Roofing felt was introduced in the 1930s, followed by breatheable membranes in the 1980s, to provide an additional layer of waterproofing under the tiles or slates. A small area of damage can be patched quite cheaply. If the damage is more extensive and the roof is leaking it is normally a sign of other problems with the roof.
The introduction of impermeable roofing felt in the 1930s introduced other problems. If water gets trapped in the roof space and there is insufficient ventilation to remove it then the water condenses on the felt and then drips onto the floor of the roof space, causing damp patches to appear on the ceiling or walls of the floor below. To solve this a roof ventilator can be installed or the roofing felt needs to be replaced with a breathable membrane which allows moisture to escape.
If you have any signs of damp patches or rips of tears in your roofing Felt give Dyson Roofing a call on 07765 257 092