Scaffold Protocol - Aberdeen City Council

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Aberdeen City CouncilSelection of TiesThe stability of a scaffold structure is dependent, among other things, on the security of theanchors used to tie it back. In many instances the anchors are the crucial element for stability.The type of tie and anchor should be selected to suit the tying requirements and the nature ofthe building facade. Refer to TG4:04 - Anchorage Systems for Scaffolding.Ties are a means of resisting inward and outward movement of scaffolds. They must be madeusing 'right angle couplers'. The strength of the structure being tied to must be established.This should be considered at the design stage.Through tiesThese are put through structure openings, such as windows. A vertical inside tube crossingthe opening is attached to the scaffold by a transom and a crossing horizontal tube on theoutside called a bridle tube. The gaps between the tubes and the structure surfaces arepacked or wedged with timber sections, to ensure a solid fit. Safe working capacity, 6.25 kN.Note: 100% proof testing is required with plastic inserts.Box tiesThese are used to attach the scaffold to suitable pillars or comparable features. Twoadditional transoms are put across from the lift on each side of the feature and are joined onboth sides with shorter tubes called tie tubes. When a complete box tie is impossible an L-shaped lip tie can be used to hook the scaffold to the structure, to limit inward movement anadditional transom. A butt transom is place hard against the outside face of the structure.Safe working capacity, 6.25 kN; Double tied: safe working capacity, 12.5 kN (two tubes andcouplers).Lip tieThis is an L-shaped arrangement to hook scaffolding behind building elements such as sills orlintels. Inward movement is resisted by a butting transom. Safe working capacity, 6.25 kN.Reveal tieThis is the least 'invasive' tie. These use an opening in the structure but use a tube wedgedhorizontally in the opening. The reveal tube is usually held in place by a reveal screw pin (anadjustable threaded bar) and protective packing at either end. Transoms tie tube links thereveal tube to the scaffold. Reveal ties are not well regarded; they rely solely on friction andneed regular checking so it is not recommended that more than half of all ties be reveal ties.Safe working loads: 3.25 kN (Friction); 6.25 kN (behind a load bearing feature).Page 37 of 46 Issue 1
Aberdeen City CouncilAnchor tiesAlso called bolt ties, these are ties fitted into holes drilled in the structure. A common type is aring bolt with an expanding wedge which is then tied to a node point (Ref TG4:04, AnchorageSystems for Scaffolding).• Provided by casting in, or drilling, and subsequently fixing a threaded anchor intothe structure• Attachment of the scaffold is by means of a ring bolt• Dependent on the structural condition of the material• Safe working capacity 6.25kN• Useful at the design stage if further scaffolding is required during the life of thestructure• Screw ties in brickwork- take care to determine safe working load which may beless than 6.25 kN. (If in doubt consult screw fixing supplier and/or manufacturer)Expanding AnchorConsiderations for the selection of anchors for tying scaffold structures:• Type of linkage to the scaffold structure• Base material and suitability of the structure• Working load compare with allowable load• The need for testing• The way loads are transferred through the ties and the direction they are applied.In some instances it is the ‘base material’ that will be the weak link in the overall design of theanchor. It should be noted that the strength of materials such as sandstone can varysignificantly across a building face, particularly where part of the face has been severelyweathered over the years.ONLY where it is impossible to incorporate a safe number of the foregoing tie types shouldrakers be considered. These are single tubes attached to a ledger extending out from thescaffold at an angle of less than 75° and securely founded. A transom at the base thencompletes a triangle back to the base of the main scaffold. The outer end of the raker shouldpreferably be clipped to a short vertical tube set into a concrete foundation or driven intocompetent ground. In some low rise scaffold situations it may be possible to connect thebottom of the rakers with a horizontal tube that will help spread any vertical loads.Page 38 of 46 Issue 1
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Page 47: BS 5975: 2008, Code of practice for

Scaffold Protocol - Aberdeen City Council

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