Estimating refurb costs.

Refurb creep kills more BRR deals than bad purchases do. You won’t have a builder’s quote at offer stage, so you estimate with rules of thumb, then protect yourself with contingency. These ranges are broad national guides — London and the South East run higher, and every property is its own argument.

The three budget tiers

Light / cosmetic (decorate, flooring, tidy the kitchen and bathroom): roughly £10,000–£25,000 on a typical 3-bed. Full refurb (new kitchen and bathroom, rewire, heating, plaster, decorate): £40,000–£60,000. Structural / extension: think in build cost per square metre — £2,000–£3,500/m² — plus professional fees, and treat it as a different class of project.

Line-item ranges

HMO conversions

Budget per lettable room— roughly £10,000–£17,000 each once en-suites, fire doors, alarms, emergency lighting and licensing compliance are counted. Six rooms at the midpoint is the £60,000–£80,000 you’ll see in serious HMO appraisals, and it’s why the commercial valuation has to outrun the spend.

The rules that keep you honest

Add 10–15% contingencyon top of every estimate — always. Respect the street ceiling: a £60,000 refurb can’t push a house past what the road will pay. And remember time is money on a bridge: every extra month of works is another month of interest, which is why the Deal Shaper feeds your works timeline straight into the bridging cost.