Extension Value Estimator
Use this tool when the planning route and likely value uplift need to be looked at together. It gives a cautious range for value added based on project type, added space, finish and planning confidence, then points you to the pages most worth opening next.
Estimate The Likely Value Uplift
Enter the current property value, choose the project type, add the likely floor area and finish level, then let the tool estimate a guided uplift range.
What This Tool Is Good For
What it answers well
It gives a practical value-added range for common extension-led projects before you rely on rough one-line rules or salesy ROI claims.
What changes the estimate most
Project type, added area, bedroom gain, finish level and planning certainty do most of the work in the range this tool produces.
What it does not do
It does not model postcode-level market conditions or replace a valuation survey, estate-agent opinion or lender valuation.
Questions This Tool Is Best At Narrowing
- How much value does an extension add?
- Is this extension worth it?
- How much value does a loft conversion add?
- Does planning permission affect value uplift?
- How much value does a side extension add?
- Which extension adds the most value?
How This Tool Fits Into The Wider Planning Process
Extension Value Estimator is intended as a quick planning aid based on common UK planning considerations and permitted development limits.
Use it to narrow the question, then move into project guides, local authority pages or formal confirmation if the scheme is close to a limit. The route can differ by country, especially once Scotland or Wales are involved.
FAQ Pages Worth Opening After The Tool
Does An Extension Add Value To A House?
Read the broader guide if you want the value question explained in plainer language first.
Read answerExtension Cost Vs Value Added
Useful when the real question is whether the likely uplift justifies the spend rather than just whether value rises at all.
Read answerWhich Extension Adds The Most Value?
Useful when you are comparing several project routes before committing to one.
Read answerDetailed Guidance Worth Opening Next
House Extensions
Useful when the value question still depends on the extension route itself.
Open guideLoft Conversions
Helpful for loft projects, bedroom gain and upper-floor value questions.
Open guidePlanning Permission
Open this when planning certainty is still the main thing affecting how realistic the value upside feels.
Open guidePermitted Development
Useful when the simpler route still looks plausible and confidence is part of the value equation.
Open guideTwo Storey Extensions
A strong next read where added floor area and bedroom gain are the main sources of uplift.
Open guideRear Extensions
Helpful when the likely uplift depends on a more mainstream rear extension route.
Open guideUse These Tools Properly
What they are for
- Reducing uncertainty at the start of the process.
- Helping you pick the right next page quickly.
- Spotting when the answer probably needs escalation.
What they do not replace
- Formal confirmation for borderline schemes.
- Local authority checks where special controls apply.
- Country-specific checking where England, Wales or Scotland follow different planning routes.
- Detailed professional advice for complex cases.