LOD Polygon reduction and Culling?

Hi Guys,

I have created some custom LOD meshes for a project which work great with one exception!

Have attached some pics which show the problem. The roof mesh is simplified as each LOD is brought into play. What then happens is that the bounding box of the roof becomes smaller than than mesh of the timbers within it and so it is being rendered by the engine as it is no longer occluded and shows ‘through’ the roof.

Was wondering if there is a way of hiding meshes when a specific mesh LOD is triggered? In this example, hiding the beams when LOD 3 for the roof is activated?

Any help really appreciated as I have a deadline.

Many thanks,