Yes you can expand your bathroom by up to 0.6 square metres or 600mm in width. This additional area can allow an entire sink or small cupboard to be installed

Also if you are looking to connect adjacent bathrooms that are sometimes available in 3-Room Improved and 4-Room HDB flats, you can even combine them into one massive bathroom by knocking down the separating wall.

You can check out more HDB guidelines here: