DIY Plans vs Professional Plans: Is It Worth Paying?
You can draw your own extension plans and submit them for planning permission. But should you? This guide weighs the costs and risks of DIY vs professional plans.
The details
When DIY plans work
For very simple projects — a basic rectangular extension with no structural complexity — DIY plans can work. Free tools like SketchUp or Floorplanner let you create basic layouts. If you are handy with measurements and comfortable with scale drawings, it is possible.
When they don't
Planning officers assess design quality, not just dimensions. Poorly drawn plans can lead to requests for amendments (delaying the decision), refusal on design grounds, or approval for something that does not actually work structurally. Building Regulations drawings require technical knowledge that most homeowners do not have.
The risk calculation
Professional plans are quoted after the survey. A refused planning application costs you weeks and a non-refundable council fee. On-site problems from inadequate drawings can cost thousands in builder variations. The professional fee is insurance against much more expensive mistakes.
| Factor | DIY Plans | Professional Plans |
|---|---|---|
| Cost | £0 (your time) | Quoted after the survey |
| Time investment | 20–40 hours | Handled for you |
| Planning success rate | Lower (poor presentation) | Higher (professional quality) |
| Building Regs compliant? | Unlikely without experience | Yes |
| Builder confidence | Low (imprecise drawings) | High (professional specification) |
| Risk of on-site changes | High | Low |
Our verdict
Professional plans remove the guesswork and give builders confidence to quote accurately. Unless you have genuine drafting experience, the cost of professional plans is one of the best investments in your project.
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