Not necessarily. All states have a law (generally known as the "statute of frauds") that requires certain types of contracts to be in writing. As the name suggests, the statute is designed to prevent fraudulent claims, especially in the case of large contracts.

If contracts listed in the statute of frauds are not in writing, they cannot be enforced. Construction contracts sometimes fall within the terms of a state's statute of frauds and therefore must be in writing.

For example, in Florida, the following types of contracts that might involve construction projects must be in writing:

• credit agreements (i.e. construction loan financing);
• contracts that cannot be performed within one year (major construction projects may fit this bill);
• contracts for the sale of goods over $500 (any contract involving expensive construction materials); and
• contracts for the sale of real property (contracts involving the sale of improved real estate).

In addition, written contracts for construction work frequently include clauses requiring that any modification of the original written agreement must also be in writing and stating that the written contract constitutes the entire agreement of the parties. Courts will generally uphold and enforce these clauses to defeat an owner or contractor's claims that there was a separate oral agreement that changed the terms of the written agreement.