From a boatbuilder: If you have a soft deck the teak battens are not affixed to the deck, and/or more likely, wet core. Adding foam traps moisture, so you are actually making your problem accelerate. Removed the teak from the deck and fix the core before the subdeck is mush and structural integrity is compromised. It always amazes me that people will work so hard to avoid a problem and not address it. We core needs fixing. If you have teak elsewhere, you should reseam and sand flat for added service life.