Start with a site visit, because the drawings won't show what's in the walls. Then price the demolition and make-safe work, the existing conditions you can't see, the phasing and occupied-building rules, and the extra labor all of that takes. Whatever you can't verify, carry as an allowance or state as a clarification, never as a silent assumption.
Check the existing panels and their spare capacity, the condition of the wiring and raceways, ceiling space, access, and everything the drawings call existing to remain. Take photos.
2
Demolition and make-safe
Disconnecting, removing and making safe existing circuits, devices and fixtures, and the disposal. Check the specs for what gets salvaged and handed back to the owner.
3
Conditions you can't see
Concealed wiring, unlabeled circuits, old equipment that won't take new breakers, and hazardous materials such as asbestos that stop the work until someone else deals with them.
4
Phasing and occupied buildings
Night or weekend work, shutdowns scheduled with the owner, temporary power to keep areas running, security escorts, and dust and noise rules. Each one costs hours.
5
Adjust the labor
Renovation work runs slower than new work: tight ceilings, fishing walls, working around occupants, and small quantities spread across the building.
6
Put the unknowns in writing
Carry an allowance for what you can't verify, or state what your price assumes, such as existing circuits being reusable as they are.
Questions estimators ask
Should I carry a contingency on a renovation bid?
Carry what you can name. An allowance for a specific unknown is easier to defend than a lump contingency, and it tells the GC what happens if the condition is worse. Whatever you don't carry, clarify in writing.
What do renovation bid documents usually leave out?
Details of the existing conditions, shutdown and phasing rules written into Division 1, and what existing to remain really means for the circuits that feed it.
Can Bidprobe review a renovation package?
Yes. Bidprobe reads the whole package, including the Division 0 and 1 phasing and occupancy requirements, and lists scope gaps, risky terms and the RFIs worth sending, each tied to the sheet or spec section it came from. It can't see inside the walls: the site visit is still yours.
Read the renovation package before you walk it.
One free bid check on every new account, no card required. Most checks come back in 5 to 15 minutes.