A slight sag between rafters is ideal as it will allow any water to drain down the felt.
How to re felt and batten a roof.
Drag it gently from one end of the roof to the other east to west or west to east.
Start at the lower edge of the roof nailing the batten into place at the centre of the rafter.
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.
This would be a big step to being properly waterproof.
Eventually i was in a position to lay felt and batten out the roofs.
If a batten end is to be set in mortar be sure an appropriate treatment has been applied.
Work along the roof taking out any excess slack in the felt but do not pull it tight.
Use a 4 inch 10 cm paintbrush or a roller to apply the paint or primer.
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.
To replace a small section of roofing felt involves stripping the tiles from the roof and replacing felt between two joists.
Joints should be directly over rafters with the batten square cut tightly butted and skewed nails.
Begin at the bottom working in horizontal lines and gradually moving upward.
This is not required for dry fix systems.