The spec suite is office's answer to a behavioral fact: small tenants lease what they can see. A ten-person firm touring raw space cannot imagine its office in it and will not wait five months for a buildout; the same firm touring a finished suite with lighting, glass, and a kitchenette signs in weeks. The spec program spends the landlord's capital to close that imagination gap in advance, and whether that spend is brilliant or stranded depends on underwriting it as what it is: manufacturing inventory ahead of demand.
The bet, stated plainly. Capital goes out now, into suites designed for tenants who do not yet exist, on the thesis that finished product leases faster and at better effective terms than raw space plus a TI allowance. The thesis is well supported where the demand is right: markets fragmented into small users, buildings competing for velocity, tenants who decide on move-in readiness. It fails where the demand is wrong: big-block markets where the eventual tenant will demolish your finishes anyway, or submarkets so soft that no amount of glass conjures a tenant, in which case the spec program has converted recoverable capital into very specific drywall.
Underwrite it like inventory, because that is the honest frame. Each suite has a manufacturing cost, the buildout. A carrying cost, the expenses and capital charge while it waits. An expected shelf time, which is the submarket's true absorption rate for that suite size, not the leasing plan's hope. And a margin, the premium in effective rent and reduced downtime that finished space actually earns over the raw-space alternative. Run those four numbers per suite and the program either pencils or it does not, and sizing decisions fall out of the same math: the suite sizes to build are the ones the submarket's tenant pool actually shops for, which the leasing brokers can tell you to the hundred feet if asked.
Two second-order effects belong in the model rather than the footnotes. Carving floors into spec suites adds corridors, which shifts feet from usable to common and nudges the building's load factor, a measurement cost that is real even though no invoice arrives for it. And a spec program changes the building's rollover economics going forward: future turnovers of finished suites cost less than first-generation buildouts, which is a genuine, durable benefit that a one-year view of the program will miss entirely.
This is another plan that lives or dies on schedule rather than concept, and PropCalc™ models it that way: each spec suite as a lease-up event with its own cost, timing, downtime, and rent, carried through coverage and returns, so the program's J-curve is visible before the capital is. Build the suites the demand can absorb, price the wait honestly, and the spec program is a velocity machine. Skip the pricing and it is a very expensive way to make vacancy look furnished.