Topband: vertical antenna and metal roof interaction

[Charles Stackhouse via Topband]

I have a 160m inverted L and an 80m 1/4 wavelength vertical hanging over the same field of radials in the woods behind my house. There are 30 radials, 20 are 110ft and 10 are 65ft long.  


I need a new woodshed. I am planning one that is 18ft w x 8 ft d x8ft h  with a sloped metal roof. The best site is 60ft from the verticals. This would actually sit on the radial field. 


Do I need to worry about significantly affecting these antennas if I site the woodshed as planned?

73, Charlie W2GN