Active job

Waterproofing needed under tile roof

Our home was built in the late 60's and has a concrete tile roof with a pitch of about 15 degrees and no layer of building paper. The roof was reconditioned and repainted a couple of years ago and is in good condition. However, our ceiling space still gets fairly damp when there is driving rain and there is flaky paint in many places on the ceiling that give evidence to water ingress. Wondering if there is an option to add a waterproof barrier under tiles to keep the ceiling dry? Open to other options as well, but don't want to replace the roof for at least another few years yet. House floor plan is about 80 square meters. Access to the ceiling cavity is through a large man-hole in the hallway