Yes—wires can sometimes be fished upward through an external wall, but only when there is a suitable continuous route between accessible openings. Insulation, pipes, framing and other concealed obstacles can block or snag a cable, and exterior-wall wiring raises safety and weatherproofing questions. A fish tape can help guide a pull; it cannot confirm that the cavity is clear or that the wiring method is safe and compliant.
What determines whether a cable can be fished up an external wall?
The key question is whether a continuous path exists from the starting opening to the destination. A trade-training guide from SkilledTradesBC describes fishing cable through a wall section, while noting that insulation, pipes and other obstructions make the pull more difficult (SkilledTradesBC, 2023).
External walls are often insulated, and their concealed spaces may also contain framing or services. A fish tape may pass through an open cavity but stop or snag when it meets these conditions. The route must be assessed rather than assumed from the position of the openings.
How insulation and existing wiring affect safety
Insulation can change how heat leaves a cable. New Zealand Building Performance says the current-carrying capacity of wiring surrounded by thermal insulation is half that of wires surrounded by air; this is its stated guidance comparison, not a universal specification for every cable or installation (New Zealand Building Performance: electrical safety in retrofitted insulation).
#1 Best Overall
- This 45FT fiberglass running wire cable electrical fish tape kit is made of fiberglass material, low friction design allows the tape to easily glide through the conduit without binding at turns, joints or couplings.
- Includes 32 rods each one 1.4ft,(3/16" diameter) with 8 attanchment:threaded brass connectors, Magnetic connector,3/16" acrylic connection, brass push ,brass hook,rope chain ,eyelet ring and pull rods.
- This fish tape kit is flexibility(don't over force), rigidity and great insulation, wear-resistant,corrosion-resistant and oxidation resistance,The extension rods can be connected together to achieve the required length, extending up to 45 feet(13.7M).
- Use for running wire through walls, attics, crawl spaces, sub-floors and suspended ceilings, Great for installing cable,wires,HDMI and so on .The bright green fish tape helps u locate and differentiate the rods from wires easily.
- The pacakge comes with a storage case ,its convenient to store.
That guidance also identifies risks that can depend on circuit rating, load and proximity to combustible materials. Some insulation products may be incompatible with cable insulation. Older VIR or TRS wiring can be fragile, and polystyrene may embrittle PVC cable insulation (New Zealand Building Performance; New Zealand Building Performance: electrical safety in retrofit insulation).
If existing wiring may be damaged, unsuitable for the cavity, or affected by insulation work, do not rely on a successful pull as proof of safety. New Zealand guidance calls for a registered electrician to check and certify safety when wiring is modified or retrofit insulation may compromise it (New Zealand Building Performance).
Rank #2
- 【High Flexibility】Material: Fiberglass. Fiberglass better than plated carbon steel, our wire puller running tools will not break when folded, faster, easier pulls: low friction design allows the fish tape to easily glide through the conduit without binding at turns, joints or couplings. Note: Do not bend forcibly while using
- 【Excellent Extensibility】Total 16pcs fiberglass rods, 1.4FT(0.42m) per rod. Diameter: 0.16" (4mm). The glow rods can be used individually or threaded together for desired length, can be extended up to 22 feet(Depends on the length of the rod you use)
- 【Multifunctional】Our electrical tool comes with 16 fish rods, brass hook, magnet search head, flexible search head, eyelet ring, fish tape fastener and a storage case. The fishing tool kit can be combined with additional kits, and a plastic storage case makes it convenient to store
- 【Application】Use for your interior and exterior electrical site wiring like, outlet, plug, socket, light fixture, ceiling fan, dimmer, switch, short runs installing electrical box, electrical panel, subwoofer box, switch box, junction box, CPU, breaker box, receptacle box, transformer, doorbell, Intercom, surveillance camera, DCC, security systems, smoke detector, thermostat, appliances, hot tub, telephone/Internet line or cable TV coax
- 【Fish Tape Fastener】Fish tape fastener is used to help fish tape more convenient to use. One side is connected with wire, the red line cap can prevent wire disconnect when pull it. Another side is connected with fish tape, which makes the wire and fish tape connect firmly
When the route crosses the exterior wall layer
A cable route that penetrates the outside wall layer needs a detail that prevents water entry. BRANZ’s 2025 article on cable penetrations cites New Zealand Building Code clause E2.3.2: “Roofs and exterior walls must prevent the penetration of water that could cause undue dampness, damage to building elements, or both.” Its discussion is specific to New Zealand; the applicable building requirements elsewhere may differ (BRANZ, “Weatherproofing cables through exterior cavity walls,” Build 207 (2025)).
Plan the weatherproofing and sealing as part of the penetration, rather than treating it as an afterthought. Where possible, avoid creating an unnecessary opening through the exterior envelope.
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Rank #3
- 【High Flexibility】Material: Fiberglass. Fiberglass better than plated carbon steel, our wire puller running tools will not break when folded, faster, easier pulls: low friction design allows the fish tape to easily glide through the conduit without binding at turns, joints or couplings. Note: Do not bend forcibly while using
- 【Excellent Extensibility】Total 36pcs fiberglass rods, 1.4FT(0.42m) per rod. Diameter: 0.16" (4mm). The glow rods can be used individually or threaded together for desired length, can be extended up to 50 feet(Depends on the length of the rod you use)
- 【Multifunctional】Our electrical tool comes with 36 fish rods, brass hook, magnet search head, flexible search head, eyelet ring, fish tape fastener and a storage case. The fishing tool kit can be combined with additional kits, and a plastic storage case makes it convenient to store
- 【Application】Use for your interior and exterior electrical site wiring like, outlet, plug, socket, light fixture, ceiling fan, dimmer, switch, short runs installing electrical box, electrical panel, subwoofer box, switch box, junction box, CPU, breaker box, receptacle box, transformer, doorbell, Intercom, surveillance camera, DCC, security systems, smoke detector, thermostat, appliances, hot tub, telephone/Internet line or cable TV coax
- 【Fish Tape Fastener】Fish tape fastener is used to help fish tape more convenient to use. One side is connected with wire, the red line cap can prevent wire disconnect when pull it. Another side is connected with fish tape, which makes the wire and fish tape connect firmly
What a fish tape can—and cannot—do
A fish tape is a guiding tool for pulling cable through a route that is accessible and passable. The SkilledTradesBC training material describes attaching cable to fish tape and pulling it through a wall section (SkilledTradesBC, 2023). The tool does not reveal the full condition of a concealed cavity, make an obstructed route clear, or establish that the cable and installation comply with local rules.
Do not use a flexible extension cord as concealed permanent wiring. OSHA’s cited restriction concerns U.S. construction wiring: flexible cords are not substitutes for fixed wiring and must not be concealed behind walls. It is not a complete residential wiring code and should not be treated as one (OSHA, 29 CFR 1926.405).
Quick Recap
Best Value
- Durable, high carbon 1/4-Inch wide spring steel fish tapes are firm yet flexible
- New protective coating reduces non-contact moisture and humidity but keeps the steel dry to touch
- Laser etched markings in 1-Foot (0.3 m) descending increments allow you to more accurately measure the length of conduit runs and determine the amount of tape left to pay out
- Slim-profile plastic tip navigates easily and reduces catching
- Optimized design of the tape housing decreases payout effort; compact size makes it a staple for your everyday tool bag
Rank #4
- This 14 FT fiberglass running wire cable electrical fish tape set is made of fiberglass material, low friction design allows the tape to go through the conduit easily without binding at turns, couplings and joints.
- Includes 10 rods each one 1.4ft,(3/16" diameter) with 8 attanchment: threaded brass connectors, Magnetic connector,3/16" acrylic connection, brass push ,brass hook,rope chain ,eyelet ring and pull rods. The pacakge comes with a plastic storage case ,its convenient to store.
- Green fish tape fastener is connected with wire, the green line cap can prevent wire disconnect while pulling and the other side is connected with fish tape.
- This fish tape kit is flexibility(don't over force), rigidity and great insulation, wear-resistant,corrosion-resistant and oxidation resistance,The extension rods can be connected together to achieve the required length, extending up to 14 feet(4.2M).
- Use for running wire through walls, attics, crawl spaces, sub-floors and suspended ceilings, Great for installing cable,wires,HDMI and so on .The bright green fish tape helps u locate and differentiate the rods from wires easily
How to decide what to do next
- Identify the route. Confirm where the cable would start and end, and whether there is a plausible continuous cavity between them.
- Account for concealed conditions. Treat insulation, framing, pipes and existing wiring as possible obstacles or safety concerns; do not assume the tape will pass freely.
- Check the cable and local requirements. The sources do not establish one method, permit rule or licensing requirement for every location. Requirements depend on where the work is done and the cable type.
- Address any exterior penetration. If the route passes through the exterior wall layer, plan a weatherproof detail that meets the rules applicable to the building.
- Bring in a qualified electrician when needed. For mains wiring, uncertain existing wiring, or questions about cable suitability and compliance, consult a licensed or registered electrician in your area.
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