What it means
When you buy a building or launch a business, you rarely use your own money alone. Instead, you build a capital stack by combining various types of funding.
Each layer in the stack has a specific cost and priority claim on the assets and cash flow if things go wrong. At the bottom of the stack sits senior debt, usually a traditional bank loan.
This is the safest slice of funding because it gets paid back first if the business struggles, meaning it carries the lowest interest rate. Above that, you might find mezzanine debt or preferred equity, which are riskier for the lender and therefore more expensive.
At the very top of the stack is common equity, which is your own money and funds from investors. This layer takes the highest risk because it gets paid last, but it also enjoys the highest potential reward if the venture succeeds.
Balancing these layers is critical for managing your overall financial risk. The order of the layers matters most when things go wrong.
Suppose a $1,000,000 project is funded by $600,000 of senior debt, $200,000 of preferred equity and $200,000 of common equity, and the assets can only be sold for $700,000. The senior lender receives its full $600,000, the preferred investors receive the remaining $100,000, and the common equity receives nothing.
Understanding how to construct this stack helps managers optimise their cost of capital. If you use too much expensive equity, you give away too much ownership.
If you use too much debt, a temporary dip in revenue could make your fixed loan payments impossible to meet. Imagine a multi-storey building where the foundation represents bank loans, the middle floors represent business partners, and the penthouse represents your own money.
The lower you are, the safer you are in a storm. The higher you are, the better your view, but the more you feel the wind.
In practice
Real-world examples
Example 1
A property entrepreneur buys a $2 million commercial warehouse. They secure a $1.2 million bank mortgage, bring in $500,000 of investor equity, and use $300,000 of their own cash. The bank covers 60% of the cost and the equity layers cover the other 40%, so the lender is well protected.
Example 2
A growing software company needs $1 million to scale operations. They raise $600,000 from venture capital investors in exchange for shares and take out a $400,000 growth loan from a bank. The investors accept the highest risk, hoping for a large payoff, while the bank wants steady repayments.
Example 3
A manufacturing firm builds a new factory for $5 million. The stack includes a $3 million senior bank loan, a $1 million equipment lease, and $1 million of retained company earnings. Using its own profits for part of the cost means it gives away no ownership.
Think of it
Imagine a multi-storey building where the foundation represents bank loans, the middle floors represent business partners, and the penthouse represents your own money. The lower you are, the safer you are in a storm. The higher you are, the better your view, but the more you feel the wind.
Formula
Calculation
Total Capital Stack = Senior Debt + Mezzanine Debt + Preferred Equity + Common Equity
Blended Cost of Capital = Sum of (Layer share of the stack x Layer cost)
Worked example. A project costs $1,000,000 and is funded by $600,000 of senior debt, $200,000 of preferred equity, and $200,000 of common equity.
- Shares of the stack: senior debt 60%, preferred equity 20%, common equity 20%
- Assumed costs: senior debt 6%, preferred equity 10%, common equity 15%
- Blended cost = (60% x 6%) + (20% x 10%) + (20% x 15%) = 3.6% + 2.0% + 3.0% = 8.6%
- The project must earn more than 8.6% a year to create value; at $1,000,000 that is $86,000 of annual return
- If the owners replaced the preferred equity with extra senior debt at 6%, the blended cost would fall to 60% x 6% + 20% x 6% + 20% x 15% = 3.6% + 1.2% + 3.0% = 7.8%, but with more fixed repayments and higher riskCase study
Seen in the real world
This is a fictional, illustrative scenario. GreenField Logistics wanted to expand its fleet depot, requiring a total investment of $4 million. The management team carefully designed their capital stack to protect the business while maintaining healthy potential returns. They approached a high street bank, which provided $2.4 million in senior secured debt at a modest 5% interest rate, sitting at the bottom of the stack.
Next, they secured $600,000 from a private credit fund through mezzanine debt, carrying an 11% interest rate. Finally, the founders and early angel investors contributed $1 million in common equity to complete the funding. The debt cost $2.4 million x 5% = $120,000 plus $600,000 x 11% = $66,000, or $186,000 a year, which the depot's rental income comfortably covered. Senior debt was 60% of the stack, mezzanine 15% and equity 25%.
Six months later, supply chain delays caused a temporary drop in rental income. Because the senior debt repayments were manageable, GreenField avoided financial distress. The thoughtful arrangement of their capital stack ensured that the business stayed afloat during rough patches while preserving future upside for the founders.
Watch out
Common mistakes
- Treating all funding sources as equal in cost and risk.
- Taking on too much high-interest debt at the bottom of the stack, risking bankruptcy during a downturn.
- Failing to align the maturity dates of different funding layers with the actual cash flow timeline of the project.
Questions
People also ask
Why is senior debt at the bottom of the stack?
It is at the bottom because it takes priority. If the business fails, senior debt gets paid back first from asset sales, making it the safest position for a lender.
How do I know what the right mix is?
The right mix depends on your risk tolerance, the stability of your cash flow, and the cost of capital available in the market for each specific layer.
Can the capital stack change over time?
Yes. Businesses often refinance debt, buy out equity partners, or add new funding layers as they grow and their financial risk profile shifts.