Most houses are expected to settle over time, but foundation sinking of more than a few inches or uneven sinking of more than an inch for every 20 feet is cause for concern. Any significant or uneven sinking should be assessed by a professional to determine the cause and perform any necessary repairs. 

The timeframe is generally a few hours, allowing for immediate use post-hydration, ensuring minimal disruption to surrounding activities.

Concrete leveling is absolutely worth it if you have sunken concrete slabs and want to restore them to level, especially if the slab is part of your home foundation. Concrete leveling is less than half the price of replacing concrete sidewalks, patios, walkways, and pool decks, and it’s about a quarter of the cost of replacing a foundation. If you also treat the underlying problem, it can be a worthwhile and permanent solution.

Polyjacking can be a permanent solution to sunken concrete if you also address the underlying issue—like poor drainage—at the same time. The polyurethane material itself can last as long as or even outlast the concrete you’re lifting it with. Your sunken concrete issue will likely return if you don’t couple polyjacking with proper drainage to prevent future soil movement and sinking.