diff --git a/src/info/ata4/bspsrc/modules/entity/EntitySource.java b/src/info/ata4/bspsrc/modules/entity/EntitySource.java
index 907d1c3e..17d7f5a4 100644
--- a/src/info/ata4/bspsrc/modules/entity/EntitySource.java
+++ b/src/info/ata4/bspsrc/modules/entity/EntitySource.java
@@ -351,8 +351,6 @@ public void writeDetails() {
         if (config.detailMerge) {
             Queue<Pair<DBrush, AABB>> detailBrushes = new ArrayDeque<>();
             Map<DBrush, Integer> detailBrushIndices = new HashMap<>();
-            Vector3f vex = new Vector3f(config.detailMergeThresh,
-                    config.detailMergeThresh, config.detailMergeThresh);
             
             // add all detail brushes to queue
             for (int i = 0; i < bsp.brushes.size(); i++) {
@@ -371,9 +369,6 @@ public void writeDetails() {
                 // get bounding box of the detail brush
                 AABB bounds = BrushUtils.getBounds(bsp, brush);
                 
-                // expand bb so it can touch the bbs of other brushes
-                bounds.expand(vex);
-                
                 detailBrushes.add(new ImmutablePair<>(brush, bounds));
                 detailBrushIndices.put(brush, i);
             }
@@ -387,7 +382,7 @@ public void writeDetails() {
                 detailBrushClump.add(detailBrush1);
                 
                 // move all touching brushes from the queue to this clump
-                clumpBrushes(detailBrushes, detailBrushClump, detailBrush1);
+                clumpBrushes(detailBrushes, detailBrushClump, detailBrush1, config.detailMergeThresh);
                 
                 // write brush clump as func_detail to VMF
                 writer.start("entity");
@@ -444,16 +439,20 @@ public void writeDetails() {
      * 
      * @param src global brush collection
      * @param dst clumped brush collection
+     * @param thresh touching threshold
      * @param target search brush
      */
-    private void clumpBrushes(Collection<Pair<DBrush, AABB>> src, Collection<Pair<DBrush, AABB>> dst, Pair<DBrush, AABB> target) {
+    private void clumpBrushes(Collection<Pair<DBrush, AABB>> src, Collection<Pair<DBrush, AABB>> dst, Pair<DBrush, AABB> target, float thresh) {
+        // expand bb so it can touch the bbs of other brushes
+        AABB targetBounds = target.getRight().expand(thresh);
+        
         Iterator<Pair<DBrush, AABB>> iter = src.iterator();
         while (iter.hasNext()) {
             // get next brush
             Pair<DBrush, AABB> other = iter.next();
             
             // is it touching the target brush?
-            if (other.getRight().intersectsWith(target.getRight())) {
+            if (other.getRight().intersectsWith(targetBounds)) {
                 // put it to destination collection
                 dst.add(other);
                 
@@ -461,7 +460,7 @@ private void clumpBrushes(Collection<Pair<DBrush, AABB>> src, Collection<Pair<DB
                 iter.remove();
                 
                 // also move all brushes that touch this brush
-                clumpBrushes(src, dst, other);
+                clumpBrushes(src, dst, other, thresh);
                 
                 // recreate iterator, since the collection may have been modified
                 iter = src.iterator();
diff --git a/src/info/ata4/bspsrc/modules/geom/BrushUtils.java b/src/info/ata4/bspsrc/modules/geom/BrushUtils.java
index e31b6153..02b576cc 100644
--- a/src/info/ata4/bspsrc/modules/geom/BrushUtils.java
+++ b/src/info/ata4/bspsrc/modules/geom/BrushUtils.java
@@ -36,7 +36,7 @@ public static AABB getBounds(BspData bsp, DBrush brush) {
         // add bounds of all brush sides
         AABB bounds = new AABB();
         for (int i = 0; i < brush.numside; i++) {
-            bounds.include(WindingFactory.fromSide(bsp, brush, i).getBounds());
+            bounds = bounds.include(WindingFactory.fromSide(bsp, brush, i).getBounds());
         }
         return bounds;
     }
diff --git a/src/info/ata4/bspsrc/util/AABB.java b/src/info/ata4/bspsrc/util/AABB.java
index b1921d03..f0704308 100644
--- a/src/info/ata4/bspsrc/util/AABB.java
+++ b/src/info/ata4/bspsrc/util/AABB.java
@@ -18,8 +18,8 @@
  */
 public class AABB {
     
-    private Vector3f min;
-    private Vector3f max;
+    private final Vector3f min;
+    private final Vector3f max;
 
     public AABB(Vector3f mins, Vector3f maxs) {
         this.min = mins;
@@ -34,17 +34,9 @@ public Vector3f getMin() {
         return min;
     }
 
-    public void setMin(Vector3f min) {
-        this.min = min;
-    }
-
     public Vector3f getMax() {
         return max;
     }
-
-    public void setMax(Vector3f max) {
-        this.max = max;
-    }
     
     public Vector3f getSize() {
         return max.sub(min);
@@ -55,15 +47,17 @@ public boolean intersectsWith(AABB that) {
                that.max.y > this.min.y && that.min.y < this.max.y &&
                that.max.z > this.min.z && that.min.z < this.max.z;
     }
-
-    public void include(AABB that) {
-        min = min.min(that.min);
-        max = max.max(that.max);
+    
+    public AABB include(AABB that) {
+        return new AABB(min.min(that.min), max.max(that.max));
+    }
+    
+    public AABB expand(Vector3f v) {
+        return new AABB(min.sub(v), max.add(v));
     }
     
-    public void expand(Vector3f v) {
-        min = min.sub(v);
-        max = max.add(v);
+    public AABB expand(float e) {
+        return expand(new Vector3f(e, e, e));
     }
 
     @Override