Balloon Risk, Payment Shock, and the Maturity Wall Inside Multifamily Loan Structure
A deal can cover its debt at 1.35 times today and come up short on the payment two years from now without the interest rate moving a single basis point.
The rate cap conversation has trained investors to watch the rate. Loan structure deserves the same attention, and it is easier to verify, because the dates are already printed in the loan documents. Nobody has to forecast them.
What the interest-only period is actually doing
During an interest-only period, the borrower pays interest and nothing else. Consider illustrative mechanics: a $20 million loan at 6.25% carries roughly $1.25 million of annual debt service while interest-only. Against $1.7 million of net operating income, coverage sits near 1.36 times. That reads as a cushion. It gets presented as one.
When the interest-only period ends and the loan begins amortizing over a thirty-year schedule, annual debt service rises to roughly $1.48 million. Coverage falls to about 1.15 times.
Occupancy did not change. Rents did not change. Expenses did not change. The calendar changed.
That is structural (vs. market) risk, and it was knowable on day one.
The number the lender is testing may not be the number in the deck
This is the part I did not appreciate until I sat on the credit side of the table. Many lenders define the debt service coverage covenant using an imputed constant: an assumed amortizing payment, applied even while the borrower is paying interest only.
So the sponsor thinks they are at 1.36 times. The bank tests something closer to 1.15 times against a 1.20 times covenant. Every payment has been made on time and the loan is still in performance default, which hands the lender control it did not have the month before.
Ask for the covenant definition. Not the debt summary. The definition.
The balloon is a separate problem, and it compounds the first one
Full-term interest-only means the balance at maturity equals the balance at origination. There is no de-leveraging along the way and no amortization cushion built up. The entire principal comes due in one payment, repaid by a sale or a refinance.
That refinance is sized on the next lender’s terms at that future date, not the ones available at closing. If the new lender requires a 9% debt yield and net operating income is $1.7 million, maximum proceeds land near $18.9 million against a $20 million balloon. The roughly $1.1 million gap is real cash, and it comes from somewhere: new equity, a capital call, higher-cost mezzanine or preferred, or a sale into whatever the market is paying that quarter.
In a full-term interest-only deal, net operating income growth is not only a return driver. It determines the viability of a refinance.
Where this sits in the current market
The Mortgage Bankers Association’s 2025 Commercial Real Estate Survey of Loan Maturity Volumes, released in February 2026, puts $875 billion, or 17 percent of the $5.0 trillion in outstanding commercial mortgages, on schedule to mature in 2026, roughly 9 percent below the 2025 figure, with 13 percent of multifamily-backed balances maturing this year. The wave is easing. It is not over.
Structure is where the concentration shows up. CRED iQ, analyzing $26.1 billion of loans securitized in 2026, found that 56% of new-issue balance carries full-term interest-only terms. In a recent sample of commercial real estate CLO collateral, apartments made up close to 80% of aggregate balance and full-term interest-only loans represented 95% of it, leaving principal paydown minimal until maturity.
And the resolution path is not costless. CRED iQ tracked 82 modified securitized loans totaling $2.36 billion from May through July 2026, and the property type modifying most is no longer hotel or office. It is multifamily. An extension typically arrives with a principal paydown, a new rate cap, funded reserves, and a fee. The option exists. It is not free.
What changes in the diligence
Ask for the amortization schedule, not the debt summary, and run coverage in year one as if amortization began at closing. If it breaks below the covenant there, the cushion is a calendar artifact.
Ask what net operating income is required to refinance the balloon at a stated debt yield, then hold that number against the business plan rather than against the projected exit price.
Ask when the interest-only period ends relative to when stabilization is projected. Sequence matters. Amortization arriving before stabilization is a materially different deal from amortization arriving after.
Ask what the extension options actually require, in dollars, and where those dollars sit today.
Closing thoughts
Interest-only is not a red flag. Used with discipline, it funds a renovation program during the stretch when cash flow is weakest and the property is least able to carry principal. That is a legitimate use of structure.
The risk is treating interest-only coverage as the deal’s coverage. That is not necessarily durable cash flow.
If amortization started tomorrow, what breaks first: the covenant, the distribution, or the reserve?
Vessi Kapoulian
Breaking down multifamily underwriting one step at a time to create educated and empowered investors
P.S. If you would like a second set of eyes on a deal or want to sharpen your underwriting through a risk lens, feel free to connect with me.
P.P.S. And if you want to go deeper into analyzing multifamily investments step by step, my Mastering Multifamily Underwriting book and the Mastering Multifamily Underwriting program walk through this process in plain English, from acquisition to exit.
Sources:
Mortgage Bankers Association, 2025 Commercial Real Estate Survey of Loan Maturity Volumes (February 2026).
CRED iQ, 2026 new-issue securitized loan analysis and commercial real estate CLO collateral review (June and July 2026), and loan modification tracking, May through July 2026.