How shared ownership mortgages work
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Quick answer: A shared ownership mortgage borrows against a share of a home — in England typically 10% to 75%, and 25% to 75% under Shared Ownership – Wales — while you pay rent on the part you don't own. Two separate assessments decide whether you can go ahead: the housing association's own affordability model, and a lender's. They measure different things, which is why a straightforward-looking case can still stall, and why the lender you end up with depends as much on the share you're buying as on your income. This guide covers how the mechanics work, without naming specific lenders or products, since which ones fit — and what they'll lend — genuinely varies and changes over time.
How buying a share works
Shared ownership lets you buy part of a home, usually from a housing association (a not-for-profit landlord that provides affordable homes), and take out a mortgage on just that part. You pay rent on the rest. On a flat, or an estate with shared areas, you also pay a service charge (a regular charge for upkeep of the building or shared spaces).
Say a home is valued at £250,000 and you buy a 40% share. Your share costs £100,000, and your mortgage and deposit are worked out on that £100,000, not the full £250,000. That's the key difference from buying a whole home.
In England, shares typically start around 10% and go up to 75%. Under Shared Ownership – Wales the range is 25% to 75%. The share you choose changes your rent, your deposit and which lenders will consider you.
Things to weigh
A smaller deposit and the option to buy more later come with costs and limits of their own, in England and in Wales:
- Rent usually goes up every year.
- You normally pay the full service charge and most repair and maintenance costs, even though you own only a share.
- Buying more shares costs more if the home's value has risen, because each new share is priced at the home's value at the time.
- There are rules on selling your share and on subletting.
- Your home may be repossessed if you do not keep up repayments on your mortgage. Falling behind on the rent can also put your home at risk.
The two affordability checks
Every shared ownership purchase has to pass two checks.
The housing association's check comes first. In England this is often the Homes England affordability assessment, which most English housing associations use. In Wales, the housing association offering the home under Shared Ownership – Wales carries out its own. It looks at your income, outgoings, deposit and the rent on the share you don't buy. It then recommends a share size, typically capping how much of your take-home pay can go on housing costs (rent and mortgage combined).
The lender's check comes second, once you have a share size in mind. It works like a normal mortgage check, except the rent on the unsold share counts as one of your monthly outgoings.
The two checks don't always agree. Passing one and only just getting through the other is common, and neither is wrong. Most of the job is matching the share size the housing association will approve with the mortgage a lender will offer on it.
Your deposit is on the share
Because the mortgage is on your share, so is the deposit. A 5% or 10% deposit on a 40% share of a £250,000 home means 5% or 10% of £100,000. That's less cash than 5% of the full price, which is one reason shared ownership appeals to people who can't yet save a full-price deposit.
Lenders don't all treat a small deposit the same way, though. Some set a higher minimum for shared ownership. New build or not, house or flat, and location can all change that minimum.
Rent and service charge count against you
Lenders count the rent on the unsold share, and any service charge on a flat or shared estate, as a fixed monthly cost, like any other regular payment.
That reduces how much a lender will offer compared with a normal purchase, where there's no rent to count. It's also why choosing your share size is a real trade-off. A bigger share means a bigger mortgage and less rent. A smaller share means a smaller mortgage but more rent, which cuts into what a lender will lend.
Why lenders differ on the share
Not every UK lender offers shared ownership mortgages, and those that do have different rules. Some limit the size of share they'll lend on, or the loan to value (the mortgage as a percentage of the share's value). Some lend on flats but not houses, or the other way round. Some lend only on new builds, or not on them at all. A handful of lenders and schemes are England-only.
We don't name lenders here, because which ones fit depends on your share, deposit, type of home and location, and lenders' rules change. What matters is that there are fewer lenders to choose from than for a normal mortgage. Picking the wrong one first can cost weeks, and the housing association won't always extend the deadline it gives you once you reserve a home.
Staircasing
Staircasing means buying a bigger share after your first purchase, say from 40% to 60%, or eventually 100%. The housing association values the home again each time. It's worth thinking about before you complete (when the purchase goes through and you get the keys). A lender that caps its lending at 75% of the share won't take you to 100% later without a new application. Some lenders also make staircasing to full ownership simpler than others.
What an adviser does
With two checks, an adviser does two jobs at once. One is making sure your figures for the housing association's assessment are complete and correct. The other is matching your share, deposit and type of home to the smaller group of lenders that offer shared ownership.
A tight or failed result on the housing association's own calculator isn't necessarily the end. The figures may need checking, or a different share size may fit, and an adviser can talk that through with the housing association directly. A decline from one lender doesn't necessarily mean every lender will decline.
You can get a rough idea of what lenders might say first with the free shared ownership mortgage calculator. Enter the full price, the share, your deposit, the rent and the service charge. It estimates how lenders' affordability checks might view those numbers, before you talk to anyone.
FAQ
Can I get a shared ownership mortgage with a small deposit?
Often, yes. The deposit is based on your share, not the full value, so 5% or 10% of the share is a realistic starting point. Which lenders accept that depends on the type of home and where it is.
Do I have to use the lender the housing association recommends?
No. Housing associations don't require a particular lender. They need to see that your assessment and mortgage offer support the share you're buying.
What happens if I can't afford the share I wanted?
The housing association's assessment will usually recommend a smaller share, and most schemes let you start smaller and staircase up later.
Is shared ownership only for first-time buyers?
No. Many schemes also accept people who've owned a home before but can no longer afford to buy on the open market. Who can apply varies by scheme and area.
General patterns around shared ownership reflect Homes England's published guidance and standard UK lending practice, checked September 2026 — no figures or thresholds here are specific to any single lender or housing association, and actual acceptance criteria vary and change over time. This guide is general information, not a personal recommendation.
Prefer to check your affordability first? Check how much you could borrow →
