diff --git a/apps/nextjs/src/components/board/layout/test/board-lanes.spec.ts b/apps/nextjs/src/components/board/layout/test/board-lanes.spec.ts
index ecb537089..72a8bc3f4 100644
--- a/apps/nextjs/src/components/board/layout/test/board-lanes.spec.ts
+++ b/apps/nextjs/src/components/board/layout/test/board-lanes.spec.ts
@@ -38,6 +38,22 @@ describe("board lanes", () => {
     expect(getBoardLaneColumnCount(layout, "right")).toBe(0);
   });
 
+  test("disables gutters for mobile layouts", () => {
+    const layout = {
+      id: "mobile",
+      name: "Mobile",
+      columnCount: 12,
+      leftGutterColumnCount: 2,
+      rightGutterColumnCount: 3,
+      breakpoint: 0,
+      role: "mobile",
+    } satisfies Board["layouts"][number];
+
+    expect(getBoardLaneColumnCount(layout, "left")).toBe(0);
+    expect(getBoardLaneColumnCount(layout, "main")).toBe(12);
+    expect(getBoardLaneColumnCount(layout, "right")).toBe(0);
+  });
+
   test("rejects ambiguous duplicate roots", () => {
     const board = new BoardMockBuilder()
       .addSection(new EmptySectionMockBuilder({ id: "main-a" }).build())
diff --git a/packages/definitions/src/section.ts b/packages/definitions/src/section.ts
index ac820c840..1ea09ae2c 100644
--- a/packages/definitions/src/section.ts
+++ b/packages/definitions/src/section.ts
@@ -1,3 +1,5 @@
+import type { LayoutRole } from "./board";
+
 export const sectionKinds = ["empty", "container"] as const;
 export type SectionKind = (typeof sectionKinds)[number];
 
@@ -21,12 +23,17 @@ export const getBoardLaneColumnCount = (
     columnCount: number;
     leftGutterColumnCount?: number | null;
     rightGutterColumnCount?: number | null;
+    role?: LayoutRole;
   },
   lane: BoardLane,
 ) => {
   const total = Math.max(1, Math.floor(layout.columnCount));
-  const left = Math.min(Math.max(0, Math.floor(layout.leftGutterColumnCount ?? 0)), total - 1);
-  const right = Math.min(Math.max(0, Math.floor(layout.rightGutterColumnCount ?? 0)), total - left - 1);
+  const left =
+    layout.role === "mobile" ? 0 : Math.min(Math.max(0, Math.floor(layout.leftGutterColumnCount ?? 0)), total - 1);
+  const right =
+    layout.role === "mobile"
+      ? 0
+      : Math.min(Math.max(0, Math.floor(layout.rightGutterColumnCount ?? 0)), total - left - 1);
   if (lane === "left") return left;
   if (lane === "right") return right;
   return total - left - right;
diff --git a/packages/validation/src/board-layout.spec.ts b/packages/validation/src/board-layout.spec.ts
index 5f73132f9..a744c81a6 100644
--- a/packages/validation/src/board-layout.spec.ts
+++ b/packages/validation/src/board-layout.spec.ts
@@ -42,4 +42,17 @@ describe("board layout gutters", () => {
       }).success,
     ).toBe(false);
   });
+
+  test("rejects sidebars on mobile layouts", () => {
+    expect(
+      boardLayoutSchema.safeParse({
+        id: "mobile",
+        name: "Mobile",
+        columnCount: 6,
+        leftGutterColumnCount: 1,
+        breakpoint: 0,
+        role: "mobile",
+      }).success,
+    ).toBe(false);
+  });
 });