Option AStrongest starting point
Two-storey rear extension
- Floor area
- 35m²
- Footprint
- 6×3.5m
- Indicative total budget
- €114,000–€244,000
- Planning
- Application likely
- Confidence
- High
- Garden impact
- Medium
- Complexity
- High
Extension feasibility · Irish homes
See what your home could become before you spend thousands designing it.
Explore realistic extension options for your own house, compare their likely space, cost, planning route and complexity, and arrive at your architect or builder conversation knowing which direction you want.
Start free with one photo · no account, no card · assessments from €49
01 Your home
Semi-detached, Dublin · rear photo · garden about 14m
02 Options that suit it
A Two-storey rear extension
35m² · €114k–€244k
B Two-storey side extension
34.8m² · €113k–€243k
C Single-storey rear extension
36m² · €124k–€256k
03 A direction
Option A looks like the strongest starting point — with the reasons, assumptions and what to verify.
Example output for a fictional Dublin semi-detached house. Indicative figures from our cost and planning model.
The decision before the design
An extension is a €50,000–€200,000 decision. Most people make it on a sketch and a guess.
ExtensionVision gives you better information before you commit — so the money you then spend on an architect, engineer and builder goes on the right idea.
What could I build?
Which extension types suit your house and plot, how much space each could add, and what each might look like on your home.
What might it really cost?
Not just the build rate. Fees, engineering, surveys, planning, contingency, kitchen and external works — the total project budget.
What do I need to check?
Whether an option may be exempt or likely to need permission, how confident that is, and exactly what to verify before paying for design.
How it works
Photo, possibilities, a decision.
- 01
Upload a photo of your home
One phone photo of the back of the house. Daylight, whole rear wall in frame.
Free · about 2 minutes
- 02
Explore realistic possibilities
Concepts drawn onto your actual house, then options sized to your plot and priorities — with what you don’t know left as unknown.
Free preview
- 03
Compare and choose a direction
Space, indicative budget, planning route, garden impact and complexity side by side, with a reasoned recommendation.
From €49
Sample assessment · fictional semi-detached house, Dublin
Three plausible ways to extend — compared on what actually matters.
Brief: open-plan kitchen and dining, an extra bedroom, add value. House about 7.2m wide, garden about 14m deep. Produced by the same model your assessment uses.
Option B
Two-storey side extension
- Floor area
- 34.8m²
- Footprint
- 2.9×6m
- Indicative total budget
- €113,000–€243,000
- Planning
- Application likely
- Confidence
- High
- Garden impact
- Low
- Complexity
- High
Option C
Single-storey rear extension
- Floor area
- 36m²
- Footprint
- 7.2×5m
- Indicative total budget
- €124,000–€256,000
- Planning
- Potentially exempt
- Confidence
- Medium
- Garden impact
- Medium
- Complexity
- Low
| Factor | Option A | Option B | Option C |
|---|---|---|---|
| Additional space | 35m² · Lower | 34.8m² · Lower | 36m² · Higher |
| Garden impact | Medium | Low | Medium |
| Planning route | Application likely | Application likely | Potentially exempt |
| Planning confidence | High | High | Medium |
| Construction complexity | High | High | Low |
| Fit with your objectives | Strong | Moderate | Moderate |
| Overall suitability | Strongest fit | Good | Strongest fit |
Recommendation
Based on the information available, Option A — two-storey rear extension — appears to be the strongest starting point.
- It fits your stated priorities (open-plan kitchen / dining, additional bedroom, add property value) better than the alternatives.
- Garden impact is medium.
This is a preliminary comparison from limited information, not architectural or planning advice. A site visit can change the ranking.
To verify before paying for design
- Upper floors must be at least 2m from any boundary.
- Windows must meet the separation distances to boundaries set out in the regulations; a flat roof may not be used as a balcony.
- Wall and roof heights must not exceed the limits relative to the existing house.
Questions for your architect
- Can a footprint of roughly 6m × 3.5m work on the actual site, and what would you change?
- Which planning route do you expect — exempted development, a Section 5 declaration, or a full application?
- What surveys do we need first (measured, topographical, drainage CCTV, structural)?
Indicative only. Figures include VAT, fees, contingency and a kitchen allowance. Not a quote, not planning advice. The full assessment adds cost breakdowns, assumptions, risks and next steps for each option.
Where this fits
Not inspiration. Not an architect. The step in between.
| Alternative | What it gives you | ExtensionVision |
|---|---|---|
| Pinterest & Houzz | Other people’s houses | What could work on your house |
| Generic AI image tools | A picture | A plausible extension, and the decision around it: space, cost, planning, trade-offs |
| Architect | Professional design, drawings and planning | Preparation for that process — a clear brief, a realistic budget and the right questions |
Then take it to a professional
Instead of starting with “we’d like an extension”, arrive with three options you’ve already weighed.
Your first meeting with an architect, architectural technologist or builder becomes a conversation about a direction — not an hour spent discovering what you want.
What you bring to that meeting
- The options you considered, and why one looks strongest
- A realistic total budget range — not just a build rate
- The planning questions that need a professional answer
- Your assumptions written down, so they can be corrected
- Specific questions for your architect and your builder
A structured starting point for the conversation — not drawings, a survey or technical documentation.
Packages
Start free. Go as deep as your decision needs.
The concept preview of your own house is free. Pay only when you want the analysis — and upgrades are charged the difference.
“I’m exploring.”
Concept Pack
€49
For homeowners still exploring ideas.
Recommended for a real decision
“I’m seriously considering this.”
Extension Assessment
€149
For homeowners who want to understand which option makes the most sense.
“I’m preparing for professional conversations.”
Professional Feasibility Report
€299
For homeowners preparing to commit serious money.
“I want a comprehensive early-stage study.”
Premium Home Study
€499
For homeowners wanting the deepest digital assessment before professional design.
Honest by design
High confidence, without false certainty.
Every figure is labelled for what it is: observed from your photo, inferred, or unknown. Unknowns lower our confidence — they are never filled in with a guess and presented as fact.
- Visualisations are conceptual images generated from your photo. They are not architectural drawings.
- Dimensions are indicative and have not been surveyed. Verify on site.
- Cost estimates are indicative ranges, not quotations, and carry no guarantee.
- Planning screening is not planning or legal advice and does not guarantee that any route applies or that permission will be granted.
- No structural assessment has been carried out.
- No measured survey has been carried out.
- Local and site-specific conditions can materially change the outcome.
- Professional advice is required before design is finalised and before any construction.
Questions
Is this a substitute for an architect?
No. ExtensionVision helps you understand your options and prepare. An architect or architectural technologist designs the project, confirms the planning route and prepares the drawings. The point is to reach that conversation with a clear brief and a realistic budget.
What do I need to start, and how long does it take?
A photo of the back of your house. Rough measurements help but are optional — anything you don’t know stays unknown and lowers our stated confidence rather than being guessed. The free concepts take about two minutes.
When do I pay?
Only after you have seen concepts of your own house. The preview is free with no card and no account. If you then want cost ranges, planning screening and a recommendation, you choose a package. Upgrades are charged the difference.
How accurate are the dimensions?
They are indicative concept dimensions based on the measurements you give us (or typical values, clearly flagged, when you don’t). Nothing is surveyed. Verify on site.
Where do the cost figures come from?
An Irish indicative cost model using €/m² ranges commonly cited for domestic extensions, adjusted for type, location and specification, plus fees, surveys, contingency and fit-out. It is not a quote. See our methodology.
Will you tell me if I need planning permission?
We screen each option against the exempted-development conditions for house extensions and tell you the likely route, our confidence and what must be verified. It is not planning advice, and only a professional or your council can confirm it.
What happens to my photo?
It is used to produce your concepts and stored against your project. You can delete the photo and all generated images from your project page at any time.
Arrive at your first architect meeting prepared.
Start with a photo. The concept preview is free.
See what your home could become