Cost Basis on New Construction

[AJ D.]

How would you account for appreciation/upgrades to a new construction build from a Cost basis perspective?

Ex) Original build was estimated to be $500k, however during the build upgrades were selected such as windows, larger patio, upgraded floors, etc.

Option A - Would you have the property reassessed after completion and use the new assessed value for cost basis? 

Option B - Use the original amount of $500k, and add the dollar value of the upgrades (windows, floors, etc.) 

Appreciate any help and if there is a 3rd option that would be great to know! Ideally, I want to make it as efficient as possible while still being compliant from an accounting/IRS perspective.