A property valuation feels like a measurement. It is an estimate produced by a professional applying a method, and knowing the method explains why valuations differ and why they lag.
The comparable method
The dominant approach for residential property.
The valuer identifies recent sales of similar properties in the area, then adjusts for differences — size, condition, location, features.
Those adjustments are judgements informed by experience rather than calculated from data, which is where valuations diverge.
The method requires comparable sales to exist, which means it works well in areas with active markets and standard housing, and poorly for unusual properties or thin markets.
The lag problem
Comparable sales are completed transactions, which reflect agreements made weeks or months earlier.
Which means valuations trail the market, and the lag matters most exactly when the market is moving fastest.
In a rapidly rising market, valuations come in below agreed prices. In a falling one, above.
Both cause transactions to collapse, which is why valuation disputes cluster at turning points.
What the lender's valuation is for
A distinction that catches buyers out.
A mortgage valuation assesses whether the property provides adequate security for the loan.
It is not a survey and does not assess condition beyond what affects security.
Which means it will not tell you the roof needs replacing, and buyers who treat it as an inspection discover this afterwards.
Surveys of varying depth are available separately and are commissioned by a minority of buyers, which is a consistent finding in market research and a consistent source of expensive surprises.
Down valuations
Where the lender's valuer assesses below the agreed price.
Which reduces the loan available, since lending is a percentage of value rather than of price, and the buyer must find the difference or renegotiate.
Challenging a valuation is possible and requires evidence — specific comparable sales the valuer may not have considered — rather than disagreement.
Success rates are modest and it is worth attempting when genuine comparables exist.
Automated valuation models
Statistical models estimating value from transaction data, property characteristics and location.
Used widely by lenders for lower-risk lending, by portals for headline estimates, and by anyone wanting a free number.
They perform reasonably in areas with dense standardised housing stock and abundant transaction data.
They perform poorly for unusual properties, in thin markets, and where condition varies substantially between similar properties, since condition is invisible to them.
Which means the free estimate you see online is more reliable for a modern estate house than for anything distinctive.
The investment approach
For income-producing property, valuation runs on yield rather than on comparables.
The rent is capitalised at a yield reflecting risk, location and lease quality, producing a capital value.
Which means the value moves with interest rates and with required returns, and it can fall while rents are stable.
Residential investors frequently apply comparable-based residential values to properties whose economics are actually income-driven, which produces inconsistent decisions.
What actually moves value
Location dominates, which is unhelpful and true.
Within a location, size and condition account for most of the rest.
Improvements rarely return their cost in full, with kitchens and bathrooms performing better than most and extensions varying enormously by area.
The improvements that reliably matter are those correcting a deficiency relative to comparable properties rather than those adding something unusual, since unusual features narrow the buyer pool.
This describes how the process works and is not advice about any transaction, which warrants a qualified surveyor and a solicitor.
What a survey actually covers
Worth separating since buyers conflate the levels.
A basic condition report gives an overview with ratings and no detailed investigation.
A homebuyer level report inspects accessible areas and identifies visible problems, and it does not lift floorboards or move furniture.
A building survey is considerably more thorough and generally recommended for older, altered or unusual properties.
None of them opens up the structure, which means concealed defects remain concealed, and the report will say so in terms buyers frequently skim past.
Leasehold and what it does to value
In jurisdictions with leasehold tenure, the remaining term affects value substantially and non-linearly.
Below certain thresholds, mortgage availability narrows and the cost of extending rises sharply.
Ground rent terms, particularly escalating ones, have made some properties difficult to sell or mortgage entirely.
Which is checkable before committing and is regularly discovered late in a transaction.
Service charges
For flats, the ongoing cost affects both affordability and value.
Major works liabilities can arrive with little warning and run to substantial sums, and reserve fund adequacy is worth asking about specifically.
Energy performance
Increasingly reflected in value as efficiency requirements tighten.
Ratings are required for sale and letting in many jurisdictions, and minimum standards for rental property have been introduced in several.
Which means a poor rating carries a future cost that buyers increasingly price in, particularly for investment purchases.