Tallyhammer
A 3D cost calculator built into a website for UK building firms, so the homeowner sees a range and the builder gets the brief. Currently in private preview.
Tallyhammer: A 3D Cost Calculator That Hands The Builder The Brief
The brief
Most homeowners start a building project with one question, what will this cost, and most builders first hear it as a phone call with nothing to price from. Cost guides online give a range, but with no picture of the house and no detail about the job. Tallyhammer is a product I am building for UK building firms to close that gap.
The idea is a website for a building firm with a 3D cost calculator built into it. A homeowner picks their house or room, chooses the work and watches the range change. The builder receives the same choices as a brief they can price from, so the first conversation starts with detail instead of a guess.
The build
Six calculators are built and running: loft conversion, single storey extension, garage conversion, kitchen fitting, bathroom fitting and home energy. The five building calculators show the house or room in 3D, and the homeowner can drag the model round to look at it. The loft, extension, garage, kitchen and bathroom calculators each run in four short steps, and the estimated range updates on screen as the choices change.
The numbers come from published UK cost guides, averaged, and last checked on 8 October 2026. Every result is labelled a budgeting guide rather than a quote, because that is what it is. The range follows the size of the house, the finish and the area, and anything the homeowner ticks under the optional step adds a line to the estimate and to the brief the builder receives.
The kitchen calculator works the same way for a room: a layout, then size and finish, then location, with an optional step for anything the builder should know.
The calculator sits inside a website. There are six template looks for different kinds of firm, from loft and extension specialists to kitchen fitters, solar installers and general builders, and each has the calculator wired in beside the usual pages for services, projects, reviews and contact.
The sample sites use made up firms and stand-in photographs, and say so in a banner on every page.
Where it stands
Tallyhammer is in private preview. The calculators and templates run, but the firms, reviews and projects on the sample sites are made up, the photographs are stand-ins and the legal pages are still drafts. There are no customers or results to report yet.
If you run a building firm and would like to see a calculator with your own name and area on it, get in touch.
Running a building firm?
A homeowner who has seen a realistic range is a better enquiry than one who has seen nothing.
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