During the last decade, tensioned wire balustrade systems have been increasing in popularity within the residential and commercial sectors. Compared to glass balustrades, tensioned wire systems provide a cost-effective solution while maintaining comparable unobstructed sightline features. Because the wire acts as the main structural component, it is necessary to understand the details of the specification, as well as the installation and the associated risks, which are not immediately obvious when viewing the system.

The majority of the wire systems used in balustrade systems employ stainless steel. For external balustrades, the most common specification is grade 316 stainless steel, and for internal applications, grade 304 is the most common. Because grade 316 has molybdenum as an alloy, it has enhanced resistance to corrosion from chloride, which is important for coastal installations or instances when road salt or cleaning agents are used. It is common practice to specify grade 304 for external balustrades in coastal or high-chloride environments, but in doing so, results in corrosion of the balustrade system in a very short time. Based on performance, the specification should be given careful consideration and not simply default to the lowest contractor bid.

Balustrades generally use wire with diameters between 3 mm and 5 mm, with 4 mm being the most common. Required tension and stiffness directly impacts the diameter and the visual weight of the installation. Horizontally arranged wire balustrades are required to withstand a horizontally applied load. According to the Building Regulations Approved Document K, most commercial and residential barriers are required to withstand a load of 0.74 kN/m for residential barriers and between 0.74 kN/m and 3.0 kN/m for commercial barriers depending on the occupancy classification of the building. The load in question is transferred to the balustrade assembly through the posts, end fittings, and the tensioning system, and the balustrade system as a whole, and not solely the wires. Balustrade system design must consider wire diameter, tension, and spacing to determine compliance.

According to Part K of the Building Regulations, the 100 mm sphere rule also governs wire spacing in balustrades. This means a 100 mm diameter sphere must not be able to pass through any opening. Horizontally arranged wires are allowed a vertical spacing of up to 100 mm. This spacing is measured at maximum sag. Wires also deflect mid-span. This must also be accounted for in the sag of a tensioned wire system, and will not be measured at a post. Balustrade systems using vertical wire spacing do not have a sag issue, but do have design challenges at the wire terminations.

The greatest variation among systems from different suppliers is in the tensioning hardware. The most common fitting in commercial systems is the swaged terminal, which provides a secure and permanent termination of the wire. Adjustable fittings are tensioned using a threaded barrel, which is an important feature because wire tension should be adjusted as the system settles. Tensioning hardware should never be adjusted from the design tension, which is specified by the manufacturer or a structural engineer. Beyond a prescribed tension, it will place excessive load on the posts and fixing points. On the other side of the spectrum, an insufficient tension will allow it to deflect and potentially place the system in violation of Part K.

Most environments require little maintenance for stainless steel wire, which is a true advantage compared to painted steel. In most environments, especially the aggressive marine, high chloride and urban environments, it should be cleaned routinely using a mild detergent and surface contaminants removed. If this is not done, crevice corrosion will occur at termination fitting. Deterioration is first noticed at the fittings and not the wire. Because of this, the fittings should be inspected annually for installed wire used externally.

When balustrading wire is routed through intermediate posts, a sleeve or grommet at the point of contact should be non-abrasive non-reactive and should not corrode stainless steel. In a humid environment, and especially with the presence of moisture, certain metals should not be in contact with stainless steel, or a form of galvanic corrosion will occur. The standard approach for this is to use nylon or PTFE, and should be specified and not left to the installer to source and procure.

Types of Wire Rope Construction

Most riggers will say, there isn’t a “best” wire rope. To understand which wire rope should be used, you should ask, “what is it being used for?”. The construction of the wire rope tells us many things, including the flexibility, fatigue resistance, and lifespan of the wire rope in its specific use case. Using the wrong construction option does not mean the wire rope will fail immediately; the real cost of the wrong choice is hidden and can be significant.

Construction Abbreviations

The construction of wire rope is explained using the number of strands and the number of wires per strand. For example, 7X7 wire rope has 7 strands of wires and each of those strands has 7 wires. So, in total a 7X7 wire rope has 49 wires. 7X19 wire rope has 133 wires. 1X19 has only 19 total wires, since it has 1 strand and no stranding.

With more wires comes the ability to get smaller diameters which means flexibility. A rope that has fewer but larger wires will be less flexible but more resistant to abrasion.

1×19: Stiff, Strong, Not for Tight Bends

1X19 rope is the stiffest rope of the three mentioned. Because the 1X19 rope has laid the 19 wires in a single strand and has no core, the rope has a high break load for its diameter, but the flexibility is essentially zero. Due to this construction, it does not tolerate being bent, wound around a drum, or pulled through a pulley.

Where is it effective? Tension applications, guard wires, balustrade cables, stays, and other applications where the rope runs straight and remains in that position. Common applications include rigging for architecture, stainless steel balustrading, and aerial ropeway guide wires. 1×19 should not be used in any application where the rope will run through bends; the outer wires will fatigue and crack in a short time for those applications.

7×7: The Flexibility Trade Off

7×7 construction is more flexible than 1×19, though it possesses moderate resistance to wear. The arrangement of the seven wires provides more movement allowing the rope to work through moderate sheave or pulley arrangements without incurring fatigue. The relatively large diameter of the wires of 7×7 construction compared to 7×19 construction also improves the surface wear when in contact with guides or abrasives.

This construction is good for general purpose applications. It is well suited to hand winches, light cranes, push-pull control cables and other applications with moderate bending over pulleys. 7×7 construction is not suited for high cycle applications where the rope is constantly tensioned and wound over a drum.

7×19: The Flexible Option

7×19 construction is the most flexible construction of the options and will allow bending with more fatigue than the other constructions. This construction is suited for drum winches, hoists, and any application where the rope will be repeatedly bent around a sheave many hundreds or thousands of times.

The drawback, however, is that 7×19 wire has greater surface area than 7×7 and 1×19 construction wires. Because of this, 7×19 wire has a tendency to wear faster than 7×7 or 1×19 wire. When using 7×19 rope on drum winches, you have to inspect the rope more frequently to check if any of the outer wires are broken.

Concerning wire rope grades (stainless 316 vs stainless 304, or wire that is galvanized vs. wire that is ungalvanized), they have separate considerations from construction. Grade has to do with the environment. Construction is important too and is about the rope’s mechanical properties and the application. For marine and chemically exposed environments rope, the construction is 316 stainless, and for general galvanized outdoor rope, it is galvanized steel rope.

One of the most important specs about wire rope is the minimum breaking load, and this is most commonly neglected. It is most important to compare the breaking load to the dynamic loads a rope will face during actual application, not to the static loads. Especially when rope is used for hoisting and pulling, static loads are often much greater, sometimes by a factor of 2. Construction of the rope is important when considering how the rope will absorb and distribute that load.

For most industrial and commercial buildings, insulated core steel doorsets are often the preferred choice. Although they are not the most economical choice, they do provide a lot of capabilities that other doors do not. Steel doorsets are modular, and as a result, can be tailored to provide a combination of features, including but not limited to, security, fire resistance, and the ability to withstand high levels of wear and tear. This modularity is the reason why these doors can be seen in distribution centers, warehouses, and food production facilities among others.

Steel doorsets consist of an insulated core that is sandwiched between two exterior sheets of steel. These can either be galvanized steel or cold-rolled steel. The core can be either foam or mineral wool. Polyurethane foam is the most common choice. It has an excellent thermal performance and is available in a variety of thicknesses. However, it is also the most flammable. Where fire resistance is the primary concern, mineral wool is a much better choice since it does not contribute to fire spread in the way that foam can. Some manufacturers also produce mineral wool-steel foam hybrid doors that try to combine both thermal performance and fire resistance. However, the performance deficits in each aspect of these doors should be examined before making a specification.

For compliance under Part L of the Building Regulations, U-value is the relevant thermal performance metric. For commercial buildings, the current version of the Approved Document L puts the limiting U-value for opaque doors that form part of the building envelope at 1.4 W/m²K. Mainstream manufacturers’ doorsets that are better than this offer U-values of 0.8 to 1.2 W/m²K, meaning there is flexibility available against the limiting U-value, which is particularly important to consider when optimizing the overall energy performance of the building. The worst performing area of the doorset, and the area of the highest thermal bridging, is generally the threshold detail. A highly insulated door that is poorly framed and detailed at the door threshold will perform far worse than the doorset’s specification would lead one to believe.

Fire rating must be outlined independently from thermal performance. In the UK, fire rated doorsets are rated by integrity and insulation: FD30 and FD60 represent the most common ratings in the residential and commercial sectors and signify thirty and sixty minutes of fire resistance, respectively. If the doorset must also inhibit the passage of smoke, then the rating in the UK changes to FD30S or FD60S. For high risk areas, plant rooms, and zones where a longer resistance period is required by a fire engineer, doorsets are rated FD90 or FD120. The UK standard for the fire-resisting doorsets is BS EN 16034. Rather than relying on manufacturer claims, doorsets should be third party certified to this standard.

Incorporating security performance into insulated steel doorsets doesn’t significantly change the construct. Some UK manufacturers have doorsets certified to LPS 1175, and compliance to PAS 24, assessed for the Secured by Design standard, can be done within standard insulated steel constructions. For most commercial applications, doorsets use multi-point locking systems. However, BS EN 1125 compliant hardware is used if the doorset needs to be a fire escape. BS EN 1125 also mandates the doorset be lockable from the interior. Selecting hardware requires careful deliberation, as a doorset designed to be a security doorset that is frequently used, and a doorset designed to be a security doorset that is infrequently used, must have a different hardware configuration.

In controlled environments, thermal insulation requirements extend beyond the doorset. Cold storage doorsets particularly have heating elements built to the frame to mitigate against icing at the seal, and doorsets must withstand the pressure that occurs when a cold air doorset is opened to the warmer ambient air. There is no mistaking the difference between a standard insulated commercial doorset and a cold storage doorset. Insulating the wrong one leads to icing at seals and energy losses that are expensive and difficult to resolve.

Steel doorsets exhibit very little adjustment flexibility after fitting compared to most door types, meaning that installation tolerances matter more with steel doorsets. The structural walls/enclosure need to be built to the correct dimensions to accommodate the steel doorset frame. Validating the dimensions of the structural opening prior to frame installation is especially necessary for the steel doorsets when compared to flexible frame doorsets as the result of fitting steel doorsets into oversize structural openings will look and function much worse compared to fitting the frame into a structural opening built to the proper dimensions.

The cable is the working component of any winch system as it is the one that bears the load and transmits the forces and is subjected to the most abuse. Many purchasers of electric winches decide on the pull limits of the winches and the specifications of the motor as their selection criteria. However, the cable should also be given due consideration during the specifications stage.

The most typical winch cable being utilized in the industrial and construction fields is steel wire rope. As per the rope’s construction – number and type of strands, number and type of wires, and the style of laying – determines the rope’s load handling, abrasion and drum winding tolerance. The construction of Caribbean plait of rope, i.e. 6×19, is also a commonly winching type and is designed to have a good combination of flexibility and abrasion resistance. On the construction of Caribbean plait rope, i.e. 6×36, has a higher number of wires in the strands leading to more flexibility and a capability of being utilized in smaller drum diameters, but a rope of 6×36 construction will have a higher surface abrasion.

Steel Wire Rope grade choices matter for industrial and construction winching applications. In simple UK cases, Zinc cables can protect against corrosion. But for more rigorous applications where corrosion protection needs are at a higher level, then the added costs and the added corrosion protection, and perhaps more corrosion protection due to almost all of the work being done by steel cables, are worth noting. Ropes by themselves with the same diameter can differ because of the steel grade.

It is also by steel rope worth mentioning with all of the inherently safe and corrosion us grade differences, the same work load can differ. Additionally, it is by steel rope worth mentioning with all of the inherently safe and corrosion us grade differences, the same work load can differ. The same can be said with all of the inherently safe and corrosion us grade differences, the same work load can differ. The same can be said with all of the inherently safe and corrosion us grade differences, the same work load can differ. The steel rope also needs to be a certain safe grade. One can also add it being corrosion us grade to all steel rope worth mentioning. And lastly, the steel rope can be worth mentioning.

Since the grade differences have to break safety at all five points, the differences have to break at a five grade safety for all applications. One can also add it being coursework grade to all steel rope worth mentioning. And lastly, the steel rope can be worth mentioning. The grade differences are all worth noting.

Swagged ferrules and cable grips are the two most common types of cable terminations found on most winch installations. Fitting a cable end with a swagged closure is a secure, permanent, and non-slip termination that is irreversible and can be a full load connector. Mechanical grips, or bulldog grips, are a popular on-site cable termination and are reversible. They require careful installation and adjustment to the specifics of the cable and load. Improper adjustment and installation of a cable grip may allow it to slip, at a fraction of the load the cable is rated at. Swagged ferrules, or fitted closure, are secure, permanent, and irreversible cable endings but require full load connector attention and care while being irreversible. Mechanical grips, or bulldog grips, are cable terminations and are reversible. They require careful installation and adjustment to the specifics of the cable and load. Improper adjustment and installation of a cable grip may allow it to slip, at a fraction of the load the cable is rated at. Swagged ferrules, or fitted closure, are secure, permanent, and non-slip terminations but also reversible. A cable grip is, in effect, a reversible bulldog grip. Proper adjustment and installation of the specifications of load and cable are crucial to the grip serving its purpose.

In accordance with the regulation of the Lifting Operation and Lifting Equipment (LOLER), a winch cable used in hoisting and lifting need to be SOTR (Satisfactory for Use at the Time of Examination). The cables and winches, minus the lifting implements and attachments, should be examined for signs of wear and fatigue, and safety of the fittings.

Recently, industry championed acceptance of a threshold for wired rope termination over a normed threshold (length of slip, free length). Kinking, crushing, or abrasiveness should also be considered whether or not the threshold is met at the slip.

Specifications often neglect practical elements like drum capacity and cable management. Stacked cable layers bend unevenly. Inner layers suffer additional stress and ultimately have shorter fatigue lives. When a winch operates at maximum drum capacity and at maximum service life, cable rotation, or specifying a drum capable of housing a full working length of cable in a single layer, is vital.

In recovery and off-road applications, many opt instead for HMPE (High Modulus Polyethylene) fibre rope alternatives. Compared to traditional steel rope, fibre rope options are lighter, don’t store as much energy under tension, and less end-use energy push is a safety hazard. These alternatives are a great fit for off-road, recovery, and specialty applications that steel rope are used in where weight and energy-storage hazards make rope snap-back and weight a concern.