How to Build an Irregular Scaffold on the Job

Inspect the work site to analyze ground conditions, obstructions, durability of the support structure to which the scaffolding will be built, proximity of any electrical wires and wind or weather hazards. Make sure the ground is also strong enough to support the weight of the scaffolding and it will not sink down.

Check all of your materials for structural safety and quality. Make sure all planks are in peak condition and free of cracks, splits, notches and any other impurities that could pose a threat of collapse.

Lay steel planks along the base of the support structure around which the scaffolding is being erected. Space vertical posts evenly so that the load on bearers and runners is distributed evenly. For light-duty jobs; the maximum length should be 4 feet between bearers and 10 feet between runners, and for heavy-duty jobs, the numbers shift to 3 1/2 and 8 feet respectively. Make sure they are centered against the wall sills of the support structure and are in secure contact with all vertical ledger bracing. Match the curvature of circular structures as closely as possible, but for scaffolds that are built around small-diameter support structures, build the foundations in a square and safety planks will be added at the corners on the top levels later.

Attach the planks with base collars. Use only drop-forged steel or malleable iron clamps to ensure durability. Make sure all vertical posts are plumb as the ground foundation is laid.

Add levels to the scaffolding. The lowest runners and bearers must be positioned at least six inches above the scaffold base. Secure runner planks with right-angle clamps at both ends to vertical posts. Runners should not be spaced more than six feet, six inches apart at the vertical, and they must be erected for the entire length of the scaffolding.

Clamp bearers (horizontal support posts) in contact above each runner so that it is securely fastened to ensure overhead support. Bearer supports are not to extend beyond the runner by more than six inches unless required by engineering specifications. Continue along the length of the scaffolding until the level is finished.

Install transverse bracing in the shape of an "X" cross pattern at all scaffolding ends and at a minimum of every third set of horizontal support posts and every fourth vertical support. These braces must extend upward diagonally to opposite ends of the scaffold structure at a 45-degree angle.

Secure ties, outrigging, guy wires or any other safety bracing as necessary. These will eliminate swaying and will brace the scaffolding for stability. These precautions are mandatory when the height of the scaffold exceeds four times its minimum base width. This is determined at each job and these numbers will always vary. Place ties as close as feasibly possible to all horizontal bearers, and bottom foundation ties must be placed no higher than four times the minimum scaffold base width, again, determined on each job. Scaffolds 3 feet or narrrower must be securely rigged at evenly spaced locations no less than 20 feet apart. Wider than 3 feet, and the rate changes to 26 feet.

Attach vertical ties at ends no further than 30 feet horizontally between one another.

Install work platforms at all decks with a minimum width of 18 inches for every plank. Plank ends must overlap their supports by a minimum of six inches, and if they do not, they must be cleated for safety. Platforms that are 10 feet long must exceed their supports by no more than 18 inches.

Install guardrails at all ends of the scaffold and at every open side. Midrails and top rails are mandatory, and minimum height requirements must be met in accordance with local building codes and regulations.

Install toeholds for people who are required to pass beneath any scaffolding platforms.

Install all ladders and access ways to work platforms. For ladder units attached on scaffoldings, place rest platforms at vertical intervals of 35 feet or less, and be sure all ladders extend 3 feet above their access platforms. Ladders should be installed as scaffolding construction progresses at designated requirement points.