Question On Roofs On Houses W/ Natural Wood Siding

[newbie pete]

Well, my first season as a roof washer is starting off pretty good. Hope all is well for you guys too. So far all the roofs I've done have been on houses with vinyl siding or painted wood siding. My question is how to clean (if I should attempt it) roofs on houses with natural wood siding. I'm using a chlorine, TSP mix to clean the roofs and don't want to bleach the natural wood siding of the houses. Does anyone have any suggestions. I was planning on just making sure the gutter systems were not leaking before attempting it and being really careful but, I dont know if it would be wise to attempt this. I have insurance and all that but I don't really feel like having any claims put in just yet if you know what I mean. Does anyone have any stories to tell about jobs they've done like this (good or bad) or any suggestions. Thanx in advance.