Finding a location under the house?

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tchart

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#281164 3-Feb-2021 09:54

I am looking at drilling a hole in my floor (in the wall cavity) to feed CAT cable to an outside router. The wall socket has a cage which means I cant drill downwards as I cant get my hand or drill bit in there - so I need to drill upwards from under the house.

Under the house there are 3 joists which makes trying to locate the exact spot from under the house a tad tricky.

I was thinking of some kind of jig to try and "reverse locate" the spot under the house.

Anybody have any better suggestions?

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#2646340 3-Feb-2021 10:03

What floor coverings do you have? I've drilled up a couple of times and each time I am sure I will stuff something up. But carpet hides all manner of sins. 😁

Usually the best you can do is measure top and bottom from a known shared point. Sometimes a plumbing or electrical fixing works. I've also had to drill a hole somewhere else I can hide it, then measured from there.

I've seen (but not used myself) this also done with a pair of strong magnets.

Dynamic

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#2646341 3-Feb-2021 10:03

How would you feel about a small hole in the floor? Once in the past, I've done this:

Found a piece of solid fencing wire.
drilled a small hole in the floorboards using a drill bit the diameter of this wire
Put a 20cm-ish length of wire into my drill, and 'drilled it down' so I could locate it when I was under the house.
Measured the distance from the wire to where I'd need to drill upwards.
Fill the hole afterwards.

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sidefx

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#2646344 3-Feb-2021 10:10

How thick is the floor? temporarily put a 2x4 or something on the floor above then use a stud finder from below? (assuming it's not between those joists?)

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tchart

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#2646346 3-Feb-2021 10:13

sidefx:

How thick is the floor? temporarily put a 2x4 or something on the floor above then use a stud finder from below? (assuming it's not between those joists?)

Thats a good idea.

tchart

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#2646348 3-Feb-2021 10:14

mdf: What floor coverings do you have? I've drilled up a couple of times and each time I am sure I will stuff something up. But carpet hides all manner of sins. 😁

Usually the best you can do is measure top and bottom from a known shared point. Sometimes a plumbing or electrical fixing works. I've also had to drill a hole somewhere else I can hide it, then measured from there.

I've seen (but not used myself) this also done with a pair of strong magnets.

Floors are laminate so the wife would kill me if there was a random hole in the floor!

wellygary

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#2646351 3-Feb-2021 10:18

"wall socket has a cage "

Do you mean there is a box in the wall that the socket is mounted to?

Removing/ and ( replacing later) a wall box is usually not that difficult

tchart

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#2646354 3-Feb-2021 10:29

wellygary:
"wall socket has a cage "

Do you mean there is a box in the wall that the socket is mounted to?

Removing/ and ( replacing later) a wall box is usually not that difficult

It's behind the gib and screwed into the frame I believe so there's no way to remove it without destroying the wall.

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chevrolux

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#2646355 3-Feb-2021 10:38

Professionally, I would have just pulled the flush box and drilled down with an appropriately long drill bit. Mostly just a 300mm with 300mm extension was more than adequate.

froob

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#2646356 3-Feb-2021 10:39

The prospect of accidentally drilling through your floors from underneath can be a bit terrifying.

Usually when I've had to do this, has had a double joist with the bottom plate of the wall centred in between and/or existing electrical or other wiring to measure off. It seems like that's not going to help you here.

I did recently add a data outlet in a wall that was added in a later renovation on top of the floor boards. After getting the rough location off the exterior walls, I found removing the underfloor insulation in the area helped me find more subtle features to get the precise location. In that case, I found an old hole in the floor boards that had been puttied, and a few nails poking out in a row along the line of the bottom plate.

Or, if you can get the wall box out as wellygary suggests, if you still can't get a drill in the space, you may still have enough space to hammer in a nail and see where it pops out underneath.

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chevrolux

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#2646357 3-Feb-2021 10:40

tchart:
wellygary:

"wall socket has a cage "

Do you mean there is a box in the wall that the socket is mounted to?

Removing/ and ( replacing later) a wall box is usually not that difficult

It's behind the gib and screwed into the frame I believe so there's no way to remove it without destroying the wall.

Just open the GIB up enough, and undo the screws. The box is still much smaller than a standard wall plate so will be covered without issue.

The hard ones are the old nailed-on metal flush boxes. But a multitool slid in to cut the nails and away you go.

jonb

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#2646367 3-Feb-2021 11:29

Should also be able to unscrew the socket box from the frame and leave it behind the gib still, out of the way, then move it back afterwards, without sawing away extra gib to pull it out.

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#2646406 3-Feb-2021 12:35

Would something like this flexible drill bit extender thingy help you get into the wall box?

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Gurezaemon

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#2646432 3-Feb-2021 13:15

Or maybe see if you could borrow a 90° adapter?

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chevrolux

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#2646437 3-Feb-2021 13:27

A bog standard screwdriver will get the flush box out in about 30 seconds.

Don't screw around with any toys like 90 degree adapters or those terrible flexi things - they actually will just end in making a mess of the GIB.

wellygary

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#2646443 3-Feb-2021 13:40

I think a photo of the box would be helpful to help recommend ways to get it out/moved sideways while you work etc.....

It would certainly be my first line of attack , rather than trying to find a way to drill up from below.... (it might eventually come to that, but seeing if drilling down from inside is possible might be easier)

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