To design a space that is eye-catching and make you stop designers apply six basic principles mixed with their experience;
Scale & Proportion
This is the first and most important principle of interior design. It is also known as the focal point. Every space needs a focal point to be visually interesting for the occupants. The purpose of emphasis is to draw the attention of the visitors or occupants to a specific point of the room.
In interior design, if you give equal importance to every wall and accessory in the room then it becomes boring and monotonous. For example, if you have a double heightened media wall you can hang some art piece above the television. This will lead the attention of the visitors to the wall as soon as they enter the room. Or, there is large lobby space in the house, you can hang a single art piece with appropriate lighting or arrange a sculpture in it such that as soon as the visitors enter the lobby their eyes automatically move towards that area.
The second important principle is a contrast that is how to put the elements in relation to each other. You can create contrast through size, color, shape, texture, material, etc. The key to creating contrast is mix and match; from the fabric of the pillow to the color of the wall, from the art piece on the wall to the rug on the floor.
Repeated contrast patterns lead to the generation of rhythm in the space. Just like music rhythm is very much important in interior design. For example, to create a nice melody you need some silent notes mixed well with music notes. Likewise in a room, there should be some series of repeated patterns along with open areas to create a harmonious look.
Rhythm helps in the visual flow of the room. You can create rhythm by duplicating the colors, shapes, patterns to create a complete harmonious design.
For example, you can match the color of the rug with the color of the pillows on the sofas and art piece the wall. This will give a unified look to the room.
The proper addition of above three elements that is emphasis, contrast, and rhythm create balance in interior design of the room. The purpose of creating balance is to give a visual feel of equilibrium in the room.
Balance can be achieved by the help of colors, patters, shapes, and textures to give a feel of unity to the room. Balance is of two types;
Symmetrical balance (One side of the room is an exact duplication of the other)
Asymmetrical balance (One side of the room compliments the other side without being exact duplicate of the other)
5. Scale and Proportion:
Scale of the room is a very important principle to be considered as it defines the size of the room and further helps in selecting the accessories for a specific size of the room. Proportion means the size of the accessories with respect to each other inside the room. For example, to compliment a large sofa you can put a medium sized side table with it. (Proportion of sofas with respect to side table is important to be considered here). Size relationship is important to be considered.
Harmony is the last and the most important principle in interior design. When all the first five principles fit properly in a room then the room gives a sense of unity and togetherness that is harmony.
The easiest way to achieve harmony in interior design is to first define the interior style which you want to use like mid-century style, modern, contemporary, industrial, etc. This will give you certain parameters about the accessories, furniture, color palette, and fabric according to the style adopted.