Staircasing Calculator: What It Costs to Buy More Shares
See what a shared ownership home costs year by year — rent, service charge and mortgage — how staircasing changes it, and how it compares with buying outright or renting.
Every assumption is shown and can be changed. Illustration, not advice.
Your figures
Illustration, not a personal recommendation- Total spend over 25 years
- £407,564
- First-year monthly cost
- £1,064
- Share owned at the end
- 25%
- Equity at the end
- £123,045
- Mortgage left at the end
- £0
| Year | Rent | Service charge | Interest | Capital repaid | Staircasing | Home value | Equity |
|---|---|---|---|---|---|---|---|
| 1 | £6,188 | £1,200 | £4,063 | £1,316 | £0 | £306,000 | £6,566 |
| 2 | £6,373 | £1,236 | £3,985 | £1,394 | £0 | £312,120 | £9,490 |
| 3 | £6,564 | £1,273 | £3,903 | £1,476 | £0 | £318,362 | £12,527 |
| 4 | £6,761 | £1,311 | £3,815 | £1,563 | £0 | £324,730 | £15,683 |
| 5 | £6,964 | £1,351 | £3,723 | £1,656 | £0 | £331,224 | £18,962 |
| 6 | £7,173 | £1,391 | £3,625 | £1,754 | £0 | £337,849 | £22,372 |
| 7 | £7,388 | £1,433 | £3,522 | £1,857 | £0 | £344,606 | £25,918 |
| 8 | £7,610 | £1,476 | £3,412 | £1,967 | £0 | £351,498 | £29,608 |
| 9 | £7,838 | £1,520 | £3,296 | £2,083 | £0 | £358,528 | £33,448 |
| 10 | £8,073 | £1,566 | £3,173 | £2,206 | £0 | £365,698 | £37,447 |
| 11 | £8,315 | £1,613 | £3,043 | £2,336 | £0 | £373,012 | £41,611 |
| 12 | £8,565 | £1,661 | £2,905 | £2,474 | £0 | £380,473 | £45,950 |
| 13 | £8,822 | £1,711 | £2,759 | £2,620 | £0 | £388,082 | £50,473 |
| 14 | £9,087 | £1,762 | £2,604 | £2,775 | £0 | £395,844 | £55,188 |
| 15 | £9,359 | £1,815 | £2,440 | £2,939 | £0 | £403,761 | £60,106 |
| 16 | £9,640 | £1,870 | £2,267 | £3,112 | £0 | £411,836 | £65,236 |
| 17 | £9,929 | £1,926 | £2,083 | £3,296 | £0 | £420,072 | £70,591 |
| 18 | £10,227 | £1,983 | £1,889 | £3,490 | £0 | £428,474 | £76,182 |
| 19 | £10,534 | £2,043 | £1,682 | £3,696 | £0 | £437,043 | £82,021 |
| 20 | £10,850 | £2,104 | £1,464 | £3,915 | £0 | £445,784 | £88,121 |
| 21 | £11,175 | £2,167 | £1,233 | £4,146 | £0 | £454,700 | £94,495 |
| 22 | £11,511 | £2,232 | £988 | £4,391 | £0 | £463,794 | £101,159 |
| 23 | £11,856 | £2,299 | £729 | £4,650 | £0 | £473,070 | £108,128 |
| 24 | £12,212 | £2,368 | £455 | £4,924 | £0 | £482,531 | £115,418 |
| 25 | £12,578 | £2,439 | £164 | £5,215 | £0 | £492,182 | £123,045 |
Your lease sets the actual rent review terms; these figures use the new model rules you selected. House prices are assumed to grow 2% a year — an assumption, and prices can fall.
No staircasing yet. Add a step to see how buying more shares changes your rent, mortgage and equity.
Planned ownership: 25%. Each step is priced at the home's assumed value in that year, plus a £350 valuation, £300 admin fee and £960 legal fee (1% steps in years 1–15: no valuation or admin fee; legal fee only if you borrow).
| Year | Staircasing cost | Paid from savings | Share owned | Mortgage balance | Rent |
|---|---|---|---|---|---|
| 1 | £0 | £0 | 25% | £69,934 | £6,188 |
| 2 | £0 | £0 | 25% | £68,540 | £6,373 |
| 3 | £0 | £0 | 25% | £67,063 | £6,564 |
| 4 | £0 | £0 | 25% | £65,500 | £6,761 |
| 5 | £0 | £0 | 25% | £63,844 | £6,964 |
| 6 | £0 | £0 | 25% | £62,090 | £7,173 |
| 7 | £0 | £0 | 25% | £60,233 | £7,388 |
| 8 | £0 | £0 | 25% | £58,267 | £7,610 |
| 9 | £0 | £0 | 25% | £56,184 | £7,838 |
| 10 | £0 | £0 | 25% | £53,978 | £8,073 |
| 11 | £0 | £0 | 25% | £51,642 | £8,315 |
| 12 | £0 | £0 | 25% | £49,168 | £8,565 |
| 13 | £0 | £0 | 25% | £46,548 | £8,822 |
| 14 | £0 | £0 | 25% | £43,773 | £9,087 |
| 15 | £0 | £0 | 25% | £40,835 | £9,359 |
| 16 | £0 | £0 | 25% | £37,723 | £9,640 |
| 17 | £0 | £0 | 25% | £34,427 | £9,929 |
| 18 | £0 | £0 | 25% | £30,936 | £10,227 |
| 19 | £0 | £0 | 25% | £27,240 | £10,534 |
| 20 | £0 | £0 | 25% | £23,325 | £10,850 |
| 21 | £0 | £0 | 25% | £19,180 | £11,175 |
| 22 | £0 | £0 | 25% | £14,789 | £11,511 |
| 23 | £0 | £0 | 25% | £10,139 | £11,856 |
| 24 | £0 | £0 | 25% | £5,215 | £12,212 |
| 25 | £0 | £0 | 25% | £0 | £12,578 |
| Option | First-year monthly | Cash paid out over 25 years | Equity at the end |
|---|---|---|---|
| Shared ownership | £1,064 | £407,564 | £123,045 |
| Buy the whole home | £1,964 | £606,619 | £492,182 |
| Rent the same home | £1,125 | £492,200 | £0 |
Buying the whole home with the same deposit needs a 98.75% loan-to-value mortgage. Most lenders cap here at 95%, so this option may not be available with this deposit.
Cash paid out and equity are shown side by side rather than combined into one answer: which matters more depends on how long you stay and what you plan to do next. If you would like a view on your own plans, an adviser can look at your situation.
These figures show what the home could cost. Whether a lender will lend on your share depends on your income, commitments and the lender's own rules for rent and service charge. Our free check takes these numbers straight into the lender search.
See which lenders could lend on thisFree. No credit search.
Found a home? Check which lenders could lend on your share
Our free check counts the rent and service charge the way lenders typically do, across 31 shared ownership lenders.
Shared ownership mortgage calculatorWhat this calculator works out
It projects the three monthly costs — mortgage, rent on the share you don't own, and service charge — year by year, then shows what buying further shares does to them. For how shared ownership itself works, read the shared ownership affordability guide, and for how the rent is set and rises, the shared ownership rent guide.
A worked example. A £300,000 home, buying 25% with a £3,750 deposit, a 5.75% mortgage over 25 years, rent at 2.75% of the unsold share and a £100 a month service charge: the first year costs about £1,064 a month and total spend over 25 years is about £407,564, leaving £123,045 of equity if prices rise 2% a year. Rent rises by CPI + 1% a year, and the example assumes CPI of 2%, the Bank of England's long-run target. CPI was 3.1% in August 2026, so the first few rent rises could be bigger than this shows.
Staircasing changes the picture. Buying another 25% in year 5 and the final 50% in year 10, both added to the mortgage, means owning 100% with total spend of about £660,638 and £492,182 of equity at the end, on the same growth assumption. Prices can fall as well as rise, and a lower value makes each step cheaper.
New model and older leases
| Rule | New model (2021+) | Older lease |
|---|---|---|
| Minimum first share | 10% | 25% |
| Minimum staircasing step | 5% | 10% |
| 1% yearly steps | Years 1–15: no landlord admin fee and an HPI-based price (no RICS valuation); legal fees may still apply, and you need a legal adviser if you borrow | Not available |
| Yearly rent increase (set by your lease, not the model) | Leases signed on or after 12 Oct 2023 usually rise by up to CPI + 1%; leases signed before then rise by up to RPI + 0.5% (some newer homes funded before that date also use RPI + 0.5%). | |
How does staircasing work, and what does it cost?
Each step is priced at the home's value at the time, so the calculator grows the price by your house price assumption. On top of the share price there is usually a RICS valuation (about £200–£500), your landlord's administration fee (about £150–£500) and your own solicitor's fees (often £500–£1,000 plus VAT, more if you borrow, when the lender may also charge valuation and arrangement fees). They are set at £350, £300 and £960 including VAT here. New-model 1% steps in the first 15 years have no admin fee and are priced from the house price index rather than a RICS valuation; the calculator adds the legal fee only when you borrow for one. You can pay from savings or add the cost to your mortgage; borrowing spreads it over the rest of your term.
Frequently asked questions
How is shared ownership rent worked out?
Rent is charged on the share you do not own. On a new home it is usually 2.75% a year of that share's value when you buy, and the limit is 3%; on a resale it starts at whatever the previous owner was paying. It then rises once a year under your lease: by up to RPI + 0.5% if you signed before 12 October 2023, and usually by up to CPI + 1% (sometimes RPI + up to 0.5%) if you signed on or after it. Your lease sets the actual terms.
What is staircasing?
Staircasing is buying more shares in your home after you move in. Each extra share is priced at the home's market value at the time, not what you originally paid, so rising prices make it dearer. Your rent falls in proportion to the share you buy, and stops once you own 100%. A service charge usually continues, especially for flats.
What changed with the new shared ownership model?
Homes under the 2021 model can start from a 10% share (previously 25%), let you buy extra shares in steps from 5% (previously 10%), and allow 1% steps each year for the first 15 years with no landlord administration fee and an HPI-based price instead of a RICS valuation (you may still pay legal fees, and you'll need a legal adviser if you borrow to buy the share). Separately, leases signed since 12 October 2023, on new-model and older-programme homes alike, usually raise rent by up to CPI + 1% instead of RPI + 0.5%. Check which model your lease uses: the calculator lets you switch.
Is shared ownership cheaper than buying outright or renting?
It depends on how long you stay, how house prices move and whether and when you staircase. The Compare tab shows cash paid out and equity at the end side by side rather than picking one for you. If you want a view on your own plans, an adviser can look at your situation.
How do I staircase to 100% and own the home outright?
You tell your landlord you want to buy more, they instruct a RICS valuation, and the price of the share is set from that valuation rather than what you first paid. You can go to 100% in one step or in several. Once you own 100% the rent stops, and on a house you would normally take the freehold; on a flat you stay leaseholder and the service charge continues.
Is staircasing worth it?
It turns rent you cannot get back into equity you own, but each step is priced at the home's value on the day, so rising prices make later steps dearer while falling prices make them cheaper. Against that sit the valuation, admin and legal costs each time, and a bigger mortgage instead of rent. The Compare tab lays the cash paid out and the equity side by side for your own figures rather than picking an answer for you.
Can I borrow more to buy extra shares?
Usually yes — you either add the cost to your existing mortgage or remortgage for the larger share, and it is assessed on your income alongside the reduced rent. Set a step to “borrow” in the calculator to see what that does to the monthly cost and to total spend.
How this calculator works, and when it was last checked
- Method
- A year-by-year projection. The mortgage on your share is repaid monthly; rent on the share you don't own rises by CPI + 1% or RPI + 0.5%, whichever your lease uses (most leases signed since 12 October 2023 use CPI + 1%), and falls in proportion when you staircase; each staircasing step is priced at the home's assumed value that year, plus valuation, landlord admin and legal fees. Every assumption is shown and can be changed — it is an illustration, not a figure from your housing association.
- Fees and rent rules last verified
- — Projection checked against independently hand-worked figures for both lease models, both rent-review indices, staircasing funded by borrowing and by savings, the 1% step rules (no valuation or admin fee; legal fee only when borrowed), and the buy-outright and renting comparisons. Fee defaults and rent-review rules checked against gov.uk and Homes England's Capital Funding Guide.
- Sources
- Who checked it
- Reviewed by Phillip Wakeling-Smith, CeMAP-qualified mortgage adviser.
Results are an estimate for general information, not a quote, an offer of credit, or advice. Your own figures depend on a lender's full assessment of your circumstances.