I'm trying to extend my network to an unconnected garage that's about 20 yards away from my house. What's the best way to do this?

  1. Is there special outdoor-rated CAT5e/CAT6 I should use?
  2. If put it in a dug trench, do I need to put it in conduit?
  3. If I run parallel to electric, how much separation do I need, and do I go UTP or STP?
  4. If I do an overhead run, how should I properly ground it against lightning?
  • Thanks for all the answers so far, they're very helpful. Does anyone have advice re: UTP vs STP if I'm going to run parallel to electric with 6" separation? Aug 31, 2009 at 15:49
  • According to code you need to have lightning arresters even if run underground. And this isn't a case of "overreaching" on the part of the code guys -- lightning can and does strike underground cables. Jul 5, 2013 at 0:33
  • If you dig do yourself and perhaps your neighbor a favor by contacting a utility marking agency. I live in Virginia and it is offered free through a state agency so you might want to start there. I ran STP using grey PVC (pretty cheap from Lowes) from my home to my shed and cut a Verizon analog phone line. While I have no idea who would even know the analog line was gone to begin with I got fined $150.00 and had to pay Verizon $250.00. An expensive lesson learned for sure.
    – user236009
    Jul 5, 2013 at 18:24
  • Make sure that both buildings are properly grounded electrically. A voltage difference of some millivolts causes compensation currents across the shield of your STP which might burn the cable and ruin your devices. A fiber optic connection or galvanic isolation would exclude such risks. Jul 10, 2013 at 13:51

14 Answers 14


Yes. This article answers most of your questions.

Is there special outdoor-rated cat5e/cat6 I should use?

"Preferably, special exterior or direct burial CAT5 cables should be used for outdoor runs instead of ordinary CAT5."

If put it in a dug trench, do I need to put it in conduit?

"Exterior-grade Ethernet cables are waterproof and thus do not require conduit."

If I run parallel to electric, how much separation do I need, and do I go UTP or STP?

"5-20cm (6-8 inches) and at least that far away from power lines or other sources of electrical interference."

If I do an overhead run, how should I properly ground it against lightning?

"Accordingly, CAT5 surge protectors should be installed as part of outdoor Ethernet networks to guard against lightning strikes."

  • 9
    In my experience, it doesn't hurt to combine both trenched conduit and direct burial wire. Expansion is great. Direct burial alone tends to get eaten rather easily if you have any sort of rat/mole/gopher digging around. Straight conduit can leak if done improperly, but the combo is a reliable combo. If you're concerned about dealing with conduit, flexible "liquid-tight" grey pvc tubing is "very" easy to route, but does cost a bit more than standard pvc.
    – Keck
    Aug 31, 2009 at 14:53
  • @Keck +1 for conduit. All wires are waterproof because they're sheathed in rubber, but you'll (hopefully) never see your telco or municipality running bare wires underground.
    – msanford
    Aug 31, 2009 at 18:18

I did the same with conduit. This way you can run regular wire inside and if you ever need to run additional wires you just feed another one through. I did this for my securtiy system and added the Cat 5 later, I am not sure that I wouldn't have just used wireless had I not already put the conduit in there.

You can now purchase outdoor rated cable, that is designed specifically to resist sunlight, moisture, and most other things.

Edit: Just a minor detail, at least minor until you need it. When you run the conduit be sure to pull a string through and tie it off at both ends. You will use that to pull any additional wires through if you need to later. Thanks to Chris Noe for pointing out my omission.

  • 10
    Pulling string through your conduit can greatly aid such future expansion.
    – Chris Noe
    Aug 31, 2009 at 13:45

I'd use conduit for ease of maintenance. If a cable goes bad, you can pull new cable though the conduit with out having to dig up and rebury the cable. I would still use an exterior rated cable.


Won't write up a full article as others seem to have done a lot better than I could... however...

No matter the temptation to save money and use standard cable - DON'T!

A few years ago, I had to go to a school that had used standard cat5 cable all over the place and across flat roofs to go building to building.

They called me in after a lightning strike killed EVERY rj45 port on switches, routers, servers, desktops... and even fried IP cameras and print servers - Everything you can imagine!

Changing over 300 NIC's was a very long job and it was expensive to replace the other network equipment.

They are now using fibre optic... Not that much of a practical solution for home networking if you already have equipment, but certainly go proper - conduit, trench e.t.c.

(or if you do go cheap, remember my contact details for the future in case you have a big job coming!!)

  • I doubt even exterior grade cable buried in a conduit will survive a lighting strike. However I shudder at the thought of cable laid across roof tops exposed to the elements.
    – Jim C
    Aug 31, 2009 at 19:21
  • I couldn't believe it, but if you take a look at many modern schools, they all do it now - just usually in conduit, thick rubber around the cables, or use fibre optic - however, again, many do it - it really depends on the layout of the building though. Aug 31, 2009 at 22:20

Have you considered using a powerline ethernet connection? Obviously you have power going to the out-bulding. No digging, no lightning strikes to worry about. Probably cheaper too. Also allows every outlet to become a computer connection.


Here in Algonquin Park (Northern Ontario, Canada) we run electrical, propane, phone and data cables everywhere underground, we use 75# black poly water pipe, it's cheap and plentiful, comes in sizes up to 4", you can make it any length with connectors and it is flexible; you can curve around rocks and roots, etc.

When burying anything, always put a 2x4 or 2x6 directly over the pipe or conduit before you bury it, cut it into 2 to 8 foot lengths depending on how straight or up and down your pipe is, then if you ever need to dig any other holes in the area you have have some form of protection, something that your shovel will hit before you carve through the pipe or conduit. Don't wimp out on the depth either, bury a minimum of 2', better yet 3 to 4' if the terrain allows, with 120/240 electrical follow your local code re depth.

Another thing is lightning, any ground strike (in the countryside) with-in 1 to 2 kilometers can induce sufficient energy into the cabling (including electrical) to damage or destroy your electronics, as said by others, protect your equipment. We've lost PLC controlled sewage and pump controllers with strikes as close as 1/2 km, and this is industrial equipment, well protected, the surge just wipes out the protection and equipment when that close.


However tempted you are to run Cat5 or Cat6 between buildings, DON'T.

Apart from the issues of lightning strikes and proximity to power cables causing interference, you can get surprisingly high differences in local earth potential due to varying soil/ground conductivity

Whilst equipment will probably handle the voltages involved, the poor schmuck who happens to put his hand on the plug won't. This may not happen for years - if ever. but it's a risk worth avoiding. Yes, there are supposed to be isolation transformers in the transceivers. Don't rely on them being there or being rated appropriately.

In addition, copper cables buried in the ground (or run overhead) will eventually suffer water ingress and corrode. Fiber-optic is immune to this failure mode.

Outdoor fiber-optic cable is cheaper than you might think, as are media converters.

Never direct-bury, for the reasons already elaborated in other posts.

It is worth putting a tracer wire in the duct as this makes it a lot easier to use cable location kit later on (eg, CAT4 and Genny). This can be anything as long as it's conductive and corrosion-resistant (unconnected at either end). You can trace a non-conductive fiber but it's a lot harder as the coupled signal is almost non-existant - personal experience having to trace a 1000m telco fiber run that had been laid 25 years previously with inadequate documentation.

I've seen people kill 2 birds with one stone on this front by using electric fence string as the draw wire. Personally I wouldn't recommend it.

The old "Do it right or do it over" cliche comes into play here. Labour costs outweigh the materials, so skimping out is simply uneconomic, long-term.


I'm retired now, but when I had my shop I had a sign that said "If you don't have time to do it right, do you have time to do it again? I ran cat5 cable to my shop (approx. 300 feet) in grey plastic pipe underground, because the powerline units seemed to be rather intermittent. Like someone said, remember to also pull a string - preferably a nylon one that won't rot - and when you pull another cable pull another string. I learned the hard way to use pipe that is way bigger than I need, as future expansion is hard to predict. The extra cost is small compared to replacing it with a bigger one later.

  • I would never let anyone run cable in the ground without a conduit, personally. Saves cost in the long run if that cable goes bad too. Jul 5, 2013 at 19:23

Check your local building codes before you begin and see if you need any permits. If you don't check and an inspector shows up later you might have to remove your handy work and end up with a fine to go with it. Doesn't take much extra time to get it right and legal.

  • on the other hand, if you ask about the building code, you are almost guaranteed to get inspected.
    – Dan Pritts
    Feb 14, 2015 at 19:14

Honestly, I would seriously consider wireless. Look around for cheap directional antennas and buy your AP's for the antenna selection. You'll find that unless you are wanting to go gigabit speeds or there are trees in line of sight between the buildings, wireless will work just fine. No digging required.


Standard Ethernet cable outside: not on the long term. It will work, but after a while the coating will degrade due to weather patters or in-trench conditions. Then the coating of the wires and then they will short out. Exterior cable should be used in such cases (it's different from the standard one because it has special coating).

The distance from power really depends on the power lines. The higher the power, the more distance you need. If it's trenched, it's better since it has full length grounding.

For the lightning protection, usually if theres anything else higher than your cable, you won't need any. On most structures I cabled, there was good lighting protection already.


I have a couple of points.

  1. Regular cat 5 surge protectors will not protect against a near lightening strike, though if you bury the cable it may withstand a lot, but a close or direct strike can arc right through the unit and continue on to burn out everything. I recommend a surge protector that is designed against lightening strikes.

  2. I would not bother to install a single cable. Cat5 cable is cheap, even outdoor rated. Install 2 or even 3 cables in a single conduit. Then if one 1 wire goes bad, you switch to a new cable, or just borrow a twisted pair from one of the other cables. That can "almost" guarantee you will never have to dig it up again. Besides, if you suddenly need a separate connection for something else, (remote POE, alarm wiring for fire or burglar alarms) you have the cable available without digging a new trench


Cat 5 and cat 6 cables can be protected with network isolators like the EN-70HD or the EN 60KDS from EmoSystems.com. These include medical grade isolation transformers good up to 8KV, whereas normal enamel coated transformers are prone to flashover during high voltage events. These devices also have TVS diodes integrated into the enclosure to suppress high voltages. They are small and just snap in-line. I have friends that have dozens of these on their high end systems for video and audio applications.


Calvin Thomas shared some of the greatest wisdom concerning pulling Ethernet cable.. Sadly it is only us Professionals who have pulled lots of cable, throughout many different environments, whom understand the value in pulling LOTS OF SPARE runs.

So let me expand on the topic:

  1. I pull a minimum of 3x what I need; and,
  2. Always give a plentiful extra amount of slack (make cables TOO LONG, longer than you think you need)

Pulling 2x the amount of cable, would ONLY protect against a failed/failing/damaged cable, with the spare (2nd) cable acting as a replacement to the bad cable.
That said, 2x the amount of cable, does NOT provide for future needs and expansion.

Pulling 3x the amount of cable needed, barely covers both damaged cables & future expansion, and thus brings me to sharing that on client site projects I oversee, I usually pull 4x the cable.

As an example, yesterday, we finished a nightmare project in which we've been working on for almost 6 weeks, involving alot of dirt moving.. We trenched 500+ ft 2+ ft deep[with high end Ditch witch].

To my point, there was a home run that I spent about a day and began. We needed a single cable, so, I naturally pulled 4. You'd think that'd be enough, right?

Heck no! Tech's spent about two days finishing that run.. So a week or two later, after burning thru all 4 lines (with one being bad and unusable because it required PoE, had to re-pull cable (just two this time). And this was PAINFUL as a result of the cable run GOING THRU about 30-50 ZIP ties [only reachable by ladder] which supported & affixed the cables. Alot of ladder moving and climbing!

Speaking about that same run, had another cable run which went an additional 100+ ft beyond to an Outdoor AP. Ironically, when cable was pulled for that particular AP, only a single spare was pulled, so 2 home run's. Fast forward, the AP cable was BAD and HAD to be replaced. You might think, no problem, they pulled a 2nd spare cable, right?

Heck no, it wouldn't be that easy, to just use a spare cable pulled at the same time. Why not? Because there was NO MORE spare cable. THE CLIENT informs us, during the project, that he needs an Ethernet cable to [a device located along that run; which was some solar controlling equipment for a massive solar panel array at distant location of the property].

The point is that, NOT ONCE, but friggin TWICE, on the same run, we had to re-pull cable. Ya know that having to RE-DO something just once is painful enough, but f'ing twice?!?!? And that happened to THE GUY [me] whom pulls MORE SPARE CABLE THAN ANY OTHER PERSON or company!

That project was so custom, that I encountered and had to deal with I think, every possible issue that could be:

  1. Ethernet runs far exceeding 100m/328ft (handled with Ubiquiti NanoSwitches; very inexpensive solution @ only $50/ea);

  2. Inline PoE switches unable to handle the necessary current for all the PoE devices downstream;

  3. Ethernet cable [following PoE standards, such as 4,5+/7,8- passive being incapable of handling downstream device current needs;

  4. No equipment or method(s) by which to even measure, test and/or identify current draw of any particular PoE device(s) or Ethernet cable;

  5. IP Cameras Infrared at night causing current draws that exceed switch and cable capacity causing many other Cameras and other PoE network devices to power cycle, rotating across many devices;

  6. Personally expecting any 24vdc PoE device to power on and function properly with 12+ vdc, which has been my experience; Discovered [only after using a LAB Bench Adjustable Voltage & Current Power Supply] that some Ubiquiti outdoor equipment (AP's & Bridges) would not power on UNDER 18vdc. This issue presented as a result of voltage drops over long cable runs, where in our case, many devices were functioning and say there was 15vdc at the device ends, while some devices (those AP's & Bridges) refused to even power on.

  7. Amcrest 4k Cameras refusing to power on... Yay.. Cameras were satellite cameras at distant locations [without home runs to PoE rack switches], and network connected via wireless Ubiquiti bridges. I had custom passively [fed] power to NanoSwitches [which powered up just fine] that passively passed thru the PoE power downstream thru all switch ports.

Not getting into all the details of the newer PoE standards, it's a headache and hassle to deal with... One of which requires the device (ie an IP Camera) to talk back and forth with the Switch, BEFORE, the switch will turn the power on and send PoE power down the Ethernet cable to the camera. In my wise logic, I assumed that if I passively injected [PoE power] [always being on] that the Cameras would power up just fine. Instead, after I identified the problem and solution, complained to my co-worker about having to custom manufacture special PoE power cables for every single dam camera. He wouldn't believe it or me and the ensuing loud verbal argument, might have led spectators to believe that it was the 4th of July.

The solution was to terminate a short patch cable in which at one end, the std passive PoE wires (4,5+/7,8- which are the Blue & Brown pairs) were not inserted into the crimped RJ45 but instead soldered [and covered with heatshrink] to a barrel power connector which plugged into each camera's power jack [beside the Ethernet jack].

  1. Ubiquiti passive PoE Injector 'bricks' [always putting out 24vdc] at a half amp (0.5 Amp) deceptively incapable of power multiple devices (2 to 4 PoE devices)

During this project, I encountered problems and hurdles, never before seen or thought of [by myself] over the past 25 years of doing this [work professionally and paid].

  1. Excess cable slack having caused a very weird issue at one location with 4 devices (PoE Switch powering 3 IP Cameras). This was a 100ft+ run of expensive Direct Burial Cat6 cable inside 1" conduit buried in an appx 2ft deep trench. Despite the Switch powering on and remaining on, and despite the cameras appearing to power on and show link lights on the switch, the Cameras were not functioning and had no network communication. I'd had a large excess of cable slack (30-50ft) in which instead of cutting off, I first coiled up into a 2.5ft long bundle with large zip ties around it to keep the cable together as a bundle. I don't completely understand what was happening, but suspect the bunbled cable behaved like a wire coil and did something weird to the power and/or data running thru that cable. After hooking up one of my custom mfr'd Inline PoE Ethernet Voltage and Amperage Current Meters, was I able to VISUALLY see the problem. The current draw was only 0.04 Amp's. This caught my attention, contrasted by all other locations drawing at least .20 to a half amp, usually was .3x or .4x Amp. Scratching my head, why this location was drawing less than a tenth of the current of any other location. Asking myself 'Whats differrent?' And I got to spend a half day, bathing in the dirt, digging up that slack, cutting it, re-terminating and then back-filling.

  2. Years ago, there was a Texas based company/business, PoE texas or something, that made & sold PoE voltage regulator pigtails (regulated 12-48vdc down to 5 or 12vdc to power PoE devices such as IP Cameras). In my case, I needed a very specialized device, solution and piece of test equipment that to my knowledge doesn't exist commercially. I ended up ordering [at inexpensive price of about $4 ea [5 for $20] a qty of Chinese made dual display digitial DC Power & Current Meters and proceeded to solder them up with a short piece of Ethernet cable with a keystone on the [input] end and an rj45 on the device end. I used them with any PoE device, unplugging ethernet cable from the PoE device, then plugged my inline meters rj45 end into the PoE device and the Ethernet cable into the keystone on the other end of my meter. The meter told me both the voltage going into the PoE device and the current being drawn [in Amps]. And for anyone whom wants to mfr such themselves, I chose to go self powered, meaning the meters were PoE powered to avoid the hassle of batteries.

  3. At PoE device locations (Single poles containing a PoE powered switch with multiple Outdoor IP Cameras) in which current demands could not be met with Manufacturer PoE injector bricks, I chose to utilize [Universal] Laptop AC Adapters capable of up to 24vdc output at a couple amps;

  4. For any longer length PoE run's, I utilized Variable Voltage 10Amp DC Power Supplies with Digital Display of the Output Voltage. We ordered these very inexpensively at $40/ea and utilized them [in the last Project} to power 7-12 PoE devices downstream. Yes, that's a $40 power supply to power a dozen PoE devices. And regardless of the length of our Ethernet cable run, we could raise or lower, the supply's output [while accounting for the voltage drop over the cable run] to precisely give us whatever voltage we desired at the cable run/devices end.

I.e. on one of our longest runs, we sent 36vdc down and had a 15vdc drop giving us about 21vdc at the PoE devices. If I wanted, could increase the power supply's output to 39vdc which would then give us 24vdc for the devices at the end of the run.

  1. Though more costly, break out the Lab Bench Power Supplies!! Having experienced 6 different PoE power related problems, and needing more information (diagnosing things) I chose to just ordered a new 10 Amp Lab Bench Supply overnight from Amazon [was about $85]. If not permanently deployed for your PoE power needs, at least utilize one or two of these for testing & diagnosing both voltage needs & outputs, but also current draw and needs. You will be able to instantly adjust voltage and/or current levels while observing the impact on your PoE devices. Note that 10Amps is likely overkill and that 2 or 5 Amp supply's may meet your needs.

  2. Overcoming standard PoE cable's max current limitations (translates to max number of downstream PoE devices in which can be powered by a single PoE cable. My solution was to send power down one of my SPARE Ethernet Cables, logically thinking, I chose to use the solid color wires (blue, brown, green, orange) for the Negative and all the White striped wires (Orange/White, Blue/Wh, Green/Wh, Brown/Wh) for the Positive and then Injected the power to the device(s) at the other end of the run by Splicing and soldering between the data and power ethernet cables

My key points are:

  1. PULL lots of extra cables on every run (a minimum of 3x your needs), as I say 'Four or more!';
  2. Waste the cable and ALWAYS plentifully give slack at both ends of your cable runs;
  3. Always run Outdoor Buried cable thru conduit! No if and or buts about it! 2021, Southern California, Home Depot, at only $4 per [10ft] section of 1" conduit, even the poor can afford it!
  4. If struggling with PoE, insert inline voltage and current meters at each end place;
  5. Utilize Lab Bench Power Supply's to light up your PoE run(s) & devices

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