Finally brewed my first batch 10/2/16, Imperial pumpkin stout, 5 gal. extract. OG was 1.074 and supposed to finish at 1.017 but has been stuck at 1.02 since 10/8/16. I used us-05 and was advised I would not need a starter. Temp has been between 70 and 66 degrees. Is it finished?
If you are obtaining consistent specific gravity readings a few days apart then your beer has reached its final gravity. You may want to let the beer 'sit' for a few more days to permit the yeast to 'clean up' after itself before packaging the beer. Cheers!
How did you determine it's supposed to finish at 1.017? If that's just what the recipe said, it may have simply been a guess by the writer, based on some sort of average for the yeast strain. But fermentability of the wort is also a big factor.
A 1.017 is not that far from a 1.020 reading, and that difference can easily be a result of faulty reading of the hydrometer's scale, or you might have slightly less liquid than what the recipe calls for. I didn't do the math, but if a 5-gallon recipe will get you to 1.017, then 4.8 gallons of finished beer (just an estimated number) might be 1.020. @VikeMan has the best advice - the beer is likely finished if you have two gravity readings at 1.020 that were taken a few days apart, so give it a few more days for the yeast to clean up after themselves and then bottle/keg.
