Single Storey Side Extension Ideas: Design, Cost & Planning Guide

A side extension is one of the most effective ways to add space, value, and functionality to your home — without the cost and upheaval of moving. Whether your plot has a wide gap down the side or a narrower passage, there’s likely more potential there than you realise.

Here are the most popular ways homeowners are using side extensions right now.

7 Side Extension Ideas Worth Considering

Open Plan Living Space — Remove an internal wall and combine a side extension with your existing ground floor to create a flowing kitchen-dining-living area. Add bi-fold doors and a roof lantern and you’ve got a space that feels twice the size of what was there before.

Bigger Kitchen — Older kitchens were built small. A side extension gives you room for an island, proper storage, and space to actually move around while cooking.

Generous Dining Room — Create a dining area that comfortably seats the whole family and your guests — not one where someone’s always wedged against the wall.

Utility Room or Pantry — Move the washing machine and dryer out of the kitchen entirely, or add a dedicated pantry with floor-to-ceiling shelving. Small addition, massive daily impact.

Extra Bedroom — Avoid the cost of moving by simply adding the room you need. A side extension bedroom can include an en-suite and built-in storage for a complete, self-contained space.

New Bathroom — An additional bathroom or shower room reduces morning queues, improves daily convenience, and adds real value to your property.

Home Office — A purpose-built workspace with natural light and proper separation from the rest of the house beats a desk in the corner of a bedroom every time.

Planning Permission: The Key Rules

Side extensions often qualify under permitted development, meaning no planning application needed — but only if your project meets these conditions. You’ll need full planning permission if the extension is wider than half the original house, exceeds the existing roof or eave height, comes within two metres of the boundary at over three metres tall, uses different exterior materials, or extends further to the rear than 4 metres (detached) or 3 metres (semi-detached or terraced).

Properties in conservation areas are also subject to tighter restrictions. And regardless of planning permission, building regulations approval is required for all side extension work.