3 4 5 Method: Your Quick Guide to Planning a Home Extension
If you’re thinking about adding space to your house, the 3‑4‑5 method can make the whole process feel less scary. It breaks down planning into three simple steps, four key checks, and five common pitfalls to avoid. By the end of this article you’ll know exactly what to do next, whether you’re extending a kitchen, adding a loft, or building a conservatory.
Step 1: Sketch, Measure, and Set a Budget (the 3‑part core)
First, grab a plain piece of paper or a free drawing app and sketch the area you want to expand. Keep it rough – just walls, doors, and windows. Next, measure the existing rooms and the space you plan to add. Write down lengths in metres or feet so you can compare easily. Finally, sit down with a calculator and list all the costs you expect: materials, labour, planning fees, and a small buffer for surprises. This three‑part routine gives you a clear picture before you talk to any builder.
Step 2: Four Essential Checks Before You Build
1. Planning permission – In the UK most small extensions fall under Permitted Development, but size, height, and proximity to neighbours matter. Check the latest rules or ask your local council.
2. Structural impact – Adding weight can affect foundations and roof load. A quick chat with a structural engineer will tell you if you need extra supports.
3. Materials compatibility – Match new bricks, windows, and roofing to the existing house. This saves you time and money on finishing work.
4. Neighbourly notice – Let the people next door know what you’re planning. It reduces complaints and keeps the project running smoothly.
Step 3: Avoid the Five Common Pitfalls
1. Under‑estimating cost – Always add at least 10% to your budget for unexpected items.
2. Forgetting drainage – New rooms need proper water runoff. Ignoring this can lead to damp later.
3. Ignoring insulation – Skipping proper insulation raises energy bills and can cause condensation.
4. Overlooking fire safety – Check that new plasterwork, doors, and wiring meet fire regulations.
5. Rushing the schedule – Give each stage (design, approval, construction) enough time. Rushing leads to mistakes and extra cost.
When you follow the 3‑4‑5 method, you turn a big, confusing project into a series of easy actions. Start with a simple sketch, run the four checks, and keep an eye on the five pitfalls. In no time you’ll have a clear plan, a realistic budget, and the confidence to talk to a builder or architect. Ready to add that extra room? Grab a pen, draw your idea, and let the 3‑4‑5 method guide you forward.
