Semi-commercial affordability and the interest cover ratio
How lenders size a semi-commercial loan using the interest cover ratio on the combined rent.
Semi-commercial affordability is assessed on the combined commercial and residential rent against an interest cover ratio, commonly 125 to 140 percent stressed. The combined rent must cover the mortgage interest by that margin at a stressed rate. Owner-occupier cases are instead tested on the trading business through debt service cover.
At a glance
- Main testInterest cover ratio (ICR)
- Typical ICR125 to 140% stressed
- Measured onCombined commercial + residential rent
- Owner-occupierDebt service cover on the trade
How semi-commercial affordability is assessed
Affordability on a semi-commercial investment loan is measured by the interest cover ratio, the ICR. It compares the rent a property produces with the mortgage interest it must pay, and the rent has to exceed the interest by a set margin.
Unlike a residential mortgage, which is sized on your salary, a semi-commercial loan is sized on the income from the property itself, the combined rent from the commercial and residential parts.
What the interest cover ratio is
The interest cover ratio expresses rent as a percentage of mortgage interest. An ICR of 130 percent means the rent is 130 percent of the interest, so it covers the interest with 30 percent to spare.
ICR = annual rental income divided by annual mortgage interest, expressed as a percentage. Lenders set a minimum, commonly 125 to 140 percent, tested at a stressed interest rate.
On semi-commercial deals lenders commonly require 125 to 140 percent. A higher required ICR means a lower loan for the same rent.
ICR on combined commercial and residential rent
The strength of a semi-commercial deal is that the ICR is tested on two income strands together. The commercial rent and the residential rent are added, and the total is tested against the interest.
That combined figure is often more resilient than a single income, because a void in one part is cushioned by the other. Well-documented leases on both the shop and the flat are what support the loan size.
How the stress rate works
Lenders do not test the ICR at the pay rate alone. They apply a stressed interest rate, higher than the actual rate, to check the rent would still cover the interest if rates rose.
| Element | Effect on loan |
|---|---|
| Higher required ICR | Smaller loan |
| Higher stress rate | Smaller loan |
| Stronger combined rent | Larger loan |
| Lower loan to value | Easier to pass |
The combination of the required ICR and the stress rate sets the maximum loan the rent will support.
Worked example: sizing a loan on ICR
Take a mixed-use property earning 30,000 pounds a year in combined rent, with a lender requiring a 130 percent ICR at a 9 percent stress rate.
| Step | Figure |
|---|---|
| Combined annual rent | 30,000 |
| Rent divided by 130% ICR | 23,077 |
| Maximum annual interest | 23,077 |
| Implied loan at 9% stress | ~256,000 |
The rent divided by the ICR gives the maximum interest the lender will allow, and that interest, divided by the stress rate, gives the maximum loan. Stronger rent or a lower stress rate lifts the loan.
Affordability for owner-occupiers
Where you trade from the commercial unit rather than let it, the ICR on rent does not apply in the same way. Owner-occupier cases are tested on debt service cover: the profit of the trading business against the mortgage payments.
The lender wants to see that the business comfortably covers the loan, usually with a margin similar in spirit to an ICR. The residential part, if let, can add supporting income.
How to strengthen your affordability
- Secure strong, documented leases on both the commercial and residential parts
- Improve the commercial covenant, for example a longer lease to a solid tenant
- Lower the loan to value with more deposit, easing the ICR test
- Evidence the trading accounts where you occupy the commercial unit
- Run the case across lenders, whose ICR and stress assumptions differ
Because each lender sets its own ICR and stress rate, the same property supports a different loan with different lenders, which is where placing the case across the panel adds value.
- Interest cover ratio (ICR)
- Rental income as a percentage of mortgage interest; lenders commonly require 125 to 140 percent, stressed.
- Stress rate
- A higher assumed interest rate lenders apply when testing affordability, to check the rent still covers the loan if rates rise.
- Debt service cover
- A business's profit measured against its loan payments, used to test owner-occupier affordability.
Semi-commercial affordability and the interest cover ratio: common questions
What is an acceptable interest cover ratio?
On semi-commercial mortgages, lenders commonly require 125 to 140 percent, tested at a stressed interest rate. The combined commercial and residential rent must cover the interest by that margin.
What is a good interest rate on a commercial mortgage?
In mid-2026, around 6.5 to 8.5 percent a year for semi-commercial investment deals and 6.0 to 7.5 percent for owner-occupiers. The rate interacts with the ICR to set the loan you can support.
How is semi-commercial affordability calculated?
By dividing the combined rent by the required interest cover ratio to find the maximum interest, then dividing that by the stress rate to find the maximum loan. Owner-occupiers are tested on business debt service cover.
What is a 1.3 interest cover ratio?
It means the rent is 130 percent of the mortgage interest, covering it with 30 percent to spare. It is a common minimum on semi-commercial investment lending.
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