Renovation estimate calculator with versioned client quotes

We are a small finishing crew — plaster, screed, tiling, painting — and every estimate we have ever made still lives in a spreadsheet that somebody copies before editing. By the time a client says yes there are four files with almost the same name, and nobody can say for certain which figure we actually promised. I want a modest web tool that keeps our pricing in one place and produces a quote I am not ashamed to hand over.

The heart of it is two reference books. The first holds works: a name, a unit (square metre, running metre, piece, point), a labour rate. The second holds materials with consumption tied to a unit of work — so many kilograms of adhesive per square metre of tiling, so many litres of primer per coat. An estimate is then assembled room by room: I pick a room, enter its area or perimeter, add lines from the reference book, and the tool multiplies everything out. Coefficients sit on top — one for the difficulty of the surface, one for ceiling height above the usual — applied to labour and shown as their own line rather than quietly baked into the rate.

Labour and materials must stay apart on screen and on paper: clients pay for them in different ways, and merging the two is exactly how arguments begin. Printing should give one tidy document with our details, the breakdown by room, two subtotals and a grand total.

Three conditions I want honoured in the terms and in the product itself:

— the estimate is preliminary until the site survey, and that sentence has to be printed on the document, not mentioned in conversation;
— rates and material consumption are maintained by us; you build the instrument and do not set our prices or advise on them;
— once a version is agreed it is frozen, and any later change goes on a separate sheet attached to it, otherwise a dispute about scope is unavoidable.

What I expect delivered:

— reference book of works: name, unit, labour rate, grouping;
— reference book of materials: name, unit, price, consumption per unit of work;
— estimates assembled by rooms, with areas and line items;
— coefficients for difficulty and ceiling height, always as visible separate lines;
— separate totals for labour and for materials, never merged;
— a print-ready client quote carrying the preliminary notice;
— versions with history: who changed what and when, and a comparison with the previous one;
— templates for typical jobs: bathroom, studio flat, walls only;
— accounts for two foremen besides mine, with editing of the reference books left to me.