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? – yoyoyoyosef Aug 31 '09 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. – Daniel R Hicks Jul 5 '13 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 '13 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. – Axel Kemper Jul 10 '13 at 13:51

13 Answers 13


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 '09 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 '09 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 '09 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 '09 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. – William Hilsum Aug 31 '09 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. – Austin T French Jul 5 '13 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 '15 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.

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