I did the same at my sons new house, His girfriend asked me to screw down a couple of floorboards in the spare bedroom, I duly obliged, I put one screw in then it struck me, 'Why were the boards taken up??
I removed the screw I'd gone straight through a 22mm copper pipe that feeds to the radiator, Luckily the system had been emptied as builders were in, Plastering and then decorating, I had to buy a length of 22mm pipe and a couple of straight through Yorkshire joints, Couldn't find my flux so had to buy some, Almost fainted at the price, A tenner for a very small tub
I got home then instantly found my large tin of copaline, I took the new tub back for a refund as i'd not opened it!!
The punctured pipe was made good and all's fine now they're in the house!!