How to Underwrite an IOS Deal (Industrial Outdoor Storage)

Industrial outdoor storage (IOS) is one of the most mispriced corners of commercial real estate, and almost no underwriting tool models it natively. Most templates force IOS into a building-based, square-foot model that gets the income unit wrong from the first cell. This guide walks through how to underwrite an IOS deal the way a working investor actually does it — on the land, with honest two-NOI math, and with the covered-land optionality priced on its own line.

What IOS actually is

IOS is low-coverage industrial land used as truck and trailer parking, container storage, equipment yards, and contractor laydown. A typical site is a few acres of stabilized, fenced, surfaced yard with maybe a small office or no building at all — "coverage" (building area ÷ land area) is often 1–5%. The tenant is paying for the yard: a place to stage trucks, drop trailers, stack containers, or store equipment close to a port, rail, or highway.

That single fact — income comes from the land, not a building — changes everything about how you underwrite it. It also sets up the thesis that makes IOS attractive: the covered land play. You buy an income-producing yard that pays rent today (covering your carry) while you hold the optionality to redevelop, re-entitle, or sell into a higher-and-better use later. You are getting paid to wait on the dirt.

Why standard underwriting breaks on IOS

Conventional industrial underwriting starts from building square footage: rentable SF × $/SF rent. Apply that to IOS and you get nonsense. On a 4-acre site with a 1,100 SF office, the "building" is a rounding error; the value and the income are in the land. Two failure modes follow:

• Wrong income unit. IOS rent is quoted on the land — gross rent per acre per year. Underwrite on in-place gross rent, $/acre, escalators, and WALT (weighted average lease term), not building SF × $/SF.
• Misleading price-per-SF. Price ÷ building SF on a 1%-coverage site produces an absurd number that tells you nothing. Track price per acre as the real density metric; show price/SF only as a footnote, and never penalize a deal for having a small building.

So step one is to throw out the building-SF frame and underwrite the yard: how much land rents, at what rate, escalating how fast, for how long, to whom.

NNN expense treatment — and why IOS has TWO NOIs

Most IOS leases are triple-net (NNN): the tenant reimburses the property-level operating expenses — real estate taxes, common area maintenance (CAM), and insurance on the improvements. That is the headline the broker sells: "true NNN, zero landlord responsibility."

It is almost never literally zero. The landlord still pays its own actual expenses, which on IOS typically means:

• Bank / financing fees and miscellaneous carry,
• the landlord's own insurance (liability/umbrella the LL carries above the tenant's),
• any landlord-paid property tax (e.g., a reassessment gap before the tenant true-up, or a portion the lease leaves with the LL),
• and a sensible reserve for fencing, lighting, surfacing, and drainage.

This creates two different NOIs, and conflating them is the single biggest IOS underwriting error:

• Broker NOI = gross in-place rent (what the OM leads with).
• True NOI = gross rent minus the landlord's actual expenses (what you actually keep).

Read the NNN lease terms carefully: confirm the reimbursements are real, check whether the expense lines hide intercompany or occupancy charges, and find out how reimbursement true-ups are handled at year-end. A lease that says NNN but quietly leaves taxes or insurance with the landlord is a meaningfully different deal.

Cap rate: broker cap vs true cap

From the two NOIs you get two cap rates against the same price:

• Broker cap = broker (gross) NOI ÷ price — the higher, more flattering number.
• True cap = true NOI ÷ price — what you actually earn going in.

The broker cap is always higher because it leaves the landlord's real costs out. Underwrite to the true cap; use the broker cap only to know what number you are negotiating against. On IOS the spread between the two is commonly 20–60 basis points — enough to change whether a deal clears your hurdle. (UpsideIQ shows both side by side; see the cap-rate calculator and broker cap vs true cap.)

Valuation: income plus the covered-land lens

Value an IOS deal two ways and hold both in view:

1. Income-based — true NOI ÷ exit cap, the standard direct-cap valuation. This is your floor: what the asset is worth purely as a yield instrument.
2. Covered-land lens — value = land + in-place income + redevelopment optionality. The land has a value independent of the current use; the in-place rent carries you while you hold it; and the option to redevelop or re-entitle is worth something on top.

Track price per acre and price per SF as reference points, but do not let a small building drag the analysis. The discipline that keeps you honest: price the optionality on its own line. Don't compress the going-in cap to make today's yield look better — that double-counts the upside and hides the real current return. Underwrite the income at its honest true cap, and value the land option separately.

Returns: set expectations correctly

A stabilized NNN IOS is a yield / income play, not a value-add story. Expect:

• Solid DSCR and cash yield — the income is contractual and the expense load is light, so coverage and cash-on-cash tend to look good.
• Modest IRR — with no big rent roll to reposition and no heavy value-add, the IRR is driven by in-place yield, escalators, and exit cap, not a step-change in NOI. A clean stabilized IOS is a single, not a home run.

The asymmetric upside, when it exists, is the covered-land optionality — but that is an option, not a base case. Underwrite the base case as income; treat redevelopment as the call option you didn't pay full price for.

Diligence checklist

Before you trust the number, confirm:

• Tenant credit — who is paying the rent, and can they keep paying it?
• Lease term + escalators — remaining term, WALT, and the contractual bumps (commonly 2.5–3.5%/yr).
• Expense reality — whether the "NNN" expense lines hide intercompany or occupancy charges; how reimbursement true-ups work.
• Dark-period / re-leasing risk — what happens at rollover: months of vacancy, the landlord absorbing the normally-reimbursed expenses during the gap, and a one-time re-leasing cost. Model it explicitly.
• Zoning / land use — the entitlement and zoning that make the redevelopment optionality real. No entitlement, no covered-land thesis.

A worked example

Take a generic stabilized IOS: roughly $1.8M purchase, ~4 usable acres, ~$133,000 gross in-place rent on a NNN lease.

• Broker cap = $133,000 ÷ $1,800,000 ≈ 7.2% — the headline.
• Now back out the landlord's actuals — say the landlord carries its own insurance, some bank/financing fees, and a small reserve totaling a few thousand dollars a year. True NOI lands below the gross, and the true cap prints meaningfully lower than 7.2%.

That spread is the whole game. The 7.2% gets you in the room; the true cap tells you whether to write the offer. Layer in escalators across the hold, a realistic exit cap, and a dark-period stress at rollover, and you have an honest read — plus a separate line for what the dirt is worth if the highest-and-best use changes.

Underwrite all of this in one place. Set your target cap, minimum DSCR, and preferred markets once, and UpsideIQ grades every IOS deal against your criteria — with broker cap and true cap shown side by side, IOS-correct landlord-actual expenses, and the covered-land lens built in.

Related teardown: How I underwrote an IOS yard — why rent-per-acre and zoning, not the cap rate, made the call.