EXPENSIVE INCHES

It's no big deal to replace a window with french doors—
as long as you stay within the original window opening
and just remove the wall beneath.
Widen the opening, however, and your'e talking $$$$.

Everyone knows that grandiose plans are expensive. But big costs can come in small increments, too: often, a matter of a few inches one way or the other can turn a bargain design into a bank-breaker. Spotting those expensive inches is crucial to optimizing your remodeling dollar.

Take a minor remodel such as replacing a window with a sliding or French door, for example. Many people figure that, since they’re tearing up the wall anyway, they ought to widen the doorway a little while they’re at it. That’s a perfect example of expensive inches. 

Design your kitchen with modular cabinet dimension in mind
and you'll save a ton of money over custom cabinets.
It's simple— just keep everything in multiples of 3".

Why?  Because the top of every window and door opening is spanned by a heavy wooden beam called a header, which continues into the wall a few inches on either side and extends nearly all the way to the ceiling. To accommodate wider doors, this header usually has to be torn out and replaced, requiring vastly more demolition and repairing of finishes, and hence adding lots of needless expense. 

The same job can be done for a lot less if the new doors are designed to fit entirely within the existing opening, thus preserving the header and the surrounding framing. In most cases, you won’t lose any functionality by doing so: the rough framing of a typical 6’ wide sliding window, for example, will handily accommodate a pair of 2’-10” french doors or a 6’ sliding door simply by removing the section of wall beneath the window.

Remember that all building materials,
such as sheet mirrors, come in standard sizes.
When you exceed them, even by a half-inch,
you're going to pay a lot more.

Kitchen remodels also contain some notoriously costly inches. For example, lowering a standard 36” high countertop “just a bit” may seem innocuous by itself, but may in turn force you to use custom-built cabinets rather than the more affordable modular kind. Deviating from the standard 3” width multiple used in modular cabinets can have the same result. So don’t be too cavalier about requesting nonstandard dimensions—while practically anything can be custom-built to your exact specifications, you’ll pay a heavy premium for it. 

In fact, sticking to standard sizes and heights will go a long way toward keeping a tight budget under control no matter what the project. Special sizes inevitably add cost, so try to become familiar with the standard building material sizes before you start your project, and work within those limits wherever possible. 

Sometimes, though, people don't add enough
inches—a small pop-out addition
such as this one will cost a fortune
relative to the space it adds.

Standard sizes even apply to a lot of materials most people consider “made to order”.  The sheet mirror typically used above bathroom vanities, for example, is stocked in 42” widths. Anything wider—even by half an inch—requires that the mirror be cut from stock the next size up.  And of course, you pay for the wasted mirror glass as well as the part you use.
  
Alas, the law of expensive inches can work in reverse as well: it can be just as bad not to add enough of them. For example, clients often ask me to enlarge a bedroom by “just moving the wall out twelve inches or so,” mistakenly thinking that moving a wall a small distance is cheaper than moving it a lot.  In reality, of course, the wall doesn’t get “moved” at all; it simply gets demolished and replaced by a new one. And since the cost of building a new wall is about the same regardless of where you put it, you’ll lower your square-foot building costs considerably by enclosing a big area rather than a small one.