Doka Frami Pad Foundation Formwork for an Airport Hangar, Camberley

Location: Camberley, Surrey
Project time: 2026

SEL designed and supplied 22.8 tonnes of Doka Frami formwork to construct 78 concrete pad foundations for a hangar at Camberley. Twenty-four four-sided Doka Frami shutters were supplied in 2m × 2m and 3m × 3m sizes, each struck, repositioned and reused through four pour cycles. SEL's Temporary Works Design engineers produced the formwork design for the scheme, covering the shutter layouts, the Dywidag tie arrangement, the restraint to the shutters and the soldier arrangement for the cast-in holding-down bolts.

The pad foundations formed the bases for the hangar's structural steel frame. Each base incorporated a holding-down bolt set that had to be held accurately in position while the concrete was placed. The main body of work required two pad sizes, 2m × 2m and 3m × 3m. That repetition made a modular panel formwork system suitable for the programme.

The shutters were designed to a maximum concrete pressure of 30kN/m² over a 1.2m maximum pour height, which carried no restriction on the rate of rise and allowed the contractor to place concrete at whatever rate the pour required.

SEL provided formwork design advice at enquiry stage, detailed pad foundation shutter design, Temporary Works Design calculations, Doka Frami equipment hire, and the Dywidag tie and restraint arrangement.

The Challenge: Forming 78 Below-Ground Pad Foundations Without 78 Sets of Formwork

The client initially proposed shuttering only the upper section of each foundation: an approximately 450mm-high shutter at ground level, with the lower 550mm subterranean portion cast directly against the sides of the excavation.

Across 78 foundations this was not a practical method as the accuracy of each base would have depended on the condition of the excavation it was formed in, and no part of the arrangement could be carried forward from one base to the next. With two repeating pad sizes on site, the shuttering method needed to be consistent across the whole programme.

The tie arrangement was the second constraint. The shutters were partially erected inside excavations rather than on open ground, so the lower tie bars could not be withdrawn from both faces after each pour. Without a change to the tie detail, a full length of Dywidag bar would have been lost on every one of the 78 bases.

Temporary Works Design for the Pad Foundation Formwork

SEL's Temporary Works Design engineers carried out the formwork design for the pad foundations. The design established the Doka Frami panel arrangement for both pad sizes, the concrete pressure the shutters were designed to, the Dywidag tie layout and recovery detail, the trench strut restraint off the surrounding bank, and the soldier arrangement holding the cast-in bolts.

Pad Foundation Formwork Design Criteria

The scheme involved 78 pad foundations in two repeating sizes, formed with 24 four-sided Doka Frami shutters at 1200mm panel height. Each pour placed approximately 1000mm of concrete, over an optional 200mm of lean mix, and each shutter was reused through approximately four pour cycles. The total weight of equipment supplied was approximately 23T.

The principal design criteria were:

The rate of rise figure has a direct effect on the pour. At a maximum pour height of 1.2m and an assumed concrete density of 25 kN/m³, a fully hydrostatic head reaches 30 kN/m² against the formwork. The Doka Frami panels are rated to 50 kN/m² concrete pressure, so no rate of rise restriction applied to the pad foundation shutters and concrete could be placed at whatever rate the pour required.

Why We Specified Full-Height Frami Panels Instead of a Shallow Ground-Level Shutter

SEL's engineers revised the shallow shutter proposal to a four-sided Doka Frami shutter running through the full working depth of the base.

The revised arrangement used 1200mm-high Doka Frami panels: sixteen 1200 × 750 universal panels to each 3m × 3m shutter, closing the 12m perimeter exactly, and a combination of 1200 × 600 standard and 1200 × 750 universal panels on the 2m × 2m shutters.

Approximately 200mm of lean mix could be placed inside the shutter as an initial pour, followed by roughly 1m of structural concrete to the top of the panels.

The change achieved two things. Every base received an identical four-sided Frami shutter regardless of the condition of its excavation, and each shutter could be struck and repositioned on the next foundation. Founding the shutters on a prepared base, with the lean mix option beneath, also removed any reliance on the excavation sides holding their profile during the pour.

How the Frami Shutters Were Restrained: Dywidag Ties and Trench Struts Off Bank

Two elements carried the principal loads on each Doka Frami pad foundation shutter. The Dywidag ties took the concrete pressure acting across the shutter, while the trench struts plumbed it and resisted wind load.

15mm Dywidag tie bar carried the concrete pressure across the Frami shutter, bearing against 700mm universal walers and secured with superplates, hexagonal nuts and universal fixing bolts. Tie plates and wingnuts were available as an alternative to the superplate. The bar is supplied in 6m lengths with a 95kN safe working load, cut to suit each tie position.

Trench struts plumbed the Frami shutters and resisted wind load, bearing back against the adjacent bank, eight to each shutter. The design allowed for a peak velocity pressure of up to 0.5 kN/m². The contractor prepared the bearing for the struts and confirmed the dimension from each shutter face to the bank.

Restraint at the bottom of the Frami panels was the contractor's responsibility under the design. Floor fixing plates were offered but were not taken as part of this package, so the shutters were founded on a prepared base and held to line by the strut and tie arrangement.

Frami panel connections were made with quick-acting and adjustable clamps, with galvanised Frami outside corner units closing the corners of each shutter.

Once the concrete had been placed to the top of the 1200mm panels, the shutter was struck, the outer Dywidag withdrawn, unused tie holes plugged and release agent reapplied before the equipment was repositioned on the next pad foundation.

Why We Designed the Dywidag Ties for Recovery in Below-Ground Pad Foundations

The excavation constraint had its greatest effect on the Dywidag tie arrangement, and the tie detail SEL's engineers developed produced the largest material saving on the scheme.

Full-length ties could not be withdrawn from a Frami shutter seated within an excavation, so the Temporary Works Design split each tie into a cast-in section and a recoverable section rather than treating the whole bar as sacrificial, and ensuring any cast in ties were not exposed to the elements.

The cast-in section was a central length of Dywidag bar with a DW15 connector nut at each end: 2.3m to 3.5m on the 3m × 3m pads and 1.3m to 1.5m on the 2m × 2m pads. The outer 600mm to 800mm ran through a plastic tube with a cone at the concrete face. After striking the shutter, the outer length was unscrewed from the connector nut, withdrawn and reused on the next foundation. The tube takes 15mm Dywidag at 22mm internal and 26mm external diameter and is supplied in 2m lengths. The cone provides 10mm of cover between the concrete face and the end of the tube.

The outer Dywidag bar, the superplates, the walers and the fixing bolts were struck and reused across all 78 pad foundations, leaving only the cast-in bar, the tubes and the cones in the ground.

Supporting Cast-In Holding-Down Bolt Sets with Soldier Units

Each pad incorporated a holding-down bolt set for the hangar's steel frame. The bolts required accurate vertical restraint, provided independently of the shutter faces.

Soldier units were set across the top of each Frami shutter, two per shutter: 2.70m units on the 2m × 2m shutters and 3.60m units on the 3m × 3m shutters. They connected to the top of the Doka Frami panels through the frame holes on 600mm lengths of Dywidag, with a superplate above the panel frame and a DW15 hexagonal nut and washers below. Timber shims between the soldier and the edge panels held the soldier 20mm clear of the concrete, restraining the bolts without loading the formwork face.

Soldier spacing was set and held using 1m scaffold tubes and Gravlock girder couplers.

The Result: 78 Pad Foundations Constructed with 24 Doka Frami Shutters

The foundation programme was completed using 24 four-sided Doka Frami shutters across 78 pad foundations, each shutter struck, repositioned and reused through approximately four pour cycles.

Supplying 24 shutters rather than 78 reduced the Doka Frami hire package to under a third of the equipment a shutter-per-base approach would have required, at a total supplied weight of 23T. Walers, superplates, fixing bolts and outer Dywidag sections were recovered from each base and reused on the next, and the material left in each foundation was limited to the cast-in central bar, the tubes and the cones.

The project demonstrates how modular panel formwork, tie detailing and Temporary Works Design can be developed together on schemes involving a large number of repeated concrete bases, where supplying separate formwork for every foundation would not be economic.

Services and Equipment Provided

• In-house Temporary Works Design and calculations for the pad foundation formwork
• Doka Frami formwork hire, 22.8 tonnes
• 2m × 2m and 3m × 3m four-sided pad foundation shutter arrangements, 1200mm high
• 1200 × 600 galvanised-frame Frami panels
• 1200 × 750 universal Frami panels with multi-hole tie bars
• 1200 galvanised outside corner units
• Quick-acting clamps and adjustable clamps
• 700mm universal walers
• Superplates, hexagonal nuts and universal fixing bolts
• 15mm Dywidag tie bar in 6m lengths, 95kN safe working load
• Plastic cones and 2m plastic tubes for tie recovery
• Trench struts for shutter plumbing and wind restraint
• 2.70m and 3.60m soldier units for holding-down bolt restraint
• Scaffold tubes and Gravlock girder couplers for soldier spacing
• Lifting hooks, 500kg safe working load
• Release agent
• Equipment selection for repeated concrete foundation pours, striking and reuse

Other Applications for Doka Frami Foundation Formwork

The same modular panel system suits other in-situ concrete substructure work where a shutter can be struck and reused:

• Pad foundations for structural steel frames
• Pile caps
• Ground beams
• Lift pit bases
• Crane bases and outrigger pads
• Plant and equipment plinths
• Retaining wall kickers and stems
• Thrust blocks
• Pumping station and tank bases
• Machine foundations with cast-in holding-down bolts

These requirements are described under a number of terms: foundation formwork, pad foundation shuttering, pad foundation formwork hire, concrete base formwork, column-base shuttering, reusable formwork for foundations and modular panel formwork. Where a scheme involves several similar bases, a modular shutter system allows the same equipment to be struck and moved through the construction sequence rather than fabricating a separate shutter for every pour. Temporary Works Design for the shutter arrangement, the ties and the restraint is normally required alongside the equipment.

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Need Formwork for Pad Foundations or Concrete Bases?

SEL supplies Doka Frami modular panel formwork for hire for concrete pad foundations, column bases, pile caps, walls and other in-situ concrete works, supported by in-house Temporary Works Design for foundation and substructure formwork.

Our engineers can develop project-specific shutter arrangements and produce the supporting design where factors such as below-ground pours, restricted tie access, repeated foundation sizes, cast-in holding-down bolts or limited positions from which to restrain the formwork rule out a straightforward shuttering solution. Equipment can also be supplied on a hire-only basis where the Temporary Works Design is being carried out elsewhere.

The Doka Frami formwork was supplied from SEL's London depot, which covers Surrey, Hampshire, Berkshire and the wider South East. Contact the London depot, or your nearest SEL depot, to discuss your project or arrange a no-obligation site visit.

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