In architecture, a deck is a constructed flat surface capable of supporting weight, similar to a floor but typically constructed outdoors and usually (though not always) connected to a building. The term is a generalization of decks as found on ships.

A deck of a house is generally a wooden platform built above the ground and connected to the main building. It is generally enclosed by a railing , for safety. Access may be from the house, through a sliding door or French doors, and/or from the ground via stairs. Residential decks are often constructed over areas of steep or rough ground that is otherwise unusable.

Larger buildings may also have decks designed in, where an upper part of the building has a smaller cross-section than a lower part. Sometimes these are open to the public as observation decks.