A feasibility study costs from £475 at Fixed Fee Plans. We test two or three massing options for your house against permitted development limits and your council's rules, and tell you which are worth drawing properly. No survey is needed for the study, so you can see what is possible before spending on one.
The question it answers is simple and expensive to get wrong: how much house can I add, and what will the council say? A feasibility study is a cheaper way to find out than a planning application and a refusal. It can also save you from an extension that the rules already allow without an application.
What can I build without planning permission?
Quite a lot, in many houses, and less than people think in conservation areas. A single-storey rear extension can project 3m from the original rear wall, or 4m on a detached house, under Class A of the General Permitted Development Order. With prior approval the larger home route allows 6m, or 8m on a detached house, outside article 2(3) land. A loft conversion can add 40 cubic metres to a terrace house or 50 to any other.
Those are limits, not entitlements. A council can remove them by an article 4 direction, and a house can have lost them earlier through a condition or an extension from a previous owner. Our desktop check looks for all of these. If a modest option needs no application at all, the study says so, even though an application would earn us more, and our permitted development checker runs the same test free.
What does a feasibility study show?
It shows volumes, not details. Each option is drawn as a simple massing on your plot: a rear extension at 3m, one at 6m under prior approval, a rear extension with a loft room above. Beside each, a table of what it needs: no application, prior approval, or a householder application, with the council's fee.
Timing matters too. A householder application that the council has not decided in 16 weeks earns a fee refund under regulation 9A of the Fees Regulations, unless you agreed a longer period, which tells you how long a consent can take and that a permitted option avoids it. Our note puts that next to the extra floor area each option gives, so you weigh square metres against time and fee, with the householder fee of £548 in the table.
What is not in the study?
A survey and detailed drawings. The study works from public maps, your photographs and any plans you have, so its dimensions are estimates until we measure. If you go ahead, a measured survey is the next step, and the survey is added only then. Our complete planning drawing service is £645 drawings + £150 survey (£795 total).
Nor does the study promise a decision. It tells you where the council's published policies point and where a conservation officer may push back, and it says so when a scheme is a gamble. For a firmer read from the council itself, our pre-application request asks the officer, and a constraints report lists the designations on the address if you only need to know the ground rules.
Is a feasibility study worth it for a small project?
For a single-storey kitchen extension on an ordinary semi, usually not: the limits are well known and our checker is free. It earns its fee on awkward sites: a corner plot, a house with a prior extension, a conservation area, a loft in a terrace, a garden office near a boundary. In those, one wrong assumption costs more than the study.
It is also useful when two options are close. A 5m extension with a roof lantern may need an application, while a 3m extension with a bigger glazed link may not. Seeing both in volume, with the fee and time beside each, makes the choice a decision, not a guess.
Frequently asked questions
How much does a feasibility study cost?
Our fee is from £475, and it is a floor: a large plot or a project with several parts is quoted in writing first. A survey is added only if you go ahead.
Do I need a survey for a feasibility study?
No. The study is a desktop exercise, with dimensions taken from maps and your photographs. A survey comes later if you proceed.
Will the study tell me whether I need planning permission?
Yes, for each option. We mark which are permitted development, which need prior approval and which need a householder application. Where the answer depends on a council's discretion, we say that too.
What happens after the study?
You decide. You can take an option to a surveyor or builder of your choice, or ask us for the measured survey and drawings, and the survey is added to the price only then.