To maintain the technical condition of the apartments, you are not allowed to change any of the technical systems or architectural layout of your apartment.

Changing your room
Want to customise your room to your own taste? This is allowed, but you must follow a few rules:

Painting / drilling / nailing
You may paint the walls in the kitchen, living room and bedroom between the baseboards on the floor and ceiling in any colour you like. It is important to use good latex paint (not smudge-proof paint). When you leave, the walls should be finished in RAL 9010. Or the next tenant must accept the coloured walls. Painting ceilings, windows, window frames, doors and baseboards etc. is not allowed.

The walls and ceiling contain many ducts. To avoid damaging these, you are not permitted to drill or hammer into these surfaces. Do not drill or hammer into windows, frames or other wooden finishes.
If you want to hang something on the walls, realize that you have to deliver the walls tight again when you leave. Holes must be greased. Be careful not to drill or nail into piping.

Tip: Attach a thin bat along the ceiling to which you can attach wall decorations, picture frames, posters, etc. This will prevent a lot of work when leaving. Do not stick posters/stickers to the wall with tape or posterbuddies/ sticky pads.

Flooring
The apartment does not come with any carpeting or rugs. Are you installing any carpeting? If so, remember that flooring has to be removed again once you leave the room for good. There should not be any glue or foam residue stuck to the floor. You can also transfer it over to the next tenant. 
Avoid making a lot of noise! Place a sound-damping layer underneath your flooring.

Curtain rails
All rooms have curtain rails. You may not remove them. You are not allowed to screw or drill into the window frames.