diff --git a/src/Polygon.ts b/src/Polygon.ts
index afd2523f..99d74510 100644
--- a/src/Polygon.ts
+++ b/src/Polygon.ts
@@ -10,6 +10,8 @@ import { ArxVertexWithColor } from '@src/types.js'
 
 export type TransparencyType = 'multiplicative' | 'additive' | 'blended' | 'subtractive'
 
+const DEFAULT_ROOM_ID = 1
+
 type PolygonConfig = {
   /** setting this to true will prevent calculation of norm, norm2 and normals properties */
   areNormalsCalculated: boolean
@@ -64,7 +66,7 @@ export class Polygon {
     this.normals = props.normals
     this.transval = props.transval ?? 0
     this.area = props.area ?? 0
-    this.room = props.room ?? 1
+    this.room = props.room ?? DEFAULT_ROOM_ID
     this.paddy = props.paddy
     this.config = { ...this.config, ...(props.config ?? {}) }
   }
diff --git a/src/Polygons.ts b/src/Polygons.ts
index 6a5ec517..a8f6e3d6 100644
--- a/src/Polygons.ts
+++ b/src/Polygons.ts
@@ -22,6 +22,10 @@ export type MeshImportProps = {
   tryToQuadify?: typeof QUADIFY | typeof DONT_QUADIFY
   shading?: typeof SHADING_FLAT | typeof SHADING_SMOOTH
   flags?: ArxPolygonFlags
+  /**
+   * room id - used when a map has portals, default value is undefined (the Polygon constructor will handle it)
+   */
+  room?: number
 }
 
 type TextureContainer = ArxTextureContainer & { remaining: number; maxRemaining: number }
@@ -140,7 +144,7 @@ export class Polygons extends Array<Polygon> {
       applyTransformations(threeJsObj)
     }
 
-    const { tryToQuadify = QUADIFY, shading = SHADING_FLAT, flags = ArxPolygonFlags.None } = meshImportProps
+    const { tryToQuadify = QUADIFY, shading = SHADING_FLAT, flags = ArxPolygonFlags.None, room } = meshImportProps
     const polygons = new Polygons()
 
     if (threeJsObj instanceof Mesh) {
@@ -221,6 +225,7 @@ export class Polygons extends Array<Polygon> {
               texture: currentTexture,
               flags: currentTexture instanceof Material ? currentTexture.flags | flags : flags,
               isQuad: true,
+              room,
             })
             if (currentTexture instanceof Material && currentTexture.opacity !== 100) {
               polygon.setOpacity(currentTexture.opacity, currentTexture.opacityMode)