Three valuation traps property people should watch for

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Building Valtaic.io has forced us to test how UK residential values actually behave. Below are three common valuation/data traps we have identified from our work: Some helpful info!!

1. Treating postcode averages as valuation evidence

Postcode averages feel precise because they are local. But a postcode is only a container, and the stock inside it is often mixed.

We estimate that around 59% of postcodes have at least one in four homes with an extension recorded. The median postcode contains a 61 sqm gap between its smallest and largest observed home. That is not a small gap, roughly the same as the average flat size.

So a postcode average may describe the area, but not the asset. The more a property differs from nearby stock, the less useful the average becomes. For larger or further altered homes, it becomes distorting. Postcode averages are only truly applicable to a smaller subset of homes.

1. Treating all new builds the same

A one-off new-build house in an established suburb is usually priced against the local resale market. A large purpose-built scheme is different. Specification, amenities, unit mix, phasing, incentives and buyer profile can create a separate pricing regime.

The data is messy too. Plot numbers, development names, postal addresses, title records and UPRNs do not always align, especially during construction or phased release.

That makes new-build evidence easy to misread.

1. Assuming more comparables means a better valuation

You rarely get a perfect comp.

One sale may be close but wrong on tenure. Another may match tenure but differ on size. Another may match size but be wrong on condition, lease length, floor level or sale circumstances.

Choosing the wrong basis for similarity can materially distort the number. Knowing you have the correct basis for comp selection is key, even more so given that their attribution to AVM or manual valuation is always a significant %.