Detectives investigating the disappearance of Lynda Spence, 27, in April 2011, noticed different floorboards in a search of a flat in West Kilbride, Ayrshire.
Accused David Parker, 38, told police during questioning that the loft conversion in his home was used to hold Ms Spence in exchange for a promised £1500.
He and three others deny torturing the businesswoman to extract financial details, murdering her and trying to hide the evidence.
Detective Constable James McAteer, 38, from Strathclyde Police, who examined the flat in Meadowfoot Road, told the trial at the High Court in Glasgow that he noticed "a few different floorboards".
Looking at a number of lettered floorboards shown in a photo to the court, he said: "I felt A, B and C had not been fitted by a tradesman but D had been."
Owner of the flat James Dillon, 42, who rented it to Parker for several years but has now sold the property, identified "two new pieces of flooring" when shown a photograph of the floor.
Parker is accused with Colin Coats, 42, Philip Wade, 42, and Paul Smith, 47.
Jurors were last week shown video footage of the loft space and police pictures of two blood spots in the bathroom area.
Ms Spence has not been seen since April 13 2011, when she left her parents' house in Glasgow after visiting her mother.
The trial, before Lord Pentland, continues.