When installing a tub with surround such as this one 

should one caulk the joint between the surround and the tub?

I've always seen it caulked, but a plumber told me that doing so is actually counterproductive and encourages mold growth. He said that the surround overlaps the tub flange, so caulk is not needed.

What say you?

What does the manufacturer of the surround say about caulking?  I put in a replacement tub and surround about two years ago and the instructions were VERY specific on where to caulk versus where to leave room for water to drain out of the system.  

when i did a similar install, i planned to put sili mostly behind the surround but ended up putting at angel between surround & tub cuz the surround was so flimsy and sili helped filled the uneven gap

@Rob Myers   that is the problem. I don't have the installation instructions. I'm just cleaning up what's already there. When we buy a house with this type of surround, invariably we find nasty, dirty, moldy caulk in that joint, usually globbed on by a homeowner who thought he knew what he was doing.

@Sylvia B.   Is there a channel at the bottom of the side with drainage holes? From what I can see in the picture this does not seem to be the case.  So going with the presumption that there is no channel you run a bead of caulk along the joint. Then smooth it out so there are no bumps.

I would use GE II 100% Silicone (White or Clear). A simple painters caulk or window / door caulk is not sufficient for any thing in a bathroom. For those who are using caulk and not silicone, this is why you have mold growth in the first place. Silicone will not have that problem and the seal will last 6 months - 12 months. 

Originally posted by @Sylvia B. :

@Rob Myers   that is the problem. I don't have the installation instructions. I'm just cleaning up what's already there. When we buy a house with this type of surround, invariably we find nasty, dirty, moldy caulk in that joint, usually globbed on by a homeowner who thought he knew what he was doing.

 When it comes to the quality surrounds which there aren't many out there, the instructions always say not to caulk the seams. The crappy ones almost always say to caulk the seams. If you don't know the manufacturer you can flip a coin or err on the side of caution and caulk the seam. 

The advantage and the reason the higher quality surrounds don't need the seams caulked is caulk is not a permanent material, so any caulking of anything is temporary and needs to be maintained over time, caulk also attracts mold and mildew, once you caulk it you are committed to caulking it again and again. So the quality surrounds have designed a better product that doesn't require the achilles heel of caulking. Caulking the one you have won't ruin it or hurt it, but you're now committed to re-caulking it forever.

@Neil Schoepp    - I was unclear. The photo is just an example to illustrate the type of surround, not mine.

@Sean Pincus   - Yes, 100% silicone caulk is what you use in the tub, I just assumed everyone knew that. But silicone doesn't stop mold growth, and there's no way I'm going to recaulk a tub every 6 months. If you do, more power to you.

@Mike F.   So if we acquire a tub that is already caulked we can't just remove all the caulk and leave it off?

If you are going to sell I suggest that you use a tile with an eyebrow this is a great selling point it should be about $300.  If you are going to keep and rent just clean the calk out and leave it as is.  This is a simple clean attractive one for the customer.

I've always felt the overlap was sufficient. With the surround being so lightweight there is nothing to keep it from flexing constantly. I don't think even the best caulk/silicone would stand up to the flexing. Once you get the first gap in the caulk/silicone then you are allowing water in that can't get back out. Trapped water and dark space = a mold breeding ground.

Originally posted by @Sylvia B. :

@Mike F.  So if we acquire a tub that is already caulked we can't just remove all the caulk and leave it off?

 If you can verify that the surround is a unit that doesn't require caulking.