Passing multiple network wires through cavity wall to outside of property

[btjtaylor]

Hi all

Long time lurker but first post here

I've purchased a property built in the 80s which has fairly standard cavity wall construction (my previous experience is on an older single skin brick property which is a little easier to work with for external cable entry)

I'm looking to install a few network points, 2 in my upstairs office, one in the living room, and one in the loft to run down to a wireless access point in the ceiling of the upstairs hallway. I want to run the cables external to the property to avoid any major replastering and then pass them all through the wall into a cupboard where my patch panel + network switch will be located. I'm also looking to run a couple of network cables out to the garage but i'll probably handle that at a later date once I figure out how the electrics get to the garage (!) I hope thats been done properly at the time of construction as the garage is the same age/style at the house so was likely done by the original builder but you never know ...

From reading around online it seems the best way to handle this is to use a PVC conduit in the wall. It seems 20mm is the standard size for this sort of job which according to the following calculator will allow 5x CAT5 cables (6mm dia) to pass through its 17mm internal diameter https://www.engineeringtoolbox.com/smaller-circles-in-larger-circle-d_1849.html - potentially I could squeeze 6 through if I really tried!

I intend to purchase the following

20mm PVC conduit

20mm PVC conduit entry (for outside the property)
https://www.screwfix.com/p/masterse...gclsrc=aw.ds&dclid=CIyl9PugltgCFcZxGwodY5wJfA

A reel of Cat5e external grade cable

I have an SDS drill and the following bits:
8x460mm
20x460mm
22x460mm
25x460mm

For the cupboard, I intend to drill through the wall with the 8mm, then work my way up through the bits until the conduit fits through - hopefully as close to 20mm as possible! Then seal up the end of the conduit with the PVC entry rubber plug and mastic round any gaps.

For the sockets in the rooms I will use an 8mm hole through to a surface mount RJ45 box on the inside wall and mastic round and clip the cables roudn the property externally.

Can anyone advise if they have attempted this kind of thing before? I think i'm OK with the boxes in the rooms it's just getting multiple wires through a wall that i'm not sure about (using a conduit etc)

Thanks in advance
Ben

 

[motorbiking]

I think it will be easier to run the cable in the floor void and up the under stairs cupboard if one exists. Its fairly easy to patch plaster and even if you are truly rubbish at it, you can always rub it down with some sand paper. Given the cost, I'd be tempted to go cat6 unless the building is massive.

 

[JohnW2]

Its fairly easy to patch plaster and even if you are truly rubbish at it, you can always rub it down with some sand paper. ...

True, but it's the decoration which is usually the issue, particularly when walls are wallpapered!

Kind REgards, John

 

[jg321]

I think it will be easier to run the cable in the floor void and up the under stairs cupboard if one exists.

And in my house (1930s semi), the under-stairs cupboard only gets you to the half-landing before the stairs turn a 90 degree angle! My network cables had to go under my kitchen floor, and up into the bathroom along with my central heating/hot water pipes. The soil pipe is also outside so I was SOL there too.

I know that the upstairs lighting circuit goes up through the middle pillar-like part of the house, along with the shower circuit. I'm yet to discover how the upstairs ring circuit gets up to the first floor though, as it's less than obvious from looking under the floorboards on the landing.

The usual advice applies - run twice as many cables as you think you need, even if they just end up coiled up under the floor. I didn't, and I need two more. Luckily we haven't started decorating the kitchen/bathroom yet, so I still have the opportunity to put some more in.

 

[oldbutnotdead]

Have a very careful recce before you start drilling- look for cables and pipework that disappear into the cavity and reappear somewhere random (you aren't meant to do it but builders often do)
Your technique sounds OK- hopefully the cavity won't be full of bead insulation that'll start cascading out when you drill through. You'll get neater holes if you do the final hole from both sides (so start with your 8mm from inside to out so you know where you are, then 15 and 20 just go halfway from inside and halfway from outside. Avoids the nasty exit crater. Top tip- make some guide blocks (bit of 4 x 2 on edge with the correct size hole in it, clamp it to the wall or just hold it against the wall and drill through it. Keeps the hole near enough horizontal and straight through the wall rather than wandering off)
Have a think about keeping the external runs totally in conduit- yes it is more work and more cost but it is much neater, avoids any UV degredation of your alleged external CAT5 and won't look rubbish in 5 years time when the cable has gone baggy between the clips. In theory you should consider metal conduit to protect against external high voltage incidents (lightning in other words)....
And you might be being a bit ambitious trying to get 6 bits of CAT5 in one piece of 20mm. Maybe in a straight line but corners will be dicey on minimum bend radius, pulling through will be very dodgy (CAT5 is not mechanically robust)

 

[Lectrician]

That “entry” you link to isn’t to enter a building with, its to enter an MK masterseal back box!

You’re over complicating a hole through a wall. Sure, sleeving the whole is a pro thing to do, but you don’t need to put anything either end of the conduit. TBH, the conduit isn’t really needed.

I would look at taking cables under the floor, look to use the airing cupboard as a riser. Once in the loft, dropping down in stud walls is quite easy, with just a tiny notch over the noggin.

 

[ban-all-sheds]

That “entry” you link to isn’t to enter a building with, its to enter an MK masterseal back box!

I hadn't clicked that link.

btj - that is basically a grommet - here's a better view of it:

 

[AnotherTom]

If you decide to go for external runs of cable without conduit, they should approach the holes in the wall from below, which may require a loop of extra cable. That way any rainwater running along the cables isn't delivered to the hole/grommet/gland/whatever.

e.g.

 

[ericmark]

I used a socket back box with a 25 mm hole in the back, and LAP grid switch brushes on the front, a small bit of conduit to stop the cavity wall filling blocking the hole and out side silicon sealant to stop insects crawling through the hole. If I need to add or replace it means new silicon sealant.

 

[echoes]

I've run some cat 5 externally in 20mm conduit where an internal route wasn't practical.
Didn't use any conduit through the walls, but used these

where the cables exit the wall. I've since run an extra cable through without too much bother.