Outline or full: how unit numbers change the choice
The choice turns on how much design you want to fix, who will build it, and how long the land sits between permission and a start. Scale changes those answers.
The outline or full application choice is not really about scheme size. It is about how much of the design you want to fix now, who is going to build it, and how long the land has to sit between permission and a start on site. Unit numbers matter because they change the answers to those three questions, not because a threshold flips the decision at ten or fifty dwellings.
A single plot goes full. A 400 unit urban extension goes outline. Everything between is a judgement, and it is made more often on the basis of who owns the land than on planning grounds.
What each route commits you to
An outline application establishes the principle of development and reserves one or more matters for later approval: access, appearance, landscaping, layout and scale. Access can be reserved or determined at outline, and determining it is usually wise because the highway authority's position is the one most likely to change a scheme.
A full application fixes everything. The drawings are the permission, and any change afterwards needs a non-material amendment, a section 73 application to vary a condition, or a fresh application.
Time limits differ in a way that matters commercially. A full permission must be begun within three years. An outline permission requires the reserved matters application to be submitted within three years, with development begun within two years of the final approval of reserved matters, so the outline route can carry a longer total runway.
| Consideration | Outline | Full |
|---|---|---|
| Detail fixed at permission | Principle, plus any matters not reserved | Everything on the drawings |
| Typical use | Land promotion, phased schemes, sites sold with consent | Owner-builders, single phase schemes |
| Total runway before a start | Up to five years across the two stages | Three years |
| Cost at permission stage | Lower design cost, same technical evidence | Higher design cost |
| Certainty for a purchaser | Principle established, design open | Fully defined product |
Parameter plans and how tightly to draw them
Parameter plans are the control mechanism on an outline application, and they are where most of the argument happens. They typically fix development zones, maximum and minimum building heights, access points, land use areas and areas of open space.
Draw them too loosely and the authority will refuse, or will impose conditions that recreate the detail you were trying to avoid. Draw them too tightly and you have taken on the cost of a full application without the benefit of a full permission.
The useful discipline is to ask, for each parameter, whether it is the thing that makes the scheme acceptable. Height next to an existing terrace usually is. The precise position of a footpath usually is not. Fix the first, leave the second.
An illustrative masterplan sits alongside the parameters. It is not binding unless a condition makes it so, and applicants should check whether the decision notice does make it so, because that changes what reserved matters can propose.
Evidence required at outline stage
The most common misconception about outline applications is that the technical evidence is lighter. It is not.
Environmental impact assessment screening applies at outline, and where an Environmental Impact Assessment is required it has to assess the worst case the parameters allow, which is why loose parameters create an expensive assessment. Flood risk, ecology, heritage, drainage and transport all have to be resolved at outline because they go to the principle.
A Transport Assessment is needed at outline wherever the trip generation crosses the threshold, and it has to be based on the maximum quantum the parameters permit. The same logic applies to affordable housing, where the Affordable Housing Statement has to address the number of units the parameters would allow rather than an illustrative figure.
Biodiversity net gain deserves particular attention on outline schemes. The gain plan has to be approved before development begins, and for phased development the regime works through plans for each phase against an overall position set at permission. Getting the habitat baseline surveyed and the metric run at outline stage is what makes the phased approach work later.
What is lighter at outline is the architectural work: elevations, materials, detailed landscape design and internal layouts.
Reserved matters timing and expiry
Reserved matters applications for major development carry a 13 week determination period, and they are determined against the outline permission and its conditions rather than against current policy in the round.
Two dates cause problems. The deadline for submitting reserved matters, usually three years from the outline, catches schemes where the site changes hands. And the requirement to begin development within two years of the final approval catches phased schemes where a later phase's approval is obtained early and then not implemented.
Where a scheme is phased, ask for reserved matters to be capable of submission in phases, and check that the wording of the condition permits it. A condition requiring all reserved matters to be submitted in a single application is a trap that has caught a good number of phased schemes.
Conditions imposed at outline and their effect
Conditions attached to an outline permission bind every reserved matters application that follows, which gives them more force than conditions on a full permission.
Read them for three things. Whether any condition effectively fixes a matter that was supposed to be reserved. Whether the conditions that bite before development starts are reasonable, given that they cannot now be renegotiated without a section 73 application. And whether the scheme's phasing is compatible with the conditions' triggers.
A condition requiring a full drainage scheme to be approved before development begins, on a scheme that will be built over eight years, needs to be phased or it becomes an obstacle at every stage.
Cost and programme comparison
Outline costs less at permission stage because the design work is lighter. It costs more in total, because two applications are prepared and determined, and because the reserved matters stage brings its own fee, its own consultation and its own risk.
The commercial case for outline is about land rather than cost. A promoter or landowner who intends to sell the site with permission is selling a principle and a set of parameters, and the purchaser wants freedom to design to their own product. A housebuilder who intends to build what they have drawn wants a full permission and a start on site.
Where the site's deliverability is the issue, the planning position interacts with housing land supply, and our note on housing land supply and site size covers how that plays out.
Committee arrangements change with scale too, and the scheme that goes to committee is the one that takes longer and carries more risk, as set out in our note on committee referral thresholds.
Where a hybrid application helps
A hybrid application seeks full permission for part of a site and outline permission for the rest. It suits schemes where one element has to start soon and the rest will follow: an access road and a first phase in detail, the remainder in outline.
Hybrids are more work to prepare and more work to determine, and they need careful drawing of the boundary between the full and outline parts, particularly where infrastructure crosses it. Where they earn their keep is programme: a spade in the ground on phase one while the market is tested for the rest.
One alternative worth knowing for small sites. Permission in principle, followed by a technical details consent, offers a two-stage route for minor housing development, with its own limits on scale. It is used far less than it might be, and it suits a landowner testing the principle on a small site without commissioning a full design.
Browse the 66 report types to see which evidence each route needs at which stage.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
What are reserved matters?
Access, appearance, landscaping, layout and scale. An outline application establishes the principle of development and reserves one or more of these for later approval. Access is frequently determined at outline rather than reserved, because the highway authority's position is the one most likely to change a scheme once it is examined in detail.
How long does an outline permission last?
The usual position is that the reserved matters application must be submitted within three years of the outline permission, and development must begin within two years of the final approval of reserved matters. That gives a longer total runway than a full permission, which must be begun within three years. Conditions can vary these periods, so read the decision notice.
Is the technical evidence lighter at outline stage?
No. Environmental impact assessment screening applies, and where assessment is required it must address the worst case the parameter plans allow. Flood risk, ecology, heritage, drainage and transport all go to the principle and must be resolved at outline. What is lighter is the architectural work: elevations, materials, detailed landscape design and internal layouts.
Is an illustrative masterplan binding?
Not unless a condition makes it so. An illustrative masterplan sits alongside the parameter plans to show one way the site could be developed. Check the decision notice, because some authorities condition substantial accordance with the illustrative material, which limits what a reserved matters application can propose and changes the value of the permission.
When is a hybrid application worth it?
When one part of a scheme has to start soon and the rest will follow, typically an access road and a first phase in detail with the remainder in outline. Hybrids take more work to prepare and determine, and the boundary between the full and outline parts needs careful drawing where infrastructure crosses it. The benefit is programme.
What is permission in principle?
A two-stage consent route for minor housing development, with permission in principle establishing the principle and a technical details consent dealing with the detail. It carries its own limits on scale and use. It suits a landowner testing whether a small site is acceptable in principle without commissioning a full design, and it is used less than it could be.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.