Channelling cables in the plaster of ceilings

[Delboybully]

With a 78mm (or whatever reasonable size) hole saw, cut a hole a few inches before the joist. Now with a long 16mm or 20mm flat wood drill bit, drill a hole through the joist. Fish your cable from one ceiling hole to another. Keep the cut outs (biscuits), get a bit of wood, batten it across the hole and replace the biscuit. Leave it to the plaster to sort out or fill it in yourself using finishing plaster (takes a bit of practice btw). Sand it down if needed and paint, job done

This is what I do except I use a 100mm hole saw and use my angle drill. He complained that I had ruined the ceiling. The plasterers sorted it out. He also made a valid point that was how do you know you are drilling in the correct position on the span of the joist without seeing the whole length.

 

[davesparks]

This is what I do except I use a 100mm hole saw and use my angle drill. He complained that I had ruined the ceiling. The plasterers sorted it out. He also made a valid point that was how do you know you are drilling in the correct position on the span of the joist without seeing the whole length.

You don't know for absoloute certain, but you should be able to identify where the walls are and measure the distance between them. Bearing in mind the positions of the holes are measured on the span not the length. The span being the distance between supports.
If a joist or beam is supported at both ends and again in the middle then it is over two spans, not one.

 

[Delboybully]

You don't know for absoloute certain, but you should be able to identify where the walls are and measure the distance between them. Bearing in mind the positions of the holes are measured on the span not the length. The span being the distance between supports.
If a joist or beam is supported at both ends and again in the middle then it is over two spans, not one.

That interesting, I didnt know that.

What about those joists that get joined by overlapping mid way across a ceiling, does the same rule apply?

 

[Paul.M]

He also made a valid point that was how do you know you are drilling in the correct position on the span of the joist without seeing the whole length.

Easy, you use a stud finder or tap your knuckles on the ceiling. Hollow,,, hollow,,, hollow,,,, not hollow, that will be a joist!

To some customers this is rocket science!!!!

 

[davesparks]

That interesting, I didnt know that.

What about those joists that get joined by overlapping mid way across a ceiling, does the same rule apply?

Span is the distance between supports, if the rule was concerned with the length then it would say length.
It doesn't matter how many joints there are, the span is still the distance between supports. Not that I've ever seen a joist with a joint in it mid span? Are you sure about this?

 

[LankyWill]

Span is the distance between supports, if the rule was concerned with the length then it would say length.
It doesn't matter how many joints there are, the span is still the distance between supports. Not that I've ever seen a joist with a joint in it mid span? Are you sure about this?

common on new builds with tgi or open span joists where future provisions for a lift has been installed.

 

[shanky887614]

easy to find.
tap, tap, stab.........swear
tap,tap, stab......hurray XD
polyfiller holes

 

[Delboybully]

Span is the distance between supports, if the rule was concerned with the length then it would say length.
It doesn't matter how many joints there are, the span is still the distance between supports. Not that I've ever seen a joist with a joint in it mid span? Are you sure about this?

I have only seen it 3 or 4 times. Maybe some builder had removed a wall incorrectly

 

[davesparks]

I have only seen it 3 or 4 times. Maybe some builder had removed a wall incorrectly

That is most likely, unless you were viewing it from above through lifted floorboards and there was in fact an RSJ installed underneath the joists where the wall used to be?