Methodology

How the estimate is calculated

House Price Derry is designed to be useful and defensible. We do not invent house sale prices. The valuation engine uses official UK House Price Index data for Derry City and Strabane, and will use Land & Property Services NI capital values as the anchor once licensed property-level records are connected.

1. Official market data

The estimate is currently based on the latest available UK House Price Index rows for Derry City and Strabane. Property-type averages are derived from official Northern Ireland property-type HPI data and scaled to the Derry average.

2. LPS capital-value anchor

LPS domestic capital values are assessed at 1 January 2005. When an exact licensed LPS record is available, the engine applies the Derry City and Strabane HPI multiplier to convert that 2005 anchor into a current guide price. The raw capital value is never shown as the estimate.

3. Area fallback

If there is no exact LPS match, the engine uses the official HPI area and property-type fallback and clearly labels the result as low confidence. This avoids pretending to have address-level data when it is not present.

4. Optional market heat signal

A current market heat signal can be enabled later. It is capped to a small influence and is never displayed as a sold-price source. If the signal is disabled or thin, the engine falls back to the HPI or LPS plus HPI basis.

Confidence and range

High confidence means an LPS match, recent HPI data, and enough market signal volume. Medium means an LPS match with thinner market signal data. Low means the engine could not find an exact LPS match, so it uses an area and property-type fallback.

Important disclaimer

This is an estimate, not a formal RICS valuation. Do not use it for legal, mortgage, tax, or investment decisions. A local agent or qualified surveyor should inspect the property before any major decision.