ᐅ Pre-drilled Holes for Recessed Lights: Any Experiences?

Hello everyone,

We would like to have openings for recessed lights in the precast concrete ceiling. Has anyone had experience with whether the holes are factory-made in the correct positions? Or did you measure and drill them on site?

Thank you very much

Ours were made in the factory, with a hollow wall box. Since you also need the electrical connections in the ceiling, all of this must be completed before the concrete is poured. There’s no saving money by retrofitting it yourself.

It's not about saving money, but rather about whether the manufacturer works that precisely. Our architect fears that the openings might not end up exactly where they should be. But it sounds like everything worked out fine for you.

What tolerance do you assume on the construction site? I’m sure the fabricator works more accurately than the group of Slovakian laborers my general contractor called masons.
If it really matters that the spots are placed exactly on the millimeter in a specific spot, then the structural shell is definitely the wrong trade for that. But I wonder where the spots absolutely have to be precisely in the right place and cannot deviate by 1-2cm (0.4-0.8 inches).

You can deviate by 2 cm (1 inch) as long as the deviation stays within the 2 cm (1 inch) line and there are no zigzag patterns on the ceiling. 😉

An electrician won’t drill with millimeter precision. And a shift of 1 or 2 cm (about 0.4 or 0.8 inches) over several meters (yards) isn’t even noticeable. People tend to overestimate their own accuracy.

But I wouldn’t expect millimeter precision when placing the precast concrete slabs either. They are simply laid down, the gaps are filled with foam insulation, and that’s it.

So it still seems most practical to me that the electrician drills the holes for the recessed lights and installs the hollow wall boxes after the precast slabs have been installed. That way, there’s the least chance for anything to go wrong…