Commuted sums for open space maintenance explained

A commuted sum for open space maintenance is a one off payment, secured through a section 106 agreement, that pays for looking after public open space once the council takes it on. Most authorities derive it the same way: an annual maintenance cost per square metre for each type of planting or surface, multiplied by a commutation period of 10, 15 or 20 years. If your scheme creates any public green space that the council will adopt, assume the open space commuted sum will appear in the heads of terms and that it will land in the appraisal as a lump sum due on transfer or on first occupation.

What catches developers out is not the principle. It is the size of the figure once a play area with equipment, a swale and two hectares of species rich grassland are priced over 20 years and indexed from the date of the agreement.

Why authorities ask for a maintenance payment

A council that adopts your open space inherits a permanent revenue cost it did not budget for. Grass cutting, annual play equipment inspections, tree safety surveys, litter and bin emptying, path repairs, pond and swale clearance, replacement planting where things die. None of that stops after the sales suite closes.

Planning obligations have to pass the three tests in regulation 122 of the Community Infrastructure Levy Regulations 2010 and in section 106 of the Town and Country Planning Act 1990. The obligation must be necessary to make the development acceptable in planning terms, directly related to the development, and fairly and reasonably related in scale and kind to it. A maintenance sum for space that exists only because of your scheme usually clears all three without argument.

Where it gets contestable is scope. A payment towards upgrading an existing park half a mile away is a different proposition from maintaining the land you are handing over, and it needs its own justification against the same tests.

How the sum is usually derived

The arithmetic is almost always the same shape, whatever the authority calls it:

• measure each maintenance typology separately (amenity grass, meadow, shrub beds, hedge, woodland, hard paths, play area, sports pitch, attenuation feature)
• apply the authority's published annual rate per square metre or per item for that typology
• multiply by the commutation period set out in the council's open space supplementary planning document
• add a sinking fund for items with a replacement cycle, play equipment above all
• index from the date of the agreement to the date of payment

Illustrative example. A scheme transfers 3,200 m² of amenity grass and 900 m² of shrub and hedge planting, plus one local area for play. Using an assumed rate of £1.20 per m² per year for grass and £3.00 per m² for shrub, purely to show the arithmetic, the planted areas alone generate £6,540 a year. Over a 15 year commutation that is £98,100 before the play equipment sinking fund and before indexation. The rates here are assumptions, not a quoted schedule. Your authority publishes its own, and they move.

That arithmetic is also where the design team earns its fee. Species rich meadow cut twice a year costs less to maintain than mown amenity grass cut sixteen times, and it scores better on biodiversity. Changing the planting specification at the masterplan stage, rather than after the heads of terms are agreed, is the cheapest lever you have.

Transfer to the authority against a management company

There are two mainstream routes, and a hybrid that is becoming more common.

The management company route avoids the commuted sum, which is why so many volume schemes use it. It does not avoid the cost. It moves the cost onto the eventual residents through an estate rentcharge or a service charge, and it moves the reputational risk onto you for as long as you hold any part of the estate.

Councils are not uniformly keen on adoption either. Several have quietly stopped adopting new open space altogether, or will adopt only land laid out to their own specification and only where the commuted sum is paid in full before transfer. Ask the parks or green spaces team early, in writing, because the development management officer often does not know the current position.

Resident service charges as the alternative

An estate charge on a freehold house is a durable obligation, and buyers and their conveyancers now read it carefully. Expect questions on the annual figure, the mechanism for increases, who audits the accounts and what happens if the managing agent stops performing.

The Leasehold and Freehold Reform Act 2024 introduced new rights for freeholders paying estate management charges, including rights to information and to challenge costs, with provisions brought into force in stages. Check what has taken effect before you rely on a particular drafting approach.

For the appraisal, the honest comparison is not "free versus expensive". It is a known capital cost now against a sales risk and a long tail of management obligation. An Open Space Assessment that sets out the typologies, areas and intended stewardship route early makes that comparison possible at the point it still influences the layout.

Securing the arrangement in the obligation

Whichever route you pick, the drafting decides how much it actually costs you. The points worth fighting over:

1. The payment trigger. On transfer, on first occupation, on the fiftieth occupation or in phased tranches tied to the phase that creates the space.
2. Indexation. Which index, from which date, and capped or uncapped.
3. The specification. A schedule of the works, areas and standards the sum is calculated against, so the figure cannot drift upwards after agreement.
4. The transfer mechanics. Who pays the legal costs, what title is transferred, and what condition the land must be in on handover.
5. Step in rights. What happens if the management company fails, and whether the council can call on a bond or a further payment.
6. The management plan. Who approves it, on what timescale, and whether approval is a precondition to transfer.

A clause that ties the sum to an indexed schedule of rates "current at the date of payment", with no cap, is a blank cheque on a scheme that takes six years to build out. Push for the rates fixed at the date of the agreement.

Long term liability and who holds it

Biodiversity net gain has changed the conversation. Under the Environment Act 2021 regime, significant on site habitat has to be maintained for 30 years and secured through a planning obligation or a conservation covenant, with monitoring and reporting. That sits alongside, not instead of, the amenity maintenance arrangement, and the two are frequently muddled in draft agreements.

Work out early whether the same body is holding both duties. A Biodiversity Net Gain Assessment that identifies which parcels carry the 30 year obligation will tell you whether the council is willing to adopt them at all, because many authorities will not take on land with a habitat management liability attached.

And if the numbers are tight, the maintenance sum belongs in the Viability Assessment alongside affordable housing and the rest of the section 106 package, not as an afterthought discovered at engrossment.

Choosing the route early

Decide the stewardship route before the layout is fixed, not when the agreement is being drafted. The questions to settle at pre-application are which parcels are intended for adoption, what the council's published rate schedule and commutation period are, whether its parks team is accepting new land this year, and which parcels carry a 30 year habitat obligation.

Budget alongside the other cash calls on the scheme. The application fee itself is a small item next to this, though it is worth knowing how planning fees are indexed each April and what the full application fee will be on your floorspace and site area when you phase the spend.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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