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. 

It’s best not to perform mudjacking in the winter unless the ground temperature remains above freezing. Freezing temperatures can cause the slurry to harden too quickly, compromising its strength and longevity. Concrete is also more susceptible to cracking and splitting in cold temperatures, so there’s a higher risk of damaging the slab during the drilling and lifting process in winter.

Polyjacking and mudjacking can both be effective solutions for sinking concrete, but they have key differences. Polyjacking, which uses expanding polyurethane foam, is often considered a better option because the foam is significantly lighter than the cementitious material used for mudjacking. This reduced weight puts less pressure on the underlying soil and lowers the risk of future sinking. Polyjacking is suitable for any sinking concrete slab, while mudjacking is typically only recommended for non-structural concrete, such as sidewalks, patios, pool decks, and driveways. The primary drawback of polyjacking is its cost, which can be up to four times higher than mudjacking—as much as $25 per square foot compared to a maximum of about $6 per square foot for mudjacking.

On average, a mudjacking repair lasts between five and 10 years, though it can sometimes last for well beyond a decade under ideal conditions. Its longevity depends heavily on several factors, including the condition of the underlying soil, environmental conditions like freeze/thaw cycles and erosion, and whether the root cause of the sinking, such as drainage issues, is resolved. Because it doesn't always fix the underlying problem of loose soil, mudjacking is often considered a temporary solution. Proper maintenance and evaluation can help extend its lifespan.