The development of structural project for buildings is of fundamental importance in the construction industry, given the fact that the buildings constructed under the provisions of a good project will surely meet the security, usability and economy. The construction is an economic activity that directly impacts on society as a whole, is of paramount importance that the professionals involved in the preparation of these projects are aware of the importance of the conception for excellent projects. This research aims to make the dimensioning sign of cross-sectional area of longitudinal tensile reinforcement (As and A's) positive and negative, massive slabs of pavement coverage of a residential building, through two different methods (theoretical and computational). For this, the methodology applied in calculating these armors, we use the theory of Bares-Czerny, as well as the use of Eberick computational tool, keeping in mind the classical concepts of engineering and norms of the Brazilian Association of Technical Standards (ABNT). After completion of these calculations, we present results in tables and graphs and are held discussions in order to evaluate which method best suits the measurement of these armor and leads to the development of structural projects that result in the execution of a safe, rational, functional structure, economic and, most importantly, meets the United Limits Last (ULL) and United Services Limits (USL). With the completion of the discussion, we conclude that both methods meet the proposed objectives. However, using the computer program, it is possible to elaborate structural projects that minimize the loads applied on the building, will become more slender and therefore more economical, with dynamic and effective results. However, we emphasize that the program serves only to assist the engineer and not replace it. The tool that is now used does not have own intelligence, this being a designer attribute. That is, the fundamental concepts of structural analysis such as the equilibrium conditions, types of bonds, stateless and stability, among others, acquired with the field of dimensional theories, hence the importance of mastery of these theoretical concepts by the engineer.