From 3ded861e438abfe1533dbded2a2867e8d69449d6 Mon Sep 17 00:00:00 2001
From: ak8abhinay <abhinay.kakunuri@gmail.com>
Date: Mon, 2 Feb 2026 03:35:14 +0000
Subject: [PATCH] Validation: Remove layer fixes for building overlaps

---
 data/core.yaml                       |  3 +-
 modules/validations/crossing_ways.js | 46 ++++++++++++++++++++--------
 2 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/data/core.yaml b/data/core.yaml
index dcbbc2e45c4..5f617e2d350 100644
--- a/data/core.yaml
+++ b/data/core.yaml
@@ -1811,7 +1811,8 @@ en:
       aeroway-waterway:
         reference: "Aeroways crossing waterways should use tunnels."
       building-building:
-        reference: "Buildings should not intersect except on different layers."
+        message: "Buildings should not intersect. If they are vertically stacked, please use the level tag instead of layer."
+        reference: "Buildings should not intersect. If they are vertically stacked, please use the **level** tag instead of **layer**."
       building-highway:
         reference: "Highways crossing buildings should use bridges, tunnels, or different layers."
       building-railway:
diff --git a/modules/validations/crossing_ways.js b/modules/validations/crossing_ways.js
index f15fe3b7487..43a6c58be2c 100644
--- a/modules/validations/crossing_ways.js
+++ b/modules/validations/crossing_ways.js
@@ -89,21 +89,36 @@ export function validationCrossingWays(context) {
             return true;
         }
 
+        // assume 0 by default; don't use way.layer() since we account for structures here
+        var layer1 = tags1.layer || '0';
+        var layer2 = tags2.layer || '0';
+
+        if (allowsBridge(featureType1) && allowsBridge(featureType2)) {
+            if (hasTag(tags1, 'bridge') && !hasTag(tags2, 'bridge')) return true;
+            if (!hasTag(tags1, 'bridge') && hasTag(tags2, 'bridge')) return true;
+            // crossing bridges must use different layers
+            if (hasTag(tags1, 'bridge') && hasTag(tags2, 'bridge') && layer1 !== layer2) return true;
+        } else if (allowsBridge(featureType1) && hasTag(tags1, 'bridge')) return true;
+        else if (allowsBridge(featureType2) && hasTag(tags2, 'bridge')) return true;
+
+        if (allowsTunnel(featureType1) && allowsTunnel(featureType2)) {
+            if (hasTag(tags1, 'tunnel') && !hasTag(tags2, 'tunnel')) return true;
+            if (!hasTag(tags1, 'tunnel') && hasTag(tags2, 'tunnel')) return true;
+            // crossing tunnels must use different layers
+            if (hasTag(tags1, 'tunnel') && hasTag(tags2, 'tunnel') && layer1 !== layer2) return true;
+        } else if (allowsTunnel(featureType1) && hasTag(tags1, 'tunnel')) return true;
+        else if (allowsTunnel(featureType2) && hasTag(tags2, 'tunnel')) return true;
+
         // don't flag crossing waterways and pier/highways
         if (featureType1 === 'waterway' && featureType2 === 'highway' && tags2.man_made === 'pier') return true;
         if (featureType2 === 'waterway' && featureType1 === 'highway' && tags1.man_made === 'pier') return true;
 
-        if (tags1.layer !== undefined && tags1.layer === tags2.layer) return false; // Warn if both have the same defined layer
-
-        const isElement1Bridge = allowsBridge(featureType1) && hasTag(tags1, 'bridge');
-        const isElement2Bridge = allowsBridge(featureType2) && hasTag(tags2, 'bridge');
-        if (isElement1Bridge !== isElement2Bridge) return true; // Either one is bridge, the other is not
-
-        const isElement1Tunnel = allowsTunnel(featureType1) && hasTag(tags1, 'tunnel');
-        const isElement2Tunnel = allowsTunnel(featureType2) && hasTag(tags2, 'tunnel');
-        if (isElement1Tunnel !== isElement2Tunnel ) return true; // Either one is tunnel, the other is not
-
-        return (tags1.layer || '0') !== (tags2.layer || '0');
+        if (featureType1 === 'building' || featureType2 === 'building' ||
+            taggedAsIndoor(tags1) || taggedAsIndoor(tags2)) {
+            // for building crossings, different layers are enough
+            if (layer1 !== layer2) return true;
+        }
+        return false;
     }
 
 
@@ -404,6 +419,7 @@ export function validationCrossingWays(context) {
                                 allowsTunnel(featureType2) && hasTag(entities[1].tags, 'tunnel');
         var isCrossingBridges = allowsBridge(featureType1) && hasTag(entities[0].tags, 'bridge') &&
                                 allowsBridge(featureType2) && hasTag(entities[1].tags, 'bridge');
+        var isBothBuildings = featureType1 === 'building' && featureType2 === 'building';
 
         var subtype = [featureType1, featureType2].sort().join('-');
 
@@ -475,8 +491,12 @@ export function validationCrossingWays(context) {
                     featureType1 === 'building' ||
                     featureType2 === 'building')  {
 
-                    fixes.push(makeChangeLayerFix('higher'));
-                    fixes.push(makeChangeLayerFix('lower'));
+                    // For overlapping buildings, do not suggest changing the `layer=*` tag.
+                    // Vertically stacked buildings should use `level=*` instead.
+                    if (!isBothBuildings) {
+                        fixes.push(makeChangeLayerFix('higher'));
+                        fixes.push(makeChangeLayerFix('lower'));
+                    }
 
                 // can only add bridge/tunnel if both features are lines
                 } else if (context.graph().geometry(this.entityIds[0]) === 'line' &&