diff --git a/src/hooks/useLine.js b/src/hooks/useLine.js
index c9de0194..30cc9ba9 100644
--- a/src/hooks/useLine.js
+++ b/src/hooks/useLine.js
@@ -172,9 +172,9 @@ export const useLine = () => {
     const isHorizontal = y1 === y2
     const isVertical = x1 === x2
     const isDiagonal = !isHorizontal && !isVertical
-    const lineLength = line.getLength()
+    const lineLength = line.attributes.planeSize ?? line.getLength()
 
-    line.attributes = { ...line.attributes, planeSize: line.getLength(), actualSize: line.getLength() }
+    line.attributes = { ...line.attributes, planeSize: lineLength, actualSize: lineLength }
 
     if (+roofSizeSet === 1) {
       if (direction === 'south' || direction === 'north') {