diff --git a/scripts/tests/production.lua b/scripts/tests/production.lua
index 8727762d1..c8a299676 100644
--- a/scripts/tests/production.lua
+++ b/scripts/tests/production.lua
@@ -27,7 +27,7 @@ function test_laen_needs_mine()
     turn_process()
     assert_equal(0, u:get_item('laen'))
     assert_equal(100, r:get_resource('laen'))
-    assert_equal(1, f:count_msg_type("error104")) -- requires building
+    assert_equal(1, f:count_msg_type("building_needed")) -- requires building
 
     u.building = building.create(u.region, "mine")
     u.building.working = true
diff --git a/src/economy.c b/src/economy.c
index 48653d0aa..5f62527ea 100644
--- a/src/economy.c
+++ b/src/economy.c
@@ -814,6 +814,7 @@ static struct message * get_modifiers(unit *u, skill_t sk, const resource_type *
     int skill = 0;
     int need_race = 0, need_bldg = 0;
     resource_mod *mod;
+    const struct building_type *btype_needed = NULL;
 
     if (btype && btype->modifiers) {
         for (mod = btype->modifiers; mod && mod->type != RMT_END; ++mod) {
@@ -838,7 +839,9 @@ static struct message * get_modifiers(unit *u, skill_t sk, const resource_type *
                     break;
                 case RMT_PROD_REQUIRE:
                     if (mod->race) need_race |= 1;
-                    if (mod->btype) need_bldg |= 1;
+                    if (mod->btype) {
+                        need_bldg |= 1;
+                    }
                     break;
                 default:
                     /* is not a production modifier, ignore it */
@@ -848,14 +851,17 @@ static struct message * get_modifiers(unit *u, skill_t sk, const resource_type *
         }
         if (mod->type == RMT_PROD_REQUIRE) {
             if (mod->race) need_race |= 2;
-            if (mod->btype) need_bldg |= 2;
+            if (mod->btype) {
+                btype_needed = mod->btype;
+                need_bldg |= 2;
+            }
         }
     }
     if (need_race == 2) {
         return msg_error(u, u->thisorder, 117);
     }
-    if (need_bldg == 2) {
-        return msg_error(u, u->thisorder, 104);
+    if (btype_needed && need_bldg == 2) {
+        return msg_feedback(u, u->thisorder, "building_needed", "building", btype_needed->_name);
     }
     *skillp = skill;
     if (savep) *savep = frac_make(save_n, save_d);
@@ -885,11 +891,6 @@ static void manufacture(unit * u, const item_type * itype, int want)
         ADDMSG(&u->faction->msgs,
             msg_feedback(u, u->thisorder, "skill_needed", "skill", sk));
         return;
-    case EBUILDINGREQ:
-        ADDMSG(&u->faction->msgs,
-            msg_feedback(u, u->thisorder, "building_needed", "building",
-                itype->construction->extra.btype->_name));
-        return;
     case ELOWSKILL:
         ADDMSG(&u->faction->msgs,
             msg_feedback(u, u->thisorder, "manufacture_skills",
@@ -1236,11 +1237,6 @@ static void create_potion(unit * u, const potion_type * ptype, int want)
         /* no skill, or not enough skill points to build */
         cmistake(u, u->thisorder, 50, MSG_PRODUCE);
         break;
-    case EBUILDINGREQ:
-        ADDMSG(&u->faction->msgs,
-            msg_feedback(u, u->thisorder, "building_needed", "building",
-                ptype->itype->construction->extra.btype->_name));
-        break;
     case ECOMPLETE:
         assert(0);
         break;
diff --git a/src/economy.test.c b/src/economy.test.c
index 842db45f8..802610880 100644
--- a/src/economy.test.c
+++ b/src/economy.test.c
@@ -527,7 +527,7 @@ static void test_modify_production(CuTest *tc) {
     test_clear_messages(u->faction);
     make_item(u, itype, 10);
     CuAssertIntEquals(tc, 28, get_item(u, itype));
-    CuAssertPtrNotNull(tc, test_find_messagetype(u->faction->msgs, "error104"));
+    CuAssertPtrNotNull(tc, test_find_messagetype(u->faction->msgs, "building_needed"));
 
     rtype->modifiers[0].type = RMT_PROD_REQUIRE;
     rtype->modifiers[0].race = test_create_race("smurf");
diff --git a/src/kernel/build.c b/src/kernel/build.c
index 36d72b109..57c172905 100644
--- a/src/kernel/build.c
+++ b/src/kernel/build.c
@@ -513,17 +513,6 @@ int build(unit * u, const construction * ctype, int completed, int want, int ski
         return ENOMATERIALS;
     if (con->improvement == NULL && completed == con->maxsize)
         return ECOMPLETE;
-    if (con->type==CONS_ITEM && con->extra.btype) {
-        building *b;
-        if (!u->building || u->building->type != con->extra.btype) {
-            return EBUILDINGREQ;
-        }
-        b = inside_building(u);
-        if (!b || !building_is_active(b)) {
-            return EBUILDINGREQ;
-        }
-    }
-
     if (con->skill != NOSKILL) {
         int effsk;
         int dm = get_effect(u, oldpotiontype[P_DOMORE]);
diff --git a/src/kernel/build.h b/src/kernel/build.h
index 39916365a..c201d900b 100644
--- a/src/kernel/build.h
+++ b/src/kernel/build.h
@@ -52,13 +52,8 @@ extern "C" {
         int reqsize;                /* size of object using up 1 set of requirement. */
         requirement *materials;     /* material req'd to build one object */
 
-        union {
-            /* CONS_BUILDING: */
-            char * name; /* building level name */
-            /* CONS_ITEM: */
-            const struct building_type *btype; /* building required to build item */
-        } extra;
-
+        /* only used by CONS_BUILDING: */
+        char * name; /* building level name */
         struct construction *improvement;
         /* next level, if upgradable. */
     } construction;
@@ -89,7 +84,6 @@ extern "C" {
 #define ENEEDSKILL -2
 #define ECOMPLETE -3
 #define ENOMATERIALS -4
-#define EBUILDINGREQ -5
 
 #ifdef __cplusplus
 }
diff --git a/src/kernel/build.test.c b/src/kernel/build.test.c
index c3fa07e65..8cd408b09 100644
--- a/src/kernel/build.test.c
+++ b/src/kernel/build.test.c
@@ -71,29 +71,6 @@ static void test_build_requires_materials(CuTest *tc) {
     teardown_build(&bf);
 }
 
-static void test_build_requires_building(CuTest *tc) {
-    build_fixture bf = { 0 };
-    unit *u;
-    const struct resource_type *rtype;
-    building_type *btype;
-
-    u = setup_build(&bf);
-    rtype = bf.cons.materials[0].rtype;
-    i_change(&u->items, rtype->itype, 1);
-    set_level(u, SK_ARMORER, 2);
-    bf.cons.type = CONS_ITEM;
-    bf.cons.extra.btype = btype = bt_get_or_create("hodor");
-    btype->maxcapacity = 1;
-    btype->capacity = 1;
-    CuAssertIntEquals_Msg(tc, "must be inside a production building", EBUILDINGREQ, build(u, &bf.cons, 0, 1, 0));
-    u->building = test_create_building(u->region, btype);
-    fset(u->building, BLD_MAINTAINED);
-    CuAssertIntEquals(tc, 1, build(u, &bf.cons, 0, 1, 0));
-    btype->maxcapacity = 0;
-    CuAssertIntEquals_Msg(tc, "cannot build when production building capacity exceeded", EBUILDINGREQ, build(u, &bf.cons, 0, 1, 0));
-    teardown_build(&bf);
-}
-
 static void test_build_failure_missing_skill(CuTest *tc) {
     build_fixture bf = { 0 };
     unit *u;
@@ -411,7 +388,6 @@ CuSuite *get_build_suite(void)
     SUITE_ADD_TEST(suite, test_build_failure_low_skill);
     SUITE_ADD_TEST(suite, test_build_failure_missing_skill);
     SUITE_ADD_TEST(suite, test_build_requires_materials);
-    SUITE_ADD_TEST(suite, test_build_requires_building);
     SUITE_ADD_TEST(suite, test_build_failure_completed);
     SUITE_ADD_TEST(suite, test_build_with_ring);
     SUITE_ADD_TEST(suite, test_build_with_potion);
diff --git a/src/kernel/building.c b/src/kernel/building.c
index bb97f57b8..31c4b3e27 100644
--- a/src/kernel/building.c
+++ b/src/kernel/building.c
@@ -41,11 +41,12 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include <util/gamedata.h>
 #include <util/language.h>
 #include <util/log.h>
-#include <selist.h>
 #include <util/resolve.h>
 #include <util/umlaut.h>
 
 #include <storage.h>
+#include <selist.h>
+#include <critbit.h>
 
 /* libc includes */
 #include <assert.h>
@@ -62,21 +63,22 @@ typedef struct building_typelist {
 } building_typelist;
 
 selist *buildingtypes = NULL;
+static critbit_tree cb_bldgtypes;
 
 /* Returns a building type for the (internal) name */
 static building_type *bt_find_i(const char *name)
 {
-    selist *ql;
-    int qi;
+    const char *match;
+    building_type *btype = NULL;
 
-    assert(name);
-
-    for (qi = 0, ql = buildingtypes; ql; selist_advance(&ql, &qi, 1)) {
-        building_type *btype = (building_type *)selist_get(ql, qi);
-        if (strcmp(btype->_name, name) == 0)
-            return btype;
+    match = cb_find_str(&cb_bldgtypes, name);
+    if (match) {
+        cb_get_kv(match, &btype, sizeof(btype));
     }
-    return NULL;
+    else {
+        log_warning("st_find: could not find ship '%s'\n", name);
+    }
+    return btype;
 }
 
 const building_type *bt_find(const char *name)
@@ -96,9 +98,15 @@ bool bt_changed(int *cache)
     return false;
 }
 
-void bt_register(building_type * type)
+static void bt_register(building_type * btype)
 {
-    selist_push(&buildingtypes, (void *)type);
+    size_t len;
+    char data[64];
+
+    selist_push(&buildingtypes, (void *)btype);
+    len = cb_new_kv(btype->_name, strlen(btype->_name), &btype, sizeof(btype), data);
+    assert(len <= sizeof(data));
+    cb_insert(&cb_bldgtypes, data, len);
     ++bt_changes;
 }
 
@@ -111,6 +119,7 @@ static void free_buildingtype(void *ptr) {
 }
 
 void free_buildingtypes(void) {
+    cb_clear(&cb_bldgtypes);
     selist_foreach(buildingtypes, free_buildingtype);
     selist_free(buildingtypes);
     buildingtypes = 0;
@@ -190,14 +199,14 @@ const char *buildingtype(const building_type * btype, const building * b, int bs
     if (btype->name) {
         return btype->name(btype, b, bsize);
     }
-    if (btype->construction && btype->construction->extra.name) {
+    if (btype->construction && btype->construction->name) {
         if (b) {
             bsize = adjust_size(b, bsize);
         }
         for (con = btype->construction; con; con = con->improvement) {
             bsize -= con->maxsize;
             if (!con->improvement || bsize <0) {
-                return con->extra.name;
+                return con->name;
             }
         }
     }
diff --git a/src/kernel/building.h b/src/kernel/building.h
index edb46edfd..a2019e4a2 100644
--- a/src/kernel/building.h
+++ b/src/kernel/building.h
@@ -83,7 +83,6 @@ extern "C" {
     bool bt_changed(int *cache);
     const building_type *bt_find(const char *name);
     void free_buildingtypes(void);
-    void bt_register(struct building_type *type);
     int bt_effsize(const struct building_type *btype,
         const struct building *b, int bsize);
 
diff --git a/src/kernel/building.test.c b/src/kernel/building.test.c
index 3d25cd9a1..c1255373b 100644
--- a/src/kernel/building.test.c
+++ b/src/kernel/building.test.c
@@ -21,14 +21,13 @@ static void test_register_building(CuTest * tc)
 
     test_cleanup();
 
-    btype = (building_type *)calloc(sizeof(building_type), 1);
-    btype->_name = strdup("herp");
     CuAssertIntEquals(tc, true, bt_changed(&cache));
     CuAssertIntEquals(tc, false, bt_changed(&cache));
-    bt_register(btype);
-    CuAssertIntEquals(tc, true, bt_changed(&cache));
 
-    CuAssertPtrNotNull(tc, bt_find("herp"));
+    btype = bt_get_or_create("herp");
+    CuAssertIntEquals(tc, true, bt_changed(&cache));
+    CuAssertPtrEquals(tc, btype, (void *)bt_find("herp"));
+
     free_buildingtypes();
     CuAssertIntEquals(tc, true, bt_changed(&cache));
     test_cleanup();
@@ -564,7 +563,7 @@ static void test_buildingtype(CuTest *tc) {
     btype = test_create_buildingtype("hodor");
     CuAssertPtrNotNull(tc, btype->construction);
     CuAssertStrEquals(tc, "hodor", buildingtype(btype, NULL, 1));
-    btype->construction->extra.name = strdup("castle");
+    btype->construction->name = strdup("castle");
     CuAssertStrEquals(tc, "castle", buildingtype(btype, NULL, 1));
     btype = bt_get_or_create("portal");
     CuAssertPtrEquals(tc, NULL, btype->construction);
diff --git a/src/kernel/ship.c b/src/kernel/ship.c
index b9ac0b170..3a7608789 100644
--- a/src/kernel/ship.c
+++ b/src/kernel/ship.c
@@ -37,13 +37,15 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include <util/event.h>
 #include <util/language.h>
 #include <util/lists.h>
+#include <util/log.h>
 #include <util/umlaut.h>
-#include <selist.h>
 #include <util/xml.h>
 
 #include <attributes/movement.h>
 
 #include <storage.h>
+#include <selist.h>
+#include <critbit.h>
 
 /* libc includes */
 #include <assert.h>
@@ -51,7 +53,8 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include <stdlib.h>
 #include <string.h>
 
-selist *shiptypes = NULL;
+selist *shiptypes = NULL; /* do not use this list for searching*/
+static critbit_tree cb_shiptypes; /* use this trie instead */
 
 static local_names *snames;
 
@@ -60,9 +63,7 @@ const ship_type *findshiptype(const char *name, const struct locale *lang)
     local_names *sn = snames;
     variant var;
 
-    while (sn) {
-        if (sn->lang == lang)
-            break;
+    while (sn && sn->lang != lang) {
         sn = sn->next;
     }
     if (!sn) {
@@ -89,29 +90,42 @@ const ship_type *findshiptype(const char *name, const struct locale *lang)
 
 static ship_type *st_find_i(const char *name)
 {
-    selist *ql;
-    int qi;
+    const char *match;
+    ship_type *st = NULL;
 
-    for (qi = 0, ql = shiptypes; ql; selist_advance(&ql, &qi, 1)) {
-        ship_type *stype = (ship_type *)selist_get(ql, qi);
-        if (strcmp(stype->_name, name) == 0) {
-            return stype;
-        }
+    match = cb_find_str(&cb_shiptypes, name);
+    if (match) {
+        cb_get_kv(match, &st, sizeof(st));
     }
-    return NULL;
+    else {
+        log_warning("st_find: could not find ship '%s'\n", name);
+    }
+    return st;
 }
 
 const ship_type *st_find(const char *name) {
     return st_find_i(name);
 }
 
+static void st_register(ship_type *stype) {
+    size_t len;
+    char data[64];
+
+    selist_push(&shiptypes, (void *)stype);
+
+    len = cb_new_kv(stype->_name, strlen(stype->_name), &stype, sizeof(stype), data);
+    assert(len <= sizeof(data));
+    cb_insert(&cb_shiptypes, data, len);
+}
+
 ship_type *st_get_or_create(const char * name) {
     ship_type * st = st_find_i(name);
+    assert(!snames);
     if (!st) {
         st = (ship_type *)calloc(sizeof(ship_type), 1);
         st->_name = strdup(name);
         st->storm = 1.0;
-        selist_push(&shiptypes, (void *)st);
+        st_register(st);
     }
     return st;
 }
@@ -234,8 +248,9 @@ void remove_ship(ship ** slist, ship * sh)
 
 void free_ship(ship * s)
 {
-    while (s->attribs)
+    while (s->attribs) {
         a_remove(&s->attribs, s->attribs);
+    }
     free(s->name);
     free(s->display);
     free(s);
@@ -250,6 +265,7 @@ static void free_shiptype(void *ptr) {
 }
 
 void free_shiptypes(void) {
+    cb_clear(&cb_shiptypes);
     selist_foreach(shiptypes, free_shiptype);
     selist_free(shiptypes);
     shiptypes = 0;
diff --git a/src/kernel/xmlreader.c b/src/kernel/xmlreader.c
index 9f671d44c..080ff4207 100644
--- a/src/kernel/xmlreader.c
+++ b/src/kernel/xmlreader.c
@@ -247,17 +247,10 @@ construction ** consPtr, construct_t type)
         con->minskill = xml_ivalue(node, "minskill", -1);
         con->reqsize = xml_ivalue(node, "reqsize", 1);
 
-        if (type == CONS_ITEM) {
-            propValue = xmlGetProp(node, BAD_CAST "building");
-            if (propValue != NULL) {
-                con->extra.btype = bt_get_or_create((const char *)propValue);
-                xmlFree(propValue);
-            }
-        }
-        else if (type == CONS_BUILDING) {
+        if (type == CONS_BUILDING) {
             propValue = xmlGetProp(node, BAD_CAST "name");
             if (propValue != NULL) {
-                con->extra.name = strdup((const char *)propValue);
+                con->name = strdup((const char *)propValue);
                 xmlFree(propValue);
             }
         }
diff --git a/src/magic.test.c b/src/magic.test.c
index 380001035..a1b55b45d 100644
--- a/src/magic.test.c
+++ b/src/magic.test.c
@@ -479,7 +479,7 @@ static void test_illusioncastle(CuTest *tc)
     CuAssertPtrEquals(tc, btype, (void *)icastle_type(a));
     CuAssertPtrEquals(tc, bt_icastle, (void *)b->type);
     CuAssertStrEquals(tc, "castle", buildingtype(btype, b, b->size));
-    btype->construction->extra.name = strdup("site");
+    btype->construction->name = strdup("site");
     CuAssertStrEquals(tc, "site", buildingtype(btype, b, b->size));
     test_cleanup();
 }
diff --git a/src/market.test.c b/src/market.test.c
index a631dbcb7..2beeaea6b 100644
--- a/src/market.test.c
+++ b/src/market.test.c
@@ -43,9 +43,7 @@ static void test_market_curse(CuTest * tc)
 
     config_set("rules.region_owners", "1");
 
-    btype = (building_type *)calloc(1, sizeof(building_type));
-    btype->_name = strdup("market");
-    bt_register(btype);
+    btype = bt_get_or_create("market");
 
     terrain = get_terrain("plain");