Concrete Garage - electrics and drilling

QuestionsQuestions

Hi - we have a concrete garage - the panel type - not that old. We want to put electricity into it using fuse box etc but how do we run the cable into the garage - I don't really want to drill the panels to create the hole for the cable just in case they shatter. Anyone added electrics - how did you do it? Thanks All

born_again

How far is the garage from the house?

Ours (2 mtr away)  is fed via armoured cable in a conduit buried at suitable depth & comes in underground. Then is mounted on a wood board screwed to the panels.

If you are not sure on electrics then get a electrician to do it.

Section62

QuestionsQuestions said:

Hi - we have a concrete garage - the panel type - not that old. We want to put electricity into it using fuse box etc but how do we run the cable into the garage - I don't really want to drill the panels to create the hole for the cable just in case they shatter. Anyone added electrics - how did you do it? Thanks All

Drilling through the panels could also give you problems keeping water out, and even a small amount getting in can play havoc with steel reinforcing.

Ideally, if you can, bring the cable up through the floor.  But if the garage is built on a decent concrete slab this might be a tough job.  The alternative could be running the cable up the wall so it can enter somewhere through the eaves, but you'd need to find a way to secure the cable to the wall (the easiest way being drilling holes for plugs and screws) which brings you back to the issue of drilling.

If you do decide to drill, use a metal detector to work out where the reinforcing steel is and avoid that at all costs.  If the masonry drill hits the steel you'll have all kinds of problems to deal with.

sheenas

Using a 20mm core drill will do the job without issues. A 32a circuit will less the 20meters run could be done without issues using  6mm armoured cable, you don’t need trunking. It would be best done by a qualified electrician so the circuit is fully tested for safety. 

Risteard

sheenas said:

Using a 20mm core drill will do the job without issues. A 32a circuit will less the 20meters run could be done without issues using  6mm armoured cable, you don’t need trunking. It would be best done by a qualified electrician so the circuit is fully tested for safety. 

If there are extraneous-conductive-parts within the garage then that cable won't be sufficient. Guesswork is not appropriate for electrical installations - this needs to be properly designed by a competent person.

QrizB

I tried drilling holes into a prefab concrete garage at my previous house (the garage would have been 25 years old or so at that time). After 5 minutes of hammer drilling with a brand new masonry bit I'd made a hole perhaps 5-10mm deep. I gave up!

stuart45

The concrete panels are normally an exceptionally hard, reinforced concrete.
Using a powerful SDS, could get through, but may also cause some damage, unless you started with smaller bits. Diamond bits without the hammer action would also get through.
However, as Section62 has mentioned, there is moisture ingress to consoder.

grumpy_codger

Many times I drilled concrete without problems, even without impacts. Without impacts or with moderate impacts you just need a masonry drillbit with sharp cutting edges (most SDS drill bits are designed differently).
I don't see any problem with moisture - the hole can be sealed if needed.

Normal cable to the outside wall of the house with a waterproof junction box.
Armored cable from the junction box to another junction box on the outside wall of the garage.
Normal cable from the junction box into the garage.
- That's how I'd do this. 

stuart45

Concrete varies a lot in strength. Garage panels are an exceptionally hard, machine vibrated one. 

Eldi_Dos

Depending on the size of the concrete raft the garage sits on.

Dig a trench at the edge of the raft to a depth where you are below the concrete raft and any compacted hardcore.
Then below where you intend to fit equipment core drill down through garage floor and any compacted material.
From the trench use a pinch bar to create a opening into where the core drill hole is.You can use a piece of metal conduit hammered in to help break through along with the pinch bar.

Once you have connected up trench and core hole rope, then pre cable a flexible sub duct and pull into place.
Before you backfill the trench put electric warning tape above cable incase any one is ever digging in the area again.

FreeBear

QrizB said:

I tried drilling holes into a prefab concrete garage at my previous house (the garage would have been 25 years old or so at that time). After 5 minutes of hammer drilling with a brand new masonry bit I'd made a hole perhaps 5-10mm deep. I gave up!

Tried drilling holes in a concrete slab in my garage with a (at the time, fairly expensive) Bosch hammer drill. Didn't get very far. Borrowed an SDS drill from a neighbour, and it breezed through.

Even although SWA cable is designed to buried in the ground without any additional protection, I'd still run it through some large smooth bore conduit. If you ever need to upgrade to a bigger cable, it just needs to be pulled through. Also worth putting a second conduit in the same trench some 100mm away for data cables.