Evidence-based negotiation
Using £ per square foot variance to justify a below-asking offer
Price per square foot is the only measure that lets you compare a two-bedroom flat with a three-bedroom terrace on the same street. Used carelessly it produces nonsense; used properly it is the backbone of an evidenced offer.
The calculation
£/sq ft = sale price ÷ internal floor area in square feet. Use registered sale prices from HM Land Registry and floor areas from the EPC register, converting square metres at 10.7639 sq ft per m².
Never mix sources of area
If your comparables use EPC floor areas, use the EPC floor area for the subject property too. Mixing an agent's generous floor plan figure with EPC comparables manufactures a variance that is not real.
Choosing comparables that hold up
- Same postcode or immediately adjacent — street-level variation in UK pricing is real.
- Same property type and built form — a mid-terrace is not a semi.
- Same tenure — leasehold with a short lease or a heavy service charge is not comparable to freehold.
- Within roughly 12 months, adjusted if the UK House Price Index shows meaningful movement for the local authority since the sale.
- At least three, ideally five. One comparable is an anecdote.
Reading the variance
- Calculate £/sq ft for each comparable and take the median rather than the mean — one refurbished outlier will drag a mean badly.
- Calculate the asking price per square foot for the subject property.
- Express the difference as a percentage of the comparable median.
- Ask what explains it: condition, extension, garden, parking, floor level, aspect, lease length, or nothing at all.
A property asking 15% above the local median £/sq ft is not automatically overpriced — it may be the best-finished house on the street. The variance is a question, and the answer is what you negotiate about.
Turning it into an offer
Take the comparable median £/sq ft, multiply by the verified floor area, and you have an evidence-derived value range. Then subtract only quantified, property-specific costs: a quoted roof repair, an EPC-listed measure priced by a contractor, a lease extension premium. Present the result as a range, not a point estimate, because that is what the evidence actually supports.
This is deliberately not a valuation. A valuation is a regulated opinion given by a qualified valuer for a specific purpose. What you are producing is a defensible negotiating position derived from public records.
Frequently asked questions
- Should I use mean or median £/sq ft?
- Median, on small comparable sets. Means are distorted by a single unusual sale.
- How do I handle a property with no EPC floor area?
- Measure at the viewing, or use the floor plan's stated area while noting that it is unverified — and label it as unverified in your own workings.
Sources
Check a property before you offer
Run any UK postcode through our free lookup for EPC bands, flood exposure, registered sold prices and recorded crime. Got a specific listing? Paste the Rightmove link for the full six-section FirstBid report.
Related guides
How to negotiate a property asking price using public evidence
A structured method for building an offer from registered sold prices, price per square foot, condition evidence and public records — instead of guessing a percentage off.
What HM Land Registry sold data really tells you about local prices
How to read Price Paid data properly — what it includes, what it leaves out, the reporting lag, and how to use it as negotiation evidence without over-reading it.
How to check true square footage against an agent's floor plan claim
Floor areas on Rightmove listings and EPCs are measured differently. Here is how to compare them properly, and what a genuine discrepancy is worth in a negotiation.