Floor

Floors are a type of object in build mode that can be placed on terrain, a foundation, or beside supports such as a wall or column. Sims will prefer walking on floor tiles over bare terrain, and can only walk on floor tiles on the upper stories of a building. A provisional floor tile are automatically created when entrance objects, such as a door or stairs, have no edge support.

Flooring comes in many different types, including tiles, linoleum, stone, masonry, and wood. Outdoor floor tiles, such as the pavement on roads and sidewalks, are also considered to be a form of flooring. The price of flooring typically varies from §2 to over §20 depending on the type of flooring.

Floor tiles can also be used to create flat roofs. This can be done simply by building floor tiles above a room. A room that is covered with a flat roof constructed out of floor tiles will still be sheltered from the weather.

Floor tiles can be rotated with the use of and  to respective direction, with the position being applied to all SHIFT-placed titles. One grid tile can even share two tiles. This is done by using the clearing key ( + Left Click) on a floor tile that is occupied by a diagonal wall, which will only leave out a diagonal half of the floor tile that's pointed at with the cursor.

Ceiling
Visible ceilings were introduced in The Sims 2: Apartment Life. Before that, ceilings were assumed to be present, but were not visible. Ceilings can be created by placing floor tiles on the floor above. A generic "popcorn ceiling" floor tile is used as the default ceiling, although players can customize the ceiling by adding any floor tile they wish to it. As ceiling tiles are technically floor tiles, they can also be used as regular floor tiles. Apartment Life also introduces a "45 Degree Angle Tool" that allows the player to view the ceiling more easily.

Ceilings are also visible in The Sims 2: Pets for console, and the feature was carried forward into The Sims 3 and The Sims 4, where ceilings are automatically created when a room is built. Ambitions reintroduces the ability to customize ceilings in The Sims 3, although the 45 degree angle tool was never reintroduced.