Every cost figure on this site is calibrated on published Irish construction data. Nothing is invented. This page is the audit trail.
Primary data sources
Three published datasets anchor every cost band on the calculator, the Snapshot AI estimator, and the editorial guides:
- SCSI (Society of Chartered Surveyors Ireland) Real Cost of New Housing & Renovation report, November 2025. The SCSI-administered cost dataset that every chartered quantity surveyor in Ireland uses. We use the residential renovation per-m² mean, the regional cost factors, and the spec-tier multipliers.
- CSO (Central Statistics Office) Construction Output Price Index, Q1 2026 release. Used to roll forward SCSI Nov 2025 figures within-quarter and to validate the labour-cost component against official inflation prints.
- Engineers Ireland day-rate guidance 2026 + RIAI Conditions of Engagement. The published fee scales and day-rate guidance for architects, structural engineers, BCAR Assigned Certifiers and Design Certifiers.
Regional uplift factors
The calculator and Snapshot AI both apply a regional cost factor before final output. The factors below are SCSI Nov 2025 derived, restated for homeowner readability:
- South County Dublin (D4, D6, D14, D18): +25% to +35%
- Dublin city centre + other Dublin postcodes: +15% to +25%
- Greater Dublin (Wicklow, Kildare, Meath commuter belt): +5% to +15%
- Cork city + suburbs, Galway city + suburbs: 0% to +10%
- Limerick city, Waterford city, Kilkenny: −5% to +5%
- Rural Munster (Kerry, West Cork, Tipperary): −10% to −15%
- Rural Connacht (Mayo, Sligo, Roscommon, Leitrim): −15% to −20%
- Rural Ulster (Donegal, Monaghan, Cavan): −15% to −25%
VAT treatment
We apply the 13.5% reduced rate on labour and materials supplied together by a contractor (Ireland’s reduced rate under VAT Consolidation Act 2010 §46(1)(c) for residential renovation). Materials bought separately by the homeowner attract the standard 23% rate. We flag this distinction in the quote analyser.
Snapshot AI calibration
The Snapshot AI estimator uses Anthropic’s Claude Sonnet 4.5 vision model. The model receives, in this order:
- A system prompt explaining the Irish 2026 cost landscape, the four scope tiers, and the dating tell-tales for Irish housing stock (Stira folding attic stairs, melamine units, avocado bathrooms, single-glazed timber sashes, painted pebbledash, Stovax stoves on dark stone hearths).
- The SCSI-derived calculator benchmark block (low/typical/high bands across four size brackets for the user’s region and spec) as a hard floor the model must respect.
- Anti-staging guidance — the model is explicitly told that Irish estate-agent photos (Sherry Fitz, DNG, Knight Frank.ie, Lisney, Savills.ie) are professionally staged and that it should anchor on age and layout, not photo polish.
- Daft.ie blocking caveat — Daft.ie sits behind Cloudflare bot protection; the tool surfaces a clear notice and users are directed to MyHome.ie or the agent’s own site.
- The user’s photo(s) or, in URL mode, every photo we can extract from the listing’s gallery (up to 8 images), plus the listing title, asking price and a 1,500-character excerpt of the description.
The model is constrained to call a structured JSON tool. The schema demands a low/typical/high cost band, a verdict bucket, 4–6 line items with rationale, a caveats list, and a confidence score 0–1.
We tested this calibration against an SCSI-aligned chartered quantity surveyor on a real Dublin south-side semi — full methodology and results in our AI cost estimation guide.
Irish-specific risk register
The Snapshot AI is prompted to consider the Irish-specific risk register that affects renovation cost but is not visible from listing photos:
- Pyrite — dwellings built 1997–2013 with hardcore infill from specific quarries (primarily north Dublin, Meath, Kildare, Westmeath).
- Mica / defective concrete blocks — Donegal, Mayo, Sligo, Clare, Limerick, parts of Tipperary; primarily dwellings built 1990–2015.
- BCAR (Building Control Amendment Regulations 2014) — Assigned Certifier and Design Certifier costs €2,500–€6,500 for any work requiring planning permission.
- BER (Building Energy Rating) — major renovations trigger nZEB compliance under Part L 2019.
- Septic tank / percolation — one in four Irish dwellings outside major cities is on private treatment.
- Section 5 declarations — uncertainty about exempted development can be resolved by Section 5 declaration (€80, 4-week turnaround).
Review cadence
We refresh the cost calibration quarterly against the latest SCSI print, CSO COPI release, and Engineers Ireland day-rate update. Editorial guides carry a “Last reviewed” date in the header.
What we don’t do
- We don’t sell leads to contractors. There are no affiliate links to builders, architects or surveyors anywhere on the site.
- We don’t train any AI model on user submissions. Snapshot and quote uploads go to Anthropic under SCCs + EU-US Data Privacy Framework and are not used for training.
- We don’t store uploaded photos or quote PDFs beyond 24 months. Deletion on request, GDPR-compliant — full detail in the privacy policy.
- We don’t accept sponsored content.
Corrections and challenges
We get things wrong. When that happens we want to know. Email admin@untangle.ie with the page URL, the figure you believe is wrong, and your source for the alternative. Confirmed corrections ship within one working week and the page’s “Last reviewed” stamp updates.
This methodology page is maintained alongside the calculator code. Last reviewed 21 May 2026 against SCSI Nov 2025 + CSO COPI Q1 2026 + Engineers Ireland day-rate guidance 2026. Next scheduled review: October 2026.