Of loft conversion applications decided in the last five years, about 4 in 5 were approved. Conservatories: more than 9 in 10. Both rates cover only the projects that needed a full planning application, and many lofts and many conservatories on houses never need one at all, because permitted development rules let you build within set limits. Here is how the common projects compare when they do go to a decision, why lofts fight hardest, and how to tell which side of the application line your project falls.
This piece is for two moments. The first is choosing: loft, extension or conservatory, usually a trade between space, budget and hassle. The second is the night before a loft application goes in, when you want to know what you are in for. Either way, the public record has an answer. Councils publish every decision they make, and we hold enough of them to read the pattern.
The approval ladder
The chart above puts every common project on one basis: full applications decided in the last five years, approved or refused, from UK council planning registers. Conservatories top the ladder at 94% approved of 11,055 decided. Loft conversions sit at the bottom at 81.8% of 20,845, below the 88.4% baseline for all full applications of every kind (257,687 decided). Three honesty notes belong right here. These are rates among projects that needed a full application; many lofts and many conservatories proceed under permitted development and never enter these records, so a refusal rate among applications is not the chance your project gets blocked. Withdrawn applications are not decisions and sit outside the rates, and lofts are withdrawn about twice as often as conservatories, which is its own signal of harder terrain. And the rates describe the mix of schemes people actually submitted, not any single proposal's odds.
Why lofts fight harder
Of the project types on that chart, lofts fight hardest, and the reason is visibility. A conservatory is low, single storey, at the back, and largely invisible from the street. A loft conversion changes the roofline, the most public part of the house. It tends to add dormers that neighbours and conservation officers look straight at, and it puts new windows at overlooking height. When we read a sample of refused loft applications, the same shapes kept appearing: dormers on the front slope facing the street, roofs raised to make headroom, and lofts riding along inside much bigger schemes, including conversions to shared houses, where the refusal was really about the whole scheme rather than the loft. None of this measures who drew the plans, and none of it is a reason to expect refusal. It is a reason to design the roof with the street in mind, because the council will judge it from there.
You may not need to apply at all
The permitted development rules below apply in England only. Scotland, Wales and Northern Ireland have their own rules with different limits. Check with your council before relying on any of them. And they are for houses: flats and maisonettes have no householder permitted development rights at all.
For a loft, the boundary runs like this. The added roof space must stay within 40 cubic metres on a terraced house or 50 cubic metres on a semi detached or detached one, and the allowance is cumulative, so any previous roof extension counts against it. No dormer may extend beyond the roof slope of the main front of the house where it faces a road, which is worth reading twice: the front dormer is both the thing permitted development forbids and the thing our refused sample was full of. The rules draw the line exactly where the arguments happen. Nothing may rise higher than the existing ridge, a dormer must sit back at least 20 centimetres from the original eaves and use materials of similar appearance to the existing house, and balconies, verandas and raised platforms are out. One hard stop: on designated land, meaning conservation areas, National Parks, the Broads, areas of outstanding natural beauty and World Heritage Sites, roof enlargements are not permitted development at all, and you are in application territory from the start. If dormers are the sticking point, rooflights that project no more than 15 centimetres from the roof plane and rise no higher than the roof are a separate, gentler allowance.
A conservatory counts as an extension in planning law, so the single storey rear extension limits decide it: up to 4 metres beyond the original rear wall of a detached house or 3 metres for any other house, no taller than 4 metres, eaves no higher than 3 metres within 2 metres of a boundary, and extensions and outbuildings together covering no more than half the land around the original house. Our extension guide covers those limits in full, including the larger extension route that needs prior approval. Two closing notes that apply to both projects. If you build under permitted development, you can ask the council for a lawful development certificate, optional but worth having as dated proof when you sell. And a loft conversion always needs Building Regulations approval whatever planning says, covering the floor structure, fire escape, stairs and insulation; conservatories under 30 square metres can be exempt, but check before you rely on it.
How long you'll wait
The wait gap points the same way as the approval gap. Of loft decisions made in the last five years, half came within 64 days and 9 in 10 within about 135; only 37.4% of the 20,843 decisions with usable dates landed inside the 8 week target for minor applications in England and Wales. Conservatories run about a week faster: half within 57 days, 9 in 10 within about 110, and 47.3% of 11,053 inside the target. Lofts sit close to the national picture in our decision-times guide; conservatories run about a week faster than it too. The reading is the same one we always give: these are decided applications only, and the slowest still-open cases are not in the sample yet.
Worth the fight?
If your project fits inside permitted development, build there: it is the same space without the contest, and the certificate gives you the paperwork. If it will not fit, or you are on designated land, or you live in a flat, you are applying, and the ladder tells you what that means. A conservatory application is genuinely easy terrain. A loft application is the one where design earns its keep, for exactly the reasons in the refusal pile: the roofline, the front elevation and the neighbours are where applications live or die, and that is a design problem before it is a paperwork problem. Our extension guide has the honest version of when an architect earns the fee and when a technologist or an experienced builder is the sensible route; the same logic applies one storey up. And whatever you decide, your own council's record for lofts and conservatories is public: our planning odds pages show it council by council, counting every decided application for that project whatever the application type, which is a wider net than the full-applications basis on this page; the methodology page explains the differences.
Questions homeowners ask
Do I need planning permission for a loft conversion?
Often not. In England, a loft conversion on a house is permitted development if the added roof space stays within 40 cubic metres on a terraced house or 50 on others, no dormer extends beyond the front roof slope facing the road, nothing rises above the existing ridge, and you are not on designated land or in a flat. Outside those limits you apply, and of loft applications decided in the last five years, about 4 in 5 were approved. Building Regulations approval is always needed either way.
Do I need planning permission for a conservatory?
Usually not. A conservatory counts as an extension in planning law, so the single storey rear extension limits decide it: within them, it is permitted development on a house in England. Where an application is needed, conservatories are the easiest terrain in our records: more than 9 in 10 decided in the last five years were approved.
Why do loft conversions get refused?
The refused applications we sampled cluster around visibility: dormers on the front slope facing the street, roofs raised to gain headroom, and lofts inside much larger schemes where the whole scheme was the problem. A refusal is a scheme refused, not a homeowner blacklisted; a refused scheme can be redesigned and resubmitted, typically with the street-facing elevation tamed.
How long does a loft conversion application take?
Of loft decisions made in the last five years in our records, half came within 64 days of the application appearing in the council's register, and 9 in 10 within about 135 days. That is about a week slower than a conservatory at the median, and about as long as full applications generally. The figures describe decided applications; agreed extensions of time are common on the slower ones.
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