How much should you offer on a house that needs work? The honest answer: it depends entirely on what the work will cost — and that is the number most buyers guess. Offers on renovation properties typically miss the real renovation cost by 20–40%, which means the offer itself was wrong before negotiation even started. Here is a method that replaces the guess.
What is the formula for offering on a renovation property?
Experienced buyers and investors work backwards from the finished value, not forwards from the asking price:
- Start with the end value — what the property would realistically sell for once renovated, based on sold prices of comparable finished properties nearby
- Subtract the real renovation cost — trade-level pricing for the actual works needed, not a per-room guess
- Subtract a contingency — 10–15% of the renovation figure for what is found once work begins
- Subtract your buffer — the reward for taking on the project; without it, you are paying finished-house money for an unfinished house
What is left is your maximum sensible offer. The asking price does not appear anywhere in that calculation — it is the vendor's opening position, not evidence of value.
What does that look like with real numbers?
| Line | Figure |
|---|---|
| Realistic finished value (comparable sold prices) | £475,000 |
| Renovation cost (assessed, trade by trade) | − £88,000 |
| Contingency at 12% | − £10,500 |
| Buffer for taking on the project | − £25,000 |
| Maximum sensible offer | £351,500 |
If the property is listed at £395,000, that gap is not cheekiness — it is arithmetic. And arithmetic is far easier to defend in a negotiation than a feeling.
Why do most buyers get the renovation figure wrong?
Because the figure is genuinely hard to know from a viewing. A rewire is not just the electrician's quote — the making good afterwards adds £3,000–£6,000 of replastering that almost never appears in the quote. A roof on a period property carries £3,000+ of scaffolding that roofing quotes routinely exclude. Damp can be a £500 ventilation fix or an £18,000 perimeter treatment, and they look similar on a wall. Buyers who guess tend to anchor on the most visible works — the kitchen, the décor — and miss the invisible ones that dominate the budget.
The negotiation advantage: an offer supported by an itemised, independent cost breakdown changes the conversation. You are no longer a buyer "trying it on" — you are a buyer showing the vendor exactly why the number is what it is. Agents take evidenced offers to vendors very differently from unexplained low ones.
How do you find out the real renovation cost before offering?
Three routes. Builder quotes are the traditional one, but good builders take weeks to visit a property you do not yet own, and three builders will quote three different scopes. Online calculators are fast but generic — they do not know your property. The third route is an independent renovation cost assessment: a construction professional prices the actual works, room by room and trade by trade, against current local rates. That is the gap NOROS exists to fill, and it is the difference between offering on evidence and offering on hope. Not sure where you stand yet? Take the free 90-second Renovation Readiness Check and see how prepared you really are.
When should you walk away instead of offering?
When the formula produces a number the vendor will never accept, the property does not work — at that price, for you, today. Walking away from a property that does not stack up is not a failure; it is the entire point of doing the numbers before exchange rather than after. The most expensive properties are the ones bought on optimism.
Every renovation job, every range — and why the cheapest quote is usually the most expensive.
Know your number before you offer.
A NOROS assessment gives you the renovation figure that makes this formula work — room by room, trade by trade, from £99. Most reports are delivered within 24–48 hours.
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