If your new hatch is a bigger size then you will need to double up the joists timbers using M10's or M12's (bolts) and a strong wood adhesive.
This should be left to a good builder/carpenter. If you have enough experience then this should be pretty straight forward.
Remember to use the right connectors/hangers. If you are having an issue with the trusses then please seek professional advice from someone who can view the property and then advise on what to do.
