Bungalow extension options: how to extend a bungalow
You can extend a bungalow in four broad directions — out to the rear, out to the side, up into the roof, or up with a whole new storey. Which one is right comes down to your plot, your roof height and what the permitted development rules let you build without a full planning application.
Start with the plot, not the plan
Bungalows tend to sit on more generous plots than the houses around them, which is why extending one is often easier than extending a two-storey home — there is usually room to go out without crowding the boundary. The trade-off is that every square metre you add at ground level is garden you lose. So the first question is not “what do I want?” but “where is the space, and am I happier giving up garden or reworking the roof?”
The four routes each suit a different situation. A rear or side extension gives you single-level living and is the simplest build. A loft conversion keeps your footprint and garden intact. Adding a full storey roughly doubles the house but is the biggest job of the lot. The rest of this page walks through each one with the rules that decide whether you can do it.
Rear, side and wraparound extensions
A bungalow is a house in planning terms, so the same permitted development limits apply as for any other single-storey home. A rear extension is the usual choice for a bigger kitchen-diner or an open-plan living space, and it often needs no planning application at all if you stay inside the depth and height limits below. A side extension works where the plot is wider than it is deep — handy for a bungalow with a driveway or side passage going spare.
A wraparound combines the two into an L-shape and gives the most ground-floor space in one go. The catch is that each part might sit inside its own permitted development limit, but added together they usually do not, so wraparounds commonly need planning permission. Ask the council before you pay for drawings.
| Permitted development limit (England, houses) | Detached bungalow | Semi or terraced |
|---|---|---|
| Single-storey rear extension depth | up to 4m | up to 3m |
| Rear depth via larger home extension prior approval | up to 8m | up to 6m |
| Maximum height | 4m overall | |
| Side extension | single storey, no wider than half the original bungalow, up to 4m high, not forward of the front wall | |
| Coverage | extensions must not cover more than half the land around the original house | |
Figures from the Planning Portal and GOV.UK permitted development technical guidance. “Original” means the bungalow as first built or as it stood on 1 July 1948 — a previous owner’s extension counts against your allowance. On designated land (conservation areas, National Parks, AONBs) side extensions are not permitted development and other limits tighten. See our permitted development rules for the full detail.
Going up: a loft conversion or a whole new storey
If the plot is tight or you would rather keep the garden, the roof is where the space is. Most bungalows convert well — they were built with plenty of roof volume and take a staircase and roof windows readily. As a working rule you want around 2.5m of clear height under the ridge before floor build-up and insulation eat into it; measure from the top of the ceiling joist to the underside of the ridge. If you fall short, you can lower the ceilings below or rebuild the roof at a steeper pitch, but that second option needs planning permission and is the priciest way to do it.
A loft conversion usually falls under permitted development within the volume allowance below. If you want to raise the walls and add a genuine first floor rather than work inside the existing roof, that is a different right — Class AA, which lets you add one storey to a single-storey house. It always needs a prior approval application, and the current fee for that is £96 per dwelling, well under the £548 householder planning fee.
| Going up | What the rules allow |
|---|---|
| Loft conversion volume | up to 50m³ added on a detached or semi-detached bungalow, 40m³ on a terrace |
| Loft roof line | must not go higher than the existing ridge, or beyond the roof slope facing the road |
| Head height (practical) | around 2.5m clear under the ridge before you start losing usable space |
| Adding a full storey (Class AA) | one extra storey, no more than 3.5m above the existing roof, total height under 18m, prior approval required |
| Class AA eligibility | bungalow built between 1 July 1948 and 28 October 2018, no windows in the side walls, not on designated land |
Loft volume and roof-line limits from the Planning Portal; Class AA conditions from the Town and Country Planning (General Permitted Development) Order as summarised on GOV.UK. Whichever route you take, a bungalow’s foundations were not designed to carry rooms above, so a structural engineer’s calculations and steel beams at the eaves are normal — budget for them.
How to choose between them
Match the route to what is actually scarce. If the garden is small or precious, go up: a loft conversion is the cheapest way to add a bedroom without touching the footprint. If you want to keep everything on one level — the reason many people choose a bungalow in the first place — a rear or side extension protects that, at the cost of some garden.
If you need to add the most bedrooms for the money, a loft usually wins. If you want to roughly double the house and are prepared for the biggest build and the prior approval process, a Class AA storey does that. And if the plot is wide and shallow, a side or wraparound extension often unlocks more usable space than pushing straight back into a narrow garden. There is rarely one right answer — there is the one that fits your plot, your budget and how you want to live.
Whatever you pick, it will need Building Regulations approval even when it is permitted development. That covers structure, insulation, fire escape and drainage, and for any room in the roof it brings stair and fire-escape rules into play. Our guide to building regulations for extensions covers what gets checked. It is also worth reading our comparison of a garage conversion instead of an extension if your bungalow has an integral garage — it is often the cheapest extra room of all.
What a bungalow extension costs
Costs swing with size, ground conditions and finish, so treat any figure as a starting point rather than a quote. As a rough guide a single-storey rear or side extension on a bungalow works out around £2,000 to £3,000 per square metre finished, while a loft conversion runs from roughly £20,000 for a simple room up to £60,000 or more if the roof is rebuilt or you add dormers and an en-suite. Adding a full Class AA storey sits at the top of that range and beyond, because you are effectively building a new floor.
Those ranges come from BestBuilders’ 2026 regional cost model (published national cost guides × a regional labour index, averaged across 519 UK towns). For a full breakdown by size and finish, see BestBuilders’ average cost of a bungalow extension guide rather than relying on a single headline number.
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