diff --git a/src/ifcquery/ifcquery/__main__.py b/src/ifcquery/ifcquery/__main__.py
index 635697b5e0..c77fb91c97 100644
--- a/src/ifcquery/ifcquery/__main__.py
+++ b/src/ifcquery/ifcquery/__main__.py
@@ -24,6 +24,7 @@ import sys
 
 import ifcopenshell
 
+from ifcquery import clash as clash_mod
 from ifcquery import info, relations, select, summary, tree
 
 
@@ -93,6 +94,14 @@ def main():
     relations_parser.add_argument("element_id", help="Element step ID (e.g. 123 or #123)")
     relations_parser.add_argument("--traverse", choices=["up"], help="Traverse hierarchy (up: walk to IfcProject)")
 
+    clash_parser = subparsers.add_parser("clash", help="Check element placement for clashes")
+    clash_parser.add_argument("element_id", help="Element step ID (e.g. 123 or #123)")
+    clash_parser.add_argument("--clearance", type=float, help="Minimum clearance distance")
+    clash_parser.add_argument("--tolerance", type=float, default=0.002, help="Intersection tolerance (default: 0.002)")
+    clash_parser.add_argument(
+        "--scope", choices=["storey", "all"], default="storey", help="Scope of elements to check (default: storey)"
+    )
+
     args = parser.parse_args()
 
     try:
@@ -131,6 +140,24 @@ def main():
             print(f"Error: Element #{element_id} not found", file=sys.stderr)
             sys.exit(1)
         result = relations.relations(model, element, traverse=args.traverse)
+    elif args.command == "clash":
+        try:
+            element_id = parse_element_id(args.element_id)
+        except ValueError:
+            print(f"Error: Invalid element ID: {args.element_id}", file=sys.stderr)
+            sys.exit(1)
+        try:
+            element = model.by_id(element_id)
+        except RuntimeError:
+            print(f"Error: Element #{element_id} not found", file=sys.stderr)
+            sys.exit(1)
+        try:
+            result = clash_mod.clash(
+                model, element, clearance=args.clearance, tolerance=args.tolerance, scope=args.scope
+            )
+        except ImportError:
+            print("Error: ifcopenshell geometry engine not available (C++ bindings required)", file=sys.stderr)
+            sys.exit(1)
 
     print(format_output(result, args.output_format))
 
diff --git a/src/ifcquery/ifcquery/clash.py b/src/ifcquery/ifcquery/clash.py
new file mode 100644
index 0000000000..bb1132e21e
--- /dev/null
+++ b/src/ifcquery/ifcquery/clash.py
@@ -0,0 +1,174 @@
+# IfcQuery - IFC model interrogation CLI
+# Copyright (C) 2025 Bruno Postle <bruno@postle.net>
+#
+# This file is part of IfcQuery.
+#
+# IfcQuery is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcQuery is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcQuery.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import annotations
+
+import multiprocessing
+import sys
+from typing import Any
+
+import ifcopenshell
+import ifcopenshell.geom
+import ifcopenshell.util.element
+
+
+def _ref(element: ifcopenshell.entity_instance) -> dict[str, Any]:
+    """Serialize an element to a compact reference dict."""
+    result: dict[str, Any] = {"id": element.id(), "type": element.is_a()}
+    if hasattr(element, "Name") and element.Name:
+        result["name"] = element.Name
+    return result
+
+
+def _get_scope_elements(
+    model: ifcopenshell.file, element: ifcopenshell.entity_instance, scope: str
+) -> tuple[set[ifcopenshell.entity_instance], str]:
+    """Return set of elements to check against and the effective scope used.
+
+    Returns (elements, effective_scope) where effective_scope may differ from
+    the requested scope if fallback was needed.
+    """
+    if scope == "storey":
+        container = ifcopenshell.util.element.get_container(element)
+        if container is not None:
+            siblings = set(ifcopenshell.util.element.get_contained(container))
+            siblings.discard(element)
+            return siblings, "storey"
+        else:
+            print(
+                f"Warning: Element #{element.id()} has no spatial container, falling back to --scope all",
+                file=sys.stderr,
+            )
+
+    # scope == "all" or fallback
+    elements = set(model.by_type("IfcElement"))
+    elements -= set(model.by_type("IfcFeatureElement"))
+    elements.discard(element)
+    return elements, "all"
+
+
+def _build_tree(
+    model: ifcopenshell.file, elements: set[ifcopenshell.entity_instance]
+) -> ifcopenshell.geom.tree | None:
+    """Build geometry tree for given elements using iterator.
+
+    Returns None if iterator fails to initialize (no geometry available).
+    """
+    geom_settings = ifcopenshell.geom.settings()
+    geom_settings.set("use-world-coords", True)
+    geom_tree = ifcopenshell.geom.tree()
+    iterator = ifcopenshell.geom.iterator(
+        geom_settings, model, multiprocessing.cpu_count(), include=list(elements)
+    )
+    if not iterator.initialize():
+        return None
+    while True:
+        geom_tree.add_element(iterator.get())
+        if not iterator.next():
+            break
+    return geom_tree
+
+
+def _format_clash(
+    clash_result, geom_tree: ifcopenshell.geom.tree, model: ifcopenshell.file
+) -> dict[str, Any]:
+    """Format a single clash result to dict."""
+    # clash result .a/.b are C++ wrapper entity_instances without .Name;
+    # look up the Python entity from the model by id for proper serialization
+    other = model.by_id(clash_result.b.id())
+    return {
+        "element": _ref(other),
+        "type": geom_tree.get_clash_type(clash_result.clash_type),
+        "distance": clash_result.distance,
+        "p1": list(clash_result.p1),
+        "p2": list(clash_result.p2),
+    }
+
+
+def clash(
+    model: ifcopenshell.file,
+    element: ifcopenshell.entity_instance,
+    clearance: float | None = None,
+    tolerance: float = 0.002,
+    scope: str = "storey",
+) -> dict[str, Any]:
+    """Check element for geometric clashes against other elements.
+
+    :param model: The IFC model.
+    :param element: The element to check.
+    :param clearance: Minimum clearance distance; if provided, runs clearance check.
+    :param tolerance: Intersection tolerance in meters (default 0.002).
+    :param scope: Which elements to check against: "storey" or "all".
+    :return: Dict with clash results suitable for JSON serialization.
+    """
+    result: dict[str, Any] = {"element": _ref(element)}
+
+    # Get scope elements
+    scope_elements, effective_scope = _get_scope_elements(model, element, scope)
+    result["scope"] = effective_scope
+
+    if not scope_elements:
+        result["pass"] = True
+        result["checks"] = {
+            "intersection": {"pass": True, "tolerance": tolerance, "clashes": []}
+        }
+        if clearance is not None:
+            result["checks"]["clearance"] = {"pass": True, "clearance": clearance, "clashes": []}
+        return result
+
+    # Build geometry tree for target element + scope elements
+    all_elements = scope_elements | {element}
+    geom_tree = _build_tree(model, all_elements)
+
+    if geom_tree is None:
+        result["pass"] = None
+        result["error"] = f"No geometry for element #{element.id()}"
+        return result
+
+    # Run intersection check
+    intersection_clashes = geom_tree.clash_intersection_many(
+        [element], list(scope_elements), tolerance=tolerance, check_all=True
+    )
+    intersection_results = [_format_clash(c, geom_tree, model) for c in intersection_clashes]
+    checks: dict[str, Any] = {
+        "intersection": {
+            "pass": len(intersection_results) == 0,
+            "tolerance": tolerance,
+            "clashes": intersection_results,
+        }
+    }
+
+    all_pass = len(intersection_results) == 0
+
+    # Run clearance check if requested
+    if clearance is not None:
+        clearance_clashes = geom_tree.clash_clearance_many(
+            [element], list(scope_elements), clearance=clearance, check_all=True
+        )
+        clearance_results = [_format_clash(c, geom_tree, model) for c in clearance_clashes]
+        checks["clearance"] = {
+            "pass": len(clearance_results) == 0,
+            "clearance": clearance,
+            "clashes": clearance_results,
+        }
+        if clearance_results:
+            all_pass = False
+
+    result["pass"] = all_pass
+    result["checks"] = checks
+    return result
diff --git a/src/ifcquery/tests/test_clash.py b/src/ifcquery/tests/test_clash.py
new file mode 100644
index 0000000000..507a4ad122
--- /dev/null
+++ b/src/ifcquery/tests/test_clash.py
@@ -0,0 +1,332 @@
+import json
+import os
+import subprocess
+import sys
+import tempfile
+
+import numpy as np
+import pytest
+
+import ifcopenshell
+import ifcopenshell.api.aggregate
+import ifcopenshell.api.context
+import ifcopenshell.api.geometry
+import ifcopenshell.api.owner.settings
+import ifcopenshell.api.project
+import ifcopenshell.api.root
+import ifcopenshell.api.spatial
+import ifcopenshell.api.unit
+
+from ifcquery.clash import clash
+
+try:
+    import ifcopenshell.geom
+
+    HAS_GEOM = True
+except ImportError:
+    HAS_GEOM = False
+
+pytestmark = pytest.mark.skipif(not HAS_GEOM, reason="ifcopenshell geometry engine not available")
+
+
+@pytest.fixture
+def model_with_geometry():
+    """Create an IFC4 model with walls that have geometric representations."""
+    f = ifcopenshell.api.project.create_file()
+    ifcopenshell.api.owner.settings.get_user = lambda ifc: (ifc.by_type("IfcPersonAndOrganization") or [None])[0]
+    ifcopenshell.api.owner.settings.get_application = lambda ifc: (ifc.by_type("IfcApplication") or [None])[0]
+
+    project = ifcopenshell.api.root.create_entity(f, ifc_class="IfcProject", name="TestProject")
+    ifcopenshell.api.unit.assign_unit(f)
+
+    site = ifcopenshell.api.root.create_entity(f, ifc_class="IfcSite", name="TestSite")
+    building = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuilding", name="TestBuilding")
+    storey = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuildingStorey", name="Ground Floor")
+
+    ifcopenshell.api.aggregate.assign_object(f, products=[site], relating_object=project)
+    ifcopenshell.api.aggregate.assign_object(f, products=[building], relating_object=site)
+    ifcopenshell.api.aggregate.assign_object(f, products=[storey], relating_object=building)
+
+    # Create geometry context
+    model_ctx = ifcopenshell.api.context.add_context(f, context_type="Model")
+    body = ifcopenshell.api.context.add_context(
+        f, context_type="Model", context_identifier="Body", target_view="MODEL_VIEW", parent=model_ctx
+    )
+
+    # Wall 1 at origin
+    wall1 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="Wall001")
+    rep1 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall1, representation=rep1)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall1], relating_structure=storey)
+
+    # Wall 2 perpendicular, crossing through wall 1
+    wall2 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="Wall002")
+    rep2 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall2, representation=rep2)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall2], relating_structure=storey)
+    matrix2 = np.array([[0, -1, 0, 2.5], [1, 0, 0, -2.0], [0, 0, 1, 0], [0, 0, 0, 1]], dtype=float)
+    ifcopenshell.api.geometry.edit_object_placement(f, product=wall2, matrix=matrix2)
+
+    # Wall 3 far away (10m offset in Y)
+    wall3 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="Wall003")
+    rep3 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall3, representation=rep3)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall3], relating_structure=storey)
+    matrix3 = np.eye(4)
+    matrix3[1, 3] = 10.0  # 10m in Y direction
+    ifcopenshell.api.geometry.edit_object_placement(f, product=wall3, matrix=matrix3)
+
+    # Wall 4 close but not overlapping (0.3m offset in Y, wall thickness is 0.2m)
+    wall4 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="Wall004")
+    rep4 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall4, representation=rep4)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall4], relating_structure=storey)
+    matrix4 = np.eye(4)
+    matrix4[1, 3] = 0.3  # 0.3m in Y (gap of 0.1m from wall1)
+    ifcopenshell.api.geometry.edit_object_placement(f, product=wall4, matrix=matrix4)
+
+    return f
+
+
+@pytest.fixture
+def model_two_storeys():
+    """Create a model with walls in different storeys."""
+    f = ifcopenshell.api.project.create_file()
+    ifcopenshell.api.owner.settings.get_user = lambda ifc: (ifc.by_type("IfcPersonAndOrganization") or [None])[0]
+    ifcopenshell.api.owner.settings.get_application = lambda ifc: (ifc.by_type("IfcApplication") or [None])[0]
+
+    project = ifcopenshell.api.root.create_entity(f, ifc_class="IfcProject", name="TestProject")
+    ifcopenshell.api.unit.assign_unit(f)
+
+    site = ifcopenshell.api.root.create_entity(f, ifc_class="IfcSite", name="TestSite")
+    building = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuilding", name="TestBuilding")
+    storey1 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuildingStorey", name="Ground Floor")
+    storey2 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuildingStorey", name="First Floor")
+
+    ifcopenshell.api.aggregate.assign_object(f, products=[site], relating_object=project)
+    ifcopenshell.api.aggregate.assign_object(f, products=[building], relating_object=site)
+    ifcopenshell.api.aggregate.assign_object(f, products=[storey1, storey2], relating_object=building)
+
+    model_ctx = ifcopenshell.api.context.add_context(f, context_type="Model")
+    body = ifcopenshell.api.context.add_context(
+        f, context_type="Model", context_identifier="Body", target_view="MODEL_VIEW", parent=model_ctx
+    )
+
+    # Wall in storey 1
+    wall1 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="GroundWall")
+    rep1 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall1, representation=rep1)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall1], relating_structure=storey1)
+
+    # Wall in storey 2, perpendicular and crossing wall1
+    wall2 = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="FirstFloorWall")
+    rep2 = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+    ifcopenshell.api.geometry.assign_representation(f, product=wall2, representation=rep2)
+    ifcopenshell.api.spatial.assign_container(f, products=[wall2], relating_structure=storey2)
+    matrix2 = np.array([[0, -1, 0, 2.5], [1, 0, 0, -2.0], [0, 0, 1, 0], [0, 0, 0, 1]], dtype=float)
+    ifcopenshell.api.geometry.edit_object_placement(f, product=wall2, matrix=matrix2)
+
+    return f
+
+
+class TestNoClashes:
+    def test_no_clashes_far_apart(self, model_with_geometry):
+        wall3 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall003"][0]
+        result = clash(model_with_geometry, wall3)
+        assert result["pass"] is True
+        assert result["checks"]["intersection"]["pass"] is True
+        assert result["checks"]["intersection"]["clashes"] == []
+
+    def test_no_clashes_empty_scope(self, model_with_geometry):
+        """A model where the element is the only one in scope should pass."""
+        # Create a model with a single wall
+        f = ifcopenshell.api.project.create_file()
+        ifcopenshell.api.owner.settings.get_user = lambda ifc: (ifc.by_type("IfcPersonAndOrganization") or [None])[0]
+        ifcopenshell.api.owner.settings.get_application = lambda ifc: (
+            ifc.by_type("IfcApplication") or [None]
+        )[0]
+        project = ifcopenshell.api.root.create_entity(f, ifc_class="IfcProject", name="P")
+        ifcopenshell.api.unit.assign_unit(f)
+        site = ifcopenshell.api.root.create_entity(f, ifc_class="IfcSite", name="S")
+        building = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuilding", name="B")
+        storey = ifcopenshell.api.root.create_entity(f, ifc_class="IfcBuildingStorey", name="GF")
+        ifcopenshell.api.aggregate.assign_object(f, products=[site], relating_object=project)
+        ifcopenshell.api.aggregate.assign_object(f, products=[building], relating_object=site)
+        ifcopenshell.api.aggregate.assign_object(f, products=[storey], relating_object=building)
+        model_ctx = ifcopenshell.api.context.add_context(f, context_type="Model")
+        body = ifcopenshell.api.context.add_context(
+            f, context_type="Model", context_identifier="Body", target_view="MODEL_VIEW", parent=model_ctx
+        )
+        wall = ifcopenshell.api.root.create_entity(f, ifc_class="IfcWall", name="OnlyWall")
+        rep = ifcopenshell.api.geometry.add_wall_representation(f, context=body, length=5, height=3, thickness=0.2)
+        ifcopenshell.api.geometry.assign_representation(f, product=wall, representation=rep)
+        ifcopenshell.api.spatial.assign_container(f, products=[wall], relating_structure=storey)
+
+        result = clash(f, wall)
+        assert result["pass"] is True
+
+
+class TestIntersectionDetected:
+    def test_overlapping_walls(self, model_with_geometry):
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1)
+        assert result["pass"] is False
+        assert result["checks"]["intersection"]["pass"] is False
+        clashes = result["checks"]["intersection"]["clashes"]
+        assert len(clashes) > 0
+        # Wall002 should be in the clashes (it overlaps wall1)
+        clash_ids = {c["element"]["id"] for c in clashes}
+        wall2 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall002"][0]
+        assert wall2.id() in clash_ids
+
+    def test_clash_has_points(self, model_with_geometry):
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1)
+        clashes = result["checks"]["intersection"]["clashes"]
+        for c in clashes:
+            assert "p1" in c
+            assert "p2" in c
+            assert len(c["p1"]) == 3
+            assert len(c["p2"]) == 3
+            assert "type" in c
+            assert "distance" in c
+
+
+class TestClearance:
+    def test_clearance_violation(self, model_with_geometry):
+        """Wall004 is 0.1m from wall1; clearance of 0.5m should fail."""
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1, clearance=0.5)
+        assert "clearance" in result["checks"]
+        # Wall004 should violate clearance
+        clearance_clashes = result["checks"]["clearance"]["clashes"]
+        clash_ids = {c["element"]["id"] for c in clearance_clashes}
+        wall4 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall004"][0]
+        assert wall4.id() in clash_ids
+        assert result["checks"]["clearance"]["pass"] is False
+
+    def test_clearance_pass(self, model_with_geometry):
+        """Wall003 is 10m away; clearance of 0.5m should pass for wall003."""
+        wall3 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall003"][0]
+        result = clash(model_with_geometry, wall3, clearance=0.5)
+        assert result["checks"]["clearance"]["pass"] is True
+        assert result["checks"]["clearance"]["clashes"] == []
+
+    def test_clearance_not_included_by_default(self, model_with_geometry):
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1)
+        assert "clearance" not in result["checks"]
+
+
+class TestScope:
+    def test_scope_storey_excludes_other_storeys(self, model_two_storeys):
+        wall1 = [w for w in model_two_storeys.by_type("IfcWall") if w.Name == "GroundWall"][0]
+        result = clash(model_two_storeys, wall1, scope="storey")
+        assert result["scope"] == "storey"
+        # No clashes because the overlapping wall is in a different storey
+        assert result["pass"] is True
+
+    def test_scope_all_includes_other_storeys(self, model_two_storeys):
+        wall1 = [w for w in model_two_storeys.by_type("IfcWall") if w.Name == "GroundWall"][0]
+        result = clash(model_two_storeys, wall1, scope="all")
+        assert result["scope"] == "all"
+        # Should detect clash with the other-storey wall
+        assert result["pass"] is False
+        clash_ids = {c["element"]["id"] for c in result["checks"]["intersection"]["clashes"]}
+        wall2 = [w for w in model_two_storeys.by_type("IfcWall") if w.Name == "FirstFloorWall"][0]
+        assert wall2.id() in clash_ids
+
+
+class TestNoGeometry:
+    def test_no_geometry_error(self, model):
+        """Element without geometry reports error."""
+        wall = model.by_type("IfcWall")[0]
+        result = clash(model, wall)
+        assert result["pass"] is None
+        assert "error" in result
+        assert "No geometry" in result["error"]
+
+
+class TestJsonSerializable:
+    def test_result_serializable(self, model_with_geometry):
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1)
+        serialized = json.dumps(result)
+        parsed = json.loads(serialized)
+        assert parsed["element"]["type"] == "IfcWall"
+
+    def test_clearance_result_serializable(self, model_with_geometry):
+        wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+        result = clash(model_with_geometry, wall1, clearance=0.5)
+        serialized = json.dumps(result)
+        parsed = json.loads(serialized)
+        assert "clearance" in parsed["checks"]
+
+
+class TestCLI:
+    @staticmethod
+    def _ifc_path(model):
+        f = tempfile.NamedTemporaryFile(suffix=".ifc", delete=False)
+        model.write(f.name)
+        f.close()
+        return f.name
+
+    def test_clash_json(self, model_with_geometry):
+        path = self._ifc_path(model_with_geometry)
+        try:
+            wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+            result = subprocess.run(
+                [sys.executable, "-m", "ifcquery", path, "clash", str(wall1.id())],
+                capture_output=True,
+                text=True,
+            )
+            assert result.returncode == 0
+            data = json.loads(result.stdout)
+            assert data["element"]["type"] == "IfcWall"
+            assert "checks" in data
+            assert "intersection" in data["checks"]
+        finally:
+            os.unlink(path)
+
+    def test_clash_with_clearance(self, model_with_geometry):
+        path = self._ifc_path(model_with_geometry)
+        try:
+            wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+            result = subprocess.run(
+                [sys.executable, "-m", "ifcquery", path, "clash", str(wall1.id()), "--clearance", "0.5"],
+                capture_output=True,
+                text=True,
+            )
+            assert result.returncode == 0
+            data = json.loads(result.stdout)
+            assert "clearance" in data["checks"]
+        finally:
+            os.unlink(path)
+
+    def test_clash_scope_all(self, model_with_geometry):
+        path = self._ifc_path(model_with_geometry)
+        try:
+            wall1 = [w for w in model_with_geometry.by_type("IfcWall") if w.Name == "Wall001"][0]
+            result = subprocess.run(
+                [sys.executable, "-m", "ifcquery", path, "clash", str(wall1.id()), "--scope", "all"],
+                capture_output=True,
+                text=True,
+            )
+            assert result.returncode == 0
+            data = json.loads(result.stdout)
+            assert data["scope"] == "all"
+        finally:
+            os.unlink(path)
+
+    def test_clash_bad_id(self, model_with_geometry):
+        path = self._ifc_path(model_with_geometry)
+        try:
+            result = subprocess.run(
+                [sys.executable, "-m", "ifcquery", path, "clash", "999999"],
+                capture_output=True,
+                text=True,
+            )
+            assert result.returncode != 0
+            assert "Error" in result.stderr
+        finally:
+            os.unlink(path)