The overlashing vs new strand build decision shows up on almost every capacity expansion in aerial telecom work. There are two paths to adding cable to a pole line. Crews can attach the new cable to the strand that is already there, or they can build a new strand from scratch. Each approach has real costs, real benefits, and specific situations where it is the right call.
This guide walks through how crews and engineers decide between overlashing and new strand construction, what factors tip the balance, and how the two approaches compare on time, cost, and long term reliability.
What Overlashing Is
Overlashing means attaching new cable to an existing strand and lashing it in with the cable already there. The new cable rides on the same support system as the old one, held in place by fresh stainless steel lashing wire that wraps the whole bundle.
The Basic Process
The crew hangs cable rollers on the existing strand ahead of the lashing machine. The new cable feeds up over the rollers and moves along the span. Once the cable is in position, the lashing machine travels the strand and wraps lashing wire around the whole bundle, tying the new cable to the existing one.
The result is a single supported bundle with the old cable and the new cable running parallel along the same strand.
Why Crews Pick It
Overlashing is faster and cheaper than building a new plant. There is no new strand to string, no new poles to permit, and no new attachment points to install. On routes where the existing infrastructure has capacity for more cable, overlashing gets the job done at a fraction of the cost.
What New Strand Construction Is
Building a new strand means running fresh support wire from pole to pole and attaching the new cable to it. The new cable is completely independent of any existing plant on the route.
The Basic Process
The crew climbs each pole or works from a bucket truck to install new attachment hardware. Then strand is pulled from pole to pole, tensioned, and secured. Once the strand is up, the cable is pulled and lashed to it just like a first time install.
The result is a new supported cable line that runs alongside the old one on the same poles but on its own hardware.
Why Crews Pick It
New strand construction is the right call when the existing plant cannot support additional load, when regulatory clearances get tight with overlashing, or when the existing strand is in poor enough condition that adding to it would create problems.
Factors That Decide Between the Two
Several practical factors push a project toward one approach or the other.
Pole Loading Capacity
Every pole has a rated load capacity based on pole class, strand size, existing cables, and expected wind and ice loads. Adding a new cable to an existing bundle changes the load. If the pole is already near capacity, overlashing might push it over the rating, which means new strand or full pole replacement becomes the only option.
Pole loading analyses get done before any overlash project on regulated lines. The results of that analysis often make the call between overlashing and building new.
Existing Plant Condition
If the existing strand is corroded, if the lashing wire has broken spots, or if the attached cable is at the end of its service life, overlashing on top of that plant creates problems. Building new gives you a fresh support system that is not carrying the risk of the old one failing.
Crews walk the route before deciding. A route where the existing plant is in solid condition leans toward overlashing. A route with deteriorating strand leans toward new construction.
Regulatory Clearances
Aerial cable has to maintain specific clearances from the ground, from other utilities on the same pole, and from crossings over roads and railways. Overlashing usually does not change strand height, but adding weight can cause sag that pushes clearances toward the limits. New strand can be set at a different height to preserve clearances.
Time & Budget Pressure
Overlashing is faster and cheaper by a wide margin. A route that would take a few weeks to build can be overlashed in a fraction of the time. For projects on tight schedules or tight budgets, overlashing is the default answer when the plant supports it.
Long Term Plans for the Route
If the existing cable is going to be retired within a few years, building a new strand and pulling the new cable independently avoids the trouble of stripping out overlashed cable later. If the existing plant is expected to stay in service indefinitely, overlashing is the cleaner long term answer.
The Practical Decision
Most capacity expansions that can be overlashed get overlashed. The cost and time advantages are large enough that overlashing is the default choice when the existing plant supports it.
New strand construction gets picked when the plant does not support overlashing, when clearances are marginal, or when the long term plan for the route calls for independent cable lines.
A Quick Rule of Thumb
If the pole loading analysis says the existing plant can carry the new cable, the strand and existing cable are in good condition, and clearances stay within limits, overlashing is the right call. If any one of those three fails, new strand construction moves into consideration.
Who Makes the Call
For most jobs, the decision starts with the engineering group that plans the route. They pull the loading analysis, review the route, and specify the approach. Crews in the field usually follow the spec but can flag issues that were not visible in the office review, such as strand conditions that look worse in person than it did on paper.
Field Notes That Change the Answer
Even a plan that specifies overlashing sometimes gets changed once the crew is on site. Common reasons include finding damaged strand that was not caught in the survey, discovering that pole clearances are tighter in the field than the loading analysis assumed, or seeing that the existing cable is in worse condition than expected.
When those issues come up, crews call back to the engineering group to confirm a change in approach. Building the easier way without checking in leads to compliance issues down the road.
The overlashing vs new strand build decision is one of the practical calls that drive almost every aerial capacity project. Get the analysis right up front and both approaches work well for the situations they suit.