Maisonette EPC Upgrade Guide
Everything landlords need to know about bringing a maisonette up to EPC C standard
Two-storey maisonette with its own front entrance in a UK residential street
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A maisonette is a self-contained home with its own front door that usually spans two floors within a larger building. That layout puts it between a flat and a house on EPC performance. It has more external wall and roof exposure than a mid-block flat buffered by neighbours on every side, but less than a detached or terraced house standing on its own. EPCGuide's analysis of a 75,000-certificate EPC sample across 15 local authorities found 33% of maisonettes are rated below C, against 25% of flats, 44% of houses, and 57% of bungalows.
For landlords that middle position is good news. Most maisonettes reach EPC C more cheaply than a house because there is less external fabric to insulate, and the measures are the standard, low-cost ones. The main complications are usually contractual rather than physical: leasehold, shared elements, and who controls the roof and communal walls. The legal minimum to let in England and Wales today is band E, so a maisonette rated D is legal to let now. This guide covers the route to C ahead of the proposed MEES deadline of 1 October 2030 for all tenancies, new and existing.
Why Do Maisonettes Sit Between Flats and Houses on EPCs?
Heat loss is about exposed surfaces, and a maisonette has more of them than a flat but fewer than a house. A mid-block flat is wrapped by heated neighbours above, below, and often on both sides, so a large share of its surfaces are internal party walls that lose almost no heat. A maisonette usually spans two floors and has its own outside walls on both, plus in many cases the roof or the ground floor as an external surface too.
Compared with a house, though, the maisonette still gets help from its neighbours. It shares party walls and often a floor or ceiling with another dwelling, so it has less external fabric than a detached or terraced house of the same floor area. That is why 33% of maisonettes sit below C against 44% of houses in the sample: fewer cold surfaces, but more than a flat.
Whether the maisonette is at the top of the building (with the roof above) or the bottom (with the ground floor below) makes a real difference to the starting score. A top-floor maisonette loses heat through the roof; a ground-floor one through the floor. Your existing EPC states which surfaces are treated as exposed, and that tells you where the points are.
Flat vs Maisonette vs House: Heat Loss Exposure
| Feature | FlatRecommended | Maisonette | House |
|---|---|---|---|
| Floors Occupied | Usually single floor | Usually two floors | Two or more floors |
| Entrance | Shared communal entrance | Own private front door | Own private front door |
| External Surface Exposure | Often buffered on most sides by neighbours | More wall and roof exposed than a mid-block flat | Most walls and the whole roof exposed |
| Control Over Fabric | Limited: much of the fabric is communal | Mixed: own walls, but shared roof or structure | Full control over the fabric |
| Share Rated Below C | 25% (EPCGuide 75,000-certificate sample) | 33% (EPCGuide 75,000-certificate sample) | 44% (EPCGuide 75,000-certificate sample) |
The 'recommended' marker here flags the flat column as the best-scoring comparison, not a recommendation. A maisonette sits between a flat and a house on exposure and on the share rated below C.
What Are the Typical Characteristics?
Maisonettes come in two main forms: purpose-built (often council or ex-council blocks from the 1950s to 1970s) and conversions of a house split into upper and lower dwellings. Construction, heating, and whether you hold the freehold or a lease all vary, so confirm the wall type, heating fuel, and tenure from the existing EPC and your lease before you plan any work.
Wall Construction
- -Cavity walls common in post-1930s purpose-built blocks
- -Solid walls in older conversions of pre-1919 houses
- -Party walls shared with neighbours lose little heat
- -Less external wall area than a house of the same size
Roof and Floors
- -Top-floor maisonettes lose heat through the roof
- -Ground-floor maisonettes lose heat through the floor
- -Roof access and ownership often shared or communal
- -A floor or ceiling shared with a heated dwelling helps
Heating
- -Gas combi boilers common in self-contained maisonettes
- -Electric heating frequent in ex-council blocks
- -Electric storage heaters drag the score down hard
- -Heat pumps harder to fit than in a house, easier than a flat
Typical Starting Condition
- -Cavities often unfilled on unimproved stock
- -Thin loft insulation on top-floor maisonettes
- -Old electric heating in ex-council examples
- -Early double glazing that ages poorly
What Are the Best Upgrades for a Maisonette?
Start with the cheap, high-impact measures you control inside your own dwelling: cavity wall insulation if the walls qualify, loft insulation on a top-floor maisonette, heating controls, and LED lighting. If the heating is old electric, switching to a more efficient system is often the single biggest gain. Save external and roof work for last, because on a maisonette that usually means involving the freeholder.
Priority Order for Maximum Impact
Maisonette Upgrade Costs and EPC Impact
| Improvement | Low Estimate | High Estimate |
|---|---|---|
| Cavity Wall Insulation (if suitable)Most post-1930s maisonettes qualify. Less wall area than a house. 8-12 EPC points. | £450 | £1,500 |
| Loft Insulation (top-floor maisonette, to 270mm)Only where you have the roof space. Big win on a top-floor maisonette. 4-8 EPC points. | £300 | £600 |
| Efficient Electric or Gas Heating UpgradeReplacing old storage heaters or an aged boiler. Largest single gain in electric-heated stock. 5-12 EPC points. | £2,500 | £4,500 |
| Internal Wall Insulation (if solid walls)For older conversions with solid walls. Less area than a house. 8-14 EPC points. | £5,000 | £10,000 |
| Smart Heating ControlsRoom thermostat + TRVs, or programmable panel controls. 2-4 EPC points. | £200 | £400 |
| Double or Secondary GlazingReplacing single or failed early double glazing. 3-6 EPC points. | £3,000 | £7,000 |
| Draught ProofingWindows, doors, loft hatch. 1-3 EPC points. | £150 | £350 |
| LED LightingSimple upgrade. 1-2 EPC points. | £100 | £200 |
| Estimated Total | £11,700 | £24,550 |
You will not need every measure. Many cavity-wall maisonettes reach C with the first two or three items, and a heating upgrade closes the gap on electric-heated examples.
Not sure how many points you need? Our EPC predictor estimates your current band from basic property details, and the upgrade cost guide breaks down every measure in detail.
How Much Does It Cost to Get a Maisonette to EPC C?
Most cavity-wall maisonettes reach EPC C for £2,000 to £6,000, cheaper than a house because there is less external fabric to treat. Electric-heated or solid-wall maisonettes cost more, typically £6,000 to £12,000, driven by the heating change or internal wall insulation. Wall type and heating fuel are the two variables that move the total, so confirm both from your EPC before you budget.
Cavity Wall, On Gas
£2,000 - £6,000
Cavity fill, loft top-up if applicable, controls, and glazing usually cover the gap from band D to C.
Electric or Solid Wall
£6,000 - £12,000
A heating change or internal wall insulation pushes costs up. Grants can cover a large share for eligible properties.
Cost Cap Threshold
£3,500
The cap in force today, including VAT. Spend it on eligible work without reaching band E and you can register a high-cost exemption. £10,000 is proposed, not yet law.
Leasehold and Communal Elements
The trickiest part of a maisonette is rarely the physics; it is the tenure. Many maisonettes are leasehold, and the lease decides what you can alter, who owns the roof and structure, and whether external work needs freeholder consent. Read the lease before you plan the expensive measures.
Freehold vs leasehold
Some maisonettes are freehold (often a house split with each half sold separately), giving you full control over your own fabric. Many are leasehold, where the structure, roof, and communal walls belong to the freeholder. Confirm which you hold, because it decides whether roof and external work is even your decision to make. Our leasehold upgrade guide covers the consent process that applies to leasehold maisonettes too.
Shared roof and structure
A top-floor maisonette benefits most from loft or roof insulation, but the roof is often shared or owned by the freeholder. You may still be able to insulate at ceiling level within your own dwelling, which is usually within your control. Establish who owns the roof before assuming roof measures are on the table.
Consent and service charges
External wall insulation and communal heating changes usually need freeholder consent and may attract service-charge contributions from other leaseholders. That can make otherwise sensible measures slow or unviable. Where the measures you are permitted to make do not reach C, a cost cap exemption may apply.
What Grants Can Maisonette Landlords Claim?
Two schemes matter most for maisonette landlords. ECO4 funds insulation and heating work but is gated on tenant eligibility and closes on 31 December 2026. The Boiler Upgrade Scheme gives £7,500 off a heat pump where one can be fitted, and landlords are eligible. The Warm Homes Plan takes over from 2027.
ECO4 (closes 31 December 2026)
Funds insulation and heating measures where your tenant receives a qualifying benefit or meets LA Flex criteria. Electric-heated ex-council maisonettes with eligible tenants are strong candidates because the scheme prioritises the worst-scoring properties. See our ECO4 guide for landlords for the eligibility detail, and apply early given the 2026 deadline.
Boiler Upgrade Scheme (£7,500)
A £7,500 grant toward an air source heat pump, open to landlords with no tenant means test. A heat pump is easier to fit in a maisonette than a flat where the pump has its own external wall or garden space to draw on, though it is harder than in a house. Full detail in our Boiler Upgrade Scheme guide.
Warm Homes Plan (from 2027)
The government's successor programme takes over after ECO4 closes, with broader landlord eligibility expected. If your tenant does not qualify for ECO4, the Warm Homes Plan is the funding route to watch from 2027. Do not wait for it if ECO4 already fits.
Use our grant checker to see which schemes your property and tenant qualify for in two minutes.
Example Upgrade Pathway
Here is a realistic example of how a two-bedroom purpose-built maisonette with cavity walls and gas heating might progress from EPC rating D to C:
Case Study: 2-Bed 1970s Maisonette, Manchester (Cavity Walls, Mains Gas)
Starting
D58 points
Target
C69 points
Frequently Asked Questions
What EPC rating do most maisonettes have?
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Many unimproved maisonettes sit in band D. EPCGuide's analysis of a 75,000-certificate EPC sample shows 33% of maisonettes are rated below C, worse than flats (25%) but better than houses (44%) and bungalows (57%). Maisonettes with cavity fill and modern heating already in place usually score high D or low C, within easy reach of the target.
Why do maisonettes score worse than flats but better than houses?
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Exposed surfaces. A mid-block flat is wrapped by heated neighbours on most sides, so it loses little heat. A maisonette spans two floors with its own outside walls and often the roof or ground floor exposed too, so it loses more than a flat. But it still shares party walls and a floor or ceiling with other dwellings, so it loses less than a house. That is why 33% of maisonettes sit below C, between flats at 25% and houses at 44%.
How do I improve the EPC rating of a maisonette?
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Start with the measures inside your own dwelling: fill the cavity walls if suitable (£450-£1,500, 8-12 points), insulate the loft on a top-floor maisonette (£300-£600, 4-8 points), add heating controls (£200-£400, 2-4 points), and switch to LED lighting. If the heating is old electric, upgrading it is often the biggest single gain.
Those measures take most band-D maisonettes to C for a few thousand pounds. Use our EPC predictor to estimate your starting point.
How much does it cost to get a maisonette to EPC C?
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Most cavity-wall, gas-heated maisonettes reach C for £2,000-£6,000, cheaper than a house because there is less external fabric to treat. Electric-heated or solid-wall maisonettes typically cost £6,000-£12,000, driven by a heating change or internal wall insulation. ECO4 and the Boiler Upgrade Scheme can cut these figures for eligible properties.
Does leasehold affect improving a maisonette's EPC?
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Yes. On a leasehold maisonette the roof, structure, and communal walls usually belong to the freeholder, so external and roof work needs consent and may attract service-charge contributions. Measures inside your own dwelling, such as cavity fill, ceiling-level insulation, heating, and glazing, are normally within your control. Do those first, and involve the freeholder only if you still fall short.
What happens if my maisonette can't reach EPC C by 2030?
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Nothing today. Band C by 2030 is a government proposal, not law: the minimum band to let in England and Wales is E, and only F and G are barred without an exemption. Government has proposed 1 October 2030 for all tenancies with no earlier date for new ones, and a £10,000 cap in place of today's £3,500, but no statutory instrument has been laid. If the rules do arrive, spending the cap without reaching the target band gives you a cost cap exemption, and a freeholder blocking external or roof work supports a consent exemption. Most cavity-wall maisonettes reach C well within the cap anyway.
Next Steps
1. Get Your Current EPC
If you do not have a recent EPC (within 10 years), commission one from a qualified assessor. This gives you your baseline score, wall type, and which surfaces are treated as exposed.
Check your EPC on GOV.UK2. Check Your Lease and Tenure
Confirm whether you hold the freehold or a lease, and what the lease allows you to alter. This decides whether roof and external measures are your decision or the freeholder's.
Read the leasehold upgrade guide3. Calculate Your Costs
Use our calculator to get a personalised estimate based on your maisonette's details and current EPC rating.
Use the Cost Calculator4. Get Professional Quotes
Obtain at least three quotes from TrustMark-registered installers for cavity wall insulation and any heating upgrade. Both are straightforward jobs inside a maisonette.
Find TrustMark tradespeople