Abstract: An improved substrate splice for roofing and the associated method for the creation of an improved substrate splice. This can be achieved by taking a fiberglass scrim that has at least one layer of nonwoven fabric positioned adjacent thereto. Splicing involves overlapping this material and heating to a temperature of between 450.degree. and 1,000.degree. F. while applying 1 to 1,000 pounds per square inch. The preferred range of temperature is between 500.degree. to 700.degree. F. with 1 to 4 p.s.i. of pressure. Two layers of fiberglass backed thermoplastic tape is applied to each side of this splice. The tape is then heated to between 450.degree. and 1000.degree. F. while also applying pressure of 0 to 1,000 pounds per square inch. The preferred range of temperature is between 500.degree. to 700.degree. F. with 1 to 4 p.s.i. of pressure.