Surgical wiring SWA through screed

[i_am_fubar]

For reasons I'm not going to elaborate on. This is my only sensible option without huge amounts of building work. And it's daft.

On the left door, is my garage, floor is 150 lower than the floor shown.
On my right is the front door. Patio 150 lower than the floor shown.
The floor is a solid slab. Strip foundations. Dual skin. No DPM other than the one under the wood floor.

I want to get a piece of 20mm SWA from the garage to under the patio.

My plan is to core drill 150mm under the door mat, drill 25mm through the screed into the large hole. Then from the large hole, through the sub-grade wall to under the patio (where I can dig a typical trench).

2 questions.
1) Will this likely cause any structural issues?
2) How would I best drill horizontally 1.1m deep?

Bonus question, how daft does this sound?

 

[kingandy2nd]

I’m not sure I follow what/why you’re core drilling under the door mat. Won’t that compromise your DPM?

If you’ve got access either side from the outside with some clearance, and an SDS drill, can’t you just drill through with something like this?

https://amzn.eu/d/29ghFgC

Will take a while and be noisy but you could get across the floor in one go.

 

[cdbe]

I love a crazy plan.

I'm guessing this is the idea:

You could use a set of these:

You'd need a big drill and start with the smallest bit, the problem is that the dust along the length of the hole jams the bit so it needs constant clearing - but if the concrete's not too hard it's possible (I managed to drill 900mm through a concrete step with just a big hammer drill, but only 12mm diameter).

The other issue over that distance is whether you can meet the hole, maybe build a jig to guide the bit.

I doubt it would compromise the dpm - but some liquid dpm when you reinstate wouldn't hurt.

I can't believe their isn't another route for the cable - even up through a bedroom and across your path to the shed - but having said that - if it works it works.

Also, 20mm SWA sounds a bit big for domestic use - maybe ask on the electrical area.

 

[pete01]

20mm isn't a size it goes from 16mm to 25mm.

 

[Murdochcat]

20mm swa could be 10mm swa 3 core

 

[Ivor Windybottom]

With so little cover there's a very real risk the hole will blow upwards, so you'll end up with a hump of shattered rubble under the flooring.

If the garage is 150mm lower then, after allowing for the body of your drill, you'll be barely beneath the floor.

My suggestion would be a better plan, depending on what you're attempting to achieve. But as you're not going to elaborate then the answer's that it's a really stupid plan.

 

[i_am_fubar]

I should clarify, 20mm OD of the cable (ish)

I think a 1500mm drill will be fine longest o could find was 1000

 

[i_am_fubar]

With so little cover there's a very real risk the hole will blow upwards, so you'll end up with a hump of shattered rubble under the flooring.

If the garage is 150mm lower then, after allowing for the body of your drill, you'll be barely beneath the floor.

My suggestion would be a better plan, depending on what you're attempting to achieve. But as you're not going to elaborate then the answer's that it's a really stupid plan.

Unfortunately, while there are other options, the involve either...
1) ripping up the kids bedroom floor
Or
2) ripping up the bathroom floor
Or
3) removing an exterior patio door to access the cavity

And all of them will end up in an unsightly cable clipped to the wall with an appropriate bend poking out from it.

This is the only option I've got that gets it underground without being visible running down the side of the house.

 

[i_am_fubar]

I love a crazy plan.

I'm guessing this is the idea:

View attachment 382005

You could use a set of these:

View attachment 382006

You'd need a big drill and start with the smallest bit, the problem is that the dust along the length of the hole jams the bit so it needs constant clearing - but if the concrete's not too hard it's possible (I managed to drill 900mm through a concrete step with just a big hammer drill, but only 12mm diameter).

The other issue over that distance is whether you can meet the hole, maybe build a jig to guide the bit.

I doubt it would compromise the dpm - but some liquid dpm when you reinstate wouldn't hurt.

I can't believe their isn't another route for the cable - even up through a bedroom and across your path to the shed - but having said that - if it works it works.

Also, 20mm SWA sounds a bit big for domestic use - maybe ask on the electrical area.

This is exactly the plan.

Closest I've ever done was drilling 45 degrees from kitchen to extension through a solid wall over 800mm for two radiator pipes. Nailed that, hope this is as successful.

While DPM will be 'restored' as best as possible, the fact noone is flagging a structural risk, I'm going to cross my fingers on the silver line (ew) bits from Zoro. A 750 bit on 3D printed guide blocks.

 

[Harry Bloomfield]

1) Will this likely cause any structural issues?

No.

2) How would I best drill horizontally 1.1m deep?

You would need to tackle it by drilling all the way through, from the outside/patio, all the way through to the garage, in one go, using a long, sds drill bit. You would need to use a level, frequently checking the bit is horizontal. Maybe start the hole with a shorter bit, then swap to a 1.5m one. It will need two of you, one drilling, one watching, helping keeping you straight.

Bonus question, how daft does this sound?

Nope, doable, with care, and a decent sds drill.

 

[i_am_fubar]

And we're off!

 

[Scally-Ho]

This is exactly the plan.

Closest I've ever done was drilling 45 degrees from kitchen to extension through a solid wall over 800mm for two radiator pipes. Nailed that, hope this is as successful.

While DPM will be 'restored' as best as possible, the fact noone is flagging a structural risk, I'm going to cross my fingers on the silver line (ew) bits from Zoro. A 750 bit on 3D printed guide blocks.

Silverline are crap SDS bits so do yourself a big favour and go upmarket to avoid destroying the screed. As it stands, a screed is very vulnerable to disruptive drilling, so good luck in your quest. IMO for what it's worth, it's a crazy idea that will be fraught with trouble. Far better to go around at ceiling height and enclose with a decent run of coving.

 

[i_am_fubar]

Every other route digs into indoor space considerably. Especially when going round corners.

I agree silver line is ****e, but I'm in over halfway and apart from the occasional stubborn but of aggregate, progress is slow, but.... Well, progressive.

I'll still need to get a 1200 / 1500 long bit to finish off, but hitting 600mm, so far, so good I hope.

 

[Harry Bloomfield]

I'll still need to get a 1200 / 1500 long bit to finish off, but hitting 600mm, so far, so good I hope.

Just keep in mind, 'The Hatton Garden Job'

 

[Ivor Windybottom]

That hole's interesting - how did that get there? Shame that the foresight didn't extend as far as putting some duct in.

Good luck, sometimes crazy plans can just work!