Winter storage failures are predictable and preventable. Furniture cracks because trapped water froze, and cushions come out moldy because they went in damp or sat in a sealed container all season. Both problems trace back to moisture, and both are solved before the furniture is ever put away.
Clean and fully dry: the highest-value step
If you do one thing, do this: clean every piece and let it dry completely before storage. Soil, pollen, food residue, and grime are the food source mold needs, and any water left in a joint or trapped in cushion foam is the moisture it needs. Wiping frames down, washing cushion covers, and then allowing everything to dry thoroughly in the sun removes both ingredients at once. Furniture put away clean and bone-dry has almost nothing to go wrong over the winter; furniture put away dirty and damp is being packed with the exact conditions that ruin it.
Freeze-thaw damage in resin, ceramic, and trapped water
The mechanism behind winter cracking is freeze-thaw action. Water that has soaked into a porous material or pooled inside hollow tubing expands as it freezes and pries the material apart, and repeated freezing and thawing widens the damage each cycle. The Federal Highway Administration’s material on freeze-thaw deterioration in porous materials describes how saturated pores develop internal pressure when water freezes, which is the same process that cracks concrete, ceramic pots, and low-grade resin furniture. The takeaway for storage is to eliminate trapped water: drain hollow frames, tip furniture so water cannot pool, empty and dry ceramic and concrete pieces, and never leave a resin chair full of rainwater to freeze solid.
Unheated garages, sheds, and condensation
An unheated garage or shed protects furniture from direct rain and snow but introduces its own risk: condensation. When outdoor temperature swings, humid air inside an uninsulated space can deposit moisture on cold surfaces, so furniture that went in dry can still get damp from the environment. Ventilation helps, as does keeping pieces up off a concrete floor that wicks and radiates cold, using pallets or blocks. Breathable covers protect against dust without sealing in humidity. The goal is a space that stays dry and allows some air movement, not a sealed box that traps whatever moisture develops.
Cushion storage: breathe, do not sweat
Cushions deserve special care because they hold moisture and feed mold if stored wrong. The deciding factor is relative humidity: mold growth becomes likely when surfaces and materials stay above a threshold of dampness for a sustained period. The EPA’s guidance on controlling moisture and humidity notes that keeping relative humidity low, generally advised below roughly 60 percent, is central to preventing mold indoors. Store cushions dry, in a container that breathes, such as a ventilated deck box or a cloth storage bag, rather than a sealed plastic bin that traps humidity against the foam and effectively incubates mildew. A packet or two of desiccant in the container is cheap insurance.
What can genuinely stay outside
Not everything needs to come in. Solid teak tolerates winter well and can be left out to silver, though it lasts longer covered. Powder-coated aluminum handles cold but benefits from a breathable cover to keep debris and standing water off. Heavy stone and concrete can stay out if fully drained and not left holding water that will freeze. For anything left outside, the prep is the same principle in miniature: clean it, make sure water cannot pool or soak in, and use a cover that sheds rain while letting the piece breathe. Everything porous, fabric, or crack-prone is better off dry and indoors until spring.