Commercial real estate debt finances income-producing property — office, multifamily, industrial, retail, hotels, and specialty sectors like data centers — against the cash flows the property generates. Because buildings are large, long-lived, and mostly financed with borrowed money, CRE credit is one of the biggest lending markets in the economy, spread across banks, insurers, securitization markets, and private debt funds.
The organizing concept is the capital stack. At the base sits the senior mortgage, secured by a first lien on the property, typically covering 50–65% of value. Above it may sit mezzanine debt — a loan secured not by the property itself but by a pledge of the equity interests in the property-owning entity, enforceable through a (relatively fast) UCC foreclosure. Preferred equity sits higher still, and common equity takes the residual. Each layer prices for its position: the senior lender accepts the lowest return for the first claim; each layer above demands more.
Three ratios anchor underwriting. Loan-to-value (LTV) measures leverage against appraised value. Debt service coverage ratio (DSCR) divides net operating income (NOI) by debt service — a DSCR of 1.25x means income exceeds payments by 25%. Debt yield divides NOI by the loan amount, giving lenders a valuation-independent measure of how much income backs each dollar of debt; it became prominent precisely because appraisals and cap rates move with markets.
Cap rates connect the credit to valuation. A capitalization rate is the ratio of NOI to price — effectively the market's required unlevered yield on the property. When interest rates rise, cap rates tend to rise, and values fall mechanically even if income is unchanged. This is why rate cycles hit CRE credit with a lag: values reset at refinancing, not continuously.
Most CRE loans are non-recourse: the lender's remedy is the property, not the sponsor's other assets, subject to "bad-boy" carve-outs for fraud, misapplication of funds, or unauthorized transfers. Loan structures split between stabilized lending (fixed-rate, longer-term, often securitized into CMBS or held by insurers) and transitional or bridge lending (floating-rate, shorter-term loans funding renovation or lease-up, the home turf of debt funds and mortgage REITs).
Securitization plays a large role. Conduit CMBS pools many mortgages into tranched securities; single-asset single-borrower (SASB) deals securitize one large loan; agency CMBS (Fannie Mae, Freddie Mac, Ginnie Mae programs) dominates multifamily. CRE CLOs securitize transitional loans and are actively managed. Tranching and enhancement mechanics follow the securitization playbook covered in our companion guide.
Credit stress in CRE usually announces itself at maturity rather than mid-term: a loan underwritten at low rates cannot refinance at higher ones without new equity, producing the "maturity wall" and "extend and modify" dynamics that dominate coverage in downcycles. Watch DSCRs at today's rates, debt yields versus lender minimums, and special servicing and delinquency rates in CMBS — these are the market's early warning gauges.