A float scaffold, also called a ship scaffold, is supported by suspension ropes that hang from overhead anchor points on a building or structure. Unlike adjustable suspended scaffolds that can be raised and lowered, a float scaffold hangs at a fixed height. The platform rests on two parallel bearers, and ropes connect those bearers to secure overhead supports above. Understanding how each part of this system works is essential for anyone building, inspecting, or working on one.
How the Platform and Bearers Work Together
The platform sits on a minimum of two bearers, which are the horizontal structural members running underneath it. Each bearer must project at least 6 inches beyond the platform on both sides, giving the ropes a place to attach without interfering with the work surface. The bearers must be securely fastened to the platform so nothing can shift during use. Think of the bearers as the skeleton that gives the platform its shape and distributes the load to the ropes above.
How Suspension Ropes Attach
The ropes are the primary support connecting the platform assembly to the structure overhead. When only two ropes are used per float, they must be arranged to create four ends, all securely fastened to overhead supports. Each rope is hitched around one end of a bearer, passed underneath the platform, then hitched around the opposite end of the same bearer. This creates a cradle effect, with enough rope left at each end for the supporting ties that reach up to the anchor points above.
The rope connections must prevent the platform from shifting or slipping in any direction. This hitching pattern locks the bearers and platform in place so the assembly hangs as a single rigid unit rather than swaying or tilting under a worker’s weight.
Overhead Anchor Points
The ropes ultimately connect to overhead supports on the building or structure itself. These anchor points can take several forms depending on the job site. Common suspension support devices include outrigger beams, cornice hooks, and parapet clamps, all of which transfer the scaffold’s load into the building’s structural members.
Outrigger beams extend from the roof or an upper floor, with the inboard end anchored and the outboard end hanging over the edge to support the ropes. The inboard ends must be stabilized either by bolting directly to the floor or roof deck, or by using counterweights heavy enough to prevent tipping. Outrigger beams are placed perpendicular to the face of the building unless obstructions make that impossible, in which case opposing angle tiebacks must be installed to compensate.
Regardless of the device used, it must be secured against movement with tiebacks. These are restraining lines installed at right angles to the building face and anchored to structurally sound points like steel beams, concrete columns, or other load-bearing members. Vents, electrical conduit, standpipes, and other piping systems are never acceptable anchor points because they cannot reliably handle the load. Tiebacks must match the strength of the suspension ropes themselves, so a weak tieback doesn’t become the failure point in the system.
Load Capacity and Safety Factors
Every suspension rope, including its connecting hardware, must be capable of supporting at least 6 times the maximum intended load without failure. This 6-to-1 safety factor accounts for wear, weather, knot strength loss, and dynamic forces like a worker shifting position suddenly. If the maximum load on a rope is 500 pounds, that rope and its hardware need a breaking strength of at least 3,000 pounds.
The scaffold components themselves, including the platform and bearers, follow a separate standard: they must support their own weight plus at least 4 times the maximum intended load. These safety margins are not optional. They are regulatory requirements under OSHA’s scaffolding standards in 29 CFR 1926, Subpart L.
What Makes Float Scaffolds Different
Float scaffolds are a type of suspension scaffold, but they differ from two-point swing stages and other adjustable systems in one key way: the ropes are fixed in length. You cannot raise or lower a float scaffold with a hoist. Workers position it at the height they need before stepping onto it, and it stays there. This makes float scaffolds simpler in design but limits their flexibility. They are most commonly used in shipbuilding and marine repair work, which is why they are also called ship scaffolds.
Because the ropes are fixed, the entire load path from platform to bearer to rope to overhead anchor is static. There are no moving parts like hoists or traction drums that could fail mechanically. The trade-off is that every connection point, especially the rope hitches around the bearers, must be done correctly from the start since there is no way to make fine adjustments once the scaffold is loaded and occupied.