Below replacement cost is the phrase doing the heaviest lifting in office investment memos right now, and like most phrases that appear in every memo, it is doing some of that lifting dishonestly. The thesis is real. It is just conditional, and the conditions are checkable, which means the phrase should be the beginning of underwriting rather than the conclusion of it.
First, compute the number honestly, because replacement cost is bigger than construction cost. Land at what land actually trades for. Hard costs at current pricing, which have not gotten cheaper. Soft costs, financing carry through a multi-year build, the tenant improvement load to fill a new building, the commissions, and the lease-up period where the finished product earns little while costing plenty. Stack all of it and replacement cost per square foot runs well past the construction number people casually quote, which, inconveniently for sellers, also means almost everything qualifies as below replacement cost if the bar is set carelessly. Set it carefully and the comparison starts meaning something.
Then apply the test that decides whether the discount protects you: would anyone rationally build office in this submarket at rents that exist today or plausibly soon. If the answer is yes at some rent, your basis advantage is real and durable, because you own the product cheaper than any future competitor can create it, and rising rents reach you first. If the answer is no rent makes construction pencil here for the foreseeable future, then replacement cost is not a floor, it is a historical artifact, and a building can sit below it indefinitely while losing money the whole time. Basis discounts protect you in markets where the asset would eventually need to be replaced. In markets with structural demand loss, there is nothing to replace, and the discount measures the distance to a floor that is not there.
The honest framework, then, is basis and income together, never basis alone. The below-replacement price sets your downside story; the lease-by-lease income path decides whether you survive long enough for the story to matter. A deep discount on a building bleeding occupancy is a slower way to lose money. A moderate discount on a building whose rollover, honestly priced, carries the debt through the trough is the actual trade, and the difference between those two deals is invisible at the basis level and obvious at the lease level.
PropCalc™ keeps both lenses in the same model: price per square foot against the income the suites really produce, rollover costs included, so the replacement-cost story has to survive contact with the rent roll before it survives contact with your capital. Basis is why office is interesting in 2026. The rent roll is whether this building is.