diff --git a/src/util/qpolygon-utils.js b/src/util/qpolygon-utils.js
index 97e1d394..3aac6cdf 100644
--- a/src/util/qpolygon-utils.js
+++ b/src/util/qpolygon-utils.js
@@ -1569,6 +1569,7 @@ export const drawGableRoof = (roofId, canvas, textMode) => {
 
       //각 포인트들을 직교하도록 정렬
       const sortedPoints = getSortedOrthogonalPoints(roofPlanePoint)
+      // logger.log(`[GABLE-H8-PLANE] planeDir ridges=${ridgeLines.length}`)
       sortedPoints.forEach((currPoint, index) => {
         const nextPoint = sortedPoints[(index + 1) % sortedPoints.length]
         const points = [currPoint.x, currPoint.y, nextPoint.x, nextPoint.y]
@@ -1617,6 +1618,7 @@ export const drawGableRoof = (roofId, canvas, textMode) => {
             if (Math.abs(rg.y1 - points[1]) >= 1) return false
             return Math.min(rg.x1, rg.x2) - 1 <= sMin && sMax <= Math.max(rg.x1, rg.x2) + 1
           })
+          // logger.log(`[GABLE-H8-CHK] seg covered=${coveredByRidge ? 'YES' : 'NO'}`)
           if (coveredByRidge) {
             return true
           }
@@ -1651,6 +1653,52 @@ export const drawGableRoof = (roofId, canvas, textMode) => {
     drawRoofPlane(backward)
   })
   roof.innerLines.push(...ridgeLines, ...innerLines)
+
+  // [VALLEY-BOX-FILL 2026-06-24] 골짜기에서 평행한 두 마루가 수직축으로 겹치면(出幅 겹침=박스),
+  //   짧은 마루 쪽 위치에 겹침구간을 잇는 세로 박스라인(라벨 B)을 채운다.
+  //   마루는 건드리지 않고(박스라인+마루) 박스 경계만 보강 → 마루 삭제해도 경계 유지.
+  {
+    const VB_EPS = 1
+    for (let i = 0; i < ridgeLines.length; i++) {
+      for (let j = i + 1; j < ridgeLines.length; j++) {
+        const a = ridgeLines[i]
+        const b = ridgeLines[j]
+        const aV = Math.abs(a.x1 - a.x2) < VB_EPS
+        const bV = Math.abs(b.x1 - b.x2) < VB_EPS
+        const aH = Math.abs(a.y1 - a.y2) < VB_EPS
+        const bH = Math.abs(b.y1 - b.y2) < VB_EPS
+        let pts = null
+        if (aV && bV && Math.abs(a.x1 - b.x1) > VB_EPS) {
+          const aMin = Math.min(a.y1, a.y2)
+          const aMax = Math.max(a.y1, a.y2)
+          const bMin = Math.min(b.y1, b.y2)
+          const bMax = Math.max(b.y1, b.y2)
+          const o0 = Math.max(aMin, bMin)
+          const o1 = Math.min(aMax, bMax)
+          if (o1 - o0 > VB_EPS) {
+            const fillX = aMax - aMin <= bMax - bMin ? a.x1 : b.x1
+            pts = [fillX, o0, fillX, o1]
+          }
+        } else if (aH && bH && Math.abs(a.y1 - b.y1) > VB_EPS) {
+          const aMin = Math.min(a.x1, a.x2)
+          const aMax = Math.max(a.x1, a.x2)
+          const bMin = Math.min(b.x1, b.x2)
+          const bMax = Math.max(b.x1, b.x2)
+          const o0 = Math.max(aMin, bMin)
+          const o1 = Math.min(aMax, bMax)
+          if (o1 - o0 > VB_EPS) {
+            const fillY = aMax - aMin <= bMax - bMin ? a.y1 : b.y1
+            pts = [o0, fillY, o1, fillY]
+          }
+        }
+        if (pts) {
+          // logger.log(`[VALLEY-BOX-FILL] box`)
+          roof.innerLines.push(drawValleyBoxLine(pts, canvas, roof, roof.textMode))
+        }
+      }
+    }
+  }
+
   // 처마선 innerLine 이 외곽선/치수를 전담하므로 roof 원본 외곽(stroke) 숨김 + 지붕선 치수(roof lengthText) 제거.
   //   외벽선(wall) 치수는 유지. (박공은 split 공용 함수를 안 거치므로 여기서 직접 처리)
   roof.set({ stroke: 'transparent' })
@@ -5934,6 +5982,27 @@ const drawRidgeLine = (points, canvas, roof, textMode) => {
   return ridge
 }
 
+// [VALLEY-BOX-FILL 2026-06-24] 골짜기 박스(出幅 겹침)의 세로변을 마루와 별개의 박스라인으로 채운다.
+//   kerabValleyOverlapLine(라벨 B) 으로 만들어 마루를 지워도 박스 경계가 남도록 한다(박스라인+마루).
+const drawValleyBoxLine = (points, canvas, roof, textMode) => {
+  const lsz = calcLinePlaneSize({ x1: points[0], y1: points[1], x2: points[2], y2: points[3] })
+  const box = new QLine(points, {
+    parentId: roof.id,
+    fontSize: roof.fontSize,
+    stroke: '#1083E3',
+    strokeWidth: 3,
+    name: LINE_TYPE.SUBLINE.VALLEY,
+    textMode: textMode,
+    attributes: { roofId: roof.id, type: 'kerabValleyOverlapLine', isStart: true, pitch: roof.pitch, planeSize: lsz, actualSize: lsz },
+  })
+  box.lineName = 'kerabValleyOverlapLine'
+  box.roofId = roof.id
+  canvas.add(box)
+  box.bringToFront()
+  canvas.renderAll()
+  return box
+}
+
 /**
  * 지붕선을 그린다.
  * @param points