diff --git a/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/SpaceOrderTest.kt b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/SpaceOrderTest.kt
new file mode 100644
index 0000000000..3270dfb757
--- /dev/null
+++ b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/SpaceOrderTest.kt
@@ -0,0 +1,260 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk
+
+import org.amshove.kluent.internal.assertEquals
+import org.junit.Assert
+import org.junit.Test
+import org.matrix.android.sdk.api.session.space.SpaceOrderUtils
+
+class SpaceOrderTest {
+
+    @Test
+    fun testOrderBetweenNodesWithOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to "a",
+                "roomId2" to "m",
+                "roomId3" to "z"
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId1", 1)
+
+        Assert.assertTrue("Only one order should be changed", orderCommand.size == 1)
+        Assert.assertTrue("Moved space order should change", orderCommand.first().spaceId == "roomId1")
+
+        Assert.assertTrue("m" < orderCommand[0].order)
+        Assert.assertTrue(orderCommand[0].order < "z")
+    }
+
+    @Test
+    fun testMoveLastBetweenNodesWithOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to "a",
+                "roomId2" to "m",
+                "roomId3" to "z"
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId1", 2)
+
+        Assert.assertTrue("Only one order should be changed", orderCommand.size == 1)
+        Assert.assertTrue("Moved space order should change", orderCommand.first().spaceId == "roomId1")
+
+        Assert.assertTrue("z" < orderCommand[0].order)
+    }
+
+    @Test
+    fun testMoveUpNoOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to null,
+                "roomId2" to null,
+                "roomId3" to null
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId1", 1)
+
+        Assert.assertTrue("2 orders change should be needed", orderCommand.size == 2)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId2", reOrdered[0].first)
+        Assert.assertEquals("roomId1", reOrdered[1].first)
+        Assert.assertEquals("roomId3", reOrdered[2].first)
+    }
+
+    @Test
+    fun testMoveUpNotEnoughSpace() {
+        val orderedSpaces = listOf(
+                "roomId1" to "a",
+                "roomId2" to "j",
+                "roomId3" to "k"
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId1", 1)
+
+        Assert.assertTrue("more orders change should be needed", orderCommand.size > 1)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId2", reOrdered[0].first)
+        Assert.assertEquals("roomId1", reOrdered[1].first)
+        Assert.assertEquals("roomId3", reOrdered[2].first)
+    }
+
+    @Test
+    fun testMoveEndNoOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to null,
+                "roomId2" to null,
+                "roomId3" to null
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId1", 2)
+
+        // Actually 2 could be enough... as it's last it can stays with null
+        Assert.assertEquals("3 orders change should be needed", 3, orderCommand.size)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId2", reOrdered[0].first)
+        Assert.assertEquals("roomId3", reOrdered[1].first)
+        Assert.assertEquals("roomId1", reOrdered[2].first)
+    }
+
+    @Test
+    fun testMoveUpBiggerOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to "aaaa",
+                "roomId2" to "ffff",
+                "roomId3" to "pppp",
+                "roomId4" to null,
+                "roomId5" to null,
+                "roomId6" to null
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId2", 3)
+
+        // Actually 2 could be enough... as it's last it can stays with null
+        Assert.assertEquals("3 orders change should be needed", 3, orderCommand.size)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId1", reOrdered[0].first)
+        Assert.assertEquals("roomId3", reOrdered[1].first)
+        Assert.assertEquals("roomId4", reOrdered[2].first)
+        Assert.assertEquals("roomId5", reOrdered[3].first)
+        Assert.assertEquals("roomId2", reOrdered[4].first)
+        Assert.assertEquals("roomId6", reOrdered[5].first)
+    }
+
+    @Test
+    fun testMoveDownBetweenNodesWithOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to "a",
+                "roomId2" to "m",
+                "roomId3" to "z"
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId3", -1)
+
+        Assert.assertTrue("Only one order should be changed", orderCommand.size == 1)
+        Assert.assertTrue("Moved space order should change", orderCommand.first().spaceId == "roomId3")
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId1", reOrdered[0].first)
+        Assert.assertEquals("roomId3", reOrdered[1].first)
+        Assert.assertEquals("roomId2", reOrdered[2].first)
+    }
+
+    @Test
+    fun testMoveDownNoOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to null,
+                "roomId2" to null,
+                "roomId3" to null
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId3", -1)
+
+        Assert.assertTrue("2 orders change should be needed", orderCommand.size == 2)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId1", reOrdered[0].first)
+        Assert.assertEquals("roomId3", reOrdered[1].first)
+        Assert.assertEquals("roomId2", reOrdered[2].first)
+    }
+
+    @Test
+    fun testMoveDownBiggerOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to "aaaa",
+                "roomId2" to "ffff",
+                "roomId3" to "pppp",
+                "roomId4" to null,
+                "roomId5" to null,
+                "roomId6" to null
+        ).assertSpaceOrdered()
+
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId5", -4)
+
+        Assert.assertEquals("1 order change should be needed", 1, orderCommand.size)
+
+        val reOrdered = reOrderWithCommands(orderedSpaces, orderCommand)
+
+        Assert.assertEquals("roomId5", reOrdered[0].first)
+        Assert.assertEquals("roomId1", reOrdered[1].first)
+        Assert.assertEquals("roomId2", reOrdered[2].first)
+        Assert.assertEquals("roomId3", reOrdered[3].first)
+        Assert.assertEquals("roomId4", reOrdered[4].first)
+        Assert.assertEquals("roomId6", reOrdered[5].first)
+    }
+
+    @Test
+    fun testMultipleMoveOrder() {
+        val orderedSpaces = listOf(
+                "roomId1" to null,
+                "roomId2" to null,
+                "roomId3" to null,
+                "roomId4" to null,
+                "roomId5" to null,
+                "roomId6" to null
+        ).assertSpaceOrdered()
+
+        // move 5 to Top
+        val fiveToTop = SpaceOrderUtils.orderCommandsForMove(orderedSpaces, "roomId5", -4)
+
+        val fiveTopReOrder = reOrderWithCommands(orderedSpaces, fiveToTop)
+
+        // now move 4 to second
+        val orderCommand = SpaceOrderUtils.orderCommandsForMove(fiveTopReOrder, "roomId4", -3)
+
+        val reOrdered = reOrderWithCommands(fiveTopReOrder, orderCommand)
+        // second order should cost 1 re-order
+        Assert.assertEquals(1, orderCommand.size)
+
+        Assert.assertEquals("roomId5", reOrdered[0].first)
+        Assert.assertEquals("roomId4", reOrdered[1].first)
+        Assert.assertEquals("roomId1", reOrdered[2].first)
+        Assert.assertEquals("roomId2", reOrdered[3].first)
+        Assert.assertEquals("roomId3", reOrdered[4].first)
+        Assert.assertEquals("roomId6", reOrdered[5].first)
+    }
+
+    @Test
+    fun testComparator() {
+        listOf(
+                "roomId2" to "a",
+                "roomId1" to "b",
+                "roomId3" to null,
+                "roomId4" to null
+        ).assertSpaceOrdered()
+    }
+
+    private fun reOrderWithCommands(orderedSpaces: List<Pair<String, String?>>, orderCommand: List<SpaceOrderUtils.SpaceReOrderCommand>) =
+            orderedSpaces.map { orderInfo ->
+                orderInfo.first to (orderCommand.find { it.spaceId == orderInfo.first }?.order ?: orderInfo.second)
+            }
+                    .sortedWith(testSpaceComparator)
+
+    private fun List<Pair<String, String?>>.assertSpaceOrdered(): List<Pair<String, String?>> {
+        assertEquals(this, this.sortedWith(testSpaceComparator))
+        return this
+    }
+
+    private val testSpaceComparator = compareBy<Pair<String, String?>, String?>(nullsLast()) { it.second }.thenBy { it.first }
+}
diff --git a/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/StringOrderTest.kt b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/StringOrderTest.kt
new file mode 100644
index 0000000000..a625362c04
--- /dev/null
+++ b/matrix-sdk-android/src/androidTest/java/org/matrix/android/sdk/StringOrderTest.kt
@@ -0,0 +1,110 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk
+
+import org.amshove.kluent.internal.assertEquals
+import org.junit.Assert
+import org.junit.Test
+import org.matrix.android.sdk.api.MatrixPatterns
+import org.matrix.android.sdk.api.util.StringOrderUtils
+
+class StringOrderTest {
+
+    @Test
+    fun testbasing() {
+        assertEquals("a", StringOrderUtils.baseToString(StringOrderUtils.stringToBase("a", StringOrderUtils.DEFAULT_ALPHABET), StringOrderUtils.DEFAULT_ALPHABET))
+        assertEquals("element", StringOrderUtils.baseToString(StringOrderUtils.stringToBase("element", StringOrderUtils.DEFAULT_ALPHABET), StringOrderUtils.DEFAULT_ALPHABET))
+        assertEquals("matrix", StringOrderUtils.baseToString(StringOrderUtils.stringToBase("matrix", StringOrderUtils.DEFAULT_ALPHABET), StringOrderUtils.DEFAULT_ALPHABET))
+    }
+
+    @Test
+    fun testValid() {
+        println(StringOrderUtils.DEFAULT_ALPHABET.joinToString(","))
+
+        assert(MatrixPatterns.isValidOrderString("a"))
+        assert(MatrixPatterns.isValidOrderString(" "))
+        assert(MatrixPatterns.isValidOrderString("abc"))
+        assert(!MatrixPatterns.isValidOrderString("abcê"))
+        assert(!MatrixPatterns.isValidOrderString(""))
+        assert(MatrixPatterns.isValidOrderString("!"))
+        assert(MatrixPatterns.isValidOrderString("!\"#\$%&'()*+,012"))
+        assert(!MatrixPatterns.isValidOrderString(Char(' '.code - 1).toString()))
+
+        assert(!MatrixPatterns.isValidOrderString(
+                buildString {
+                    for (i in 0..49) {
+                        append(StringOrderUtils.DEFAULT_ALPHABET.random())
+                    }
+                }
+        ))
+
+        assert(MatrixPatterns.isValidOrderString(
+                buildString {
+                    for (i in 0..48) {
+                        append(StringOrderUtils.DEFAULT_ALPHABET.random())
+                    }
+                }
+        ))
+    }
+
+    @Test
+    fun testAverage() {
+        assertAverage("${StringOrderUtils.DEFAULT_ALPHABET.first()}", "m")
+        assertAverage("aa", "aab")
+        assertAverage("matrix", "element")
+        assertAverage("mmm", "mmmmm")
+        assertAverage("aab", "aa")
+        assertAverage("", "aa")
+        assertAverage("a", "z")
+        assertAverage("ground", "sky")
+    }
+
+    @Test
+    fun testMidPoints() {
+        val orders = StringOrderUtils.midPoints("element", "matrix", 4)
+        assertEquals(4, orders!!.size)
+        assert("element" < orders[0])
+        assert(orders[0] < orders[1])
+        assert(orders[1] < orders[2])
+        assert(orders[2] < orders[3])
+        assert(orders[3] < "matrix")
+
+        println("element < ${orders.joinToString(" < ") { "[$it]" }} < matrix")
+
+        val orders2 = StringOrderUtils.midPoints("a", "d", 4)
+        assertEquals(null, orders2)
+    }
+
+    @Test
+    fun testRenumberNeeded() {
+        assertEquals(null, StringOrderUtils.average("a", "a"))
+        assertEquals(null, StringOrderUtils.average("", ""))
+        assertEquals(null, StringOrderUtils.average("a", "b"))
+        assertEquals(null, StringOrderUtils.average("b", "a"))
+        assertEquals(null, StringOrderUtils.average("mmmm", "mmmm"))
+        assertEquals(null, StringOrderUtils.average("a${Char(0)}", "a"))
+    }
+
+    private fun assertAverage(first: String, second: String) {
+        val left = first.takeIf { first < second } ?: second
+        val right = first.takeIf { first > second } ?: second
+        val av1 = StringOrderUtils.average(left, right)!!
+        println("[$left] < [$av1] < [$right]")
+        Assert.assertTrue(left < av1)
+        Assert.assertTrue(av1 < right)
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/MatrixPatterns.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/MatrixPatterns.kt
index d8532c77c8..841e833271 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/MatrixPatterns.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/MatrixPatterns.kt
@@ -71,6 +71,9 @@ object MatrixPatterns {
     private const val LINK_TO_APP_ROOM_ALIAS_REGEXP = APP_BASE_REGEX + MATRIX_ROOM_ALIAS_REGEX + SEP_REGEX + MATRIX_EVENT_IDENTIFIER_REGEX
     private val PATTERN_CONTAIN_APP_LINK_PERMALINK_ROOM_ALIAS = LINK_TO_APP_ROOM_ALIAS_REGEXP.toRegex(RegexOption.IGNORE_CASE)
 
+    // ascii characters in the range \x20 (space) to \x7E (~)
+    val ORDER_STRING_REGEX = "[ -~]+".toRegex()
+
     // list of patterns to find some matrix item.
     val MATRIX_PATTERNS = listOf(
             PATTERN_CONTAIN_MATRIX_TO_PERMALINK_ROOM_ID,
@@ -146,4 +149,12 @@ object MatrixPatterns {
     fun extractServerNameFromId(matrixId: String?): String? {
         return matrixId?.substringAfter(":", missingDelimiterValue = "")?.takeIf { it.isNotEmpty() }
     }
+
+    /**
+     * Orders which are not strings, or do not consist solely of ascii characters in the range \x20 (space) to \x7E (~),
+     * or consist of more than 50 characters, are forbidden and the field should be ignored if received.
+     */
+    fun isValidOrderString(order: String?) : Boolean {
+        return order != null && order.length < 50 && order matches ORDER_STRING_REGEX
+    }
 }
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/room/accountdata/RoomAccountDataTypes.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/room/accountdata/RoomAccountDataTypes.kt
index 0e80c307b4..96eb86c0d6 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/room/accountdata/RoomAccountDataTypes.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/room/accountdata/RoomAccountDataTypes.kt
@@ -20,4 +20,5 @@ object RoomAccountDataTypes {
     const val EVENT_TYPE_VIRTUAL_ROOM = "im.vector.is_virtual_room"
     const val EVENT_TYPE_TAG = "m.tag"
     const val EVENT_TYPE_FULLY_READ = "m.fully_read"
+    const val EVENT_TYPE_SPACE_ORDER = "org.matrix.msc3230.space_order" // m.space_order
 }
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/SpaceOrderUtils.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/SpaceOrderUtils.kt
new file mode 100644
index 0000000000..844a5adcb4
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/SpaceOrderUtils.kt
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.api.session.space
+
+import org.matrix.android.sdk.api.util.StringOrderUtils
+
+/**
+ * Adds some utilities to compute correct string orders when ordering spaces.
+ * After moving a space (e.g via DnD), client should limit the number of room account data update.
+ * For example if the space is moved between two other spaces with orders, just update the moved space order by computing
+ * a mid point between the surrounding orders.
+ * If the space is moved after a space with no order, all the previous spaces should be then ordered,
+ * and the computed orders should be chosen so that there is enough gaps in between them to facilitate future re-order.
+ * Re numbering (i.e change all spaces m.space.order account data) should be avoided as much as possible,
+ * as the updates might not be atomic for other clients and would makes spaces jump around.
+ */
+object SpaceOrderUtils {
+
+    data class SpaceReOrderCommand(
+            val spaceId: String,
+            val order: String
+    )
+
+    /**
+     * Returns a minimal list of order change in order to re order the space list as per given move.
+     */
+    fun orderCommandsForMove(orderedSpacesToOrderMap: List<Pair<String, String?>>, movedSpaceId: String, delta: Int): List<SpaceReOrderCommand> {
+        val movedIndex = orderedSpacesToOrderMap.indexOfFirst { it.first == movedSpaceId }
+        if (movedIndex == -1) return emptyList()
+        if (delta == 0) return emptyList()
+
+        val targetIndex = if (delta > 0) movedIndex + delta else (movedIndex + delta - 1)
+
+        val nodesToReNumber = mutableListOf<String>()
+        var lowerBondOrder: String? = null
+        var index = targetIndex
+        while (index >= 0 && lowerBondOrder == null) {
+            val node = orderedSpacesToOrderMap.getOrNull(index)
+            if (node != null /*null when adding at the end*/) {
+                val nodeOrder = node.second
+                if (node.first == movedSpaceId) break
+                if (nodeOrder == null) {
+                    nodesToReNumber.add(0, node.first)
+                } else {
+                    lowerBondOrder = nodeOrder
+                }
+            }
+            index--
+        }
+        nodesToReNumber.add(movedSpaceId)
+        val afterSpace: Pair<String, String?>? = if (orderedSpacesToOrderMap.indices.contains(targetIndex + 1)) {
+            orderedSpacesToOrderMap[targetIndex + 1]
+        } else null
+
+        val defaultMaxOrder = CharArray(4) { StringOrderUtils.DEFAULT_ALPHABET.last() }
+                .joinToString("")
+
+        val defaultMinOrder = CharArray(4) { StringOrderUtils.DEFAULT_ALPHABET.first() }
+                .joinToString("")
+
+        val afterOrder = afterSpace?.second ?: defaultMaxOrder
+
+        val beforeOrder = lowerBondOrder ?: defaultMinOrder
+
+        val newOrder = StringOrderUtils.midPoints(beforeOrder, afterOrder, nodesToReNumber.size)
+
+        if (newOrder.isNullOrEmpty()) {
+            // re order all?
+            val expectedList = orderedSpacesToOrderMap.toMutableList()
+            expectedList.removeAt(movedIndex).let {
+                expectedList.add(movedIndex + delta, it)
+            }
+
+            return StringOrderUtils.midPoints(defaultMinOrder, defaultMaxOrder, orderedSpacesToOrderMap.size)?.let { orders ->
+                expectedList.mapIndexed { index, pair ->
+                    SpaceReOrderCommand(
+                            pair.first,
+                            orders[index]
+                    )
+                }
+            } ?: emptyList()
+        } else {
+            return nodesToReNumber.mapIndexed { i, s ->
+                SpaceReOrderCommand(
+                        s,
+                        newOrder[i]
+                )
+            }
+        }
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/SpaceOrderContent.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/SpaceOrderContent.kt
new file mode 100644
index 0000000000..a8578347c8
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/SpaceOrderContent.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.api.session.space.model
+
+import com.squareup.moshi.JsonClass
+import org.matrix.android.sdk.api.MatrixPatterns
+
+/**
+ * {
+ * "type": "m.space_order",
+ *   "content": {
+ *       "order": "..."
+ *   }
+ * }
+ */
+@JsonClass(generateAdapter = true)
+data class SpaceOrderContent(
+        val order: String? = null
+) {
+    fun safeOrder(): String? {
+        return order?.takeIf { MatrixPatterns.isValidOrderString(it) }
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/TopLevelSpaceComparator.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/TopLevelSpaceComparator.kt
new file mode 100644
index 0000000000..8af4f3a149
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/space/model/TopLevelSpaceComparator.kt
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.api.session.space.model
+
+import org.matrix.android.sdk.api.session.room.model.RoomSummary
+
+// Can't use regular compare by because Null is considered less than any value, and for space order it's the opposite
+class TopLevelSpaceComparator(val orders: Map<String, String?>) : Comparator<RoomSummary> {
+
+    override fun compare(left: RoomSummary?, right: RoomSummary?): Int {
+        val leftOrder = left?.roomId?.let { orders[it] }
+        val rightOrder = right?.roomId?.let { orders[it] }
+        return if (leftOrder != null && rightOrder != null) {
+            leftOrder.compareTo(rightOrder)
+        } else {
+            if (leftOrder == null) {
+                if (rightOrder == null) {
+                    compareValues(left?.roomId, right?.roomId)
+                } else {
+                    1
+                }
+            } else {
+                -1
+            }
+        }
+//                .also {
+//            Timber.w("VAL: compare(${left?.displayName} | $leftOrder ,${right?.displayName} | $rightOrder) = $it")
+//        }
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/util/StringOrderUtils.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/util/StringOrderUtils.kt
new file mode 100644
index 0000000000..83c8585941
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/util/StringOrderUtils.kt
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.api.util
+
+import java.math.BigInteger
+
+object StringOrderUtils {
+
+    val DEFAULT_ALPHABET = buildString {
+        for (i in 0x20..0x7E) {
+            append(Char(i))
+        }
+    }.toCharArray()
+
+    // /=Range(0x20, 0x7E)
+
+    fun average(left: String, right: String, alphabet: CharArray = DEFAULT_ALPHABET): String? {
+        return midPoints(left, right, 1, alphabet)?.firstOrNull()
+    }
+
+    fun midPoints(left: String, right: String, count: Int, alphabet: CharArray = DEFAULT_ALPHABET): List<String>? {
+        if (left == right) return null // no space in between..
+        if (left > right) return midPoints(right, left, count, alphabet)
+        val size = maxOf(left.length, right.length)
+        val leftPadded = pad(left, size, alphabet.first())
+        val rightPadded = pad(right, size, alphabet.first())
+        val b1 = stringToBase(leftPadded, alphabet)
+        val b2 = stringToBase(rightPadded, alphabet)
+        val step = (b2.minus(b1)).div(BigInteger("${count + 1}"))
+        val orders = mutableListOf<String>()
+        var previous = left
+        for (i in 0 until count) {
+            val newOrder = baseToString(b1.add(step.multiply(BigInteger("${i + 1}"))), alphabet)
+            orders.add(newOrder)
+            // ensure there was enought precision
+            if (previous >= newOrder) return null
+            previous = newOrder
+        }
+        return orders.takeIf { orders.last() < right }
+    }
+
+    private fun pad(string: String, size: Int, padding: Char): String {
+        val raw = string.toCharArray()
+        return CharArray(size).also {
+            for (index in it.indices) {
+                if (index < raw.size) {
+                    it[index] = raw[index]
+                } else {
+                    it[index] = padding
+                }
+            }
+        }.joinToString("")
+    }
+
+    fun baseToString(x: BigInteger, alphabet: CharArray): String {
+        val len = alphabet.size.toBigInteger()
+        if (x < len) {
+            return alphabet[x.toInt()].toString()
+        } else {
+            return baseToString(x.div(len), alphabet) + alphabet[x.rem(len).toInt()].toString()
+        }
+    }
+
+    fun stringToBase(x: String, alphabet: CharArray): BigInteger {
+        if (x.isEmpty()) throw IllegalArgumentException()
+        val len = alphabet.size.toBigInteger()
+        var result = BigInteger("0")
+        x.reversed().forEachIndexed { index, c ->
+            result += (alphabet.indexOf(c).toBigInteger() * len.pow(index))
+        }
+        return result
+    }
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/accountdata/DefaultRoomAccountDataService.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/accountdata/DefaultRoomAccountDataService.kt
index d43c1d3217..caeeb3bf53 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/accountdata/DefaultRoomAccountDataService.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/accountdata/DefaultRoomAccountDataService.kt
@@ -26,8 +26,8 @@ import org.matrix.android.sdk.api.session.room.accountdata.RoomAccountDataServic
 import org.matrix.android.sdk.api.util.Optional
 
 internal class DefaultRoomAccountDataService @AssistedInject constructor(@Assisted private val roomId: String,
-                                                                  private val dataSource: RoomAccountDataDataSource,
-                                                                  private val updateRoomAccountDataTask: UpdateRoomAccountDataTask
+                                                                         private val dataSource: RoomAccountDataDataSource,
+                                                                         private val updateRoomAccountDataTask: UpdateRoomAccountDataTask
 ) : RoomAccountDataService {
 
     @AssistedFactory
diff --git a/newsfragment/3501.feature b/newsfragment/3501.feature
new file mode 100644
index 0000000000..c0602dda3f
--- /dev/null
+++ b/newsfragment/3501.feature
@@ -0,0 +1 @@
+User defined top level spaces ordering (#3501)
\ No newline at end of file
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpaceListAction.kt b/vector/src/main/java/im/vector/app/features/spaces/SpaceListAction.kt
index b8b6cb4667..12d4b40f42 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpaceListAction.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpaceListAction.kt
@@ -26,6 +26,9 @@ sealed class SpaceListAction : VectorViewModelAction {
     data class LeaveSpace(val spaceSummary: RoomSummary) : SpaceListAction()
     data class ToggleExpand(val spaceSummary: RoomSummary) : SpaceListAction()
     object AddSpace : SpaceListAction()
+    data class MoveSpace(val spaceId: String, val delta : Int) : SpaceListAction()
+    data class OnStartDragging(val spaceId: String, val expanded: Boolean) : SpaceListAction()
+    data class OnEndDragging(val spaceId: String, val expanded: Boolean) : SpaceListAction()
 
     data class SelectLegacyGroup(val groupSummary: GroupSummary?) : SpaceListAction()
 }
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpaceListFragment.kt b/vector/src/main/java/im/vector/app/features/spaces/SpaceListFragment.kt
index f50ba90221..0a67977e6c 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpaceListFragment.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpaceListFragment.kt
@@ -17,9 +17,11 @@
 package im.vector.app.features.spaces
 
 import android.os.Bundle
+import android.view.HapticFeedbackConstants
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import com.airbnb.epoxy.EpoxyTouchHelper
 import com.airbnb.mvrx.Incomplete
 import com.airbnb.mvrx.Success
 import com.airbnb.mvrx.fragmentViewModel
@@ -54,6 +56,53 @@ class SpaceListFragment @Inject constructor(
         spaceController.callback = this
         views.stateView.contentView = views.groupListView
         views.groupListView.configureWith(spaceController)
+        EpoxyTouchHelper.initDragging(spaceController)
+                .withRecyclerView(views.groupListView)
+                .forVerticalList()
+                .withTarget(SpaceSummaryItem::class.java)
+                .andCallbacks(object : EpoxyTouchHelper.DragCallbacks<SpaceSummaryItem>() {
+                    var toPositionM: Int? = null
+                    var fromPositionM: Int? = null
+                    var initialElevation: Float? = null
+
+                    override fun onDragStarted(model: SpaceSummaryItem?, itemView: View?, adapterPosition: Int) {
+                        toPositionM = null
+                        fromPositionM = null
+                        model?.matrixItem?.id?.let {
+                            viewModel.handle(SpaceListAction.OnStartDragging(it, model.expanded))
+                        }
+                        itemView?.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS)
+                        initialElevation = itemView?.elevation
+                        itemView?.elevation = 6f
+                    }
+
+                    override fun onDragReleased(model: SpaceSummaryItem?, itemView: View?) {
+//                        Timber.v("VAL: onModelMoved from $fromPositionM to $toPositionM ${model?.matrixItem?.getBestName()}")
+                        if (toPositionM == null || fromPositionM == null) return
+                        val movingSpace = model?.matrixItem?.id ?: return
+                        viewModel.handle(SpaceListAction.MoveSpace(movingSpace, toPositionM!! - fromPositionM!!))
+                    }
+
+                    override fun clearView(model: SpaceSummaryItem?, itemView: View?) {
+//                        Timber.v("VAL: clearView ${model?.matrixItem?.getBestName()}")
+                        itemView?.elevation = initialElevation ?: 0f
+                    }
+
+                    override fun onModelMoved(fromPosition: Int, toPosition: Int, modelBeingMoved: SpaceSummaryItem?, itemView: View?) {
+//                        Timber.v("VAL: onModelMoved incremental from $fromPosition to $toPosition ${modelBeingMoved?.matrixItem?.getBestName()}")
+                        if (fromPositionM == null) {
+                            fromPositionM = fromPosition
+                        }
+                        toPositionM = toPosition
+                        itemView?.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS)
+                    }
+
+                    override fun isDragEnabledForModel(model: SpaceSummaryItem?): Boolean {
+//                        Timber.v("VAL: isDragEnabledForModel ${model?.matrixItem?.getBestName()}")
+                        return model?.canDrag == true
+                    }
+                })
+
         viewModel.observeViewEvents {
             when (it) {
                 is SpaceListViewEvents.OpenSpaceSummary -> sharedActionViewModel.post(HomeActivitySharedAction.OpenSpacePreview(it.id))
@@ -74,7 +123,7 @@ class SpaceListFragment @Inject constructor(
     override fun invalidate() = withState(viewModel) { state ->
         when (state.asyncSpaces) {
             is Incomplete -> views.stateView.state = StateView.State.Loading
-            is Success -> views.stateView.state = StateView.State.Content
+            is Success    -> views.stateView.state = StateView.State.Content
         }
         spaceController.update(state)
     }
@@ -86,6 +135,7 @@ class SpaceListFragment @Inject constructor(
     override fun onSpaceInviteSelected(spaceSummary: RoomSummary) {
         viewModel.handle(SpaceListAction.OpenSpaceInvite(spaceSummary))
     }
+
     override fun onSpaceSettings(spaceSummary: RoomSummary) {
         sharedActionViewModel.post(HomeActivitySharedAction.ShowSpaceSettings(spaceSummary.roomId))
     }
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpaceListViewState.kt b/vector/src/main/java/im/vector/app/features/spaces/SpaceListViewState.kt
index b57a5d364b..7482f4881e 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpaceListViewState.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpaceListViewState.kt
@@ -29,7 +29,9 @@ data class SpaceListViewState(
         val myMxItem : Async<MatrixItem.UserItem> = Uninitialized,
         val asyncSpaces: Async<List<RoomSummary>> = Uninitialized,
         val selectedGroupingMethod: RoomGroupingMethod = RoomGroupingMethod.BySpace(null),
-        val rootSpaces: List<RoomSummary>? = null,
+        val rootSpacesOrdered: List<RoomSummary>? = null,
+        val spaceOrderInfo: Map<String, String?>? = null,
+        val spaceOrderLocalEchos: Map<String, String?>? = null,
         val legacyGroups: List<GroupSummary>? = null,
         val expandedStates: Map<String, Boolean> = emptyMap(),
         val homeAggregateCount : RoomAggregateNotificationCount = RoomAggregateNotificationCount(0, 0)
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryController.kt b/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryController.kt
index 78eb232cf6..828308007b 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryController.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryController.kt
@@ -62,7 +62,7 @@ class SpaceSummaryController @Inject constructor(
         buildGroupModels(
                 nonNullViewState.asyncSpaces(),
                 nonNullViewState.selectedGroupingMethod,
-                nonNullViewState.rootSpaces,
+                nonNullViewState.rootSpacesOrdered,
                 nonNullViewState.expandedStates,
                 nonNullViewState.homeAggregateCount)
 
@@ -127,6 +127,7 @@ class SpaceSummaryController @Inject constructor(
                         countState(UnreadCounterBadgeView.State(1, true))
                         selected(false)
                         description(host.stringProvider.getString(R.string.you_are_invited))
+                        canDrag(false)
                         listener { host.callback?.onSpaceInviteSelected(roomSummary) }
                     }
                 }
@@ -139,7 +140,6 @@ class SpaceSummaryController @Inject constructor(
         }
 
         rootSpaces
-                ?.sortedBy { it.roomId }
                 ?.forEach { groupSummary ->
                     val isSelected = selected is RoomGroupingMethod.BySpace && groupSummary.roomId == selected.space()?.roomId
                     // does it have children?
@@ -154,8 +154,12 @@ class SpaceSummaryController @Inject constructor(
                         id(groupSummary.roomId)
                         hasChildren(hasChildren)
                         expanded(expanded)
+                        // to debug order
+                        // matrixItem(groupSummary.copy(displayName = "${groupSummary.displayName} / ${spaceOrderInfo?.get(groupSummary.roomId)}")
+                        // .toMatrixItem())
                         matrixItem(groupSummary.toMatrixItem())
                         selected(isSelected)
+                        canDrag(true)
                         onMore { host.callback?.onSpaceSettings(groupSummary) }
                         listener { host.callback?.onSpaceSelected(groupSummary) }
                         toggleExpand { host.callback?.onToggleExpand(groupSummary) }
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryItem.kt b/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryItem.kt
index a7432571ed..6cffabd851 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryItem.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpaceSummaryItem.kt
@@ -51,6 +51,7 @@ abstract class SpaceSummaryItem : VectorEpoxyModel<SpaceSummaryItem.Holder>() {
     @EpoxyAttribute var countState: UnreadCounterBadgeView.State = UnreadCounterBadgeView.State(0, false)
     @EpoxyAttribute var description: String? = null
     @EpoxyAttribute var showSeparator: Boolean = false
+    @EpoxyAttribute var canDrag: Boolean = true
 
     override fun bind(holder: Holder) {
         super.bind(holder)
diff --git a/vector/src/main/java/im/vector/app/features/spaces/SpacesListViewModel.kt b/vector/src/main/java/im/vector/app/features/spaces/SpacesListViewModel.kt
index d7d7af4ca5..d30d20fdd4 100644
--- a/vector/src/main/java/im/vector/app/features/spaces/SpacesListViewModel.kt
+++ b/vector/src/main/java/im/vector/app/features/spaces/SpacesListViewModel.kt
@@ -28,23 +28,30 @@ import dagger.assisted.AssistedInject
 import im.vector.app.AppStateHandler
 import im.vector.app.RoomGroupingMethod
 import im.vector.app.core.platform.VectorViewModel
+import im.vector.app.features.session.coroutineScope
 import im.vector.app.features.settings.VectorPreferences
 import im.vector.app.group
 import im.vector.app.space
 import io.reactivex.Observable
-import io.reactivex.functions.BiFunction
 import io.reactivex.schedulers.Schedulers
 import kotlinx.coroutines.launch
 import org.matrix.android.sdk.api.extensions.tryOrNull
 import org.matrix.android.sdk.api.query.ActiveSpaceFilter
 import org.matrix.android.sdk.api.query.QueryStringValue
 import org.matrix.android.sdk.api.session.Session
+import org.matrix.android.sdk.api.session.events.model.toContent
+import org.matrix.android.sdk.api.session.events.model.toModel
 import org.matrix.android.sdk.api.session.group.groupSummaryQueryParams
 import org.matrix.android.sdk.api.session.room.RoomSortOrder
+import org.matrix.android.sdk.api.session.room.accountdata.RoomAccountDataEvent
+import org.matrix.android.sdk.api.session.room.accountdata.RoomAccountDataTypes
 import org.matrix.android.sdk.api.session.room.model.Membership
 import org.matrix.android.sdk.api.session.room.model.RoomSummary
 import org.matrix.android.sdk.api.session.room.roomSummaryQueryParams
 import org.matrix.android.sdk.api.session.room.summary.RoomAggregateNotificationCount
+import org.matrix.android.sdk.api.session.space.SpaceOrderUtils
+import org.matrix.android.sdk.api.session.space.model.SpaceOrderContent
+import org.matrix.android.sdk.api.session.space.model.TopLevelSpaceComparator
 import org.matrix.android.sdk.api.session.user.model.User
 import org.matrix.android.sdk.api.util.toMatrixItem
 import org.matrix.android.sdk.rx.asObservable
@@ -143,37 +150,86 @@ class SpacesListViewModel @AssistedInject constructor(@Assisted initialState: Sp
                 }.disposeOnClear()
     }
 
-//    private fun observeSelectionState() {
-//        selectSubscribe(SpaceListViewState::selectedSpace) { spaceSummary ->
-//            if (spaceSummary != null) {
-//                // We only want to open group if the updated selectedGroup is a different one.
-//                if (currentGroupId != spaceSummary.roomId) {
-//                    currentGroupId = spaceSummary.roomId
-//                    _viewEvents.post(SpaceListViewEvents.OpenSpace)
-//                }
-//                appStateHandler.setCurrentSpace(spaceSummary.roomId)
-//            } else {
-//                // If selected group is null we force to default. It can happens when leaving the selected group.
-//                setState {
-//                    copy(selectedSpace = this.asyncSpaces()?.find { it.roomId == ALL_COMMUNITIES_GROUP_ID })
-//                }
-//            }
-//        }
-//    }
-
     override fun handle(action: SpaceListAction) {
         when (action) {
-            is SpaceListAction.SelectSpace -> handleSelectSpace(action)
-            is SpaceListAction.LeaveSpace -> handleLeaveSpace(action)
-            SpaceListAction.AddSpace -> handleAddSpace()
-            is SpaceListAction.ToggleExpand -> handleToggleExpand(action)
-            is SpaceListAction.OpenSpaceInvite -> handleSelectSpaceInvite(action)
+            is SpaceListAction.SelectSpace       -> handleSelectSpace(action)
+            is SpaceListAction.LeaveSpace        -> handleLeaveSpace(action)
+            SpaceListAction.AddSpace             -> handleAddSpace()
+            is SpaceListAction.ToggleExpand      -> handleToggleExpand(action)
+            is SpaceListAction.OpenSpaceInvite   -> handleSelectSpaceInvite(action)
             is SpaceListAction.SelectLegacyGroup -> handleSelectGroup(action)
+            is SpaceListAction.MoveSpace         -> handleMoveSpace(action)
+            is SpaceListAction.OnEndDragging     -> handleEndDragging()
+            is SpaceListAction.OnStartDragging   -> handleStartDragging()
         }
     }
 
 // PRIVATE METHODS *****************************************************************************
 
+    var preDragExpandedState: Map<String, Boolean>? = null
+    private fun handleStartDragging() = withState { state ->
+        preDragExpandedState = state.expandedStates.toMap()
+        setState {
+            copy(
+                    expandedStates = expandedStates.map {
+                        it.key to false
+                    }.toMap()
+            )
+        }
+    }
+
+    private fun handleEndDragging() {
+        // restore expanded state
+        setState {
+            copy(
+                    expandedStates = preDragExpandedState.orEmpty()
+            )
+        }
+    }
+
+    private fun handleMoveSpace(action: SpaceListAction.MoveSpace) = withState { state ->
+        state.rootSpacesOrdered ?: return@withState
+        val orderCommands = SpaceOrderUtils.orderCommandsForMove(
+                state.rootSpacesOrdered.map {
+                    it.roomId to (state.spaceOrderLocalEchos?.get(it.roomId) ?: state.spaceOrderInfo?.get(it.roomId))
+                },
+                action.spaceId,
+                action.delta
+        )
+
+        // local echo
+        val updatedLocalEchos = state.spaceOrderLocalEchos.orEmpty().toMutableMap().apply {
+            orderCommands.forEach {
+                this[it.spaceId] = it.order
+            }
+        }.toMap()
+
+        setState {
+            copy(
+                    rootSpacesOrdered = state.rootSpacesOrdered.toMutableList().apply {
+                        val index = indexOfFirst { it.roomId == action.spaceId }
+                        val moved = removeAt(index)
+                        add(index + action.delta, moved)
+                    },
+                    spaceOrderLocalEchos = updatedLocalEchos
+            )
+        }
+        session.coroutineScope.launch {
+            orderCommands.forEach {
+                session.getRoom(it.spaceId)?.updateAccountData(RoomAccountDataTypes.EVENT_TYPE_SPACE_ORDER,
+                        SpaceOrderContent(order = it.order).toContent()
+                )
+            }
+        }
+
+        // restore expanded state
+        setState {
+            copy(
+                    expandedStates = preDragExpandedState.orEmpty()
+            )
+        }
+    }
+
     private fun handleSelectSpace(action: SpaceListAction.SelectSpace) = withState { state ->
         val groupingMethod = state.selectedGroupingMethod
         if (groupingMethod is RoomGroupingMethod.ByLegacyGroup || groupingMethod.space()?.roomId != action.spaceSummary?.roomId) {
@@ -224,24 +280,43 @@ class SpacesListViewModel @AssistedInject constructor(@Assisted initialState: Sp
             excludeType = listOf(/**RoomType.MESSAGING,$*/
                     null)
         }
-        Observable.combineLatest<User?, List<RoomSummary>, List<RoomSummary>>(
-                session
-                        .rx()
+
+        val rxSession = session.rx()
+
+        Observable.combineLatest<User?, List<RoomSummary>, List<RoomAccountDataEvent>, List<RoomSummary>>(
+                rxSession
                         .liveUser(session.myUserId)
                         .map {
                             it.getOrNull()
                         },
-                session
-                        .rx()
+                rxSession
                         .liveSpaceSummaries(spaceSummaryQueryParams),
-                BiFunction { _, communityGroups ->
+                session.accountDataService().getLiveRoomAccountDataEvents(setOf(RoomAccountDataTypes.EVENT_TYPE_SPACE_ORDER)).asObservable(),
+                { _, communityGroups, _ ->
                     communityGroups
                 }
         )
                 .execute { async ->
+                    val rootSpaces = session.spaceService().getRootSpaceSummaries()
+                    val orders = rootSpaces.map {
+                        it.roomId to session.getRoom(it.roomId)
+                                ?.getAccountDataEvent(RoomAccountDataTypes.EVENT_TYPE_SPACE_ORDER)
+                                ?.content.toModel<SpaceOrderContent>()
+                                ?.safeOrder()
+                    }.toMap()
                     copy(
                             asyncSpaces = async,
-                            rootSpaces = session.spaceService().getRootSpaceSummaries()
+                            rootSpacesOrdered = rootSpaces.sortedWith(TopLevelSpaceComparator(orders)),
+                            spaceOrderInfo = orders
+                    )
+                }
+
+        // clear local echos on update
+        session.accountDataService()
+                .getLiveRoomAccountDataEvents(setOf(RoomAccountDataTypes.EVENT_TYPE_SPACE_ORDER))
+                .asObservable().execute {
+                    copy(
+                            spaceOrderLocalEchos = emptyMap()
                     )
                 }
     }
diff --git a/vector/src/main/res/drawable/bg_space_item.xml b/vector/src/main/res/drawable/bg_space_item.xml
index 0362a9a8df..158a6769ba 100644
--- a/vector/src/main/res/drawable/bg_space_item.xml
+++ b/vector/src/main/res/drawable/bg_space_item.xml
@@ -20,7 +20,7 @@
 
     <item>
         <shape>
-            <solid android:color="@android:color/transparent" />
+            <solid android:color="?android:colorBackground" />
         </shape>
     </item>