When I was training as a mediator I observed a mediation involving a property development.  Although both parties had obtained valuation evidence from surveyors, a joint report, setting out where they agreed, disagreed and why they disagreed had not been prepared.  Accordingly, on the day of the mediation, there were perhaps more issues in dispute than there might otherwise have been.  A settlement was not reached.  

I was recently involved in a mediation involving a property where valuation evidence hadn't been obtained prior to the mediation. Again,on the day of the mediation, with no agreed valuation, settlement proved to be out of reach. 

Would the parties have settled if there had been valuation evidence?  Perhaps, or perhaps not.  However  both parties would have had one less issue in dispute, which would have increased the chances of a settlement.

I urge parties in property mediations, and those advising them, to strongly consider trying to agree valuations in advance of the mediation, if necessary obtaining valuation evidence, and seeking to narrow the issues in dispute.