A self-storage expansion should be underwritten as a development and operating transition. Existing occupancy can indicate demand, but it does not prove that additional units will lease at the same rates, speed, or margin. The investor must test incremental customers, competitive supply, unit mix, approvals, infrastructure, construction, and the cash required before stabilization.
The examples below are hypothetical and do not state current Chicago storage demand, construction costs, or local approval requirements.
Separate current performance from incremental demand
Review existing unit occupancy, square-foot occupancy, achieved rents, concessions, inquiries, move-outs, and inventory by type. A full small-unit category does not establish demand for large units or climate-controlled space.
Ask whether occupancy is being maintained through discounts or rates below alternatives. Expansion may cannibalize existing units or force pricing changes across the facility. Model the entire property rather than treating new units as independent income.
Use actual inquiry records and competitive evidence where available. A waitlist can be useful, but distinguish qualified customers, duplicate entries, timing, and willingness to pay the proposed price.
Public Storage’s filing provides a primary example of sector operating and development context. Its portfolio results do not establish demand at a particular Chicago-area site. Public Storage 2025 Form 10-K
Map the competitive pipeline
Identify existing competitors, expansions, projects under construction, approved projects, and proposals. Distinguish stages and verify status through official records and market research. A proposal is not completed supply, but ignoring it can overstate the absorption opportunity.
Compare actual product: unit sizes, access, climate features, customer experience, location, rates, concessions, and marketing. Gross square footage alone does not show direct competition.
Ask how competitors might respond. More promotional pricing or marketing can reduce achieved income even when occupancy rises. Do not assume new supply affects only lease-up speed and leaves rent unchanged.
Extra Space Storage’s filing discusses sector operating risks. Use it to frame supply, rent, and customer questions, then establish the local assumptions with target-property evidence. Extra Space Storage 2025 Form 10-K
Establish what can actually be built
Obtain a site plan, boundary and rights review, zoning analysis, design, utility assessment, drainage review, and construction scope appropriate to the project. Land shown as unused may be needed for access, stormwater, setbacks, easements, or existing operations.
For Chicago parcels, use the official zoning framework and property-specific documents with qualified advisers. Existing storage use does not automatically approve every expansion, height, layout, or operating arrangement. Chicago zoning atlas provision
Determine net rentable area after circulation, systems, offices, and other nonrentable space. A construction budget based on gross building area and revenue based on the same gross area can overstate returns.
Investigate whether expansion disrupts existing customers, access, security, or utilities. The original facility may lose revenue during construction, and those effects belong in the project economics.
Build a complete sources-and-uses schedule
Include land if applicable, site work, structure, systems, doors, security, technology, professional fees, permits, testing, contingency, financing, carry, marketing, and initial operating deficits.
Show committed funding and its conditions. Construction draws, retainage, lender holdbacks, and reimbursement timing can require owner advances. A project fully funded on an annual summary can still run out of cash between draws.
Use a scope-based contingency and identify unresolved items. A round percentage is not a substitute for investigating uncertain utilities, drainage, environmental conditions, or off-site rights.
Keep existing property debt and operations in the model. Expansion can change covenants, collateral, insurance, taxes, and lender consent. Coordinate with the actual lender before assuming the project can proceed under existing terms.
A hypothetical expansion model
Assume an expansion creates 15,000 net rentable square feet at a complete economic cost of $1.8 million. At hypothetical stabilized occupancy of 85% and achieved annual rent of $18 per occupied square foot, gross rental revenue is $229,500.
Assume other net recurring income is $5,000 and incremental operating expense is $75,000. Incremental NOI is $159,500. The simplified stabilized yield on $1.8 million is 8.86% before financing and later capital.
At 70% occupancy and $16 achieved annual rent, rental revenue is $168,000. With the same other income and expense assumption, NOI is $98,000 and yield is 5.44%. Some expenses may vary, so a full model should reflect actual behavior.
The difference shows that occupancy and rent interact. A spreadsheet that reaches 85% occupancy quickly while preserving the highest advertised rate may overstate the investment.
Model lease-up monthly
Project available inventory, move-ins, move-outs, occupied area, rates, concessions, collections, marketing, and operating costs by month. Tie the opening date to actual construction and approvals.
Distinguish gross move-ins from net absorption. If customers move from older units into new units, the expansion may look busy while total property revenue grows less than expected.
Estimate the cash trough and add a credible slower case. The owner may need to fund interest, operating deficits, marketing, and repairs before stabilized income arrives. Uncommitted refinancing is not a reliable source for those obligations.
If development completes in phases, model each phase’s cost and available inventory. A phased approach can reduce risk but may increase unit costs or prolong disruption.
Test price and product flexibility
Determine whether the unit mix can be changed economically if demand differs. A flexible design can help, but conversion still requires cost, time, and potentially approval. Do not treat flexibility as free.
Compare a smaller project, delayed project, or no-build case. High existing occupancy may support modest improvements or pricing changes rather than immediate expansion. The alternative use of equity has a cost.
Evaluate management and technology capacity. More units may require additional staffing, systems, security, or marketing expertise. A marginal expense assumption should reflect actual capability.
Test phased construction and cannibalization explicitly
Compare building the full program, completing a smaller first phase, and delaying development. Use consistent demand, rent, expense, and financing assumptions so the comparison reflects scope rather than different optimism.
A hypothetical first phase adding 6,000 rentable square feet may cost more per square foot than a 15,000-square-foot program because site work, design, and infrastructure are not proportional. It can still reduce capital at risk if demand is uncertain. Model the fixed cost incurred now, the cost deferred, and whether later work disrupts occupied units.
Track customer movement within the facility. If 30 existing customers relocate into new space, the expansion’s occupied area rises while old inventory becomes vacant. The property needs new external demand to replace those units or a clear plan to repurpose them. Gross expansion move-ins should not be counted as net absorption automatically.
Consider a hypothetical new wing earning $120,000 gross rent while the old building loses $30,000 because customers transfer or pricing changes. Incremental gross revenue is $90,000 before added expense, not $120,000. If the model assumes the old units refill quickly, that is a separate leasing assumption requiring support and marketing cost.
Use a completion decision gate before committing to later phases. Review achieved rates, external move-ins, concessions, customer tenure, operating margin, construction cost, and remaining competition. A high opening occupancy produced by discounted internal transfers is different evidence from sustained new-customer demand at supportable rates.
Review the financing consequences of phasing. A lender may require a defined collateral package, completion scope, minimum equity, or other conditions. The investor cannot assume it may stop midway or redirect reserved funds without consent. Align the construction strategy with actual documents.
Finally, keep the no-build asset in the comparison. Existing operations may offer a lower-risk return through maintenance, technology, management, or selective unit conversion. Expansion should outperform those alternatives after complete cost and risk, rather than appear attractive only because undeveloped land is treated as having no opportunity cost.
A phased strategy is valuable when it creates a real option to respond to evidence. It is less valuable when the first phase commits nearly all infrastructure cost and leaves an unusable site unless the rest is built. Have the design and financial team identify which costs and obligations are truly avoidable before assigning flexibility a benefit.
Before valuing the completed project, compare net rentable area in the final plans with the revenue model. Changes to corridors, mechanical space, access, or unit configuration can reduce earning area even when total construction cost remains unchanged or increases.
Reprice changes before committing the next construction draw.
Plan financing and exit together
A construction or bridge loan can mature before stabilization under a slower case. Model extensions, fees, reserves, recourse, and takeout conditions from actual proposals.
Calculate refinance proceeds using supportable stabilized cash flow and current-at-the-time assumptions rather than total construction cost alone. A completed project can have a refinance gap if income disappoints or financing conditions change.
For sale, distinguish current operations from projected stabilization. A buyer may require a return for taking the remaining lease-up risk. Do not capitalize eventual peak NOI as today’s completed-project value without adjustment.
Proceed when incremental demand, feasible construction, full funding, and downside lease-up support acceptable returns. Reprice or reduce scope when the project is too dependent on optimistic absorption. Decline when the plan needs new inventory to fill immediately at untested rates to meet debt obligations.