Drilling from outside into ceiling void

[Ron Lowe]

Hi, all.

I need to run an overflow pipe from an airing cupboard in the centre of a house to outside.

I've got a hatch in the airing cupboard floor, and if I stick my head into the hatch, I can see the external wall 12 feet away along the void space. ( parallel with the rafters, fortunately. ) I don't have a 12 foot long drill bit, so...

I'd like to drill into this space from the outside, and shove the pipe from the outside all the way in to my hatch.

The trick is knowing the right spot to drill, from the outside!

What I'd really like is a 'super laser' I could shine from the hatch all the way through external wall, which would shine through to the outside, showing me where to drill!

The only way I can think to do it is a series of intricate X-Y measurements, from the hatch all the way to a window frame as a reference between inside and out, and then measure X-Y from the window frame on the outside. However, I'm not confident that the cumulative error would be good enough, and that I would not end up drilling into another room! The X error is not too important, but I only have a few inches of tollerance in the Y axis before I end up above the floor or below the ceiling!

I could of course lift the carpet in the room with the outside wall, and make an other hatch next to the wall and drill from the inside out, but I was hoping for a clever way to avoid that...

[The3rd Earl Of Derby]

You need a strong magnet and a compass.

Position the compass as near to the brickwall? inside as possible where you want to drill the hole. Get someone to watch the compass needle inside whilst you guess where the hole is going to be and slide the magnet over the brick wall area. The compass needle should be parrell to the wall for obvious reasons :-)

If this works I'll eat my hat.

[The3rd Earl Of Derby]

Only if someones got a 12' neck. :-)

[Dave H.]

Hi Ron, Take a suitable length of narrowish (3/16" - 1/4"?) clear[1] plastic tubing, some water and food dye (eg colouring for scrummy cake icing), and place brightly-coloured water in tubing, couple of feet each end clear of water, thumbs of self and assistant over the ends, take one end out of the window (ok, you can use bungs instead of the thumbs!), hold end "A" above/below floor so water level is appropriate for pipe's hole, other end (end "B") outside and roughly right (open ends uppermost, of course...). NOW remove the bungs, water levels will... er... level in a couple of seconds, a bit of raising and lowering one or both ends will soon see Robert becomer your parent's sibling.

Hope that helps (and is understandable - a lot easier to do than to explain!) Dave H. (The engineer formerly known as Homeless)

[1] actually, only the last few feet at each end need to be clear

[Ron Lowe]

Yes, a hydraulic U-tube with a long flexible hose is a clever idea for finding equal levels at 2 places.

Good suggestion.

[Ron Lowe]

Ah, a magnet, yes. Good idea.

It would be easier to put the magnet on the end of a bit of flexible pipe, and maneouver it to the inside of the wall, then perform the compass survey on the outside.

Safer than a collumnated gamma source and geiger counter :-)

[Harry Bloomfield]

Ron Lowe pretended :

Take as many measurements from fixed object which pass through the wall as you can - windows, other pipes and etc.. Transfer each measurement to the outside drawing a partial radius in chalk, where all the chalk marks intersect should be where you need to drill. To confirm an accurate height up the wall, use a long level through an open window - measure down to the floor on the inside, mark the same height down on the outside allowing for the floor board thickness. Measure your depth under floor and mark that on the outside, then simply following the brick courses to transfer the marks to where needed for the hole or use a long level and a piece of wood.

Take a deep breath and drill using as small a drill as is long enough to minimise damage, just to confirm the position, then the correct size once confirmed. If it comes out where intended, give yourself a pat on the back.

[Owain]

Attach a 12' length of pipe to a gas blowtorch. Wait until a cold day. Blowtorch the inside of the wall. Use a thermal imaging camera on the outside of the wall to locate the hot spot.

Run the overflow pipe through the large hole knocked by the fire brigade to gain access to the void :-)

Use 12' length of stick to hold an electric buzzer against the wall. Use stethoscope to locate source of buzzing on outside wall.

Owain

[Guy King]

The message from "Ron Lowe" contains these words:

A friend of mine's mum did this in the 70s to get a heating pipe through. Water level took care of the up and down, and the rest she did with careful measurements, laying out right-angled lines on the floor with masking tape. The wall was three feet thick (old cottage with new extension) and about the same, 12 feet from the aperture.

She got it within about 1/4"!

[Harry Bloomfield]

Guy King formulated the question :

There you go, you just need Guy's friends mum :-)

[Richard Cole]

Or get the compass reading against the wall at floor level immediately above (or ceiling level immediately below) then adjust down (or up) by the height of the void.

Richard Web pages:

- caravanning, - personal web site and I loves the domain name for email.

[Chris Bacon]

The floor is your datum. From a convenient nearby window, find where on the outside wall the floor level is relative to the outside wall. Follow the bricks to wherever you want to drill, drop down by whatever measurement you want (e.g. two brick courses) and drill.