New-Build Rental Valuation in London: How to Check the Developer's Rent Estimate
Short answer: A developer's rent estimate is built to support a sale, usually before the block completes and before any flat has let. A new-build rental valuation prices the first let from comparable evidence — borough, bedroom count, specification, floor level and service charge — and sets the advertised rent that becomes your ceiling under section 56 of the Renters' Rights Act 2025.
Most new-build landlords come to us with a number already. It arrived in the sales pack, it is printed to the pound, and it was written long before anyone stood in the flat. It is a starting point, not a valuation of the let.
What is a new-build rental valuation?
It answers one question: what will this flat let for, this month, to a real tenant. Not what it should be worth. Not what the yield needs to be.
The method is comparable evidence. RICS puts it plainly in its professional standard: comparable evidence "is at the heart of virtually all real estate valuations" (RICS, Comparable evidence in real estate valuation, 1st edition, reissued as a professional standard April 2023). New-builds are the hard case, because on day one the block has no lettings history of its own.
Is the developer's rent estimate accurate?
It is a different instrument, produced at a different time, for a different purpose.
The estimate exists to support a sale. It is normally written before completion, sometimes before the show flat is finished, for a scheme with no lettings track record. By the time you need a letting figure it can be a year or more old, and the market it described has moved. That does not make developers dishonest — a sales-pack figure is doing a legitimate job, helping a buyer judge whether the purchase makes sense. It is not the job of pricing a tenancy in a live market on a specific Monday morning.
The advertising regulator applies its own test: estimated rental values and gross yields must be supported by adequate evidence, and the basis of the calculation made clear. In 2018 the ASA upheld complaints on exactly that point about a Central London development's rental investment factsheet, ruling the quoted rents and yields had not been shown to be representative of comparable properties in the local postcode area (ASA ruling, CBRE Ltd, 10 October 2018).
So the useful question is not whether anyone lied. It is what evidence sits behind the number, and how old it is. Ask for the comparables. If they exist, you have a figure worth advertising. If not, you have an estimate.
How do you value a first let when no flat in the block has let yet?
You price off the two things you do have: the wider borough at the right bedroom count, and the attributes of the unit. Then you adjust, line by line, and show the working.
| What we adjust for | Why it moves the number |
|---|---|
| Bedroom count against the borough | The bedroom-level borough average is the anchor — the widest reliable evidence that exists on day one. |
| Floor area (rent per sq ft) | Two-bed against two-bed is a blunt comparison. Rent per square foot makes non-identical flats comparable. |
| Specification | Named appliances (Neff, Siemens, AEG), worktops, flooring, storage. Tenants notice specification and pay for it. |
| Floor level and aspect | Height carries a premium, but it is not linear and it flattens. A flat facing a light well does not let at the brochure figure. |
| Outside space | A usable balcony or terrace is a real premium. A Juliet balcony rarely is. |
| What the rent includes | Concierge, gym, parking, broadband — some of it is priced in, some is not. |
| Completion date | A flat completing in November is not the same asset as the identical flat completing in August. |
Where the evidence is thin we widen the range and say why. A confident single number with nothing behind it is worth less than a band you can defend. The full method is in how we price a new-build first let.
How much does the borough change the answer?
More than most sales packs allow for. ONS figures for June 2026, published 22 July 2026.
| Borough (new-build districts) | 1-bed | 2-bed | 3-bed | Annual change (all property) |
|---|---|---|---|---|
| Tower Hamlets — Canary Wharf | £1,972 | £2,394 | £2,721 | +2.7% |
| Newham — Royal Wharf, Stratford, Canning Town | £1,630 | £1,993 | £2,209 | +4.15% |
| Brent — Wembley Park | £1,575 | £1,932 | £2,266 | +0.60% |
| Greenwich — Peninsula, Kidbrooke | £1,541 | £1,906 | £2,210 | +5.0% |
| London (all) | £1,740 | £2,205 | £2,607 | +2.2% |
Read the two-bed column. Tower Hamlets to Greenwich is a gap of £488 a month on the same bedroom count — £5,856 over a year — between two boroughs a river apart, both with substantial new-build stock. A pack figure carried across from a different scheme in a different borough is not a comparable. It is a coincidence.
One caution, and it matters. The ONS Price Index of Private Rents measures the whole private rented stock in each borough — Victorian conversions, ex-local-authority flats and new-build together. Your flat is not the average, and a new-build does not let at the average. The borough figure at your bedroom count is the anchor because it is the widest reliable evidence that exists on day one; the line-by-line adjustments set out earlier are what move you off it. We make those adjustments from our own three-year Rightmove and Zoopla dataset, and we show the working rather than quote a blanket new-build uplift — that gap is not one number, and it moves by district, by scheme and by month. We track each ONS print in the London Rent Review.
Does the service charge or communal heating affect the rent?
Both, and neither shows up in a yield table.
The service charge is usually your cost, not the tenant's, on a standard assured tenancy of a leasehold flat. It does not change what a tenant will pay — it decides what the let is worth to you. A high service charge against a modest rent is where new-build returns quietly disappear, and it is the figure most often missing from a first conversation. CAP's advertising advice on new-build and off-plan homes, updated 25 November 2025, says marketers should make clear any additional or ongoing costs such as service charges, and how they are calculated.
Communal heating is different, because the tenant pays it. Many London blocks supply heat and hot water from a communal network, billed separately from rent, and tenants weigh the total monthly cost of the flat rather than the rent line alone. Since 27 January 2026 new consumer protection rules have applied to heat networks in Great Britain, regulated by Ofgem, covering registration, fair pricing, standards of conduct and billing — so the heat charge is now something you can explain in the listing rather than something a tenant discovers.
We ask for the service charge, the heat arrangement and what is included before we price. A valuation that ignores the bills is not a valuation.
When should a new-build flat be advertised?
Timing is part of the valuation, not a separate decision. Our three-year Rightmove and Zoopla dataset is consistent on four points:
- August has the highest enquiries-to-listings ratio of the year. More demand chasing fewer homes.
- Weeks 3 and 4 of a month draw 5-10% more enquiries than weeks 1 and 2.
- Monday morning is the optimal launch slot.
- The Four-Week Rule: never advertise more than four weeks before availability. Go early and the listing ages out of prime portal position while the flat is still unavailable — and you cannot re-list to get that position back. It is spent.
A flat completing in August, launched on a Monday in the second half of the month, starts from the strongest position the calendar offers. One completing in December does not, and the valuation should say so rather than pretend the month is neutral.
Why does the day-one figure matter more under the Renters' Rights Act 2025?
Because it is now a ceiling and a floor at once.
Section 56 of the Renters' Rights Act 2025, in force since 1 May 2026, requires every written advertisement or offer to state a single specific proposed rent, and prohibits inviting, encouraging or accepting an offer above it. Section 21 no-fault eviction is abolished and all assured tenancies are periodic (Renters' Rights Act 2025; GOV.UK, Guide to the Renters' Rights Act). The only lawful route to raise rent during a tenancy is a prescribed-form notice under section 13 of the Housing Act 1988, as amended — at least two months' notice, and no more often than once every 52 weeks, with the tenant free to refer the proposed rent to the First-tier Tribunal under section 14.
So the arithmetic runs both ways:
- Too high and the flat sits. You burn prime portal position in the first fortnight, re-advertise lower, and cannot accept a stronger offer to make the void back — section 56 forbids it.
- Too low and you have capped the tenancy. You climb from the number you chose, once a year, through a notice the tenant can challenge.
This is where we are less popular than we might be, and we accept that. We won't take a property on at a price we don't believe it will let at — not to win an instruction, and not to match a sales-pack figure whose evidence we have not seen. The full reasoning is in why we turn down an instruction priced wrong.
What should you ask for in a new-build rental valuation?
Whoever produces it, ask for five things in writing:
- The comparable evidence, not the conclusion — which flats, what specification, what they let for, how long they took.
- A range with reasoning. Thin evidence should produce a wider band and an explanation, not false precision.
- The launch date and why, against availability and the Four-Week Rule.
- The service charge and heat arrangement, and what each does to your net position.
- The section 56 strategy and the review point — what you advertise, why that is the right ceiling, and what evidence would justify moving it.
If the developer's figure survives all five, advertise it with confidence. If it does not, you have caught the mistake in the one week where catching it is still free.
Book a free new-build rental appraisal
Send us the flat — address, floor, plan, specification, service charge and the figure from your pack. We are lettings and management only, so we have no sale-side interest in flattering it. As at June 2026 we manage around 117 homes across roughly 35 London postcode districts, and we will show you the comparables behind our answer.
Book a free new-build rental appraisal — or see how we handle a whole block on new-build specialists. Weighing up management too? Start at landlords.
Sources
- Renters' Rights Act 2025, section 56 (requirement to state a specific proposed rent; prohibition on inviting, encouraging or accepting offers above it; in force 1 May 2026) — https://www.legislation.gov.uk/ukpga/2025/26/section/56
- Housing Act 1988, section 13 (increases of rent under assured tenancies; prescribed-form notice, minimum two months, 52-week interval, tenant application to the appropriate tribunal under section 14), as amended by the Renters' Rights Act 2025 — https://www.legislation.gov.uk/ukpga/1988/50/section/13
- Guide to the Renters' Rights Act, GOV.UK (abolition of section 21; all assured tenancies periodic; annual rent increase to market rate; rental bidding ban) — https://www.gov.uk/government/publications/guide-to-the-renters-rights-act/guide-to-the-renters-rights-act
- Office for National Statistics, Private rent and house prices, UK: June 2026, released 22 July 2026 (Price Index of Private Rents). Contains public sector information licensed under the Open Government Licence v3.0 — https://www.ons.gov.uk/economy/inflationandpriceindices/bulletins/privaterentandhousepricesuk/june2026
- RICS, Comparable evidence in real estate valuation, 1st edition, reissued as a professional standard April 2023 ("Comparable evidence is at the heart of virtually all real estate valuations") — https://www.rics.org/profession-standards/rics-standards-and-guidance/sector-standards/valuation-standards/comparable-evidence-in-real-estate-valuation
- Advertising Standards Authority ruling, CBRE Ltd, 10 October 2018 (estimated rental values and average gross yields in a Central London development investment factsheet; complaints upheld; evidence and basis of calculation required) — https://www.asa.org.uk/rulings/cbre-ltd-a18-439184.html
- CAP advice, Property: New build and off plan homes, updated 25 November 2025 (making clear additional and ongoing costs such as service charges) — https://www.asa.org.uk/advice-online/property-new-build-and-off-plan-homes.html
- Ofgem, Heat networks regulation: consumer protection (new consumer protection rules launched 27 January 2026) — https://www.ofgem.gov.uk/guidance/heat-networks-regulation-consumer-protection