Internal Birdcage Scaffold
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Generally when someone thinks of a birdcage scaffold, they automatically picture a massive scaffolding structure similar to what they have seen on bridges and power lines, this is not always the case. Yes, there are birdcage scaffolds erected with thousands upon thousands of metres of scaffold tube but did you know that you can get really small birdcages no bigger than your living room?
The definition of a birdcage is an independent scaffold which has a grid of standards or legs, as some people know them, normally positioned at regular intervals in parallel rows and uniformly spaced apart. The standards are joined together with a grid of ledgers and transoms at every lift and the top lift being boarded to form the working platform area. In some instances, the outside bays of the perimeter of the birdcage may be boarded out, providing access to work on the walls of the building.
Internal birdcages can be erected to provide access for many tasks but are mainly requested for works on light fittings, ceilings, ventilation, asbestos abatement, sprinkler systems glazing, alarm systems, roof work, painting & decorating, tanks and vessels.
It is important to remember that internal birdcage scaffolds are more likely than any other type of scaffold to be supported on an existing structure or floor, so it is particularly important to verify that the loads imposed by the birdcage can be safely supported.
External birdcages can be erected to provide access for works on bridges, aqueducts, power lines and open steelwork.
A TG20 birdcage can be either free-standing, tied or butted in one or both directions.
A butted scaffold needs to be firmly butted against a permanent structure, usually the perimeter walls at the top lift, at maximum intervals of 2 bays.
If physical ties are used on an internal scaffold, it should be tied at the top lift at alternative standards, whereby an external scaffold may require ties every lift or alternate lift, at every standard or alternate standard, depending on the exposure to wind and the dimensions of the birdcage. If the scaffold is free-standing its height must not exceed its maximum height to base ratio. For internal scaffolds the ratio is 3:1 and for external scaffolds this ratio is reduced to 1:1.
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How to Erect a TG20:21 Compliant Birdcage
Maximum bay dimensions are restricted to a specific load class which there are three types.
Load class 1 is for access only, has a maximum loading of 0.75KM/m2 and maximum bay size is 2.1m x 2.1m (9 boards)
Load class 2 is for light duty work, has a maximum loading of 1.5KN/m2 and a maximum 1.9m x 1.9m (8 boards)
Load class 3 is for general purpose work, has a maximum loading of 2.0KN/m2 and a maximum bay size of 1.7m x 1.7m (7 boards)
The first lift is erected at the prescribed leg centres relating to the load class.
A base lift is erected in 1 single bay to form a starting square.
The first lift at 2metres high is erected. The standards are coupled together with right angle couplers and a ledger is run through.
Further standards are placed at the desired bay length.
Structural transom tubes are then fixed to the standards at right angles, staggering the tube lengths, using load bearing double couplers
The remaining base lift is erected in the same uniform grid pattern.
A Façade brace is then erected from the lowest point of a standard linked diagonally upwards to the adjacent bay using swivel couplers on both sides.
The first lift is then boarded out from below.
Using a ladder to access the first lift, erect a minimum single handrail as soon as practicable.
Once in place, the next row of structural transoms can be erected using load bearing double couplers.
Façade braces are then chased up from the ones below using a zig zag pattern to ensure stability.
Ledgers are then installed using load bearing double couplers, keeping the standards plumb.
Transoms can then be erected. Boarding out again from below also introducing a temporary ladder access point.
Erect all further lifts following the same method.
Install ties as previously discussed and to TG4.
Working lifts must have board transoms spaced every 1.2m apart and at each end of the board. The board is to extend no greater than 150mm from the transom and no less than 50mm.
All ledger joints should be staggered to prevent sleeve couplers falling into the same bays for strengthening purposes.
Facade bracing to be secured over one lift by one bay continuing every other bay and also continuing up to the top lift using swivel couplers 300mm within the node point. These should be set at an angle of approximately of 45º with a preferred range of 35º to 55º.
Please Note: Any birdcage that is to be erected outside the scope of TG20:21 should be firstly designed by a suitably qualified design scaffold engineer.
Why choose our internal birdcage scaffolding services?
- Personal service designed around your needs
- Full drawings provided for full project management
- Full design to completion service
- Strong Health and Safety culture
- Fully trained and experienced staff with on-site management
- Years of experience at complex structures
- Highest quality materials and maintenance
- National Access & Scaffolding Confederation (NASC) member
- Fully guaranteed and insured
- We help build your reputation
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