We are in the process of purchasing a home built in 1962 with in ceiling radiant heating powered by a boiler. Out contractor has reviewed the plans for the house and informed us that the spacing for the copper tubing in the ceiling is 1.5" which is clearly not enough to add recessed lighting. He is telling us that he is uncomfortable even installing a light fixture for fear of hitting one of the tubes and wrecking the system. Has anyone had experience with piping of this density and lighting renovations?

My brother has electric in ceiling radiant. That can be one of the drawbacks, it puts the ceiling off limits for future large scale renovations...

Can it be dug into and the plumbing re-routed to accept lights? Of course it can, copper is vey workable. Is it going to be costly and time consuming? Most likley... Are you going to have trouble finding someone willing to risk hacking into it? Most likley.

Is this a general contractor you are working with? Have you consulted a plumber, preferably one with experience in heating systems?

I'd be surprised if the plumbing is actually 1.5" o.c. which would be a HUGE radiator, and likely very high pumping head. I has to be some other spacing.

You should be able to find the pipes with a radio frequency pipe-finder or multi-scan tool, eg:

https://www.milwaukeetool.com/instruments/inspection-and-detection/2291-20

Tools of this type are typically a couple hundred USD, give or take, but it's cheaper than trying to repair 50 year old copper pipe embedded in a cemeticious plaster.

Recessed lighting in upper floor ceilings are a bad idea in the first place, since it punches holes in the thermal & pressure boundary of the house.

As Dana suggests it is unlikely that the tube spacing is 1.5". 6-12 inches was common. Thermal imaging is an option but turning up the thermostat in a cool room will likely reveal every tube touch.

Surface mount fixtures are much easier to make air-tight.

Consider low voltage lighting.