On 22/09/2018 22:57, Mathew Newton wrote:
On Saturday, 22 September 2018 22:42:11 UTC+1, JimK wrote:

Mmm but how do you get at them once they're found? Are you thinking
you/he'll be able to reuse the top deck? Might be cheaper for him
to just rip it up & renew than tit about attempting to find &
remove screws buried in roof compound? How thick is the roof
coating anyhow?

The membrane should be around 1-2mm thick and so I was intending on
just gouging/scraping it away from the screw heads once located.

The top deck will be scrap as I don't imagine it'd be cost effective
to try and remove the membrane from the entire surface to enable
reuse.

Ask him the cost to himself of redoing the roof. Then suggest/accept 50%
refund and take the risk yourself. It will probably last 25 years or more.