These are pictures of decks inspected by my company, Magpie Property Inspections of homes in Parker Colorado and Castle Rock Colorado. The first two photos were taken of a deck which has deteriorated to the point that walking on it caused the decking to break exposing the joists underneath. As you can see, the joists and framing members supporting the deck are all rotted and in poor condition. This deck should be removed and replaced. The deck is almost 30 years old and appears to have incurred so much repeated moisture exposure without needed maintenance it is literally falling apart.
The last two photos were taken of a cantilevered deck in similar condition. Cantilever decks are often not supported with posts at the end, and are attached to the joists or beams inside the structure, protruding openly. These decks need to be maintained and monitored carefully as they can become very hazardous when they deteriorate to the condition we have found here. We recommend having vertical supports installed on all decks where possible to help provide stable support as the materials wear. With the weight of people and property added, this deck could collapse and cause injury. It should be replaced just like the other deck pictured.
Decks are great additions to a home, but they are also an area of mandatory maintenance to prevent situations like this from occurring. They should be inspected from on top and underneath several times a year. Look for dark discoloration, splitting members, loose hangers and connections and materials with a generally weathered appearance. If your deck is several years old, it is a good idea to have a professional take a look to make sure it is still safe.