Depending on the scale and complexity of your development, you may require building regulations drawings and approval in addition to structural engineering calculations. Structural engineering calculations involve the assessment of a structure's load-bearing capacity and strength, as well as its size and shape. They also include evaluations of a structure's ability to resist forces due to wind and earthquakes. Calculations involve calculating the appropriate materials and strength of components to be used in a given structure and analyzing the safety of a structure's design.
To quote and produce structural engineering calculations we require your architect drawings, that show the design. The architectural design from the planning stage will determine exactly what is required for structural engineering calculations. The cost of structural engineering calculations will depend on the scale and complexity of the design. Large and simple could be cheap, whereas small and complex could be expensive.
It is strongly recommended that you do not pay for structural engineering calculations until you have planning approval for your development. Planning approval is never guaranteed and who wants to pay for structural engineering calculations if planning permission is refused? Also, if your design changes during the planning process, you will need a new set of building regulations drawings and structural engineering calculations, at additional cost.