I always ask where permission is needed, and almost always get a yes.
In the 40 Years I'v Been Detecting, I remember Hearing "NO" three times.
Twice at Churches & once at an Empty House.
I may have forgot a few, at the moment so I'll say 10 times in 40 years. ?
Funny thing is, Some People seem to think hearing the word "No" will cause them to Shrivel up and Die or something.? ?I just want to say, I'm still alive?

when you ask, ask with Confidence of hearing a "Yes"
jeff
P.S.
The easiest way I know, is to walk up to the owner, Care Taker , whoever..............
Smile say "HI" ,
Introduce Myself,
Explaine Myself,
Ask them IF their the One to Ask,
And then Ask.
the LAST TIME, I asked Permission was thru EMail.
I saw an 18th. Century house with a for sale sign. No one was home.
I took the name of the Real Estate Agent Down and went home.
I found her listing on my computer & EMaild her.
I explained Myself & asked If she Knew How I could Ask.
She Forwarded My EMail to the Owner.
The Owner Contacted me and said Yes, but I had to do it before
the Buyer Signed the Final Papers. (The House was already sold)