This would be a big step to being properly waterproof.
How to re felt and batten a roof.
Work along the roof taking out any excess slack in the felt but do not pull it tight.
A slight sag between rafters is ideal as it will allow any water to drain down the felt.
When the first length is complete lay the next layer of felt on top of the first so that it overlaps by at least 100mm 4 inches horizontal overlaps where one roll ends and the next one is started should be at least 150mm 6 inches.
I had been using tarpaulins over the trusses but they can only do so good a job and when the wind blows the damn things rustle like mad the rain then finds its own lovely little route to somewhere you don t want it.
This is not required for dry fix systems.
Eventually i was in a position to lay felt and batten out the roofs.
Joints should be directly over rafters with the batten square cut tightly butted and skewed nails.
To replace a small section of roofing felt involves stripping the tiles from the roof and replacing felt between two joists.
Apply waterproof paint or primer to promote felt attachment.
Start at the lower edge of the roof nailing the batten into place at the centre of the rafter.
Begin at the bottom working in horizontal lines and gradually moving upward.
Where wind driven rain is working under the roof and causing leaks then the felt will need to be replaced.
This will cost around 460 510 made up of.