True blueprint symbols are rare now; most house plans are generated in CAD, computer-aided design. If paper copies for building a house are needed by someone, they are often produced in black line, making what are called prints, drawings or floor plans.
Still, architecture students are told, nagged really, that the quality of their drawings is paramount. Until the client has the structure, all he or she can see are some very expensive drawings. They had better look good. At the same time, drawings are revised frequently, and so drafting output has to be high. CAD was a vital innovation.
House designs and their symbols
Blueprints were a terrific innovation in their day too, reproducing architects' and engineers' directions with speed and accuracy. Their symbols are still used on modern prints and drawings, for installation of HVAC (heating, ventilation and air-conditioning), plumbing and electricity. Other architectural symbols show doors and windows, stairs and rooflines, the sorts of things that are often understood intuitively by clients who look at plans but are illustrated with style anyway.
HVAC: building a livable house
It’s a question of flow with HVAC; the air comes out here and goes there, where it is taken up and handled again. So arrows on plans show airflow. Building codes also have much to say about HVAC (as they do about every other aspect of construction), and so, notations will show clearances and fire protection.
HVAC is not always represented the same way. A legend helps explain the symbols. Also, the people who work in HVAC have a good idea of what to expect and where.
Some plumbing symbols look like a stylized representation of an object, and some look nothing like whatever it is. A bathtub is an oval within a frame, much like many bathtubs from above. Yet a shower is a rectangle with an X through it or an X with a tidy circle at the intersection, nothing like a shower. Toilets and bidets do resemble the actual fixtures, and so do sinks as a rule. The actual conduits for water and waste are sited precisely, and for good reason.
In general, the symbols that will be read by electricians look nothing like the things they represent. In fact, they look like figures lifted from circuit diagrams. Here, too, precision is important, and it is often the working electricians who supply it.
The symbols of architectural drafting are not consistent. Windows are reproduced in several different ways, from outlines meant to show transparency to parallel diagonal lines meant perhaps to show reflections. That may be one reason many set of plans come with legends that translate the stylish symbols to understandable instructions.
Still, doors and windows that open into or out of a room are drawn with arcs that show the paths they travel, and architects often have their finishes illustrated with loving care. Dimensions are called out from line to line, and five minutes of study will show how elegantly it is done.
Building a house
Building a house is a collaborative process, and building a larger structure is even more of one. The prints add structure to the process and help the complicated work flow in something like order. Architecture is a creative trade, but building is an eminently practical profession.