Garage court infill: a four unit application walkthrough

A four unit infill scheme on a redundant garage court lives or dies on three things: whether a refuse vehicle can get close enough, whether the new windows can be placed without overlooking the houses that surround the court, and whether surface water can go anywhere. Policy support for infill on previously developed land is usually the easy part. The walkthrough below follows one such application from first sketch to decision notice.

Everything that follows is illustrative. The site, the numbers and the conditions are composites assembled to show how the pieces fit together, not a record of a real application.

The site and the starting layout

The site is a 0.09 hectare garage court behind a 1960s estate of two-storey semis, bought from the freeholder after the last tenancies lapsed. Eighteen lock-up garages, four of them structurally failed, on a continuous concrete slab with a tarmac apron. Rear gardens of 11 existing houses back onto it on three sides. Flood Zone 1. No conservation area, no listed buildings, no Tree Preservation Order on the site itself.

Access is a 4.2 metre wide tarmac strip between two of the existing semis, 31 metres long, with a 1.8 metre close-boarded fence on each side.

The first sketch put four two-bedroom houses in a terrace along the northern boundary, facing south into a shared parking area. It survived about a week. The terrace put four sets of first-floor windows 9 metres from the rear elevations of the houses to the north, and the parking layout gave the refuse vehicle nowhere to turn.

Access, tracking and the refuse problem

Two separate standards bite here and they pull in different directions.

Approved Document H to the Building Regulations expects a collection vehicle to be able to get within 25 metres of the waste storage point, and the occupier to carry waste no more than 30 metres to that store. Approved Document B expects a pumping appliance to reach within 45 metres of all points inside each dwelling, or shorter hose-laying distances where the appliance cannot get closer.

With a 31 metre access and a shallow site, a vehicle entering the court would have had to reverse out. That is the point at which many highway authorities object, and Manual for Streets discourages reversing manoeuvres on shared surfaces used by pedestrians.

The resolution in this case was to stop trying to bring the freighter in. The layout was redrawn with a bin store immediately inside the access, 4 metres from the adopted kerb line, screened with a brick wall and a timber gate, and a swept-path tracking drawing was prepared showing the freighter stopping on the existing highway with a 20 metre carry distance to the store. Carry distance from the furthest dwelling to the store came out at 27 metres, inside the 30 metre figure.

The access width was increased to 4.8 metres for the first 6 metres by setting back a fence and a hedge, giving a vehicle entering for deliveries or for emergencies room to pass a pedestrian. Fire service access was demonstrated by hose-laying distance rather than by appliance access, with the furthest habitable room 38 metres from the point an appliance could stand.

Four parking spaces plus one visitor space, laid in permeable block paving, with cycle storage in each rear garden. No turning head, because nothing larger than a car needed to turn.

Overlooking and the separation distances applied

The council's householder design guide in this illustration set 21 metres between facing habitable room windows and 13.5 metres between a habitable room window and a blank elevation or boundary. Those figures are common in adopted supplementary planning documents, but they are local, so check the guide that applies before you draw anything.

Nine metres was never going to work. Three moves fixed it.

The terrace was broken into two pairs and rotated so that the main elevations face each other across the court rather than facing the existing rear gardens. That produced 21.4 metres window to window between the new pairs and left blank gables towards the two tightest boundaries.

First-floor rear windows were restricted to bathrooms and a landing, specified as obscure-glazed and top-hung above 1.7 metres from finished floor level. Habitable rooms at first floor were served from the front and the gable ends only.

Rear garden depths were set at 10.5 metres, which put the new rear building line 12.8 metres from the nearest existing rear boundary and 24 metres from the nearest existing rear elevation. A 45-degree test was run in plan and section from the centre of the nearest ground-floor rear window of each affected neighbour, and all four cleared it.

The single-storey rear projections originally proposed on all four units were dropped from two of them. Sometimes the answer is less building.

The boundary trees and what the survey found

Two sycamores and a line of leyland cypress sat on the southern boundary, inside neighbouring ownership with crowns overhanging the court.

A survey to BS 5837:2012 categorised one sycamore as B2 and the other as C2, with the cypress line as C2. Root protection areas were calculated at 12 times stem diameter as a radius, which put the B2 sycamore's protection area across the proposed position of the visitor parking space and part of one rear garden. The tree survey and arboricultural impact assessment carried the calculation, the constraints plan and the method statement.

The visitor space moved onto a no-dig cellular confinement build-up within the root protection area, designed in the arboricultural method statement with the existing concrete slab left in place beneath it as a load-spreading layer. No excavation inside the protection area, no level change, and a tree protection plan showing Heras fencing on the BS 5837 alignment for the duration of works.

Ownership mattered more than the categories. The trees belong to the neighbours, so the applicant had no right to prune them beyond overhanging growth to the boundary, and the scheme had to work with the crowns where they are. A similar sequence, where a protected tree reshaped a driveway rather than a parking space, is set out in the tree that stopped a driveway.

Biodiversity net gain was straightforward in arithmetic and fiddly in evidence. The baseline was almost entirely sealed surface, which scores nothing in the statutory metric, so the 10% gain required under the Environment Act 2021 was met on site through garden planting, a native hedge along two boundaries and a small area of species-rich grassland. The metric and the biodiversity gain plan have to be completed by a competent person and the plan approved by the authority before development begins, so the Biodiversity Net Gain Assessment draft was prepared as a brief for the ecologist rather than as the submitted document.

Drainage with no connection available

There was no public surface water sewer within reach, and the water undertaker declined a new connection to the combined sewer without evidence that infiltration had been tested first.

Infiltration testing to BRE Digest 365 was carried out in three trial pits. Two gave usable rates in the made ground above the clay. The third did not. That split result decided the layout as much as the trees did, because the soakaway had to sit in the two-thirds of the site where infiltration worked, which is where the visitor parking had been.

The final strategy used permeable paving over a sub-base storage layer across the parking court, discharging to a soakaway sized on the measured infiltration rate, with a shallow attenuation void and a flow control as a fallback for the 1 in 100 year event plus the climate change allowance. Climate change allowances are revised periodically, so take the current figure for the relevant river basin district from the Environment Agency rather than from an older report. Exceedance was routed across the surface of the parking court towards the access, away from the dwellings and away from the neighbours' gardens.

The drainage strategy set out the hierarchy, the test results, the calculations and the maintenance arrangements, the last of which the lead local flood authority asked about twice. A scheme where the drainage answer drove the whole layout is covered in a self build plot where drainage decided the layout.

The documents submitted and why

A four unit scheme is a minor application, so the statutory list is short and the local validation list is where the work is.

1. Application forms, ownership certificate B with notice served on the neighbouring tree owners, and the fee.
2. Location plan, block plan, existing and proposed site plans, floor plans, elevations and sections, plus a street scene.
3. Planning statement setting out the development plan position, the previously developed land argument and the housing land supply context.
4. Design and access statement. Not statutorily required for a minor scheme outside a conservation area, and asked for by the local validation list, which is the usual reason it gets written.
5. Arboricultural impact assessment, method statement and tree protection plan.
6. Preliminary ecological appraisal and the statutory biodiversity metric with the gain plan to follow by condition.
7. Drainage strategy with infiltration test results.
8. Swept-path tracking drawing and a refuse and recycling strategy.
9. Construction management plan, because the access passes between two occupied houses.
10. Community Infrastructure Levy additional information form. The 100 m2 minor development exemption does not help here, because the scheme creates new dwellings.

No transport statement. Four units generate too few trips to need one, and the tracking drawing answered the highway authority's actual question.

The conditions attached

Permission came with the usual three year commencement condition under section 91 of the Town and Country Planning Act 1990, plus eleven others. The ones that cost money were the pre-commencement conditions: approval of the construction management plan, implementation of tree protection in accordance with the approved method statement, and submission of the final drainage details with the maintenance plan. The biodiversity gain condition is deemed to be attached and the gain plan had to be approved before work started.

Obscure glazing to the identified first-floor rear windows was conditioned, as was removal of permitted development rights for extensions and roof alterations, which is normal on a tight backland layout where the approved separation distances leave no slack.

Browse all 66 PlanScope report types to see which of them a scheme of this shape normally needs.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.