No question is too basic. That is the whole point.

Usually because they are pricing different things. One may include structural steel, scaffolding or finishes another excludes. Compare scope line by line before comparing totals.

For most domestic projects, ten to fifteen percent is a sensible starting point, and higher for older properties where the ground and structure hold surprises.

Look for consistent paperwork, references you can actually visit, clear insurance, a willingness to sign a contract and calm answers to difficult questions.

A change to the agreed scope of work. It should be described, priced and agreed in writing before it is built, not discovered on a later invoice.

Sometimes, for materials ordered in advance. It should be proportionate, documented and matched to something tangible, never a large sum for goodwill.

A signed contract, an agreed scope and drawings, a payment schedule, a programme, insurance details and building control notification.

Write down what you have observed, ask for a short site meeting and request the relevant records. Early, calm questions resolve far more than late, angry ones. You can bring this to the clinic.

Dated stages with dependencies, not a single end date. It should show inspections, lead-in items and the decisions you need to make and by when.

A walkthrough, an agreed snagging list, certificates, warranties, manuals and a clear route for anything that appears later.