A duplex is not simply a larger flat. It is one demise across two storeys, which changes three things buyers rarely ask about: how the terrace is demised and who repairs it, how escape from the upper level works, and how the service charge treats the second floor and the stair void. The market backdrop is favourable; these three are what decide whether the specific flat is.
Duplex penthouses almost always come with terraces, and a terrace over habitable space is a waterproofing liability. Whether it is demised to you or licensed, and who repairs the structure beneath it, is the single most expensive line in the lease.
A flat on more than one storey has its own provisions under the building regulations. On a survey this is where duplexes throw up problems, and it is far cheaper to know before you offer.
Apportionment is usually by floor area — so ask how the stair void is measured, and whether you are paying twice for space you only use once.
Our fee is paid by the seller. What that buys you is somebody reading the lease plan rather than the brochure.
Areas, budget, and whether the second floor is doing a real job for you — guest suite, studio, principal bedroom. It changes which layouts are worth viewing and which are simply larger.
Lease plan, terrace demise and repairing obligation, fire strategy for the upper storey, deed of certificate, remediation position and three years of service charge accounts.
Duplexes have a narrower buyer pool than lateral apartments, which cuts both ways. It is a slower resale and it is a stronger negotiating position for you now.
Almost every duplex penthouse comes with terrace space, and terraces are where the money goes wrong. Establish two things from the lease plan rather than the particulars: whether the terrace is demised to you or merely licensed, and who is responsible for the waterproofing and the structure beneath it.
A terrace sits over habitable space — either your own lower floor or somebody else’s flat. If the membrane fails, the cost and the disruption are substantial and the argument about responsibility is worse. Check also whether the lease restricts what can be placed on it, whether planning conditions limit hours of use, and whether the balustrade meets current standards, because replacing one on a high-level terrace is not a small job.
A flat arranged on more than one storey is treated differently from a single-level flat under the building regulations, because a fire on the lower floor can cut off the only internal stair. Depending on the design and the height, that can require a protected stairway, an alternative means of escape from the upper storey, or a sprinkler or suppression system.
Service charge apportionment in most blocks is calculated by floor area. On a two-storey demise that raises a question nobody asks: how is the stair void measured? In some schemes the upper-floor area includes the void over the stair, so you are contributing on space you cannot occupy. It is rarely enormous, and it is worth knowing.
More materially, ask for three years of actual accounts rather than the estimate, the sinking fund balance, and every section 20 consultation completed and pending. In a tower with concierge, lifts, plant and leisure facilities the service charge is usually the largest recurring cost after the mortgage, and a duplex pays a larger share of it than a one-bedroom flat on the same floor.
A duplex penthouse sits at the top of a tall building, so the building safety regime applies — relevant buildings are at least 11 metres or five storeys. Qualifying lease status is fixed by reference to 14 February 2022 and you inherit it: a lease that did not qualify then does not begin qualifying because it changes hands.
Where the lease qualifies, cladding remediation cannot be charged to the leaseholder and non-cladding contributions are capped and spread over ten years, with costs paid since 28 June 2017 counting toward the cap. Ask for the leaseholder deed of certificate, the landlord’s certificate, the fire risk assessment, any external wall survey and the remediation programme with its funding route — before you offer, not at report on title.
Duplexes appeal to a narrower buyer pool than lateral apartments of the same value. Many purchasers at this level actively prefer single-floor living, and the internal stair rules out part of the market entirely. That makes a duplex slower to resell than an equivalent lateral flat, and it should be reflected in what you pay.
In the current prime market that works in your favour. With super-prime values forecast to soften a further two to three per cent through 2026 and an unusual volume of stock on the market following the non-dom departures, a property with a narrower audience is a property where a well-evidenced offer gets taken seriously.
Usually less per square foot, not more. The internal stair removes part of the buyer pool — a good number of purchasers at this level specifically want single-floor living — so duplexes are typically slower to resell and should be priced accordingly. Ask for comparable sold evidence for duplexes rather than for the building generally, because mixing the two flatters the asking price.
Whether it is demised to you or licensed, and who repairs the waterproofing and the structure beneath it. A terrace sits over habitable space, so a failed membrane is expensive and the argument about responsibility is worse than the repair. Then check the balustrade against current standards and whether planning conditions restrict hours of use or what can be placed on it.
Because a fire on the lower floor can cut off the only internal stair. Flats on more than one storey are treated differently under the building regulations and may need a protected stairway, an alternative escape route or suppression. It is also where previous owners’ alterations cause problems — an opened-up stairwell or a removed door can compromise a strategy that was compliant when built. Ask for the fire strategy for the apartment before you offer.
Yes, as it does to any flat in a building of at least 11 metres or five storeys. The key point is that qualifying lease status was fixed at 14 February 2022 and you inherit it — a non-qualifying lease does not start qualifying because you buy it. Ask for the leaseholder deed of certificate first; if the seller cannot produce one, you are buying uncertainty and it should be priced.
No. Our fee comes from the seller. What it buys you is someone reading the lease plan, the terrace clause and the fire strategy with the same care as the photographs — and telling you when a beautiful apartment sits above a problem.
