"The blows of the great hammers shake the walls of their houses and disturb the rest of them and their servants, day and night, and spoil the wine and ale in their cellar, and the stench of smoke from the sea-coal used in the forge penetrates their hall and chambers."
Thankfully the zoning laws now prevent this happening to you, but the basics of ironwork haven't changed that much since King Henry VIII squeezed himself into his suit of armour. Small workshops still heat individual pieces of metal in furnaces until they are malleable enough to be beaten into shape on the anvil and then bent in a form.
New technology has changed the speed, flexibility and possibilities of iron design, especially with production work. With hand forged ironwork each artisan still creates his work with an individual style which (may not be immediately apparent to the casual eye but is nevertheless) an inherent part of the beauty of hand made creations.
Modern Architectural Ironwork is often perceived as the finishing touches to a building and its budget. The latter is often near its limit when ironwork is being considered. There is no doubt that ironwork, like any hand made item can get expensive. However, properly executed and positioned ironwork can add many times more than it's cost to a property, and as such should be considered an appropriate investment.
In the early 1900's Los Angeles witnessed a revival of Spanish colonial design incorporating authentic metalwork . Today houses of quality incorporating authentic ironwork, especially from this era are sought after and often mimicked; indeed ironwork of all periods is now greatly appreciated not only for it's artistic merits but also for it's value-adding potential.
Practically all building materials are either cast or carved; iron alone is heated in a furnace and wrought on an anvil. The natural inclination with a project involving metal is to design it with the tools you are most familiar with and simply signify 'wrought iron' as the material. However, one should not expect a blacksmith to fabricate in iron what a wood carver could make in wood or a foundry to cast in iron or bronze. It helps to be aware of the process; for instance the difference between wrought, forged and cast iron. 'Wrought' is iron bent in a form. 'Forged' means hammered and shaped on an anvil when hot, usually prior to being wrought or added to a wrought design. 'Cast iron' is heated iron poured hot into a mold and then included in a design.
Cast iron has the benefit of mass production. Once the mold is made, which may be very intricate, many copies can be produced (in either iron, aluminum, or even plastic!) for reasonable cost. Consequently a design may look very intricate, it may be made of iron, but it is not hand-forged wrought iron which would take considerably more time to fabricate. Each type of iron has its own design quality, yet may be combined effectively. Cast iron elements used sparingly to accentuate a wrought design can be very appealing.
As with any design choice it helps enormously to have clearly defined parameters for your project.
Knowing examples of styles and techniques which you like and dislike will greatly aid your interaction with the designer and blacksmith.