Active job

Enlarge Roof Cavity Access

I am requiring the roof access cavity to be increased in size to improve roof access for central heating system. currently the access hole is approximately --- , but require at least --- for the new unit. I have been looking at attic stairs, but think the ceiling joists may be an issue (estimating these are 400-450mm apart) as our roof is tile so is quite heavy. If attic stairs are possible, we can supply. As per photo, the joists run horizontal to the picture. Location of access is in room between kitchen and laundry.