Architecture vs building
Architecture and a building are two different things that a project needs both of: architecture is the discipline of designing, the set of decisions that decide what to build, and a building is the physical structure that results, the thing that stands on the ground. The difference is the difference between the plan and the thing planned, and the page that follows sets the two apart, explains where they meet on a project, and answers the question of which one a person is really paying for when they hire an architect.
The difference between the design and the structure
The difference between architecture and a building is the difference between a decision and a thing, and it is a difference that shows up in the cost. Architecture is a set of decisions made before anything is raised, about the spaces, the materials, the structure and the way a person moves through the building, and it exists as drawings and as a set of specifications. A building is the result of those decisions made real, in concrete and steel and glass, and it exists in space and takes up the ground. The architecture can be changed on paper for a small cost, but the building can only be changed by taking it apart, and that difference in the cost of a change is the whole of the distinction. A person can redraw a plan in an hour, but they cannot redraw a wall that has already been poured, and the discipline exists to get the drawings right before the cost of the building is spent.
Where the two meet on a project
Architecture and a building meet on a project in the construction documents, which are the drawings and the specifications that carry the design into the making, a set that runs to 30 to 60 sheets for a house and several hundred for a larger building. The documents are the product of the architecture and the input to the building, and they are the single point where the design becomes the structure. The architect draws them, the builder reads them, and the building that stands is the building the documents describe. The meeting is also in the construction administration phase, when the architect reviews the work on site and the design is tested against the ground, the materials and the weather. A building that matches its documents is a project where the two met well, and a building that does not match them is one where the meeting failed, either because the documents were vague or because the making cut corners. The documents are the bridge between the two, and the discipline's skill is in drawing them clearly enough that the bridge holds.
Why the difference matters to the person who commissions a building
The difference between architecture and a building matters to the person who pays for both, because the two are bought at different times and for different reasons. The architecture is bought before the building exists, as a decision about what to build, and it is paid for as a percentage of the construction cost, usually 6 to 12 percent. The building is bought after the design is done, as the making of the thing, and it is the large part of the cost, the rest of the 100 percent. The commissioning person's decision on the architecture is a decision that controls the building, because a good design that is built right the first time saves money and a poor one costs more, and the discipline's value is measured in the quality and the cost of the structure that results. A person who understands the difference understands that they are paying for the decision as much as for the thing, and that the decision is the part that is hard to get right after the fact.
How the two are different from the architect and the builder
The difference between architecture and a building is mirrored in the difference between the people who do them, and the two roles are as different as the two things. The architect is the one who makes the decisions of the design, a licensed professional who signs the documents and stands behind them, and the builder is the one who raises the structure, a contractor and a team of trades who make the building from the documents. The architect works in the design, the builder works in the making, and the two hand the documents between them. A building needs both, because a design that is never built is only a drawing, and a structure that is never designed is only a pile of materials. The difference between architecture and a building is, in the end, the difference between thinking the building and making it, and a good project is the one where the thinking was done well enough that the making had to be done only once.