What Is a Capital Stack? Layers, Order, and Cost

A capital stack is the set of financing layers funding a commercial real estate deal, ranked by who gets paid first. Senior debt sits at the bottom and is repaid before anything else. Common equity sits at the top and is repaid last, after every other layer has been made whole.

The ranking is the whole point. Position in the stack sets the price of each layer, the remedies each lender holds in a default, and how much of your own balance sheet is exposed.

What is a capital stack?

Most deals do not use every layer. A stabilized building bought with a bank loan and the sponsor's cash has a two-layer stack. The middle layers appear when the senior lender stops short of the total capital the project needs and the sponsor will not, or cannot, fill the gap alone.

The capital stack from most secure to least secure

Ordered by claim, strongest first:

Senior debt is the first mortgage. The lender records a lien against the real estate itself, which makes it the cheapest capital in the stack and the first to be repaid.

Its size comes from the lender's sizing tests rather than from a rule of thumb, and the binding test varies by deal. Loan-to-value, debt service coverage and debt yield each produce a maximum loan, and the smallest of the three governs. On construction and value-add projects, loan-to-cost joins the list, because the lender is funding a budget spent before the property performs. Loan-to-value stays in the test, measured against a prospective as-completed or as-stabilized appraised value rather than an as-is one.

Mezzanine debt fills the gap above the senior loan. What secures it is the structural detail that matters.

A mezzanine loan is made to the parent of the property-owning entity. It is secured by a pledge of that parent's ownership interests, which are personal property governed by Article 9 of the Uniform Commercial Code. A mezzanine lender in default forecloses on that pledged ownership interest and takes over the entity that holds the building.

Article 9 provides for foreclosure outside a judicial process. The law firm White and Williams describes a UCC foreclosure of a mezzanine loan as typically a 45- to 90-day process. A New York mortgage foreclosure, by contrast, can take well over a year (White and Williams, Commercial Real Estate Mezzanine Loan Foreclosures).

That speed comes with a real limitation. If the mortgage lender forecloses first or takes a deed in lieu, the mezzanine loan is wiped out, because the entity whose interests were pledged no longer owns the property. The pledged interests survive; what they are worth does not.

The two lenders therefore sign an intercreditor agreement at closing. It sets out what the mezzanine lender must do to foreclose without losing its position. Common conditions include curing the senior loan's defaults and posting a replacement guarantor the senior lender accepts (Pillsbury on intercreditor agreements).

If you have read about a lender perfecting an interest by filing a financing statement, the mechanism is the same one covered in our explainer on UCC filings on a business loan.

Preferred equity occupies roughly the same economic position as mezzanine debt but is structured as an equity interest. It receives a stated return before common equity receives anything. It holds no lien and no foreclosure right, so its remedies on a default are contractual: control rights, removal of the sponsor as manager, a forced sale provision. Preferred equity appears most often when the senior lender's documents prohibit a mezzanine pledge outright.

Common equity is the sponsor and its investors. It is paid last, absorbs the first dollar of loss, and keeps whatever remains after every layer beneath it is satisfied.

Why the order sets the price

Each step up the stack surrenders something concrete. Senior debt holds a recorded lien on real property. Mezzanine debt trades that for a pledge of ownership interests, which is faster to enforce but wiped out if the senior lender acts first.

Preferred equity gives up the lien entirely and keeps only contract remedies. Common equity holds no claim at all until everyone else is repaid.

Price tracks that loss of protection. Senior debt is the cheapest capital in the stack and common equity is the most expensive, with the middle layers priced between them. Published ranges for each layer move with the rate environment, the asset type and the sponsor. Treat any chart of "typical" costs as a starting point and ask each capital source for a term sheet.

The practical consequence for a borrower: adding a layer raises your blended cost of capital and hands somebody new a set of rights over your deal. Filling a gap with mezzanine debt at a double-digit rate is a decision about control as much as about cost.

Where the SBA 504 loan sits in the capital stack

The published guides to SBA 504 financing describe the 50/40/10 split and stop there. The interesting part is what that split looks like when you draw it as a stack, because it inverts the rule that governs every private deal.

An SBA 504 project is financed by three sources, and the regulation says so directly.

Drawn as a stack on a $2,000,000 project:

The Office of the Comptroller of the Currency, which supervises national banks, describes the same tiering from the bank's side.

The inversion worth knowing about

In a private stack, subordination costs money. The mezzanine lender sits behind the senior lender and charges more for the privilege. In a 504 deal, the subordinated layer is frequently the cheaper of the two, and it is fixed for far longer.

The reason is that the CDC's 40 percent is not priced off its lien position at all. It is funded by a debenture carrying a 100 percent SBA guarantee, and its rate is set when the SBA sells that debenture into the bond market. The OCC notes that the CDC loan's rate is fixed and its term is 20 or 25 years for real estate.

The bank's first-lien loan is negotiated directly with the borrower, and its rate can be fixed or variable. Its minimum term comes from 13 CFR 120.921(a): at least 7 years when the 504 loan runs 10 years, and at least 10 years when the 504 loan runs 20 years. That provision names no 25-year case, because it predates the 25-year debenture. If your CDC piece is a 25-year note, ask the CDC in writing which third-party minimum it applies rather than assuming the 20-year rule carries over.

So the borrower ends up with a second-lien layer fixed for the full 20 or 25 years, sitting underneath a first-lien layer whose rate can reset years earlier. The refinance risk in a 504 stack lives in the senior position, which is backwards from a conventional deal. When you plan the exit, plan it around the bank note and ask for its fixed-rate period in writing, separately from its amortization.

Two limits govern the second layer's size. The CDC portion is capped at $5 million for most projects and $5.5 million for small manufacturers and qualifying energy projects (SBA, 504 loans).

The borrower's contribution also rises with risk. Under 13 CFR 120.910 it is at least 15 percent for a business that has operated two years or less, and at least 15 percent for a limited or single-purpose property. When both conditions apply, the minimum is 20 percent. A special-purpose building bought by a startup therefore produces a 50/30/20 stack rather than 50/40/10.

If you are weighing this structure against the alternatives, our breakdown of SBA 7(a) vs. 504 covers which program fits which project, and the SBA 504 for commercial real estate guide covers eligibility and occupancy. You can size both notes in the SBA loan calculator, and run a conventional first mortgage in the commercial real estate loan calculator.

Capital stack vs. distribution waterfall

These two terms get used interchangeably and describe different things.

The capital stack is the ranking. It tells you who holds which claim and in what order those claims are satisfied. It is a static picture of the deal's capitalization.

The distribution waterfall is the arithmetic that pays those claims out. It takes a dollar of operating cash flow or sale proceeds and routes it down the ranking. Senior debt service first, then mezzanine, then the preferred return, then the split between the sponsor and its investors. Most of a waterfall's complexity lives inside the common equity layer, where promote tiers and IRR hurdles decide how the sponsor and the limited partners divide the upside.

A deal can have a plain three-layer stack and a waterfall that runs three pages. The stack gives you your ranking. The waterfall is where you find out what that ranking is actually worth at a given sale price.

Where your personal balance sheet enters the stack

Position in the stack determines the collateral. Your personal balance sheet determines whether the deal gets funded at all.

On an institutional deal, sponsor recourse is usually narrow. Both the mortgage lender and the mezzanine lender take a non-recourse carve-out guarantee, sometimes called a bad-boy guarantee. It gives them recourse against the sponsor for specific acts such as fraud, misappropriation of rents, or a voluntary bankruptcy filing. Each lender also runs a net worth and liquidity test on whoever signs it, which is the point at which a personal financial statement enters the file.

On an SBA 504 project, the exposure is broader and part of it is set by regulation. Under 13 CFR 120.160(a), holders of at least a 20 percent ownership interest generally must guarantee the loan, and that rule reaches the CDC's SBA-backed note.

The bank's first-lien note carries no SBA guarantee, so recourse on that piece follows the bank's own credit policy. Banks funding 504 projects commonly ask the same owners to guarantee it. Confirm which notes your guarantee covers before you sign, because the two are separate documents. Our explainer on SBA 504 personal guarantee requirements covers who gets pulled in and on what terms, and what a personal guarantee is covers the mechanics.

Every one of those guarantors files SBA Form 413, dated within 120 days of submission. The SBA Form 413 guide walks the form section by section, and the SBA personal financial statement template gives you the layout to start from.

The maturity calendar is why this matters right now.

Every one of those maturities is a stack being rebuilt. When debt service coverage is the binding test, a senior loan that reprices at a higher rate sizes smaller. That opens a gap somebody has to fill, and each new layer brings its own guarantor test. The Mortgage Bankers Association forecasts total commercial mortgage origination volume rising to $805.5 billion in 2026 from the $633.7 billion expected in 2025, with much of that activity coming from refinancing rather than acquisition.

How to read a stack before you sign

Three questions answer most of what a borrower needs to know about a proposed structure.

Who forecloses on what? Ask each capital source what it holds. A recorded mortgage, a pledge of your LLC interests, or nothing but a contract. The answer tells you what each party can take and how quickly.

What resets first? Find the shortest maturity in the stack and work backward from it. In a 504 deal that is usually the bank note, not the debenture. In a bridge-plus-mezzanine structure it is often both at once.

Who signs, and for how much? Map every guarantee before the term sheets are signed, because the guarantor test is what stalls files. Each signer needs a current personal financial statement, and on an SBA deal a stale one restarts the clock.

More on the underwriting side of these deals is in our commercial real estate loan terms breakdown, the types of commercial real estate loans overview, and the rest of the commercial real estate archive. If you are managing a portfolio and refreshing statements each time a lender asks, the commercial real estate investor workflow covers how to keep them current.