Source, read, constrain, offer
Barn conversion permitted development, the envelope and class Q sheets and the site file, built for the developer who reads a plot before the offer
Curtilo is for the person who reads plots in England and Wales for a living: the small developer with a barn on the market and one question first, the land sourcer with a spreadsheet of sites and a column of guesses, the self-builder with a house whose side return looks wide enough.
Free for 14 days. No card needed.
- No account
- No card
- No sign-up
Curtilo Pro is £49 per month for your whole team, billed monthly.
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- free tools on this site the answer is never behind a login, because the offer goes in whether or not the developer signed up
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- providers' own published prices, compared in the Permitted Development Limits
- £49
- per month, whole team Free: £0
- The small developer, land sourcer or self-builder in England and Wales who reads a plot before making an offer, with a barn, a wide side return or a field edge in front of them and a spreadsheet of sites to keep
- Not the applicant running an application through the authority, not a homeowner with a project question and no site, not an ecologist, not a resident after a council service, not a landlord after a yield, and not anyone looking for a legal opinion or a valuation of a named plot
Tools
The sheets a plot is read with before the offer
The free sheets on this site read the extension envelope on a house from its own width, depth and curtilage, and the class Q route on an agricultural building from its own floorspace and the dwellings proposed, with no account.
Then the paid plan keeps the site file as the record, so the curtilage, the rights read, the constraints found and the offer made stop living in a spreadsheet and a browser tab on the council's map.
- Free Side extension permitted development: the envelope sheet Put in whether the house is detached, its width and depth, the curtilage around it, the outbuildings already on it and whether it sits on designated land, and see the rear depth, the side width, the outbuilding room and the ground floor area the plot may gain without an application. 212Ground floor area the plot can gain without an application, square metres
- Free Class Q permitted development: the barn conversion sheet Put in the agricultural building's floorspace, the dwellings proposed, the rear wall an extension could run along and what the holding has already converted, and see the floorspace per dwelling, the headroom under the caps, the dwellings left and the extension the class allows. 150Floorspace per dwelling, square metres (the class Q per-dwelling cap applies)
Free to use. No account, no card, no sign-up.
In figures
Permitted Development Limits
7 to 56day
Range of the published figures
7 sources with a published figure, read 18 October 2026.
Curtilo Pro
£49
per month, whole team
The sheet is yours. Curtilo Pro keeps the plot it read.
Upgrading turns the sheet into the record. The envelope sheet becomes a plot with an address on it; the class Q sheet becomes a reading the file keeps against the barn and its holding; every constraint found is recorded against the plot with the date and where it was read; the appraisal and the offer sit on the same file. Export is always available, so the site history is yours whether or not you stay.
- Send an envelope sheet or a constraints schedule from inside the record
Free for 14 days. No card needed.
Curtilo Pro is £49 per month for your whole team, billed monthly. Billed monthly. Cancel any time from your account page. Price and renewal terms are shown before checkout.
A plot is one record, and it usually lives in a spreadsheet, the agent's particulars and a browser tab on the council's constraints map
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Every house read for what it may gain without an application, before the offer
Most overpaid plots were bought on a side return that turned out to be on designated land, or an outbuilding scheme that the half-curtilage rule had already used up. Reading the rear depth, the side width and the outbuilding room from the house's own measurements, and writing the reading down, is the appraisal, and it is the one most developers make after the completion statement.
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Every agricultural building read against class Q's caps and the holding's history
A class Q reading that forgot the conversion the holding already made under the same class is a reading that fails at prior approval. Keeping the floorspace, the dwellings, the extension and what the holding has used against the building, and reading the headroom from them, is what turns a hope into a route.
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Every constraint against the plot it was found on, with the date and where it was read
A tree preservation order found after exchange is a redesign nobody budgeted. Holding the conservation area, the article 4 direction, the order, the green belt line and the net gain position against the plot, with the day they were read, is what makes the next plot in the same authority start from a record rather than a search.