Most renovation budgets are built on hope rather than analysis. A homeowner gets one quote, rounds it down in their head, adds a vague "buffer" they never actually set aside, and starts the project. When it ends 30 percent over budget, it feels like bad luck. It was predictable from the start. Building a renovation budget that holds requires a different approach from the beginning. Here's how to do it in concrete steps. Step 1: Define the Scope Before You Ask for a Quote Contractors quote what they're given. If your scope is vague, the quote will be vague, and vague quotes have a way of growing as the project clarifies itself. The homeowner ends up surprised. The contractor believes they're accurately billing for the work that was actually needed. Before you contact a single contractor, write down in specific terms what you want done.…