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How to choose comparable property sales

A practical sequence for turning an exact-postcode transaction list into a small, explainable evidence set.

Published by PropertyMetrics Research DeskLast reviewed: 13 August 2026

2 minute read. Practical research method for use with public property records.

Start with the property you are actually researching

A transaction becomes useful only in relation to a clearly described subject property. Record the address, property type, tenure, approximate size, condition, completion state and any material lease terms before choosing comparables.

PropertyMetrics can retrieve registered transactions for an exact postcode, but it cannot see a survey, internal floor area, refurbishment quality or a lease. Those missing facts should narrow confidence rather than be silently assumed.

  • Treat the postcode result as a candidate list, not as an automatic valuation set.
  • Do not mix freehold houses and leasehold flats merely because they share a postcode.
  • Keep asking prices separate from registered completion prices.

Prefer similarity before recency

A recent transaction can still be a poor comparison when it is a different property type or tenure. Begin with the closest physical and legal match, then consider how much market time has passed.

Micro-location matters. A main road, school catchment boundary, station approach, conservation area or different side of the same street can change how buyers behave. Public transaction data does not resolve those differences for you.

Record every adjustment as a hypothesis

PropertyMetrics lets you enter a positive or negative adjustment for each selected sale. The amount is not an automated valuation. It is a visible hypothesis that should have a reason such as condition, floor area, lease length or plot difference.

If you cannot write a specific reason for an adjustment, leave the amount at zero and mark the difference as unresolved. A transparent unknown is stronger evidence than a precise-looking number without support.

Know when the set is too weak

One transaction is a reference point, not a market. A set with different types, tenures, completion dates or unknown condition should remain labelled weak even when its prices cluster closely.

The evidence-set score in the workspace checks only count, property type, tenure and recency. It does not measure floor-area similarity, condition or legal risk, so it must never be described as valuation confidence.

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