A project can take anywhere between 1 month to a year or more depending on the scope of work and the type of project. On average, loft conversions take 6-10 weeks to complete. Basement conversions take between 8 to 20 weeks. Renovations, extensions and refurbishment take 6 months on average. New builds usually take 5 months to a year depending on the size of the project and the planning required.