Time lapse of steel re-bar support. The rebar is the structural part of the pool building process. The rebar specifications are determined by a structural engineer who does all the necessary calculations to ensure the pool has structural integrity. Close up of steel rebar support. These calculations are reviewed by the city and verified by our staff as well as the city inspector during construction. For most pools, rebar can be completed in one day. For large ppols, diving swimming pools, water features, spas and swim up bars, additional time may be requireed.