Developing spreadsheets and programming have many common aspects. It is a common programming practice to handle complex problems by separating them into smaller, more manageable units. Similar approach should apply to spreadsheet. Do not attempt to create a spreadsheet that will handle "everything".

It is much more flexible to develop, maintain and use several smaller spreadsheets (modules) to perform a series of calculations (e.g. obtain load combinations for external loads, calculate internal forces, and design reinforcement) than to perform all the work in one large spreadsheet. Individual modules must have clearly defined interfaces between them. Modular approach also makes it possible to reuse a component for a different series of calculations.