For a north-facing courtyard with minimal direct sunlight, the persistent challenges are dampness, slow evaporation, and the rapid growth of moss or mildew on furniture surfaces. To avoid constant scrubbing and early deterioration, you must choose materials that are inherently non-porous, quick-drying, and resistant to fungal colonization.
First, powder-coated aluminum is the top recommendation. It is completely non-porous, does not absorb water, and the coating seals the metal surface so moss has no foothold. Even in constant shade, aluminum stays dry within minutes after rain, and it never rots or warps.
Second, high-density polyethylene (HDPE) synthetic lumber – often sold as recycled plastic lumber – is excellent. This material is waterproof, does not wick moisture, and can be cut and assembled like wood but never molds. It is heavier than aluminum but stable and ideal for benches or table bases.
Third, consider teak wood – but only the heartwood from sustainably grown trees. Teak contains natural oils that repel water and resist fungal attack. However, avoid cheap teak or other hardwoods like oak or ash, which will stay damp and grow green slime. To enhance performance, apply a teak sealer every six months.
Fourth, synthetic rattan (polyethylene wicker) with a powder-coated aluminum frame works well if the weave is tight and the cushions are removable. The key is to ensure the rattan is UV-stabilized and waterproof; otherwise, the inner weave traps moisture. Always choose outdoor-grade cushions with quick-dry foam and a water-repellent cover.
Fifth, fiberglass-reinforced concrete or cast stone is a heavier option for permanent seating or planters. It is non-porous when properly sealed, but you must re-seal the surface annually to prevent micro-cracks from trapping moisture.
Finally, avoid untreated wood, iron (which rusts), and open-cell foam cushions. For any material, place furniture on gravel or a slatted deck to allow airflow underneath, and tilt tabletops slightly to let water run off. Add a ceiling-mounted fan or a small dehumidifier if the courtyard is enclosed, but with the right materials list above, you can enjoy a low-maintenance, moss-free outdoor space even in deep shade.