and anti-slip. The first two are the workhorses of vertical formwork, where the film's job is to release the concrete cleanly and protect the phenolic film surface from damage between pours. The third is specified where people stand on the panel: scaffolding boards, walkboards, access platforms and roofing planks, where grip matters as much as release.
The film acts as a weather barrier while construction is underway. Phenolic film surfaces resist moisture, abrasion and the alkaline environment of fresh concrete, enabling the reuse cycles the manufacturer quotes. Film weight is published as 165 g/㎡ for smooth surfaces and 130 g/㎡ as the lighter alternative, and the choice between them follows the same logic as the thickness: the more demanding the position, the heavier the film that makes sense.
Adhesives and reuse cycles
The adhesive options listed on the product page range from E0, E1, E2, MR, WBP to Phenolic Dynea. For formwork the structural choices are the exterior grades: WBP and phenolic systems that keep the veneer bonds intact through repeated wetting, pressing and stripping. Interior grades also appear because the category serves both formwork and interior buyers, and the glue class is one more place where the specification has to match the job.
Reuse is where the specification pays back. The product page states that high-grade film faced plywood can handle 10–20 reuse cycles in concrete pouring, and that range is a budgeting input rather than a promise: a panel reused ten times costs one-tenth as much per pour as a single-use panel, before any price is discussed. The range depends on edge and surface maintenance between pours, so the sites that get the upper end of it are the ones that seal edges and clean faces as a matter of routine.
Sizing panels to the formwork system
The published sizes are 1220 × 2440 mm, 1250 × 2500 mm and 1500 × 3000 mm, or customised up to a maximum of 1830 × 3830 mm. On a high-rise, size is a handling decision as much as a coverage decision: the panel has to be lifted, carried and fixed by crews working at height, and a panel that is too large for the crew slows the cycle. The standard sizes exist because they balance coverage against handling, and the custom option exists because some structures need neither.
A Film Faced Plywood specification for a high-rise programme therefore has four parts: thickness from the load guidance, core from the load path, film from the position, and size from the handling plan. Fix those four before the quotation and the comparison between suppliers happens on the same panel; leave any of them open and the comparison happens on adjectives.
| Position | Quoted thickness | Core logic |
|---|---|---|
| Heavy formwork, walls, columns | 18 mm | Balanced hardwood core for the floor cycle |
| Bridges, high-load platforms | 21 mm and above | Dense hardwood core for span and point load |
| Walkboards, scaffolding, access platforms | Anti-slip film | Grip surface plus sealed edges |
| Standard floor panels | 1220 × 2440 or 1250 × 2500 mm | Coverage balanced against crew handling |
Worked example: contact area per sheet
Example: one 1250 × 2500 mm sheet covers 1.25 m × 2.5 m, which is 3.125 m² of contact area. Ten reuse cycles mean a single sheet yields 10 × 3.125 = 31.25 m² of poured surface across its working life. A wall face of 300 m² therefore needs about 300 ÷ 31.25 = 9.6, so roughly ten sheets at ten reuses each.
Example: the same arithmetic prices the reuse range. At five reuses the sheet delivers 5 × 3.125 = 15.625 m², and the 300 m² wall needs about 19.2 sheets. The difference between the two counts is the value of edge and surface maintenance, expressed in sheets rather than adjectives. Both steps are planning estimates on published figures, labelled as examples.
Frequently asked questions
Which thickness should high-rise formwork be?
Heavy formwork calls for 18 mm as the standard thickness, while bridge decks and high-load platforms require 21 mm or more. The thickness follows the load path, not the building height alone.
How many times can a panel be reused?
High-grade film faced plywood, according to the product page, can handle 10–20 reuse cycles in concrete pouring work. The actual number depends on how edges and surfaces are maintained between pours, so the count is a range rather than a fixed figure.
What is the difference between the core options?
The product page lists six options: birch, eucalyptus, acacia, white hardwood, rubber and combi. Acacia is described as high-strength hardwood with superior load-bearing capacity, eucalyptus as maximum strength with high compression resistance, and combi as a hybrid that balances strength, weight and cost.
From the load path to a specification
A high-rise formwork specification is a short document once the load path is drawn. The wire mesh product page covers the positions where crews stand, and the ordinary black film faced page covers the economical end of the vertical formwork range. With thickness, core, film and size fixed from the load path, the quotation that comes back can be compared line by line against the same four inputs.
Figures cited here come from the vendor's online documentation checked 29 Sept 2026[1].