It's the question we get more than any other, and the honest answer is: it depends on your deck. But there are some good rules of thumb for Chicago, and some clear signs that tell you when it's time.
Start with the floor. Horizontal surfaces — the boards you walk on and the treads of your stairs — take direct sun all summer, sit under snow all winter and carry every footstep. On most decks around here they need cleaning and a fresh coat of sealer-stain every one to two years. Vertical surfaces like rails, spindles and posts shed water and see far less wear, so they usually go about three years.
Then look at the conditions. A deck under heavy tree cover stays damp and grows mildew faster. A south-facing rooftop deck fades faster. Pets, pools, hot tubs and planters all speed up wear in the spots they touch. And very dense hardwoods like ipe or tigerwood don't absorb stain deeply, so they typically need a light clean and re-coat every year.
The easiest test is water. Sprinkle some on the boards: if it beads up, the sealer is still working. If it soaks in and darkens the wood within a minute, the protection is gone and water is getting into the wood — which in a Chicago winter means freezing, swelling and splitting.
Other signs it's time: grey, weathered fibres on the surface, colour worn off in the traffic paths, green or black mildew spots, and boards that look dry or start to check and crack.
When we reseal, we don't just paint over the old coat. The deck is cleaned with a low-pressure wash and cleaner that lifts the grey fibres and mildew without furring the wood, left to dry, and then given a penetrating sealer-stain — Ready Seal or Armstrong Clark — that soaks into the wood instead of forming a film. That's why it wears away gradually rather than peeling, and why the next coat goes on easily.
If you're not sure whether your deck needs it this year, email a few photos to frederick@laraspowerwash.com or call (312) 869-4688. The estimate is free, and we'll tell you straight if it can wait another season.