The installation of a lintel above a door depends on various factors such as the weight of the structure above the door, the size of the opening, and the type of construction.
A lintel is a horizontal support beam typically made of steel, wood, or reinforced concrete. Its purpose is to distribute the weight of the structure above the opening, such as the wall or load-bearing elements, and ensure the stability and safety of the door frame.
In your case, if the original door frame did not have a lintel and the bricks above the door were supported by soldier bricks (vertical bricks) and additional rows of bricks, it is possible that those bricks were providing the necessary structural support. However, without a detailed understanding of the specific construction and load-bearing requirements, it is difficult to determine whether the current setup is safe and sufficient.
To ensure the structural integrity and safety of your door frame, it is highly recommended to consult a qualified structural engineer or a professional contractor. They will be able to assess the situation on-site, evaluate the load-bearing requirements, and provide appropriate recommendations. They may advise you to install a lintel or suggest alternative measures to ensure the stability of the door frame and the overall structure.
It's important not to rely solely on online advice when it comes to structural safety. Reach out to a professional who can evaluate your specific situation and provide expert guidance.