Tips for drilling downlight holes

Does anyone have tips for precise drilling of downlight holes between floors?

My floor joists are 400-450mm apart and with air con ducting and everything I need to be exteremely precise.

Am planning to mark on the floor where each downlight hole should be but would love to hear if anyone has any other tips and tricks.

Measure at the ceiling height before plaster and mark on a drawing. Keep the drawing just for the lights. Plaster add 10 to the wall so subtract 10mm from each measurement. Remember it is not just about position and available space but what the positioning will do to the balance of the room. You may also need to allow for fans, ducts etc. Also some down lights have the globe on the side and may take space greater than the hole size.
electricians generaly mark on the floor with dimensions and use a laser level, vertical to mark the ceiling after plaster.

Cheers for that. Can you recommend a cheaper method of marking instead of laser level?

It will take me forever to manually measure out 80+ downlights atceilig height

chalk line

Do you mean use chalk to mark out location of downlights in the floor?
I couldn't rely on that. Chalk comes off way too easily for my liking.

I looked at your question again. I guess i mis understood what your trying to do. Chalk line could have been used on the ceiling if you trying to get then in a straight line. Remeber you can plan all you like were to put the downligths, however what happens if your plaster puts battons in the middle of where they are going??

Battens have already been installed. So have the downlight powerpoints.

My issue is that because it's a double storey house I am unable to check from the roof cavity to make sure I'm not drilling through floor joists/ceiling battens or structural beams.

The time taken to measure the 80 plus downlights is probably less than the time to repair a few holes drilled in the wrong spot or worse repairs to ducts or pipes in the space. In the end for me nothing beats actually measuring what you want against what you have and recording it on paper for later use, If there was an easy way we all be using it.
Battens are in and everything elase is in place so decide the line of mutiple lights and measrue off the other dimensions. Use 2 people and another as a scribe but be sure they understand what they are writing down.

Alternative, Plumb bob on a string and crayon or permanant marked that will stay on the floor and be acurate enough for later posiotions. It all depends on the level of accuracy you can get away with and the errors you are willing to risk.

if doing before flooring is layed (which is best) measure and mark on the floor... a simple plumbob will be fine then mesure from the nearest wall and take photos.. lots of photos....

Thank you all!!!

I am now considering getting a dewalt laser plumb bob. Has anyone used this particular one before? I'm hoping it will speed up the process a lot...

Is marking spray can the best thing to permanently mark the floor?

What an awesome thread, will be down downloghta after build also so this is handy information.

Also, what is the best way in drilling. Any particular drill bit is best to use?

Hi,
In my opinion, the best way, is to temporarily mark the floor (slab) with a crayon, below where you would like the sparky to run the cables in the ceilig for the downlights, then after its been lined with plasterboard, simply measure from the nearest wall to get your lines straight, no need to get extremely fussy imo, particularly with white downlights in a white ceiling!, best time to drill is before painting, so you can see where the rafters/trusses/ceiling timbers are, give each hole a quick dust off after you've cut the hole so you dont get dust in the paint, (painter should dust off before painting anyway),
You can buy a special drill kit from the hardware store with all the common sizes in it, to drill the holes in the plasterboard. under $30 from memory contains about 5 holesaws.
cheers
woodchip

Is this dewalt laser plumb bob any good?



DW082K Features

* Self-Leveling plumb bob is accurate to ± 0,2mm/m
* Self-Leveling up to 4° surface angle, finds plumb in seconds - no vials or knobs to adjust
* One button operation is fast & easy to use
* Focused laser beam keeps dot small even over long distances for improved accuracy & visibility
* Cross-hair beam pattern helps user find center of beam
* Rubber overmolded housing helps maintain calibration under jobsite conditions
* Locating magnets hold Laser Plumb Bob to metal track for easy positioning
* Kit box protects unit and helps maintain calibration when stored in gang box

Thanks for that woodchip! I hadn't thought of that.

The only thing is, we've got ceiling battens throughout. I guess we now only need to worry about where the trusses are (in the opposite direction to ceiling battens).

Diggin up an old thread i came across. The best way is to measure them with a tape measure and write down on the house plans. I was a sparky 10 years ago and it perfectly every time. Downlights in a new house is easy. Then ate fit off time simply measure and then punch a guide hole through the plaster. Then to double check before drilling with a hole saw get a coat hanger bent at a 90 degree angle that is the size of the radius plus about 5 or 10 mm. Then put it in the whole and then keep twisting around while moving up and down. If anything is there you'll know it because you'll hit it. It's easy to move them slightly and often there will be no need to even patch the small hole because it is likely you will 0nly need to move it 5 or 10mm at most if you measured it properly at rough in. Mark all downlights and check them first then go around with a hole saw and cut them all out at once.

Wiring downlights is as simple as twisting 2 wires together if you are running from an existing light but read up on the correct method for running the wires eg. drilling through joists and bearers and not over the top and make sure you clip them all at regular intervals. I can't remember the reg's anymore but i believe it used to be about 30cm apart max.

Any more complex than that and i recommend that you get a licensed electrician.