The Risk Nobody Underwrites

You don't own a commercial property for the life of its mortgage. You own it for 5 to 10 years, and then you refinance. The interest rate environment at that moment determines whether your deal survives or demands a capital call.

Most investors underwrite the going-in numbers: today's NOI, today's rate, today's DSCR. They close the deal feeling confident. Five years later, rates have moved 200 basis points, the property can't cover the new debt service, and the lender requires a paydown to close the gap. That paydown comes out of the investor's pocket, sometimes seven figures.

This is not a hypothetical scenario. It is the single most common way CRE deals fail, and it is entirely preventable with a calculation that takes less than five minutes.

Why CRE Loans Force Refinancing

Residential mortgages are typically 30-year fixed-rate loans. You lock a rate and forget about it for three decades. Commercial real estate does not work this way.

Most CRE loans have 5, 7, or 10-year terms with 25 or 30-year amortization schedules. The loan is structured as if it will be repaid over 30 years, but the entire remaining balance comes due in 5 to 10 years. At that point, you must either refinance, sell, or pay off the balance in cash.

This structure means every CRE investor is making an implicit bet on future interest rates, whether they realize it or not. The question is not "what rate am I getting today?" The question is "what rate will I get when this loan matures?"

The Federal Reserve's Stress Test: +150 Basis Points

The Federal Reserve's Dodd-Frank Act Stress Testing (DFAST) framework is the standard methodology banks use to evaluate their CRE loan portfolios. The severely adverse scenario typically includes interest rate increases of at least 150 basis points above current levels.

This is not a doomsday scenario. This is the regulatory baseline for what banks must plan for. Between 2022 and 2024, the federal funds rate moved over 500 basis points. The DFAST +150 basis point scenario is not conservative. It is the bare minimum any serious underwriter should test.

If your deal breaks at +150 basis points above today's rate, you do not have a deal. You have a rate bet. And rate bets in commercial real estate are bets with seven-figure consequences.

The Maturity Wall: 2021-2022 Loans Coming Due

Between 2020 and 2022, commercial real estate lending hit record volumes. Deals were originated at historically low interest rates (3.0% to 4.5%) and at peak property valuations. Cap rates compressed below 4% in many markets. Investors paid aggressive prices, financed them cheaply, and projected rent growth that would bail out any remaining risk.

Those loans are now maturing into a different world. The 10-year Treasury has settled in above 4%. CRE lending spreads have widened. All-in rates for conventional commercial mortgages sit between 6.0% and 7.5% depending on property type and leverage. For many borrowers, that is 200 to 300 basis points above their original rate.

The math is punishing. A $10M loan at 3.5% has annual debt service of roughly $539,000 on a 30-year amortization. The same loan at 6.5% has annual debt service of roughly $758,000, an increase of $219,000 per year. If the property's NOI hasn't grown enough to absorb that gap, the borrower faces a choice: inject equity or hand back the keys.

This is the maturity wall, and it is not theoretical. NBER Working Paper 31970 found that by 2023, 14% of all commercial real estate loans were in negative equity, meaning the loan balance exceeded the property's market value. For office properties, that figure was 44%. Nearly half of all office mortgages were underwater.

Worked Example: The $8M Loan That Breaks

Here is a straightforward deal that looks acceptable on paper and fails under stress.

The setup:

  • Loan amount: $8,000,000
  • Interest rate: 6.5%
  • Amortization: 30 years
  • Annual NOI: $750,000

Current debt service and DSCR:

At 6.5% on a 30-year amortization, monthly payments on $8M are approximately $50,560. Annual debt service: $606,720.

DSCR = $750,000 / $606,720 = 1.24x

That 1.24x clears most lender minimums by a thin margin. Conventional lenders typically require 1.20x to 1.25x depending on property type. This deal would get financed. An investor looking only at the going-in numbers might feel comfortable.

Stressed at +150 basis points (8.0%):

At 8.0%, monthly payments on $8M rise to approximately $58,720. Annual debt service: $704,640.

Stressed DSCR = $750,000 / $704,640 = 1.06x

That 1.06x is below every conventional lender's threshold. If rates are 150 basis points higher when this loan matures, the property cannot qualify for a refinance at the same leverage. The borrower will need to either pay down the loan balance or find a lender willing to accept below-market coverage, which typically means higher pricing, worse terms, or both.

The cash shortfall is real: the gap between 1.25x DSCR (lender minimum) and 1.06x (stressed reality) means the property needs roughly $134,000 more in annual NOI, or the borrower needs to pay down approximately $1.1M of the loan balance, to qualify for a refinance.

Stressed at +250 basis points (9.0%):

At 9.0%, monthly payments on $8M rise to approximately $64,370. Annual debt service: $772,440.

Stressed DSCR = $750,000 / $772,440 = 0.97x

Below 1.0x, the property cannot cover its own debt service. It is cash-flow negative. The owner is writing checks every month to stay current on the loan. At this point, the deal has failed. The owner must inject capital, sell at a loss, or default.

The distance between a "fine" deal at 6.5% and a defaulting deal at 9.0% is 250 basis points. That is well within the range of normal interest rate cycles.

The IO-to-Amortizing Cliff

Bridge loans and value-add financing often include interest-only (IO) periods, typically 2 to 3 years. During the IO period, the borrower pays only interest, no principal. This makes the initial debt service look manageable.

Here is what happens when amortization starts.

Same $8M loan at 7.0% with a 3-year IO period:

During IO, annual debt service is interest only: $8,000,000 x 7.0% = $560,000.

With $750,000 NOI, the IO-period DSCR is $750,000 / $560,000 = 1.34x. Comfortable.

When the IO period ends and the loan converts to 30-year amortization, annual debt service jumps to approximately $638,880.

Amortizing DSCR = $750,000 / $638,880 = 1.17x

That is a 14% increase in debt service overnight, with no corresponding change in property income. If the value-add business plan did not execute as projected, if rent growth stalled, if vacancy increased, that 1.17x can easily slip below 1.0x.

The IO cliff is one of the most common causes of distress in transitional lending. The deal was never stable. It was temporarily solvent because the lender deferred principal repayment. Many sponsors underwrite to the IO-period DSCR and present that number to investors without disclosing what happens when amortization begins.

When you see a deal underwritten with IO debt service, ask one question: what is the DSCR when amortization starts? If the sponsor cannot answer that immediately, that is a red flag.

Default Statistics: 1 in 6 Commercial Mortgages

Academic research on approximately 18,000 commercial mortgages issued between 1972 and 1997 (Esaki et al., studied in Geltner Chapter 18) found that roughly 1 in 6 commercial mortgages defaults over its lifetime. The default rate peaks around year 6, which aligns precisely with when most CRE loans mature and require refinancing.

The most revealing data point: loans originated at peak values defaulted at dramatically higher rates. The 1986 vintage, originated near the top of the 1980s real estate cycle, had a 28% lifetime default rate. Loans originated after the correction (1992 vintage) defaulted at less than 5%.

Recovery rates compound the pain. Lenders recover roughly 69% of loan value at foreclosure, but only 34% through final disposition after workout costs, carrying costs, and distressed-sale discounts. Equity investors in defaulted deals typically recover nothing.

The parallel to today is direct. Loans originated in 2021 and 2022 at peak valuations and record-low rates are the current cycle's equivalent of the 1986 vintage. Whether they follow the same default trajectory depends entirely on whether borrowers can refinance. That depends on rates. Which is why stress testing is not optional analysis. It is survival math.

Three Stress Tests Every Deal Needs

Institutional underwriters do not run one stress scenario. They run at least three, and they require the deal to survive all of them.

1. Rate Stress: +150 Basis Points

Add 150 basis points to the current rate. Recalculate debt service and DSCR. If the DSCR drops below your lender's minimum (typically 1.20x to 1.25x), you have refinancing risk.

This test answers: can I refinance this loan when it matures if rates have risen moderately?

2. NOI Stress: -15% Decline

Reduce NOI by 15%. This simulates a recession-level income decline from higher vacancy, rent reductions, or expense increases. Recalculate DSCR at the current rate.

This test answers: can the property survive an economic downturn without defaulting?

For context, multifamily NOI declined roughly 5% to 10% in the 2008-2010 downturn, while office NOI declined 15% to 25% depending on market. A 15% haircut is a reasonable adverse scenario for most property types.

3. Combined Stress: +150 Basis Points and -15% NOI

This is the scenario that separates resilient deals from fragile ones. Apply both stresses simultaneously. If the DSCR stays above 1.0x under combined stress, the deal can survive a bad refinancing environment during an economic downturn. If it drops below 1.0x, you are relying on favorable conditions in both the capital markets and the operating environment. That is a bet, not an investment.

Returning to our $8M example under combined stress:

Stressed NOI: $750,000 x 0.85 = $637,500 Stressed debt service at 8.0%: $704,640 Combined DSCR: $637,500 / $704,640 = 0.90x

The property is deeply cash-flow negative under combined stress. This deal requires everything to go right. That is the definition of a fragile investment.

The Mental Model

Every commercial real estate deal carries two types of risk: operating risk (will the property perform?) and capital markets risk (can I refinance?). Most retail investors focus exclusively on operating risk. They study the rent roll, tour the property, analyze the market. They ignore capital markets risk entirely, treating the current interest rate as a permanent fixture.

It is not. Interest rates are cyclical. The loan constant on your debt will change at maturity. If you have not stress tested that change, you have underwritten half the deal.

The framework is simple. Run the three stress tests. If the deal survives all three, the risk is manageable. If it breaks under rate stress alone, you need a lower LTV, a higher cap rate, or a different deal. If it breaks under combined stress, be honest about the level of risk you are accepting.

Strong debt yield provides additional confirmation. A debt yield above 10% means the property's NOI is substantial relative to the loan amount, providing a cushion against both rate and income volatility. A debt yield below 8% with thin DSCR coverage is the profile of deals that end up in distress.

The difference between a sophisticated CRE investor and a retail buyer is not intelligence. It is the willingness to underwrite the downside before committing capital. Running these three stress tests takes five minutes. Skipping them can cost you years of returns and hundreds of thousands of dollars.

Where to Go Next

  • Understand the metric that determines loan survival. Read DSCR Explained for the full framework on how lenders evaluate debt coverage.
  • Learn how lenders decide your maximum loan amount. Read How Lenders Size Your Loan for the constraints that control leverage.
  • Know whether leverage is helping or hurting you. Read Positive vs Negative Leverage to understand when borrowing more amplifies returns and when it destroys them.
  • See where we are in the cycle. Read Real Estate Cycles for the historical patterns that drive rate environments, valuations, and default waves.

Sources

  • NBER Working Paper 31970, "Monetary Tightening, Commercial Real Estate Distress, and US Bank Fragility" (2023): 14% of CRE loans in negative equity, 44% for office
  • Federal Reserve DFAST stress testing methodology: +150 basis point severely adverse scenario
  • Geltner et al., "Commercial Real Estate Analysis and Investments," 2nd Edition (2007), Chapter 18: Mortgage default risk, vintage effects, recovery rates
  • Esaki et al., "Commercial Mortgage Defaults: An Update" (2002): study of ~18,000 ACLI mortgages 1972-1997, 1-in-6 lifetime default rate, year-6 peak