The permit drawings establish whether you may build. The construction drawings establish how. One does not replace the other.
A recurring question: are construction drawings necessary once the permit is granted? In many cases they are not legally required. In practice, however, this documentation determines whether the contractor builds what you imagined, and whether the quotations you receive can be compared at all.
The difference
| Permit / notification drawings | Construction drawings | |
|---|---|---|
| Purpose | Demonstrating regulatory compliance | Describing precisely how it is built |
| Scale | Typically 1:100 | Typically 1:50, junctions 1:5–1:20 |
| Content | Plans, sections, elevations, technical description | Junctions, build-ups, schedules, details |
| Audience | The authority | The contractor |
What is included
- Dimensioned floor plans for every storey, with openings and lintels.
- Build-ups: floor, wall and roof layer by layer, with materials named.
- Junction details: plinth, eaves, window installation, terrace threshold.
- Schedules: windows and doors, metalwork and joinery.
- Finishes and furniture layouts, where these form part of the commission.
- Engineering drawings: structure, mechanical services, electrical installation, energy calculation.
Why it pays for itself
For three concrete reasons. First, quotations are only comparable if they cover the same technical content. Without construction drawings, the cheaper quotation often simply contains less.
Second, decisions improvised on site are the most expensive kind. If a junction has not been drawn, somebody will work it out on the scaffold — well, if you are fortunate, and otherwise as a defect that appears years later.
Third, in a dispute the construction drawings are the document against which performance can be measured. Without them it is hard to prove that what was built is not what was agreed.
How much detail
Not every building needs the same depth. For a straightforward farm building of conventional construction, concentrating on the critical junctions is enough. For a complex house, where thermal bridging, vapour control and exposed structures all matter, detailed development pays for itself.
I agree the appropriate depth at the outset — there is no point paying for drawings the construction will not use.