[jeffy]

Your attenuation has less to do with your yeast than your recipe and procedure. You can use a super attenuative yeast but if your grain bill is heavy on the un-fermentables you will not get the same attenuation as you would if your recipe had no crystal and lots of cane sugar. The attenuation numbers on the yeast are a general guidline but not terribly accurate to the real world. So in a situation with under attenuation you could be looking at lots of causes

poor yeast health due to low aeration, underpitching, old yeast, ferm temp etc
poor fermentability of wort due to high mash temp, lots of old or dark extract, lots of crystal malts, poor conversion etc.

Speaking from experience if you have a beer that has stalled out at 1.040 and rousing the yeast didn't help it is unlikely that adding a new yeast will do anything. you are left with a few options

drink it as is
blend it with another, very attenuated beer
throw it out and start over
add bean-o  and then throw it out and start over.

You forgot add brett and wait.  That's what I did with the one I had last year.  I missed my strike temp way too high and probably destroyed all the enzymes in the time it took to cool the mash.  Strong Scotch ale that finished at 1.040.  Pitched brett b and had a pelicle soon after.

[morticaixavier]

good call, another option.

[Joe Sr.]

What would you do if your gravity readings were >10% under-attenuated? Bottle and accept a sweeter beer? Leave it alone longer? Add more yeast? Stir yeast cake? Cross post in every forum?

I suppose all could be viable answers, I'm just looking for a consensus as to what most of you do in this situation.

Rousing the yeast was a good idea.  You can also try to warm up the fermenter at the same time.

I've only encountered this with Belgian Saison yeast, which I find to be a real PITA to use but will probably use again, and have found that patience, lots and lots of patience, is required.  I have lots of overcarbed bottles of saison due to not being patient enough after rousing the yeast, warming the carboy and waiting.  The gravity dropped a little bit, but it seemed to be stalled.  Apparently not.

Luckily, I used champagne bottles so I have not had any explosions.  But the corks come flying out.  Which can be dangerous in itself.

[Will's Swill]

I've had two stall out recently, neither of which responded to rousing the yeast.  One of them I tried raising the temp up pretty high without getting any additional gravity drop.  In both cases I pitched a small starter at high krausen and got the FG down close to where I wanted it.  YMMV.

[SpanishCastleAle]

This is exactly why I only check it twice and the second one is caught as I'm racking to the keg.  The rare stuck fermentations I've had did not respond to rousing, raising the temp, adding yeast energizer (usually a combination of all three).  Since the yeast were obviously not up to the task I figure it's best to get it off the stressed yeast.  So ime, usually once the original pitch of yeast has stopped, it's done, it ain't going any further and racking is the next step.

As for what to do when a fermentation is stuck, ime the best methods to fix it are (in order):
Rack it onto the yeast cake of a 'good' fermentation (or add the cake to the keg).  Do not aerate.
Add properly hydrated dry yeast.  Dry yeast doesn't need O2 so you don't have to worry about the fact that you don't aerate (which you definitely don't want to do at that point).
Krausen it.

After any of these had run their course I would then do closed keg-to-keg transfer.

[bluesman]

More than often twice. Before fermentation (OG) and just before racking (FG). I like to use the airlock as an indicator of the fermentation process, so when the airlock activity subsides (typically 1-2 weeks for ales/2-3 weeks for lagers), I'll take a gravity reading and proceed to racking if it's wher I think it should be based on the recipe and the yeast. It comes with experience. The more beer you brew, the better your instincts.

[beersk]

I wait until at least a week, often 2, then check it.  And if you can't take a gravity reading without contaminating your beer, perhaps you should consider taking up knitting for a hobby! 

Man, you don't give knitting enough credit!  That sh*t's hard!

I take a reading when the krausen falls and before I keg.

[denny]

I wait until at least a week, often 2, then check it.  And if you can't take a gravity reading without contaminating your beer, perhaps you should consider taking up knitting for a hobby! 

Man, you don't give knitting enough credit!  That sh*t's hard!

I'm all too aware of that...I learned to knit when I was in 2nd grade.  I remember my Dad's horror when some of my friends came over to get me to go out and play football with them and I told then I'd be there as soon as I finished the row I was on!

[dbeechum]

Your momma had you done up in one of those boy's dresses didn't she. Don't fret! Those were popular when you were born around the turn of the century!

[tschmidlin]

Your momma had you done up in one of those boy's dresses didn't she. Don't fret! Those were popular when you were born around the turn of the century!

Denny's baby picture is a daguerreotype.

[denny]

Your momma had you done up in one of those boy's dresses didn't she. Don't fret! Those were popular when you were born around the turn of the century!

Denny's baby picture is a daguerreotype.

Wrong...it's a cave painting!

[cenosillica]

I ahh... don't know what to say... Perhaps I'm getting more information than I bargained for?

[oscarvan]

I wait until at least a week, often 2, then check it.  And if you can't take a gravity reading without contaminating your beer, perhaps you should consider taking up knitting for a hobby!  

Man, you don't give knitting enough credit!  That sh*t's hard!

I'm all too aware of that...I learned to knit when I was in 2nd grade.  I remember my Dad's horror when some of my friends came over to get me to go out and play football with them and I told then I'd be there as soon as I finished the row I was on!

Montessori School? Same here..... knitting, embroidery, crochet..... To all the testosterone knights..... buzz off. I can still pull out a needle and thread and make happen what I need to happen. And as far as a bunch of guys chasing a ball.....get your own ball. OK, back to "carbonation checks".....

[pyrite]

Your attenuation has less to do with your yeast than your recipe and procedure. You can use a super attenuative yeast but if your grain bill is heavy on the un-fermentables you will not get the same attenuation as you would if your recipe had no crystal and lots of cane sugar. The attenuation numbers on the yeast are a general guidline but not terribly accurate to the real world. So in a situation with under attenuation you could be looking at lots of causes

poor yeast health due to low aeration, underpitching, old yeast, ferm temp etc
poor fermentability of wort due to high mash temp, lots of old or dark extract, lots of crystal malts, poor conversion etc.

Speaking from experience if you have a beer that has stalled out at 1.040 and rousing the yeast didn't help it is unlikely that adding a new yeast will do anything. you are left with a few options

drink it as is
blend it with another, very attenuated beer
throw it out and start over
add bean-o   and then throw it out and start over.

You forgot add brett and wait.  That's what I did with the one I had last year.  I missed my strike temp way too high and probably destroyed all the enzymes in the time it took to cool the mash.  Strong Scotch ale that finished at 1.040.  Pitched brett b and had a pelicle soon after.

I had a similar issue when I over shot my mash temps when I was tinkering with decoction mashing.

I brewed 5gallons of a dopple bock @ 7% a month ago, and the FG read 1.022 which is a bit high for my taste.  I first thought about adding some brett but then thought it wouldn't fit the style.  If it were a Scotch ale or some other ale I might give it a go but it's a lager.  So instead, I'm going to blend it with a lager fermented with the same German Bock Lager yeast that reached a FG of 1.012.  I think this will fix the problem, by just waiting another month until the next lager batch is done and then I'll  blend the two batches.  

[denny]

Montessori School? Same here..... knitting, embroidery, crochet..... To all the testosterone knights..... buzz off. I can still pull out a needle and thread and make happen what I need to happen. And as far as a bunch of guys chasing a ball.....get your own ball. OK, back to "carbonation checks".....

I don't know if Montessori had even thought of a school when I was in school in IA in the 50s/60s.  There sure as heck weren't any around where I lived at any rate,