RICS Red Book Valuation · London & the South East
Roof space valuations for a loft conversion
"Buying the loft above you should be a fair deal on both sides. We weigh the value it adds to your home against the value it takes from whoever owns it — so the price you agree holds up to scrutiny."
— Richard Stacey MRICS, Director and RICS Registered Valuer
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What it is
An impartial Market Value of roof space being bought or sold for a loft conversion
Usual basis
Around half the development profit — uplift in value, less the cost of the works
Best evidence
Architect's plans and a builder's estimate for the proposed conversion
Turnaround
Usually within a week of the inspection; tighter deadlines often possible
A loft is one of the few ways to add real space to a London home without moving. But if you don't own the roof space, you have to buy it first — and a fair price rests on what the conversion adds, what it costs to build, and what the space is worth to the person selling it.
Do I own the loft space above my flat?
Not necessarily — and this is the first thing to check. Many leaseholders assume that because the loft hatch sits inside their flat, the roof space belongs to them. Often it doesn't. In a great many leases the loft is retained by the freeholder, even where it can only be reached through your flat.
Read your lease carefully before you do anything else, and look at exactly what is included in your demise. If the roof space isn't yours, converting it without first acquiring it can be an expensive mistake. We have seen leaseholders extend into space they didn't own — which can leave the freeholder in a ransom position, able to demand a high price or insist the work is undone.
How can I acquire the roof space?
There's no automatic right to buy roof space, so it comes down to agreement with whoever owns it. There are three routes — the loft can be bought on its own, or, if you're a leaseholder, folded into a wider piece of leasehold reform.
ROUTE 01
By direct negotiation with the freeholder
The straightforward route: you and the freeholder agree a price, and the lease is then altered — usually by a deed of variation — so your demised area includes the loft. Our valuation is what feeds that negotiation, setting out what should fairly be paid.
We value it · you agree the priceROUTE 02
As part of a lease extension
When you extend your lease, the demised area can be redrawn at the same time — so the roof space is brought into your flat within the same deal. One negotiation and one set of legal costs, rather than tackling the loft as a separate transaction later.
Lease extensions →ROUTE 03
Through collective enfranchisement
When leaseholders club together to buy the freehold, the loft can — by agreement among the participants — be transferred out of the freeholder's ownership and into the demise of the upper-floor flat as part of the purchase.
Buying the freehold →A practical point on enfranchisement
The loft can be traded within the deal
Where a building is bought collectively, the participants decide between themselves how the loft is handled. We often see the owner of the upper-floor flat agree to contribute more than their otherwise fair share of the cost of buying the freehold, in return for the other participants agreeing that the roof space becomes part of their demise. It's a negotiated trade — and getting the value of the loft right is exactly what makes that trade fair to everyone at the table.
How is the value of roof space for a loft conversion worked out?
The value of the loft is tied to what a conversion would add to the rest of the property. In broad terms we look at four figures: the value of the property before a conversion, the value after it (the difference being the uplift), the cost of carrying out the works, and the profit left once those costs are taken off the uplift.
In most cases, roughly half of that profit represents a fair price for buying the roof space — the gain being shared between the person creating the value and the person giving it up. It isn't a fixed rule, and the right split depends on the building, the parties and the circumstances, but it's the principle most roof space valuations start from.
Illustration only — figures vary by property
An illustrative example to show the method, not a quote. The 50/50 split is a starting point, not a guarantee — the actual figure turns on the evidence and on what each side brings to the negotiation.
Why are architect's plans and a builder's estimate so important?
Because they remove the guesswork. The two figures that drive the whole valuation — the value after conversion and the cost of building it — both depend on what is actually going to be built. With an architect's drawings we can see the size, layout and quality of the finished space. With a builder's estimate we have a real cost rather than an assumption.
Without them, we have to make those assumptions ourselves, and they may or may not match what you intend to do. The report is far more reliable — and far more persuasive to the other side — when it's built on real plans and real costs. If you're serious about the conversion, getting these in place first is usually time and money well spent.
Why has buying loft space become harder than it used to be?
Construction costs have risen sharply in recent years, and that has squeezed the profit in many loft conversions. When the cost of the works eats up more of the uplift in value, there's less profit to share — and so less room to agree a price that works for both buyer and seller.
That makes the numbers matter more than ever. Schemes that would have stacked up comfortably a few years ago can now be marginal, which is exactly why an evidence-based valuation — grounded in current build costs and current sale values — is worth having before you negotiate.
How much should I expect to pay the freeholder for the loft?
There's no standard tariff. The price reflects the profit a conversion would generate in that specific building, and as a starting point that profit is often split around the middle between the parties. But several things move it:
- The size and quality of what can be built, and whether it adds a bedroom and bathroom or simply more space
- Current sale values in the area, which set the value after conversion
- Current build costs, which determine how much of the uplift is left as profit
- Any loss or inconvenience to the seller — for example if the loft has another use, or if access affects other flats
- The relative negotiating positions of the parties
Our role is to set out a fair, defensible figure under the RICS Red Book — not to argue one side's corner, unless we are specifically instructed to advise a single party.
Can the freeholder refuse to sell the loft space?
Yes. The roof space belongs to whoever owns it, and there is no automatic right to buy it the way there is with a lease extension or buying the freehold. In practice many freeholders are willing to sell, because the space is usually worth more to the flat below than it is to them. But a willing seller still needs a price — and where the loft can only be reached and used by one flat, the owner of that space can be in a strong position.
A clear, impartial valuation helps both sides reach agreement quickly. We're often appointed jointly by buyer and seller for exactly this reason: an independent figure gives everyone a sensible basis to negotiate from.
Does planning permission or building regulations approval mean I own the loft?
No — and it's an important distinction. A loft conversion will often need building regulations approval and may need planning permission, but neither is the same as owning the space. This holds even where the local authority is your freeholder: granting planning consent and selling you the roof space are two entirely separate things. Always sort out ownership before you start work.
Who can you act for — leaseholder, freeholder or both?
However you come to us, the report is an impartial RICS Red Book opinion of Market Value. We can be instructed in three ways:
Appointed by the leaseholder
You instruct us; we give you the valuation. You use it to negotiate the price with the freeholder — who may bring in their own surveyor.
Appointed by the freeholder
The freeholder instructs us; we give them the valuation. They use it to negotiate with the leaseholder — who may bring in their own surveyor.
Jointly appointed by both
Leaseholder and freeholder instruct us together, and we produce one impartial figure both sides rely on — often the quickest way to reach agreement.
Where we're jointly appointed, our job is to find the fair price both parties can rely on. They're then free to agree terms on that basis — or to decide the deal isn't for them.
How long does a roof space valuation take?
Once we've inspected, we're normally able to provide our report within a week, and we can often meet tighter deadlines where needed. Larger or more complex matters may take a little longer — if so, we'll flag the implications with you at the outset rather than leave you guessing.
Considering buying or selling roof space?
Tell us about the property and what you're planning, and we'll explain how a valuation would work and what it would cost.
Why instruct Websters for a roof space valuation?
At Websters we are Chartered Surveyors regulated by the Royal Institution of Chartered Surveyors, and our valuers are RICS Registered. We provide valuation advice in compliance with the RICS Valuation – Global Standards, the 'Red Book' — a quality-assured process built on consistency, objectivity and transparency, so the figure we give you stands up.
Our services span most of London and surrounding areas, including Hertfordshire, Buckinghamshire, Essex, and parts of Surrey and Sussex. If you'd like to discuss buying or selling roof space for a loft conversion, we're happy to talk it through.
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Request your roof space valuation
Tell us about the property and the proposed loft conversion, and whether architect’s plans or a builder’s estimate are available. We’ll come back to you with how a valuation would work and what it would cost.