This study provides fire investigators new methods and guidelines for conducting calcination depth measurements and analyzing heat impact on gypsum wallboard relative to fire patterns. The study findings increase the likelihood of positive ignitable liquid residue (ILR) identification on typical building materials (composite furniture materials, plywood, vinyl, and carpet/pad). The procedure used enables investigators to assess objectively burn patterns on various flooring materials in order to determine whether the source of the pattern is the burning of flammable liquid or other combustible materials, such as furniture or plastic toys. The procedure used provides a means to measure the calcinations depth of gypsum wallboard for pattern analysis to aid in fire origin determination and fire impact severity. The results of this study have been incorporated into the Society of Fire Protection Engineers (SFPE) Handbook of Fire Protection Engineering (5th edition, 2016) and the National Fire Protection Association (NFPA 921 Guide for Fire and Explosion Investigations (2017).