Outdoor rooms are most successful when their size conforms to their intended use. For example, an intimate private patio should probably be about the size of an intimate indoor sitting room. A barbecue cooking and eating area intended for entertaining should be about the same size as a kitchen-dining room combination of comfortable dimensions inside the house.
If a style of entertaining calls for large interior rooms, the outdoor rooms should also be large. Be careful, however, because there’s a tendency to make outdoor spaces much bigger than they need to be, which can lead to uncomfortably large areas lacking a feeling of enclosure. The most desirable places to sit outdoors are like the backwaters of a stream, where eddies exist out of the way of fast-moving water. They provide a feeling of repose and a restful sense of apartness.
Try creating smaller spaces within a larger one by placing tubs of plants or groupings of furniture to simulate edges of space. The modification can be made more permanent by alternating paved areas with planting beds filled to a pleasing height. In a landscape that is being redone, look critically at the existing living spaces, and be daring. Make spaces smaller or larger, or move them to a different part of the yard.
General rules about space have so many exceptions that they are useful only as starting points. One such rule states that space is most comfortable when it has a relationship to the scale of the human form. A landscape can achieve relative human proportions whether the scale is large or small. A large garden with a view of mountains in the distance can be as human in scale as a small rock garden — if the view is open and expansive. However, if the garden is narrow and lined on both sides by tall trees, the distant mountains will appear too tall in proportion to the size of the lot.