diff --git a/src/ifcgeom/kernels/cgal/CgalKernel.cpp b/src/ifcgeom/kernels/cgal/CgalKernel.cpp
index 514d26f469..6b9603f4be 100644
--- a/src/ifcgeom/kernels/cgal/CgalKernel.cpp
+++ b/src/ifcgeom/kernels/cgal/CgalKernel.cpp
@@ -40,7 +40,7 @@ void CgalKernel::remove_duplicate_points_from_loop(cgal_wire_t& polygon) {
 	}
 }
 
-CGAL::Polyhedron_3<Kernel_> ifcopenshell::geometry::utils::create_polyhedron(std::list<cgal_face_t> &face_list) {
+CGAL::Polyhedron_3<Kernel_> ifcopenshell::geometry::utils::create_polyhedron(std::list<cgal_face_t> &face_list, bool stitch_borders) {
 
 	// Naive creation
 	CGAL::Polyhedron_3<Kernel_> polyhedron;
@@ -49,7 +49,15 @@ CGAL::Polyhedron_3<Kernel_> ifcopenshell::geometry::utils::create_polyhedron(std
 
 	// Stitch edges
 	//  std::cout << "Before: " << polyhedron.size_of_vertices() << " vertices and " << polyhedron.size_of_facets() << " facets" << std::endl;
-	CGAL::Polygon_mesh_processing::stitch_borders(polyhedron);
+	
+	if (stitch_borders) {
+		// we have a map of points now in the builder, it's maybe not necessary anymore to stitch_borders?
+		// size_t ne = polyhedron.size_of_border_edges();
+		CGAL::Polygon_mesh_processing::stitch_borders(polyhedron);
+		// size_t ne2 = polyhedron.size_of_border_edges();
+		// std::wcout << (ne - ne2) << " removed" << std::endl;
+	}
+	
 	polyhedron.normalize_border();
 	if (!polyhedron.is_valid(false, 1)) {
 		Logger::Message(Logger::LOG_ERROR, "create_polyhedron: Polyhedron not valid!");
@@ -1000,8 +1008,12 @@ bool CgalKernel::process_as_2d_polygon(const taxonomy::boolean_result* br, std::
 	loops.clear();
 	std::transform(wires.begin(), wires.end(), std::back_inserter(loops), wire_to_polygon_2);
 
+	auto& op_0_matrix = *extrusions[0]->matrix.components;
+	Eigen::Vector4d op_0_dir;
+	op_0_dir << (*extrusions[0]->direction.components), 0;
+	op_0_dir = op_0_matrix * op_0_dir;
 	z0 = op_0_matrix_2_3;
-	z1 = z0 + extrusions[0]->depth * (*extrusions[0]->direction.components)(2);
+	z1 = z0 + extrusions[0]->depth * op_0_dir(2);
 
 	if (z1 < z0) {
 		std::swap(z0, z1);
diff --git a/src/ifcgeom/kernels/cgal/CgalKernel.h b/src/ifcgeom/kernels/cgal/CgalKernel.h
index 39587319ac..45dcb564bb 100644
--- a/src/ifcgeom/kernels/cgal/CgalKernel.h
+++ b/src/ifcgeom/kernels/cgal/CgalKernel.h
@@ -53,24 +53,24 @@ public:
   }
   
   void operator()(CGAL::Polyhedron_3<Kernel_>::HalfedgeDS &hds) {
-    std::list<Kernel_::Point_3> points;
-    std::list<std::list<std::size_t>> facet_vertices;
+    // std::list<Kernel_::Point_3> points;
+	std::map<Kernel_::Point_3, size_t> points;
+    std::vector<std::vector<std::size_t>> facet_vertices(face_list->size());
     CGAL::Polyhedron_incremental_builder_3<CGAL::Polyhedron_3<Kernel_>::HalfedgeDS> builder(hds, true);
     
+	size_t i = 0;
     for (auto &face: *face_list) {
-      facet_vertices.push_back(std::list<std::size_t>());
       for (auto &point: face.outer) {
-        facet_vertices.back().push_back(points.size());
-        points.push_back(point);
+		  auto p = points.insert({ point, points.size() });
+		  if (p.second) {
+			  builder.add_vertex(point);
+		  }
+		  facet_vertices[i].push_back(p.first->second);
       }
+	  i++;
     }
     
-    builder.begin_surface(points.size(), facet_vertices.size());
-    
-    for (auto &point: points) {
-//      std::cout << "Adding point " << point << std::endl;
-      builder.add_vertex(point);
-    }
+    builder.begin_surface(points.size(), facet_vertices.size(), 0, CGAL::Polyhedron_incremental_builder_3<CGAL::Polyhedron_3<Kernel_>::HalfedgeDS>::ABSOLUTE_INDEXING);
     
     for (auto &facet: facet_vertices) {
       builder.begin_facet();
@@ -92,7 +92,7 @@ namespace geometry {
 namespace utils {
 	IFC_GEOM_API CGAL::Polyhedron_3<Kernel_> create_cube(double d);
 	IFC_GEOM_API CGAL::Polyhedron_3<Kernel_> create_cube(const Kernel_::Point_3& lower, const Kernel_::Point_3& upper);
-	IFC_GEOM_API CGAL::Polyhedron_3<Kernel_> create_polyhedron(std::list<cgal_face_t> &face_list);
+	IFC_GEOM_API CGAL::Polyhedron_3<Kernel_> create_polyhedron(std::list<cgal_face_t> &face_list, bool stitch_borders=false);
 	IFC_GEOM_API CGAL::Polyhedron_3<Kernel_> create_polyhedron(const CGAL::Nef_polyhedron_3<Kernel_> &nef_polyhedron);
 	IFC_GEOM_API CGAL::Nef_polyhedron_3<Kernel_> create_nef_polyhedron(std::list<cgal_face_t> &face_list);
 	IFC_GEOM_API CGAL::Nef_polyhedron_3<Kernel_> create_nef_polyhedron(CGAL::Polyhedron_3<Kernel_> &polyhedron);