Loft hatch installation

[wonderwire]

I want to install a new loft hatch (a completely new job, cutting into the plasterboard ceiling).

However, I've been up into the loft through another access and we have some unusual 'criss-crossing' ceiling joists. Each are 4in x 2in beams and are c.60cm apart, like below:

Is this likely to be a structure inappropriate for a loft hatch (e.g. I know you aren't supposed to cut certain beams in a roof that are load bearing), or can I insert one using the usual process of adding support timbers before/after cutting to frame the entrance?

Has anyone experience of this type of roofing before? Is it common?

Thanks

 

[catlad]

Not usual round here, has it not had a false ceiling.

 

[wonderwire]

No, it's not a false ceiling. It's an extension on an old part of the building, so maybe that's it?

Alternatively, I am told this could be the result of a previous water tank being in the roof?

 

[garyo]

Or maybe the original rafters are only 100mm deep and a previous owner has then counter battened in order to provide space for a further 100mm of insulation whilst still being able to lay down some useful floor boards. Do the rafters all look the same age, or does one later pre-date the other?

Can you see the feet of the rafters? Which layer is actually structural (sitting on the wall plate, or bedded in to the wall)?