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Running coax and cat6 inside wall cavity from loft

x1nick

Active Member
Understand that this is generally a bad idea, but my mum could do with a new TV cable running and network connectivity in the lounge.

I have been told that running the cables outside is not an option! :lesson:

The house is over 50 years old and has no cavity wall insulation, I have also been up into the loft to investigate and I can see what looks to be a piece of wood on the top of the brick walls? (marked in red below)

18942326-40b4-4e86-8aa4-b0b3e8333b06_zps35745fa9.jpg


I have read the best way to drop cables is to:
Drill a 1" hole where you want cables to come out
Using string with weight attached, drop into cavity wall with excess string
Use something to try pull the string through the 1" hole

Anyone got any input on this? Would like to do it as cheaply as possible :)
 

YitEarp

Banned
Similar situation is where I needed to drop cable through was to use extendable nylon rods they are cheap and invaluable for tasks like this I think you can achieve a good range of length with them too depending on your situation. That being said string is fine but I found the rods rigid and were easy enough.

You need to find out what type of wall you are looking at also and if there is actually a void there? Is it dot and dab or timber frame?

Is it single skin or double skin walls?
 

x1nick

Active Member
My reason for string was that the cable exit would be about 1ft from ground level. Figured with excess string dropped from above the exit there is a pretty good chance of catching the string.

Please excuse my lack of knowledge in anything posted below!

Is double skin where you have two brick walls with a small gap in between?

As for type of wall, I am pretty sure there is a void in between the two brick walls with a gap of an inch or two as when I drilled for a cable before you could feel the open space after clearing the first layer.
 

YitEarp

Banned
You will be ok with your method I imagine yes double skin is that type of method. Best to get all your cable in place then and get those walls cavity filled for free while you may still be able to! What are you running? I see you mentioned cat6 but that's not needed unless you are planning on something that requires it. cat5 is fine if you just want to network a tv infact if you don't want to go that route just run a homeplug to access the internet features.
 

x1nick

Active Member
One rg6 cable for TV
And 2x cat6 only using cat6 because that's what I have spare! Want to try do this without spending anything really

Don't think my mum wants cavity wall insulation, think she heard some stories of it making whole walls damp and was put off.
 

Geps

Well-known Member
Just to raise a couple of issues here that you need to think about.

Firstly, double skinned wall is not the same as a cavity wall. A double skinned wall is one that is of solid construction - that is, no air gap. The double refers to the fact that it's built up of two layers of brick which are tied together typically with another brick perpendicular to the wall.

Secondly, it's thought of extremely bad practice to run cables in the cavity of the walls. The outer skin isn't waterproof, meaning the face of the bricks inside the cavity can have water on them, increasing the moisture in the air. Further to this, when the cable drops vertically it tends to have some flex in it that can bridge the cavity (that is, touch both sides). It then allows water from the outer leaf to then touch the inner leaf, not a particularly big concern, but it can go down the lead and water can come out the bottom hole and indeed into the AV equipment if the cable isn't routed carefully. If you insist on doing it this way, consider allowing the cable to sag beneath the bottom hole, this way the water will drip/collect at the bottom.

Thirdly, the preferred method for these situations, IS to run the cable outside in trunking or if the cable is rated accordingly, just clipped to the wall. Again, the trunking should enter 'uphill' into the property to avoid water running onto the inner skin.

Finally, for the cable routing itself, I forget what it's called but there is a tool that is essentially a stick with a magnet on it. You fix a magnet to the cable, and whilst feeding through the cable from one side, the stick with the magnet then 'grabs' the cable as it gets close - it just saves you needing to line up the holes perfectly.

HTH,
 

x1nick

Active Member
Figured I am going to give this a go anyway. Running them externally would be much easier! But unfortunately not an option here.

I had read about the moisture travailing from the outer wall to the inner wall. I figure with the excess cable and sealing the hole with silicone it shouldn't be a massive concern?
 

Geps

Well-known Member
To be honest, you can probably leave off the silicone. The droop will take care of any liquid water and the size of hole will allow negligible amounts of water vapour through.
 

S D I

Banned
Geps post at 5.04pm. is absolutely correct however I have been routing cables down cavity walls for over 10 years, had no problems up to now with damp and a lot of these wiring looms are still working today.

I cannot remember seeing moisture in a vented cavity for many years although as Geps states, the outer skin is considered porous.

My favourite method if there is room is to route smooth bore flexible ducting down the cavity to facilitate adding cables later without fishing around for them

It is not uncommon to knock a whole brick out in the attic or an upstairs room and the same on the ground floor to make it easy to fit 63mm flexible ducting.

We come across a lot of variations of insulation which complicates things but nothing is insurmountable.

Happy fishing!

Steve
 

Johnyb

Active Member
There is no issue with running cables externaly, as long as you purchase cable specificaly designed for this purpose. One thought on running within the cavity - I would use the rods, as its not uncommon for there to be obstructions left from careless builders. So the rods should be able to work around these.... :)
 

S D I

Banned
FYI. I have had standard cable looms including HDMI cables (not sold as weatherproof) working down cavities for ten years.

I don't know of a supplier for weatherproof HDMI cables, weatherproof UTP's are common of course but I only use them in underground ducting.
 

neoof86

Active Member
Hi x1nick,

Can you let me know how you get on, I will be retro fitting some cables in some of the other rooms during our extension. I have managed to pull some of the cables through but the living room is going to be a nightmare! I could run them outside and up the wall but I am not sure how quickly the cables would degrade compared to them being in the wall. The only other room will be the playroom but again this has an outside wall and is not usually visible but it would be nice to have them in the wall.

All the others I can put in place during the building work.
 

x1nick

Active Member
As promised

Up in the loft I found the cavity, no need to drill anything up there but had to use a mirror and torch to work out where it was

photo.JPG


Dropped some string down with an old drill bit taped onto the end :rolleyes:

Unfortunately my measurements were 5cm out (or the string didn't drop perfectly) so the string didn't fall right behind the hole

At first I had only drilled a 1" hole which is impossible to fish the string out

So made it a little bigger and using some 2.5mm solid copper from the shed I made a hook and grabbed the string no problem :thumbsup:

photo2.JPG


And then carefully pulled 1 cat6 cable and some old solid core copper cable to pull the other coax and cat6 through!

The string felt like it was going to snap so many times when pulling the cables up the wall but I managed to do it first time :)

photo3.JPG
 

x1nick

Active Member
I had a look today at another point where I wanted to do another drop. No chance of dropping anything there as it's all bricked up!
 

x1nick

Active Member
TV coax will be terminated in the loft as the distribution amp is already up there (can remove the white cable running on the outside of the house then :O)

Network needs dropping down to the cloak room where the networking kit lives, not too sure how I am going to work this one just yet as can't find an opening in the cavity.
Thinking about trying to pull cables back through the wall in the bedroom above and then running under the floor where there are already a bunch of network runs.
 

YitEarp

Banned
Looking forward to some more progress as this is exactly what I want to do. Have same issues with running feeds into under stairs other than that I shall terminate all in loft.
 

YitEarp

Banned
You having another attempt this weekend? Thinking of starting mine as the coax for the broadband I want to run into the loft and run a server rack from there plus terminate the tv with the powered splitter amplifier that they supplied me with.

I don't know if I should take it externally or try to get it up two floor via the void in the walls (which I doubt I have due to cavity wall insulation)

Once its up there though im set as I can install keystone jacks to the rooms I want with a coax/cat wallplate

Just knowing where to start!
 

neoof86

Active Member
Hi x1nick,

Thanks for the pics and tips on how you have done this. Sorry for the delay exciting news my end. What kind of tv amp are you using in the loft?
 

x1nick

Active Member
You having another attempt this weekend? Thinking of starting mine as the coax for the broadband I want to run into the loft and run a server rack from there plus terminate the tv with the powered splitter amplifier that they supplied me with.

I don't know if I should take it externally or try to get it up two floor via the void in the walls (which I doubt I have due to cavity wall insulation)

Once its up there though im set as I can install keystone jacks to the rooms I want with a coax/cat wallplate

Just knowing where to start!

It's all finished now, if you have wall insulation I'd say there is no chance of running a cable in there. I had enough trouble without it!

Hi x1nick,

Thanks for the pics and tips on how you have done this. Sorry for the delay exciting news my end. What kind of tv amp are you using in the loft?

Some Labgear one from screw fix, seems to do the job just fine.

Wouldn't it be easier to chase the cable down the interior wall and simply drill down from loft > Upstairs floor > downstairs ceiling?

Not if it requires new wall paper! In this case the cavity wall was the only real option.

This is the exit where the network kit lives, as you can see I have made a massive mess of this hole! Measurements were near enough perfect as you can see the two strings I dropped almost in the middle :thumbsup:

photo4.jpg


This hole was a pain to do as there was no open top cavity, so found the top of the brick and drilled in at an angle until I was in the cavity.
Probably the wrong way of doing it but it worked.

For anyone else doing this a few tips I would recommend which would have saved me a ton of time

  • Measure height of all rooms, including floor thickness!
  • Use something very light to drop down the wall, string worked well for me
  • Mark the string at 1m marks, use this to make sure your dropping the full height that you measured earlier
  • Old drill bits work very well, there thin and heavy so don't get caught on much
  • Just run the cables on the outside of the wall :laugh:
 

YitEarp

Banned
Is that the under stair cupboard? Wow that's a big hole or just the camera lens

Are you planning on filling that up as moisture can and probably will build up there.
 

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