diff --git a/docs/requirements.md b/docs/requirements.md
index 641fbb5..99be4f8 100644
--- a/docs/requirements.md
+++ b/docs/requirements.md
@@ -555,9 +555,9 @@ The screen is divided into two columns: a main column (75% width) containing the
 - REQ-UI-BUILD-GRID: All placeable building types are shown as a flat grid of buttons with no grouping. Tunnel Entry and Tunnel Exit share a single **Tunnel** button (REQ-BLD-TUNNEL-MODE) rather than one button each.
 - REQ-UI-BUILD-COST: Each button caption shows the building name and its building block cost, e.g. "Belt: 2 Blocks".
 - REQ-UI-BUILD-ICON: Each build button shows an icon alongside its caption. Icons are SVG files loaded at runtime from `data/icons/buildings/` (a sibling of the config directory, read the same way as `visuals.toml`), one file per button named after the building's id (e.g. `belt.svg`, `reprocessing_plant.svg`). The shared Tunnel button (REQ-UI-BUILD-GRID) uses `tunnel_entry.svg`; the Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) uses `deconstruct.svg`. Each icon is a rounded colored "chip" bearing a white line glyph, the chip color following the building's fill color in `visuals.toml`. A missing icon file leaves the button with its caption and no icon; it is not an error.
-- REQ-UI-BUILD-TOOLTIP: Each building-type button shows a hover tooltip with the descriptive text defined for that building type in `buildings.toml` (the optional per-building tooltip field). This tooltip is distinct from the recipe/schematic selection tooltip (REQ-UI-SELECT-TOOLTIP). If a building type defines no tooltip text, its button shows no tooltip. The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) is not a building type and has no config-defined tooltip.
+- REQ-UI-BUILD-TOOLTIP: Each building-type button shows a hover tooltip with the descriptive text defined for that building type in `buildings.toml` (the optional per-building tooltip field). This tooltip is distinct from the recipe/schematic selection tooltip (REQ-UI-SELECT-TOOLTIP). If a building type defines no tooltip text, its button shows no tooltip. The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) is not a building type and so has no config-defined tooltip; it instead shows its own refund tooltip defined in REQ-UI-DECONSTRUCT-BUTTON.
 - REQ-UI-BUILD-DISABLED: Buttons for buildings the player cannot currently afford are shown as disabled. A disabled button's icon (REQ-UI-BUILD-ICON) is rendered in a greyed variant, with its colored chip background recolored grey while the white glyph is retained.
-- REQ-UI-DECONSTRUCT-BUTTON: A dedicated **Deconstruct** button is shown in the build button grid. Clicking it toggles deconstruct mode on and off, equivalent to the Q deconstruct toggle (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while deconstruct mode is active.
+- REQ-UI-DECONSTRUCT-BUTTON: A dedicated **Deconstruct** button is shown in the build button grid. Clicking it toggles deconstruct mode on and off, equivalent to the Q deconstruct toggle (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while deconstruct mode is active. The button shows a hover tooltip stating the deconstruction refund (REQ-BLD-DECONSTRUCT): that deconstructing a fully-built building returns `world.toml [world].refund_percentage` percent of its building block cost once deconstruction completes, and that a construction site removed before it finishes building is refunded in full. When `refund_percentage` is 100% both cases yield the same refund, and the tooltip is simplified to state the single refund percentage without distinguishing the two cases. Unlike the building-type button tooltips (REQ-UI-BUILD-TOOLTIP), this tooltip is not config-defined text but is composed from the refund percentage.
 
 ### Blueprint Panel
 
diff --git a/src/ui/BuildButtonGrid.cpp b/src/ui/BuildButtonGrid.cpp
index 465866a..02d9252 100644
--- a/src/ui/BuildButtonGrid.cpp
+++ b/src/ui/BuildButtonGrid.cpp
@@ -143,6 +143,19 @@ BuildButtonGrid::BuildButtonGrid(Simulation* sim, const GameConfig* config,
     m_deconstructButton->setIcon(loadBuildingIcon(
         QString::fromStdString(m_iconDir) + "/deconstruct.svg"));
     m_deconstructButton->setIconSize(kIconSize);
+    // Refund tooltip composed from world.refund_percentage (REQ-UI-DECONSTRUCT-BUTTON,
+    // REQ-BLD-DECONSTRUCT). A finished building refunds the configured percentage; a
+    // construction site removed before it is built is refunded in full. When the
+    // percentage is 100% both cases coincide, so the tooltip is simplified to one case.
+    const int refundPercentage = m_config->world.refundPercentage;
+    const QString deconstructTooltip = (refundPercentage >= 100)
+        ? tr("Deconstruct buildings. Refunds %1% of the building block cost.")
+              .arg(refundPercentage)
+        : tr("Deconstruct buildings. A finished building refunds %1% of its building "
+             "block cost once removed; a construction site removed before it is built "
+             "is refunded in full.")
+              .arg(refundPercentage);
+    m_deconstructButton->setToolTip(deconstructTooltip);
     layout->addWidget(m_deconstructButton, row, col);
     connect(m_deconstructButton, &QPushButton::clicked, this, [this]() {
         EventManager::getInstance()->sendEventImmediately(