Plantation shutters in South San Francisco

Out-of-square openings

With 70% of homes built before 1980, many openings have had decades to settle. Measure each one's width at the top, middle and bottom, and both diagonals. If the diagonals differ by more than about ¼ inch, add a mounting frame in the designer, or choose an outside mount so the shutter covers the uneven edges.

How to measure

Replacement windows

51% of homes went up between 1950 and 1979, and most of them have had their original windows replaced since. A replacement window often sits further into or out of the wall than the old one, so the depth you have for an inside mount may differ from window to window in the same house. Measure every opening rather than copying one.

Choosing a louver size

Dry summers, wet winters

Barely any of the year's precipitation falls in June, July and August; most comes in the cool months. Wood takes on moisture in the wet season and gives it back in the dry one, so expect the panels to feel slightly tighter in winter than in summer. Fit them in the season you're in, and leave the hinge screws a quarter turn from tight until they've been through both.

A mild year

Few days here are very hot or very cold, so louvers spend most of the year on everyday work: angling daylight off the TV, giving privacy from the street, and opening wide on a fine morning. That makes louver size more a matter of view than of shade; bigger louvers leave more open glass.

Choosing a louver size