On a £3 million facility at 8%, with interest rolling up over 18 months, total interest cost runs to approximately £360,000 – and a 2% rate increase during that same term adds a further £90,000 on top. The headline monthly rate quoted at application stage genuinely tells you very little about what a rolled-up facility actually costs by the time you reach exit.
What Rolled-Up Interest Actually Means
Our UK Development Finance hub covers the wider lending landscape; this piece focuses specifically on how interest genuinely accumulates across a facility’s term. With rolled-up interest, interest accrues throughout the build but isn’t actually paid until the facility is redeemed, avoiding the need for monthly payments during construction. This is genuinely the default structure across UK development finance, since it preserves cash flow for the build itself rather than tying up funds in monthly interest servicing.
Why Rolled-Up Interest Genuinely Compounds Rather Than Simply Accruing
It’s worth understanding this distinction clearly: because rolled-up interest is added directly to the outstanding balance, subsequent interest is then calculated on that larger figure – interest genuinely charged on interest, not simply the original sum borrowed. Over an 18 or 24-month term, this compounding effect adds a genuinely meaningful sum beyond what a simple, non-compounding calculation would suggest.
Why Interest Isn’t Charged on the Full Facility From Day One
It’s worth understanding one further nuance clearly: interest is generally calculated only on funds genuinely drawn at any given point, not on the maximum facility amount from the outset. A £2 million facility doesn’t automatically mean paying interest on £2 million from day one – if only part has been drawn, borrowing costs reflect the amount actually outstanding, rising only as further tranches are released, which is exactly why the drawdown schedule itself genuinely shapes your total interest bill alongside the headline rate.
Why Rolled Interest Eats Into Your Borrowing Capacity, Not Just Your Final Bill
This is worth understanding as the genuinely more significant point: because rolled-up interest forms part of the facility itself, it sits inside your loan-to-cost calculation from day one. This means the interest you’ll eventually owe is already competing for space within your maximum facility, alongside the actual construction costs you need funded – a rolled-up structure genuinely reduces the funds available for the build itself, not simply the amount you’ll owe at the end.
Current Rates Worth Benchmarking Against
Development finance rates in 2026 typically sit between 0.65% and 1.10% a month, roughly 8% to 13% annualised, with well-structured residential schemes by experienced developers accessing the lower end and higher-leverage or first-time developer cases sitting toward the top.
Why the Total Cost Runs Considerably Higher Than the Rate Alone Suggests
Total cost across a 12-month facility, once every fee and the rolled-up interest itself are properly accounted for, commonly runs to 12-18% of the loan amount – a genuinely different figure to the headline monthly rate multiplied out simply. It’s worth requesting a full, itemised total cost illustration from any lender before comparing offers on rate alone.
A Genuine Illustration of the Compounding Effect Itself
On a comparable facility where simple, non-compounding interest would have totalled £37,260, the genuine compounding effect on rolled-up interest over a 12-month term added a further £1,364 to the final bill – a real, quantified illustration of why rolled-up interest isn’t simply the rate multiplied by the term.
Why Switching to Serviced Interest Can Genuinely Save Money on Longer Facilities
For facilities extending beyond 12 months specifically, switching from rolled-up to serviced interest, where you pay interest monthly rather than letting it accumulate, typically saves 5-12% of total interest cost. It’s worth discussing this specifically with your broker if your own cash flow position genuinely allows for monthly servicing, rather than defaulting to rolled-up simply because it’s the standard structure.
Why Mezzanine Layers Genuinely Amplify This Effect
Our Mezzanine Finance page covers layering additional, typically also rolled-up debt behind your senior facility; it’s worth understanding a mezzanine layer commonly carries a genuinely higher rate than senior debt, meaning the compounding effect across your full capital stack is amplified considerably beyond the senior facility alone, particularly on a scheme running toward the longer end of its programme.
Why Higher-Leverage Structures Genuinely Compound the Cost Further
Our Stretched Senior Debt page covers a single, higher-leverage facility reaching further into your total cost requirement; it’s worth understanding a larger drawn balance across the same term genuinely means a larger absolute sum compounding throughout, even where the headline rate itself looks broadly comparable to a lower-leverage alternative.
Why Exit Timing Is the Genuine Critical Input, Not Just the Rate
The effective cost of a rolled-up facility genuinely compounds over time, making your realistic exit timeline as important an input as the rate itself when comparing offers. Our Development Exit Finance page covers the route worth considering if your original facility term is genuinely at risk of running over, since continuing to compound rolled-up interest on an overrunning development can meaningfully erode your final profit margin beyond what a delayed but properly refinanced exit would cost instead.
Stress-Testing Your Own Numbers Against a Rate Rise
It’s worth modelling your own facility assuming rates hold steady, but genuinely stress-testing against a further 1-2 percentage points above your quoted rate – given how meaningfully a modest rate movement compounds across an 18-month rolled-up facility, as our opening £90,000 example illustrates clearly.
Getting Your True Cost Genuinely Modelled Before You Commit
Given how much genuinely depends on your specific term, leverage, and whether rolled-up or serviced interest better suits your cash flow, it’s worth having a proper conversation about your realistic all-in cost before comparing headline rates alone. Get in touch with details of your scheme and facility term, and we’ll help you understand what a facility will genuinely cost by the time you reach exit.
Frequently Asked Questions
Why is interest rolled up rather than paid monthly on development finance?
To preserve cash flow during the build – rolled-up interest avoids tying up funds in monthly payments, with the full amount settled instead when the facility is redeemed.
Does rolled-up interest genuinely compound, or simply accrue?
It genuinely compounds – because rolled-up interest is added to the outstanding balance, subsequent interest is then calculated on that larger figure.
Am I charged interest on the full facility from the day it’s agreed?
Generally not – interest is typically calculated only on funds actually drawn at any given point, rising as further tranches are released rather than applying to the maximum facility from day one.
Does rolled-up interest affect how much I can actually borrow for construction?
Yes, genuinely – since it sits inside your loan-to-cost calculation from day one, it competes for space within your maximum facility alongside your actual build costs.
Can switching to serviced interest genuinely save money?
Often yes on facilities beyond 12 months – switching from rolled-up to serviced interest typically saves 5-12% of total interest cost, provided your cash flow genuinely supports monthly payments.
What’s the realistic total cost of a development finance facility, not just the rate?
Commonly 12-18% of the loan amount across a 12-month term once every fee and the rolled-up interest itself are properly accounted for.
Get in touch with details of your scheme and facility term, and we’ll help you understand your genuine all-in cost before you commit.
