Modern industrial and recreational buildings are often realized in steel because it offers strength, speed of erection and a lightweight envelope. However, when the structure must accommodate a corrosive and humid environment, such as a public swimming pool, designers must balance material efficiency with durability and safety. My thesis investigates this balance by designing a short steel hall with low-stiffness beam–column connections and examining how the introduction of roof bracing affects its structural performance. The case study is a 22 m by 15 m hall consisting of five portal frames set 5.5 m apart. The 10° pitched roof is supported by HEA 260 interior columns and HEA 180 corner columns; intermediate rafters vary between IPE 330 and IPE 240 profiles, while the longitudinal beams are SHS 70×70×3 tubes. Cross-shaped bracing bars of Ø16 mm steel connect the purlins at the gable walls and across the roof plane. This configuration was analysed in AxisVM using the Eurocode suite and the Hungarian National Annex. Permanent loads included the self-weight of the steelwork, roof cladding and pool deck; variable actions comprised snow, wind, temperature, seismic and accidental fire loads. Both linear and geometric-nonlinear analyses were performed, and the semi-rigid connections were checked against Eurocode 3 rules. Two structural models were studied. The first omitted roof bracing and relied solely on portal action to resist horizontal loads. The second introduced roof and end-wall bracing, thereby tying the frames together. The results of the first-order and second-order analyses showed that the braced model had significantly greater lateral stiffness and smaller internal forces in the intermediate frames. Whereas the unbraced hall required larger sections (IPE 360, HEA 300, IK 480) and still approached serviceability limits, the braced hall achieved acceptable deflections with the smaller HEA 260 and HEA 180 columns and variable IPE 330 rafters. Overall steel weight fell from about 13 t in the unbraced model to 8.6 t in the braced one, translating into lower material costs and a smaller surface area exposed to the corrosive pool atmosphere. The roof bracing also allowed the beam–column connections to be treated as nominally pinned, simplifying fabrication and reducing bolting demands. Dynamic analysis using the response spectrum method showed that the fundamental vibration modes of the braced hall were around 2.5 Hz and that seismic actions in the X and Y directions produced modest displacements well within Eurocode 8 limits. Imperfection loads applied in both axes demonstrated that the second-order effects were small thanks to the bracing. A fire design assessment, based on the ISO 834 curve and section factors, indicated that most members could withstand 15 minutes of standard-fire exposure without protection; only a few SHS 70×70×3 braces approached their critical temperature and would benefit from a thin intumescent coating or a slightly thicker tube. By combining rigorous analysis with practical design decisions, this thesis illustrates how a thoughtfully detailed bracing system can unlock substantial material savings and performance improvements in a low-stiffness steel hall. The findings support the use of roof bracing in single-storey structures where economic efficiency and serviceability are priorities and provide a template for future designs in similarly demanding environment.