diff --git a/Server/Scripts/ServerChunkManager.cs b/Server/Scripts/ServerChunkManager.cs
index 5170f0e..71a24f0 100644
--- a/Server/Scripts/ServerChunkManager.cs
+++ b/Server/Scripts/ServerChunkManager.cs
@@ -233,13 +233,39 @@ namespace IslaApocalypse.Server
 		/// Turns a map-pixel position into a world surface height, with bounds clamping.
 		/// Same mapping used everywhere else: raw 0-1 heightmap value scaled into the
 		/// usable vertical band of the chunk.
+		///
+		/// The position handed in is usually FRACTIONAL (road path points land between
+		/// heightmap cells), so we read the four cells around it and blend — bilinear
+		/// interpolation — rather than snapping to whichever cell we happen to land in.
+		///
+		/// Why that matters: snapping made the height jump by a whole cell's worth the
+		/// instant a point crossed a cell boundary, and hold perfectly flat until it did.
+		/// Along a road whose points sit less than a metre apart, that produced a fine
+		/// metre-scale staircase — the "washboard". Blending makes the height vary
+		/// continuously as the position moves, so the staircase has nothing to stand on.
 		/// </summary>
 		private float HeightAtPixel(Vector2 pixel)
 		{
-			int px = Mathf.Clamp((int)pixel.X, 0, _blueprint.MapSize - 1);
-			int py = Mathf.Clamp((int)pixel.Y, 0, _blueprint.MapSize - 1);
+			int max = _blueprint.MapSize - 1;
+
+			// The four heightmap cells surrounding this position.
+			// At the very edge of the map x1/y1 clamp back onto x0/y0, which makes the
+			// blend a harmless no-op instead of reading out of bounds.
+			int x0 = Mathf.Clamp(Mathf.FloorToInt(pixel.X), 0, max);
+			int y0 = Mathf.Clamp(Mathf.FloorToInt(pixel.Y), 0, max);
+			int x1 = Mathf.Clamp(x0 + 1, 0, max);
+			int y1 = Mathf.Clamp(y0 + 1, 0, max);
+
+			// How far between those cells we actually are, 0 to 1 on each axis.
+			// Clamped so a position outside the map can't push the blend past its corners.
+			float fx = Mathf.Clamp(pixel.X - x0, 0.0f, 1.0f);
+			float fy = Mathf.Clamp(pixel.Y - y0, 0.0f, 1.0f);
+
+			// Blend across X on the near row and the far row, then blend those two down Y.
+			float nearRow = Mathf.Lerp(_blueprint.HeightMap[x0, y0], _blueprint.HeightMap[x1, y0], fx);
+			float farRow  = Mathf.Lerp(_blueprint.HeightMap[x0, y1], _blueprint.HeightMap[x1, y1], fx);
+			float raw     = Mathf.Lerp(nearRow, farRow, fy);
 
-			float raw = _blueprint.HeightMap[px, py];
 			return Mathf.Clamp(raw * (Constants.CHUNK_HEIGHT - 5), 2.0f, Constants.CHUNK_HEIGHT - 2.0f);
 		}