While it might be tempting to use indoor furniture cushions on your outdoor furniture when it's under a roof or covered patio, this is generally not recommended. Even when protected from direct rain, outdoor environments present several challenges that indoor cushions aren't designed to handle.
Outdoor furniture cushions are specifically engineered with weather-resistant materials that can withstand humidity, temperature fluctuations, morning dew, and occasional moisture exposure. Indoor cushions typically lack these protective features, making them vulnerable to mold, mildew, and rapid deterioration in outdoor conditions.
Even under a roof, cushions remain exposed to higher humidity levels, temperature changes, and potential water exposure during windy rain. The fabrics used for indoor cushions aren't treated to resist UV radiation, which can still affect them indirectly in covered outdoor spaces. Additionally, indoor cushion filling materials tend to absorb and retain moisture rather than quickly drying like outdoor-specific foam.
For occasional short-term use, indoor cushions might work temporarily on covered outdoor furniture, but for long-term protection and comfort, investing in properly designed outdoor cushions is the wiser choice. They provide better durability, moisture resistance, and overall performance in semi-protected outdoor environments.