If you have an overhead canopy between the two, I would definitely use that. Ideally build it with a removable lower lid so you have an easily accessible 'service corridor' for any future expansion.

I too am really confused why you'd intentionally want to run all the cables out to a different structure - it's just not something that makes a lot of sense.

Put the switch in the house and if you want all the networking equipment in the shed run and fibre which is literally cheaper than copper these days.

When a cable runs outdoors, you can use gel filled outdoor cable. 
BUT

Before it enters the house, it needs to change to standard indoor cable or Low Smoke Zero Halogen (LSZH). You shouldnt be running outdoor cable into the building as its a fire smoke/gas risk. Normally this is done by using scotchloks or a punchdown block inside an external enclosure on the external wall. 

However NEC regulations in the USA allow it to be run up to 50 feet into commercial buildings and in single dwellings provided the width of the cable or bundle doesnt exceed 7mm.    

Here, no building inspector is really going to know what it is and i dont think we have any local codes.    

Personally, I'd run a few 32mm or 40mm ducts between the building attics with nice big sweeping bends so you can just use standard indoor cable and pull through more if you need in the future. 

Another option is to bring the ducts up into the walls and then have a removable wall panel so you can access them. Would be real handy if you ever want to install security cameras, gate control, water or an alarm system in the future.   

See if your local electrical wholesaler has some 32mm or 40mm semi-rigid "subduct" they can sell you a few lengths of. 
Or even some thick-walled alkathene water pipe from the local farming supply wholesaler.   

In a 40mm duct you probably dont want to be running more than 10x cat6 cables. Not only for extra space and movement if you want to pull through another one or replace one, but also to reduce cross-cable interference. 

We don't really seem to care about LSZH stuff here. We probably should but I've never seen anyone, inspectors or specifiers, terribly concerned about it. Especially if it's in an enclosed wall cavity. It's something of another matter if it's above a drop ceiling.

Definitely agree with future proofing for more cables. I'm personally a big fan of removable panels - this will make it easier if future expansions demand new services or other unpredictable extensions.

Would really recommend a seperate distribution board in the main house. If you lack space these are easily able to be put into a wall cavity in a hallway etc.

I think there's some argument to be had that two distribution boards could require two UPSs, whereas feeding everything from the garage only requires one. An option could be to have a switch for 'non-critical' items in the house, and ~5 linking cat6 cables to the garage. PoE feed the APs and anything else that you want running in a power cut from the garage, and patch through.

That assumes you care that much about a power failure, though.

Cost (wasted ports - might need 2x 24-port switches in house and 1x24 in garage where 2x24 total would have been sufficient) and noise (though fanless PoE switches are now available) are probably the main reasons for locating everything in the garage.

Personally I'd suggest having a distribution/patch panel inside the main house and then have that linked to the garage. If you want overkill you can have a 10gb fibre link like I do :-P

Ahhh, the old fire risk of Gel filled cables, some of you may or may not be aware that in a past life/job I was employed by a company that shared the MoE SNUP programs project management. I was employed as an engineer to oversee technical and design apects, this I did for approx 5yrs.

During that time whilst the MoE were scribing cabling standards this matter arose and I was duly dispatched to get an understanding of the issue. Accordingly I reached out to various technical folk in the insurance industry, who in return reached out to their European and North American community for comment. Long story short, there is no documented case in the western world of a fire in a building that was caused by gel filled cables or infact any insurance report that identified that gel filled cables had in anyway contributed or been in any way responsible for the continued spread of fire. End result it was deemed a low risk.

That said, in the MoE's case I recall (was some time ago) we wrote into the standards that a gel filled external cable (fibre or copper) was not to enter more than 15m, if by that time it had not found the BD (building distributor cabinet) then you had to build a CP or fibre cassette containment to transition to internal rated cabling for the remainder of the pathway to the BD. I would reckon in 99% of cases the BD was encounted before 15m.

So keeping this in mind and based on the OP's task, as per my original recommendation, I would site an inwall cabinet in the house to place a patch panel and distribution switch, then use 2-3 copper ties or a fibre run back to the garage in outdoor rated cabling. To terminate all house outlets right back to the garage with gel filled cables is potentially problematic from fire point of view. But as said, very low risk, and for practical reasons ill advised.

Cyril

Thanks for all the valuable feedback/input. Interesting to see same examples of longevity of standard cable buried in conduit and will think about the entrance of conduit in to the garage running up the wall.

Yes it is a covered walkway between buildings so am looking at using this for my above ground path.

I will favour the split option using the likes of U/G cable or fibre - can I run fibre under grounds in conduit? (I an guessing similar concerns with moisture ingress etc.)

Will also consider how I would do UPS in a split system.

Hi, ideally you use polyethelene sheathed fibre for underground which is readily available pre terminated, this is typically a loose tube design.

You can put standard tight buffered PVC or LSZH sheathed fibre in a damp environment and not get too concerned with damage as long as you dont experience perafrost conditions (southern SI maybe??). So the aramid yarn of tight buffered fibre is typically gel coated to help resist moisture, however if moisture does get to the fibre strands it can shatter them in freezing conditioins. Typically this is not an issue in NZ (except perhaps the deep south). If it were me I would put the fibre in the overhead deck run, then you can use anything including a long fly lead, just be carefull not to damage it when pulling other cables through.

Cyril