If you are thinking of renting out your HDB flat or rooms in Singapore, regardless if its 1, 2, 3, 4, 5 or executive rooms HDB flat. You might want to do partitioning inside of your HDB flat if your space and design allows. According to HDB website at http://www.hdb.gov.sg/fi10/fi10324p.nsf/w/HomeRenoGuidelinesBuilding?OpenDocument#RentedCommonArea. You will require to follow the HDB guidelines/conditions as stated below. However, when you had decided to build your new room with partition; Do discuss with your licensed HDB contractor first. And show your licensed contractor the guidelines/conditions from HDB so that the both of you can design and brainstorm the best solution and design to create a room which is suitable for rental purposes. Most contractors however will have limited design recommendation, but their cost to you to create a new room will be cheaper. If your goal is to create a nice and convenient room design for your future tenant and also which sink in with your current HDB flat’s overall interior design concept. You might want to set yourself a renovation budget first. Next, read up the varies small home design concepts for rooms (E.g. IKEA’s small space living, etc). Once you have some idea on what and how you want your room to look like. You can then search for an Interior designer to discuss about your room design idea. The interior designer will then be able to advise you on what is possible and what is not possible for HDB flats. There are many free interior designer advises in Singapore Expo halls, where usually there are Home Design expo/events held by Interior design companies. You can bring alone your HDB flat’s floor plan and discuss/brain storm with them and at the same time collect several quotation for your comparison purposes.