diff --git a/attributs.py b/attributs.py
index 5113767..492b9bd 100644
--- a/attributs.py
+++ b/attributs.py
@@ -410,6 +410,18 @@ class intAttr(Attr):
 
     python_type = int
 
+    def __add__(self, obj):
+        if isinstance(obj, self.__class__):
+            return self.value.__add__(obj.value)
+        else:
+            return self.value.__add__(obj)
+
+    def __sub__(self, obj):
+        if isinstance(obj, self.__class__):
+            return self.value.__sub__(obj.value)
+        else:
+            return self.value.__sub__(obj)
+
     def parse_value(self, val):
         if self.python_type(val) < 0:
             raise ValueError("Valeur entière invalide : %r" % val)
@@ -418,6 +430,28 @@ class intAttr(Attr):
     def __unicode__(self):
         return unicode(self.value)
 
+class floatAttr(Attr):
+
+    python_type = float
+
+    def __add__(self, obj):
+        if isinstance(obj, self.__class__):
+            return self.value.__add__(obj.value)
+        else:
+            return self.value.__add__(obj)
+
+    def __sub__(self, obj):
+        if isinstance(obj, self.__class__):
+            return self.value.__sub__(obj.value)
+        else:
+            return self.value.__sub__(obj)
+
+    def parse_value(self, val):
+        self.value = self.python_type(val)
+
+    def __unicode__(self):
+        return unicode(self.value)
+
 class boolAttr(Attr):
 
     python_type = bool
@@ -815,7 +849,7 @@ class droits(Attr):
         return self.value in modifiables and super(droits, self).is_modifiable(liste_droits)
 
 @crans_attribute
-class solde(Attr):
+class solde(floatAttr):
     python_type = float
     singlevalue = True
     concurent = False