Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

Thanks
Roger