Have 2 problems
1) @Rogerio said is right, you used "sucess": when the correct way is "success":
But now with jquery you can use the following methods:
- jqXHR.done(function( data, textStatus, jqXHR ) {});
 - An alternative construct to the success callback option, the - .done()method replaces the deprecated- jqXHR.success()method. Refer to- deferred.done()for implementation details.
 
- jqXHR.fail(function( jqXHR, textStatus, errorThrown ) {});
 - An alternative construct to the error callback option, the - .fail()method replaces the deprecated- .error()method. Refer to- deferred.fail()for implementation details.
 
- jqXHR.always(function( data|jqXHR, textStatus, jqXHR|errorThrown ) { });
 - An alternative construct to the complete callback option, the - .always()method replaces the deprecated- .complete()method.
 - In response to a successful request, the function's arguments are the same as those of - .done(): data, textStatus, and the jqXHR object. For failed requests the arguments are the same as those of- .fail(): the jqXHR object, textStatus, and errorThrown. Refer to- deferred.always()for implementation details.
 
- jqXHR.then(function( data, textStatus, jqXHR ) {}, function( jqXHR, textStatus, errorThrown ) {});
 - Incorporates the functionality of the - .done()and- .fail()methods, allowing (as of jQuery 1.8) the underlying Promise to be manipulated. Refer to- deferred.then()for implementation details.
 
Read about in: http://api.jquery.com/jquery.ajax/
A type, you using "npiso="+valorpiso, but this not encoding, prefer use json, like this: { npiso: valorpiso } (Jquery auto encoding data)
2) Don't use repeated IDs in HTML, this repeate ID by results number:
while($dados=mysql_fetch_array($result)){
     echo "<div id='caixa'>";
Use class= instead of id=
First, update Jquery to last version
Javascript:
$.ajax({
    "type": "POST",
    "url": "getpiso.php",
    "data": { "npiso": valorpiso }
}).done(function(data) {
    console.log(data);
    $(".list_caixa").html(data);
}).fail(function(err) {
    console.log("Failed", err);
}).always(function() {
    console.log("complete");
});
"HTML":
 $piso1=$_POST["npiso"];
 $result=mysql_query("select * FROM rooms where floor='$piso1' ");
 while($dados=mysql_fetch_array($result)){
     echo "<div class='list_caixa'>";
     echo "<p>$dados[block].$dados[floor].$dados[room]</p>";
     echo "</div>";
 }