When planning an extension, most people focus on cost — but the next biggest question is always:“How long will it take?” I took a bit of time to turn a real construction programme into a clear timeline, so you can better understand the process (See the reference programme here ) For a typical 5m x 4m rear extension, the build duration is usually around 14 weeks. However, construction isn’t a simple linear process — many stages actually overlap.For example, carpentry, plumbing