Create a visually pleasing transition from the outdoors in by carrying the same hard-surface flooring from an adjoining outdoor patio to your three-season room. The room might only have its walls supported by in-ground piers or footings with no foundation. In areas where winter ground heaving isn't an issue, the interior "floor" simply can be a level sand base on which to support brick pavers or concrete blocks. Alternatively, you can cover a concrete slab base with brick or block flooring, as long as doorway thresholds are high enough to clear them.
Today's indoor-outdoor carpeting is ideal for three-season rooms, and it comes in more options than the fake grass of yesteryear -- and even that doesn't look as cheesy as it used to. Carpet with quality ultra-violet ray protection lasts longer than untreated carpeting when it's exposed to unleashed sunlight. Indoor-outdoor carpeting is available in richly colored solids, mottled neutrals, and even interesting and playful patterns, such as multi-colored floral prints, that transport you to a "garden" without your having to step outside and mingle with insects. Low-pile carpets are easier to keep clean than high-pile varieties -- especially important if the room has outdoor access.
Good Old Wood
Installing reclaimed-lumber flooring in a three-season room is more than ideal. Gracefully aged, pre-faded wood won't end up badly sun-beaten and patchy under furniture. Using reclaimed-wood flooring labels you an unofficial "recycling star," and it provides visual warmth and rusticity that suits the outdoorsy vibe of a space where the many outdoor views are its "art."
Stone Your Craft
Natural or engineered stone or tile flooring is fitting in a window-wrapped space. Solar heat warms stone, tile and concrete flooring, which retain heat, unlike carpet and wood. You'll appreciate a little heat underfoot whether you're enjoying a morning coffee or entertaining on a summer's eve. Slate, granite, travertine, or earthy stamped or stained concrete, for example, plays into an outside-in setting without the unpredictable wind, rain and cool temperatures that go with lounging alfresco.
Pulling the Rug Out
No matter what type of flooring is under it, a rug helps to protect it, but not all rugs are equal. A sisal or seagrass rug is a mediocre choice for sunny but dry areas; unless you rotate them every month or so, they'll fade unevenly. Some quality rugs, such as well-made wool rugs with durable dyes, withstand fading better than others. Installing easy-to-open window treatments -- remote-control-operated blinds or roller shades, for instance -- that you can close when you're not using the sun-filled room, is an optimal way to protect whatever flooring you choose.