Yes, you can usually stay living in the house during the work. Most access is through the existing landing, so the builders are not tramping through your main living spaces all day. There is dust and noise, as with any building project, but it is manageable for most households.
The main thing to plan for is the point when the stair opening is formed. That is the day or two of heavier disruption, because it connects the attic to the floor below and opens the ceiling up. Around that stage there is more mess and noise than usual, and it helps to keep children and pets clear of the area while it happens. The rest of the build is steadier and easier to live alongside.
Good contractors make a real difference here. We seal off the work area with dust screens to keep dust out of the rest of the house, and we tidy up at the end of each day rather than leaving the place in a state. Materials are managed so hallways and stairs stay usable, and we are mindful that you are living around the work.
Some households prefer to be out for the noisiest day or two, particularly if someone works from home or there is a young baby, but that is a personal choice rather than a requirement. If you have specific concerns, for example a home office or shift work, mention them at the free assessment and we can plan the noisier stages around you. You can also read how we work in our step by step process or learn more about us.