MBC timberframe - new external wiring for internet cable

[ragg987]

Having lived in our new house for 10 months, I am on the verge of chucking out my BT line for internet and switching to a village supplier who mounts a small dish at roof level that points to a central receiver.

 

This is not a scenario I had catered for and have no ready-made solution to bring this cable into my house. The closest I have is a small duct into which I supply the aerial lead, though the inside of this duct is in our upstairs bathroom and sealed and boarded up. I would ideally install the wi-fi router centrally inside the building to give max coverage - this is on ground floor (as we have a basement) so quite a way away from aerial point. In a traditional build we could simply run the cable externally and drill a hole into the brick at ingress point.

 

So, question is how can I proceed with providing this cable into my house without destroying the integrity of the MBC cellulose insulation fill plus the air-tightness we worked hard to achieve? Any sensible ideas welcome...

 

Wall construction is (outside to inside) render, render mesh, render carrier, cavity, MBC external board (OSB?), cellulose, internal board, cavity, fermacell, plaster, paint.

[Jeremy Harris]

It's not too hard to do, but does need some special tools.  I made up a very long 6mm timber drill, by turning down a drill shank, drilling the end of a length of 6mm studding and brazing the two together (I did it this way to maintain concentricity).  This is long enough to drill through around 370mm or so, IIRC.  The other tool I made up was a turned up cone of acetal, that is a very tight fit into the end of a bit of 20mm plastic cable conduit.

 

The technique is to find a suitable location, away from studs and battens, and drill a long pilot hole that slopes slightly down towards the outside.  I did mine from inside to outside.  Next, drill a larger hole with a hole saw (say, around 30mm diameter) through the inner skin only (in your case the Fermacell).  Then drill a 20mm diameter hole with a hole saw through the inner timber vapour proof board.

 

Next, go outside and repeat this process.  Use a 40mm hole saw to drill an oversize hole in the external render and carrier, then a 20mm hole in the outer OSB skin.  The cellulose will stay packed in place.

 

Then comes the fun bit.  Starting from either inside or out, whichever is easier (I went from inside to out) poke the bit of 20mm plastic conduit, with the conical end, into the hole and try very hard to aim it at where you think the hole is on the other side.  I found it useful to take a vertical and horizontal offset measurement from datum points when I had the very long 6mm pilot drill in place (I took the long drill bit out of the chuck to take these measurements, whilst it was still poking right through the wall), as a guide to get the angle right.  The cone on the end of the conduit will compress the cellulose out of the way, and the point of the cone should make finding the hole on the other side easier (although it will be fun, I can assure you............).

 

Once you have the conduit through, push it out enough so that you can remove the cone.   Smear some sealant (I used Sikaflex, but CT1 would do as well) around the outside of the conduit, on the INSIDE bit, close to the 30mm hole.  Push the conduit back in so that the sealant bonds to the vapour proof board well.  It helps to rotate the conduit a bit when doing this, and use loads of sealant to try and get a bead around the joint with the inner board.  Leave the conduit oversize, so it pokes out too far at this stage.  Next, go back outside and squirt some low expansion foam around the annular gap between the conduit and the 40mm hole in the rendered face.  It's worth masking up the face of the render to avoid getting foam on it.

 

Let the foam go off, then trim back the foam and the conduit, so that it's flush with the wall.  On the inside, do the same, use foam and trim it back.  When all has cured, fit the cable and squirt some low expansion foam as deeply into the conduit as you can get from the outside, to seal around the cable, then bond an outdoor cable cover on with a downward facing slot, like this one: http://www.satgear.co.uk/fk21

 

On the inside, do the same, but fit one of these types of cover: http://www.satgear.co.uk/fk22 .  Fit the inner cover before the foam has cured - it should just slot down inside the conduit.

 

If you're stuck, I can post you the long drill I made up, plus the acetal cone that fits into 20mm conduit.

Edited September 6, 2017 by JSHarris
several typos.........

[ragg987]

@JSHarris, you're a star, this is just the kind of practical info that I need. I guess I could do this on the external wall near my plantroom and run the cable behind the render carrier from roof level to give a nicer appearance, though I imagine getting the dangling cable from roof level to the hole at ground(ish) level might prove tricky.

 

This has given me the confidence to proceed - awaiting quotes from the service provider before I decide. Those custom tools of your might come in handy - I will reach out if needed, really appreciate the offer.

[Jeremy Harris]

You can get those outdoor cable covers in white, too, if you hunt around.  I've just spotted that they are cheaper and available in multiples on ebay, search for "cable wall entry white" and you'll find them.  You could use one indoors as well if it's not in a critical location, and that would then allow a 40mm hole inside (it's the 32mm external diameter of the round ones that restricts the internal hole size).

[Russdl]

I'm resurrecting this thread in the search for advice on getting cables through the timber frame, we clearly are not so far along the build process as @ragg987 , our MBC timber frame has only just gone up but we have no cellulose insulation yet.

 

There are various places where we would like outside lights, power for blinds and sockets etc. What is the best way to do it? Just get a chuffing great long drill (as per @JSHarris) drill a pilot hole all the way through the frame and then a hole saw inside and outside and slide the conduit in, or is that old school and there is an even smarter way of doing it these days?

[Jeremy Harris]

If the insulation isn't yet blown in, then take advantage of that and stick lengths of conduit through the walls wherever you think you may need to feed wires.  It's a lot easier to do this without the cellulose.

 

Use the same technique, a very long 6mm drill to drill the pilot hole, then a hole saw either side to drill to suit the conduit.  There's no need for the cone I made up, just cut the end of the conduit at an angle and it will make lining it up with the outer hole easier.

[Russdl]

20 minutes ago, JSHarris said:

just cut the end of the conduit at an angle and it will make lining it up with the outer hole easier

 

@JSHarris Excellent. Just that little tip is probably going to save £50 going in to the swear jar!

[ragg987]

Yes much easier at the start - I bought some flexi-ducting off internet and used that in various places. MBC even sealed it all prior to the pressure test. Just try to plan ahead and get all your cabling requirements sorted at this stage - e.g. wiring for external lights, aerials, telephones. And lesson from me - if you are pulling services to a zone zero (in our case plant room) might be worth adding a spare conduit with pulling string as it is harder after completion.