If they aren t level adjust the string line until a level aligned with it shows a slight slope.
How to tell if fascia board is level for gutters.
Snap a chalk line to indicate the top of the gutter.
Press the board tightly against the ends of the rafters so the top edge is level with the tops of the rafters.
Ask a helper to assist you so you don t have to lift the fascia board yourself.
Thankfully there are ways to counter this damage.
Making sure the gutter system is properly installed is key to preventing water from damaging your fascia board.
First consider leafguard gutters or a similar covered gutter system that will prevent clogs and splashing.
A loose gutter system can also damage your boards as it pulls away from the wood.
If your fascia boards are level you can use them as a reference for sloping the gutters.
Also make sure your gutter piping is firmly attached to your fascia board.