Drilling prefab concrete

[pc1966]

I have been asked about putting in a couple of network cables that need to go through the internal walls of a building. It appears to be constructed of large prefab concrete slabs, I guess they might have rebar in them but no one knows for sure. I have reasonable access to both sides once the false ceiling panels are moved.

Any advice on how best to drill something like a 10-20mm hole for the cable(s) to pass through?

 

[brianmoooore]

Miss the rebar. An SDS will drill it easily enough, but make sure you have a spare bit, because if you hit the bar anything but dead centre, your bit will no longer have a tip.
Metal detector/cable finder thing with adjustable sensitivity might just give a clue to the rebar position.

 

[loz2754]

Start with an 8mm bit and work your way up. If you hit metal, alter the angle slightly, or reposition your pilot hole.
I've had some success with a hole saw on a bit extender whenever I've hit the rebar.

 

[hasel5]

use a Hilti SDsS bit should munch throughg

 

[Robson689]

You can get 20mm bits for an SDS drill I have one a metre long just make sure you've got a decent drill so it doesn't rip your hand off if you do snag the rebar

 

[pc1966]

Thanks folks. I have a 1m long 10mm and 22mm SDS drill bits, but might go with 10mm as enough for a single cable. I'm not sure how theick the walls are yet but get the impression it is no more than 20cm.

Someone else was supposed to be doing this, but several weeks later it has not been done, which is why it now looks like I need to sort out something

 

[hasel5]

Should be easy if only 200 mm just use a new bit and a fully charged battery

 

[pc1966]

Should be easy if only 200 mm just use a new bit and a fully charged battery

My SDS drill is a 10 year old 230V AEG thing, works quite well but not as convenient as modern battery ones!

 

[ruston]

If it is a post WW2 prefab they are as hard as hell and do have reinforcing. If I remember correctly they used whinstone chippings in the mix , if you hit one it will feel like rebar.
If you take your time and keep the bit cool ( I know) you will get through , just take your time.

 

[Zerax]

There are specialist companies for this kind of job... if you decide it's not for you.

 

[Zerax]

I heard a story a while ago about a company that were drilling a hole into one of the supports for the Nat West Tower in London. Apparently, they hit one of the main rebars (I'm guessing it was a large hole and a large rebar). Created all sorts of issues with H&S and structural engineers etc... At the end they decided the building was probably still safe, without any major repair work.

That was probably 30+ years ago... and it's still standing.

 

[pc1966]

It is post WW2, probably 60s build by the look of things. If it can be done with a SDS bit then I would try, otherwise beyond my tools/experience.

It is for a charity organisation that has rooms both sides of the corridor, and rubbish wifi as a result. Originally someone was going to put in larger holes (30-40mm) and run in 6 or so CAT-6 cables, but for wifi alone I can get by with one for the repeater.

There already is wired networking in the other room (of various eras) but so far nobody seems to know where the wall mounted socket's cables all go!

 

[ruston]

I have done one with an SDS. It was post war .Probably one of the first.
The SDS managed ok as long as you take your time and do not dog it. A bit like drilling hard steel , just give it a bit respect.

 

[Vortigern]

If you already have RJ45 sockets why put new cable in, surely just test at the comms cab with a network tester at the RJ45 socket and then use that patch to put internet on/???

 

[pc1966]

If you already have RJ45 sockets why put new cable in, surely just test at the comms cab with a network tester at the RJ45 socket and then use that patch to put internet on/???

I can't find the other comms cabinet!

The main room where the Virgin modem is and wifi point had 15 working sockets wired to a patch panel in a small 19" box, mounted around 2m above the floor. They are now in use and they no longer have to rely on wifi to the desktops.

The other rooms are wired in to wall RJ45s but no one knows where they terminate

They might go to some other room they don't have access to, or even to another floor. The building & rooms have changed use/hands many times before their friend got use of a couple of rooms on the 2nd floor for her charity project.