Give every estimator the same property file
Provide the same fixture inventory, visible-pipe photographs, branch map, access notes, renovation history and known strata constraints to each estimator. Include the property address and municipality so permit questions begin from the same facts. If one contractor receives a more complete inspection or different assumptions, the resulting totals are not directly comparable. Record the date and version of the package supplied. Add later discoveries to all active bidders or clearly note which proposal incorporates them before ranking the prices.