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 calculator currently uses Q2 2026 benchmarks.

Your report shows the data period used. The property-type benchmarks are modelled from official Northern Ireland property-type prices, scaled by the ratio between the Derry and Northern Ireland all-property averages. They are district-level estimates, not observed prices for a particular Derry neighbourhood or individual home.

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.

The calculator accepts BT47, BT48, BT49 and BT82 postcodes. A postcode match is not an inspection of your home or evidence of a sale on your street. For homes outside Derry City and Strabane, the Derry-based benchmark needs particular care when comparing local prices.

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.

5. Current-market calibration

A 1.064 current-market calibration is applied to the modelled point estimate and its range. This is a 5% reduction from the previous engine following local homeowner feedback, while retaining a modest adjustment above the underlying model. The multiplier is recorded in each result so it can be reviewed as stronger local evidence is collected.

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.