Survey valuation lower than offer price - how to renegotiate?

[whatafineday]

Could i use the survey valuation to renegotiate the price? It's a survey that i paid for not the bank. Am cash buyer but asked for a valuation estimate as I was curious. Well it came in at about 5% below the offer price, as the survey does identify a few issues that i did not pick up in viewing, such as drainage.

How should i renegotiate? Send them the survey? We do it over email or phone?

EA and seller shouldn't be surprised by this as I've been trying to get quotes from structural engineers (given the design of the house it's not a job for the ordinary plumber. Builder needs to be involved). But so far I've not had any luck. Nobody is willing to provide any number based on just photos. And seller wants to exchange this week. Unlikely to agree to any further survey.

Any tips on how i should do this? FTB here....

I would say your right and both the agent and vendor will be expecting that you might want to re negotiate.
Personally I would do it by carefully worded ultra polite email, not telephone. You can then make sure you cover fully all the reasons you feel your original offer is now more than you feel comfortable paying, using both the valuation discrepancy and the issues which were not apparent at the time of offering.
You would be daft not to do this.