This document describes a test method for the determination of the activity concentrations of the radionuclides radium-226, thorium-232 and potassium-40 in construction products using semiconductor gamma-ray spectrometry. This document describes sampling from a laboratory sample, sample preparation, and the sample measurement by semiconductor gamma-ray spectrometry. It includes background subtraction, energy and efficiency calibration, analysis of the spectrum, calculation of the activity concentrations with the associated uncertainties, the decision threshold and detection limit, and reporting of the results. The preparation of the laboratory sample from the initial product sample lies outside its scope and is described in product standards. This document is intended to be non product-specific in scope, however, there are a limited number of product-specific elements such as the preparation of the laboratory sample and drying of the test portion. The method is applicable to samples from products consisting of single or multiple material components.