I bought a house one year ago.?

Now i find that there was water leakage and damage on the outside wall which was hidden by the vinyl sidings. The seller did not declare anything in the disclosure nor did the inspector find anything. Is the seller responsible or can they be sued?
You should have gotten a warranty with the sale (usually the seller pays for this as part of his closing costs). Check to see if you bought one and if it is still in effect.

If not, you can sue the previous owner and the inspector (if there was one).
You can only win a suit if YOU can PROVE that the seller knew there was damage, and lied.

Did your agent run a CLUE report before you insured the house, to see if the prior owner had put in any claims?? Like a water damage claim? Any idea how old the siding is? Can a neighbor tell you if the siding was added to deliberately cover up the water damage?

If none of the above, I think you're going to be stuck on this one. . .
Unfortunately, your house, your problem. If you had an agreement/guarentee, you'd be covered, although it doesn't sound like you did. Also, the only thing you could possibly do is sue the inspector, and that's as far as you could 'succesfully' go.

Sorry.
NO SUEING! It's not their fault unless you have proof.
And you bought the house. It's mostly your fault.

Answers:
I would get someone in there so you can determine that it happened before you bought the house. Then go after the seller to fix the damages.
Unless you got some sort of guarantee with your house, I'd say it's not the seller's problem. You've lived there quite awhile now.
Unless you can prove that seller knew about it and didn't tell you, you have no recourse. you hired your own inspector and he didn' t discover it. But you can't go after the inspector either since (I'm sure) somewhere on the report, it says they do not guarantee they saw everything (or something of that nature). So, you can't sue anybody and it is unfortunately your problem. The only thing you can do is to look over your home insurance policy under water damage. Is the damage is due to plumbing, etc. it may be covered by your policy. Good luck.
You can go after the seller, but make sure you have documentation to prove that ownership of the house.

If you live in the state of California, you will want to do your research before you file a claim. A water damage loss could prevent you from getting insurance in the future & create problems if you try to sell the home within a 36 month period.
You can sue anybody for anything; the question is whether you have a shot of winning. You really need a lawyer who knows your state's laws to review all your documentation - particularly the disclosure, inspection report, and leakage and damage report.
nope if it was sold as AS IS i afraid your responsible but thats why hpefully u have insurance
Seller can't be sued anymore