diff --git a/src/bindings/bind_building.c b/src/bindings/bind_building.c
index 1a220b4e5..97432bfca 100644
--- a/src/bindings/bind_building.c
+++ b/src/bindings/bind_building.c
@@ -170,13 +170,7 @@ static int tolua_building_set_owner(lua_State * L)
 {
   building *b = (building *) tolua_tousertype(L, 1, 0);
   unit *u = (unit *) tolua_tousertype(L, 2, 0);
-  unit *o = b ? building_owner(b) : NULL;
-  if (o && o != u) {
-    freset(o, UFL_OWNER);
-  }
-  if (u) {
-    fset(u, UFL_OWNER);
-  }
+  building_set_owner(b, u);
   return 0;
 }
 
diff --git a/src/gamecode/creport.c b/src/gamecode/creport.c
index 0f37b9685..8c63cd9e3 100644
--- a/src/gamecode/creport.c
+++ b/src/gamecode/creport.c
@@ -1351,24 +1351,26 @@ static void cr_output_region(FILE * F, report_context * ctx, seen_region * sr)
         ru && ru->type == &at_travelunit; ru = ru->next) {
         unit *u = (unit *) ru->data.v;
         if (cansee_durchgezogen(f, r, u, 0) && r != u->region) {
-          if (!u->ship || !fval(u, UFL_OWNER))
-            continue;
-          if (!seeships)
-            fprintf(F, "DURCHSCHIFFUNG\n");
-          seeships = true;
-          fprintf(F, "\"%s\"\n", shipname(u->ship));
+          if (u->ship && ship_owner(u->ship)==u) {
+            if (!seeships) {
+              fprintf(F, "DURCHSCHIFFUNG\n");
+            }
+            seeships = true;
+            fprintf(F, "\"%s\"\n", shipname(u->ship));
+          }
         }
       }
       for (ru = a_find(r->attribs, &at_travelunit);
         ru && ru->type == &at_travelunit; ru = ru->next) {
         unit *u = (unit *) ru->data.v;
         if (cansee_durchgezogen(f, r, u, 0) && r != u->region) {
-          if (u->ship)
-            continue;
-          if (!seeunits)
-            fprintf(F, "DURCHREISE\n");
-          seeunits = true;
-          fprintf(F, "\"%s\"\n", unitname(u));
+          if (!u->ship) {
+            if (!seeunits) {
+              fprintf(F, "DURCHREISE\n");
+            }
+            seeunits = true;
+            fprintf(F, "\"%s\"\n", unitname(u));
+          }
         }
       }
     }
diff --git a/src/gamecode/economy.c b/src/gamecode/economy.c
index 6b99573a8..0deab6870 100644
--- a/src/gamecode/economy.c
+++ b/src/gamecode/economy.c
@@ -1105,51 +1105,6 @@ static boolean maintain(building * b, boolean first)
   return true;
 }
 
-#ifdef COLLAPSE_CHANCE
-static void gebaeude_stuerzt_ein(region * r, building * b)
-{
-  unit *u;
-  int n, i;
-  int opfer = 0;
-  int road = 0;
-  struct message *msg;
-
-  for (u = r->units; u; u = u->next) {
-    if (u->building == b) {
-      int loss = 0;
-
-      fset(u->faction, FFL_MARK);
-      freset(u, UFL_OWNER);
-      leave(r, u);
-      n = u->number;
-#ifdef COLLAPSE_SURVIVAL
-      for (i = 0; i < n; i++) {
-        if (rng_double() >= COLLAPSE_SURVIVAL) {
-          ++loss;
-        }
-      }
-#endif
-      scale_number(u, u->number - loss);
-      opfer += loss;
-    }
-  }
-
-  msg =
-    msg_message("buildingcrash", "region building opfer road", r, b, opfer,
-    road);
-  add_message(&r->msgs, msg);
-  for (u = r->units; u; u = u->next) {
-    faction *f = u->faction;
-    if (fval(f, FFL_MARK)) {
-      freset(u->faction, FFL_MARK);
-      add_message(&f->msgs, msg);
-    }
-  }
-  msg_release(msg);
-  remove_building(&r->buildings, b);
-}
-#endif
-
 void maintain_buildings(region * r, boolean crash)
 {
   building **bp = &r->buildings;
@@ -1159,12 +1114,6 @@ void maintain_buildings(region * r, boolean crash)
 
     /* the second time, send a message */
     if (crash) {
-#ifdef COLLAPSE_CHANCE
-      if (!maintained && (rng_double() < COLLAPSE_CHANCE)) {
-        gebaeude_stuerzt_ein(r, b);
-        continue;
-      }
-#endif
       if (!fval(b, BLD_WORKING)) {
         unit *u = building_owner(b);
         const char *msgtype =
diff --git a/src/gamecode/laws.c b/src/gamecode/laws.c
index 8d1c4b229..61e0989df 100644
--- a/src/gamecode/laws.c
+++ b/src/gamecode/laws.c
@@ -1203,7 +1203,7 @@ static void nmr_death(faction * f)
   if (rule) {
     unit *u;
     for (u = f->units; u; u = u->nextF) {
-      if (u->building && fval(u, UFL_OWNER)) {
+      if (u->building && building_owner(u->building)==u) {
         remove_building(&u->region->buildings, u->building);
       }
     }
@@ -1526,7 +1526,6 @@ static cmp_building_cb get_cmp_region_owner(void)
 
 static int display_cmd(unit * u, struct order *ord)
 {
-  building *b = u->building;
   char **s = NULL;
   const char *str;
   region *r = u->region;
@@ -1538,19 +1537,19 @@ static int display_cmd(unit * u, struct order *ord)
   switch (findparam_ex(str, u->faction->locale)) {
   case P_BUILDING:
   case P_GEBAEUDE:
-    if (!b) {
+    if (!u->building) {
       cmistake(u, ord, 145, MSG_PRODUCE);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (building_owner(u->building)!=u) {
       cmistake(u, ord, 5, MSG_PRODUCE);
       break;
     }
-    if (!fval(b->type, BTF_NAMECHANGE) && b->display && b->display[0] != 0) {
+    if (!fval(u->building->type, BTF_NAMECHANGE) && u->building->display && u->building->display[0]) {
       cmistake(u, ord, 278, MSG_EVENT);
       break;
     }
-    s = &b->display;
+    s = &u->building->display;
     break;
 
   case P_SHIP:
@@ -1558,7 +1557,7 @@ static int display_cmd(unit * u, struct order *ord)
       cmistake(u, ord, 144, MSG_PRODUCE);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (ship_owner(u->ship)!=u) {
       cmistake(u, ord, 12, MSG_PRODUCE);
       break;
     }
@@ -1581,15 +1580,15 @@ static int display_cmd(unit * u, struct order *ord)
     break;
 
   case P_REGION:
-    if (!b) {
+    if (!u->building) {
       cmistake(u, ord, 145, MSG_EVENT);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (building_owner(u->building)!=u) {
       cmistake(u, ord, 148, MSG_EVENT);
       break;
     }
-    if (b != largestbuilding(r, get_cmp_region_owner(), false)) {
+    if (u->building != largestbuilding(r, get_cmp_region_owner(), false)) {
       cmistake(u, ord, 147, MSG_EVENT);
       break;
     }
@@ -1682,7 +1681,7 @@ rename_building(unit * u, order * ord, building * b, const char *name)
       }
     }
   } else {
-    if (!fval(u, UFL_OWNER)) {
+    if (owner!=u) {
       cmistake(u, ord, 148, MSG_PRODUCE);
       return -1;
     }
@@ -1814,7 +1813,7 @@ static int name_cmd(unit * u, struct order *ord)
         cmistake(u, ord, 144, MSG_PRODUCE);
         break;
       }
-      if (!fval(u, UFL_OWNER)) {
+      if (ship_owner(u->ship)!=u) {
         cmistake(u, ord, 12, MSG_PRODUCE);
         break;
       }
@@ -1857,7 +1856,7 @@ static int name_cmd(unit * u, struct order *ord)
       cmistake(u, ord, 145, MSG_EVENT);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (building_owner(b)!=u) {
       cmistake(u, ord, 148, MSG_EVENT);
       break;
     }
@@ -2881,7 +2880,9 @@ static void reorder(void)
               cmistake(u, ord, 258, MSG_EVENT);
             } else if (v->building != u->building || v->ship != u->ship) {
               cmistake(u, ord, 259, MSG_EVENT);
-            } else if (fval(u, UFL_OWNER)) {
+            } else if (u->building && building_owner(u->building)==u) {
+              cmistake(u, ord, 260, MSG_EVENT);
+            } else if (u->ship && ship_owner(u->ship)==u) {
               cmistake(u, ord, 260, MSG_EVENT);
             } else if (v == u) {
               cmistake(u, ord, 10, MSG_EVENT);
@@ -2895,7 +2896,9 @@ static void reorder(void)
                 sorted = true;
                 break;
               case P_BEFORE:
-                if (fval(v, UFL_OWNER)) {
+                if (v->ship && ship_owner(v->ship)==v) {
+                  cmistake(v, ord, 261, MSG_EVENT);
+                } else if (v->building && building_owner(v->building)==v) {
                   cmistake(v, ord, 261, MSG_EVENT);
                 } else {
                   unit **vp = &r->units;
@@ -2990,7 +2993,7 @@ static int renumber_cmd(unit * u, order * ord)
       cmistake(u, ord, 116, MSG_EVENT);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (ship_owner(u->ship)!=u) {
       cmistake(u, ord, 146, MSG_EVENT);
       break;
     }
@@ -3018,7 +3021,7 @@ static int renumber_cmd(unit * u, order * ord)
       cmistake(u, ord, 145, MSG_EVENT);
       break;
     }
-    if (!fval(u, UFL_OWNER)) {
+    if (building_owner(u->building)!=u) {
       cmistake(u, ord, 148, MSG_EVENT);
       break;
     }
@@ -4068,12 +4071,6 @@ static void maintain_buildings_1(region * r)
   maintain_buildings(r, false);
 }
 
-#ifdef COLLAPSE_CHANCE
-static void maintain_buildings_2(region * r)
-{
-  maintain_buildings(r, true);
-}
-#endif
 static void reset_moved(unit * u)
 {
   freset(u, UFL_MOVED);
@@ -4246,11 +4243,6 @@ void init_processor(void)
   }
   add_proc_global(p, &demographics, "Nahrung, Seuchen, Wachstum, Wanderung");
 
-#ifdef COLLAPSE_CHANCE
-  p += 10;
-  add_proc_region(p, &maintain_buildings_2, "Gebaeudeunterhalt (2. Versuch)");
-#endif
-
   if (!global.disabled[K_SORT]) {
     p += 10;
     add_proc_global(p, &reorder, "Einheiten sortieren");
diff --git a/src/gamecode/laws_test.c b/src/gamecode/laws_test.c
index e8fbd1895..fce2fa060 100644
--- a/src/gamecode/laws_test.c
+++ b/src/gamecode/laws_test.c
@@ -54,7 +54,6 @@ static void test_rename_building(CuTest * tc)
   f = test_create_faction(rc_find("human"));
   u = test_create_unit(f, r);
   u_set_building(u, b);
-  fset(u, UFL_OWNER);
 
   rename_building(u, NULL, b, "Villa Nagel");
   CuAssertStrEquals(tc, "Villa Nagel", b->name);
diff --git a/src/gamecode/report.c b/src/gamecode/report.c
index 79d2c8e54..e08b198d5 100644
--- a/src/gamecode/report.c
+++ b/src/gamecode/report.c
@@ -1382,7 +1382,7 @@ static void durchreisende(FILE * F, const region * r, const faction * f)
     for (a = abegin; a && a->type == &at_travelunit; a = a->next) {
       unit *u = (unit *) a->data.v;
 
-      if (r != u->region && (u->ship == NULL || fval(u, UFL_OWNER))) {
+      if (r != u->region && (!u->ship || ship_owner(u->ship)==u)) {
         if (cansee_durchgezogen(f, r, u, 0)) {
           ++maxtravel;
         }
@@ -1399,7 +1399,7 @@ static void durchreisende(FILE * F, const region * r, const faction * f)
     for (a = abegin; a && a->type == &at_travelunit; a = a->next) {
       unit *u = (unit *) a->data.v;
 
-      if (r != u->region && (u->ship == NULL || fval(u, UFL_OWNER))) {
+      if (r != u->region && (!u->ship || ship_owner(u->ship)==u)) {
         if (cansee_durchgezogen(f, r, u, 0)) {
           ++counter;
           if (u->ship != NULL) {
@@ -1565,7 +1565,7 @@ report_template(const char *filename, report_context * ctx, const char *charset)
           unitid(u), u->name, u->number, get_money(u));
         if (wrptr(&bufp, &size, bytes) != 0)
           WARN_STATIC_BUFFER();
-        if (u->building != NULL && fval(u, UFL_OWNER)) {
+        if (u->building && building_owner(u->building)==u) {
           building *b = u->building;
           int cost = buildingmaintenance(b, r_silver);
 
@@ -1578,7 +1578,7 @@ report_template(const char *filename, report_context * ctx, const char *charset)
               WARN_STATIC_BUFFER();
           }
         } else if (u->ship) {
-          if (fval(u, UFL_OWNER)) {
+          if (ship_owner(u->ship)==u) {
             bytes = (int)strlcpy(bufp, ",S", size);
           } else {
             bytes = (int)strlcpy(bufp, ",s", size);
diff --git a/src/kernel/build.c b/src/kernel/build.c
index 4804c7d1c..e718ff5b2 100644
--- a/src/kernel/build.c
+++ b/src/kernel/build.c
@@ -376,7 +376,6 @@ int destroy_cmd(unit * u, struct order *ord)
       /* all units leave the building */
       for (u2 = r->units; u2; u2 = u2->next) {
         if (u2->building == b) {
-          freset(u2, UFL_OWNER);
           leave_building(u2);
         }
       }
diff --git a/src/kernel/config.h b/src/kernel/config.h
index 30145886d..510678c27 100644
--- a/src/kernel/config.h
+++ b/src/kernel/config.h
@@ -68,13 +68,6 @@ extern "C" {
 /* Chance of a monster attack */
 #define MONSTERATTACK  0.4F
 
-/** Chance of an unmaintained building crashing */
-/* #define COLLAPSE_CHANCE 0.4F */
-#undef COLLAPSE_CHANCE
-/** chance to survive the crash of a building */
-/* #define COLLAPSE_SURVIVAL 0.5F */
-#undef COLLAPSE_SURVIVAL
-
 /* Bewegungsweiten: */
 #define BP_WALKING 4
 #define BP_RIDING  6
diff --git a/src/kernel/move.c b/src/kernel/move.c
index f0d484650..d6600e05d 100644
--- a/src/kernel/move.c
+++ b/src/kernel/move.c
@@ -2597,13 +2597,13 @@ void movement(void)
             set_order(&u->thisorder, NULL);
           } else {
             if (ships) {
-              if (u->ship && fval(u, UFL_OWNER)) {
+              if (u->ship && ship_owner(u->ship)==u) {
                 init_tokens(u->thisorder);
                 skip_token();
                 move(u, false);
               }
             } else {
-              if (u->ship == NULL || !fval(u, UFL_OWNER)) {
+              if (!u->ship || ship_owner(u->ship)!=u) {
                 init_tokens(u->thisorder);
                 skip_token();
                 move(u, false);
diff --git a/src/kernel/unit.c b/src/kernel/unit.c
index 3b1fdcf3b..f4dd38596 100644
--- a/src/kernel/unit.c
+++ b/src/kernel/unit.c
@@ -795,32 +795,21 @@ void u_set_ship(unit * u, ship * sh)
 void leave_ship(unit * u)
 {
   struct ship *sh = u->ship;
-  if (!sh) return;
+
   u->ship = 0;
+  if (sh->_owner==u) {
+    sh->_owner = ship_owner(sh);
+  }
   set_leftship(u, sh);
 }
 
 void leave_building(unit * u)
 {
-  struct building *b = u->building;
+  building * b = u->building;
 
-  u->building = NULL;
-  if (b && fval(u, UFL_OWNER)) {
-    unit *u2, *owner = NULL;
-    freset(u, UFL_OWNER);
-
-    for (u2 = u->region->units; u2; u2 = u2->next) {
-      if (u2->building == b) {
-        if (u2->faction == u->faction) {
-          owner = u2;
-          break;
-        } else if (owner == NULL)
-          owner = u2;
-      }
-    }
-    if (owner != NULL) {
-      fset(owner, UFL_OWNER);
-    }
+  u->building = 0;
+  if (b->_owner==u) {
+    b->_owner = building_owner(b);
   }
 }