Documents for a swimming pool building in a rear garden

An enclosed pool building in a back garden is an outbuilding in planning terms, so the garden swimming pool building documents you need depend first on whether it fits inside Class E of Schedule 2 Part 1 of the General Permitted Development Order 2015. Many do. The ones that do not usually fail on height, on the proportion of garden covered, or because the plant makes enough noise at the boundary to need assessing whether or not the building itself is permitted.

The plant is the part nobody plans for. A building can be entirely lawful while the pump running at six in the morning generates a statutory nuisance complaint.

Whether the building falls within permitted development

Class E covers buildings and enclosures within the curtilage of a dwellinghouse required for a purpose incidental to the enjoyment of the dwellinghouse. A swimming pool is expressly within that idea, and the Order refers to swimming pools and enclosures in the class.

The conditions are what decide it. The building has to be to the rear of the principal elevation. It cannot have more than one storey. Height limits apply, with a lower maximum where any part of the building is within 2 metres of the curtilage boundary. No verandas, balconies or raised platforms above a stated height. And the total area covered by buildings within the curtilage, other than the original house, is capped at half the curtilage area excluding the ground the original house stands on.

Class E is withdrawn or restricted in several situations. On designated land, which includes conservation areas, National Landscapes, National Parks, the Broads and World Heritage Sites, buildings at the side of the house are excluded and other limits tighten. An Article 4 direction can remove the right entirely. And for a listed building, listed building consent is required for works affecting the building or anything within its curtilage, whatever the Order says about planning permission.

Our note on when a garden office stops being incidental covers the incidental test itself, which applies to a pool building in the same way. A pool building used as a gym and a home office with a pool in the corner may not be incidental at all.

Curtilage coverage and height limits

Two measurements decide most cases, and both should be done properly rather than scaled off a title plan.

Coverage: measure the curtilage, subtract the footprint of the original house, halve the result, then add up the footprint of every existing outbuilding plus the proposed pool building. A pool building is large, and an existing garage and shed can already have used most of the allowance. Pool surrounds, decking above the stated height and plant enclosures all count if they are buildings or enclosures.

Height: the roof form matters because the maximum depends on whether the roof is dual-pitched, and the height is measured from the highest ground level adjacent to the building. On a sloping garden that reference point is not where people assume. And within 2 metres of the boundary the maximum drops sharply, which for a building needing internal height over a pool usually means moving it inboard rather than lowering it.

Where the building will be close to a boundary that has never been settled, read our note on disputed boundaries and permitted development measurements before you commit, because a few hundred millimetres decides the height limit.

Plant noise to the neighbouring boundary

Pool plant runs long hours and is often housed in a lightweight enclosure against a fence, which is the worst place for it.

The sources are the circulation pump, the heat pump or boiler, the dehumidification unit in an enclosed pool hall, and any automatic cover motor. Air source heat pumps for pool heating are considerably larger than domestic space heating units and they run at night when background levels are lowest.

Where houses are close, an assessment against BS 4142:2014+A1:2019 comparing the rating level with the measured background at the nearest neighbouring window is the document that answers an objection. A Noise Impact Assessment is worth commissioning before submission where the plant will be within a few metres of a boundary or where the neighbour has already raised it.

Design fixes that work: put the plant room inside the pool building rather than in a separate enclosure, locate it on the elevation furthest from neighbours, specify units by sound power level rather than by brand, fit anti-vibration mounts and flexible connections, and set a timer so the pump does not run overnight. Acoustic louvres on plant room ventilation cost little at design stage and are awkward to retrofit.

Note that the separate permitted development right for domestic air source heat pumps under Part 14 has its own conditions, including noise requirements, and heating a swimming pool may fall outside what that class allows. Check it rather than assuming the heat pump is covered.

Drainage, backwash and discharge

Pool water is not clean water and it cannot simply go to a soakaway or a watercourse.

Backwash from the filter carries chlorinated water and solids. The normal route is a connection to the foul sewer, which needs the sewerage undertaker's agreement, and undertakers usually want flow rates and a description of the discharge. Emptying the pool for maintenance produces a far larger volume, and the discharge arrangement has to cope with it or be staged.

Where there is no foul connection and the property is on a septic tank or package treatment plant, chlorinated water will damage the biological process. The options are a separate holding tank with tankered removal, dechlorination before discharge, or a soakaway designed specifically for the purpose with the environmental regulator's position checked. Do not assume.

Surface water from the roof of the building is a separate question. On a large pool building the roof area is enough to change the site's runoff, and where the garden already floods or the plot is constrained, a Drainage Strategy may be needed even for a householder scheme.

Trees and root protection in the garden

Mature garden trees are the constraint most often discovered after the slab is designed.

A pool needs an excavation, and an excavation inside a root protection area is exactly what a tree officer will refuse. Where a tree is protected by an order, or the property is in a conservation area where trees above a size threshold are protected through a notification procedure, works affecting the tree need consent or notice in their own right.

Get a survey to BS 5837:2012 before fixing the pool position. It costs far less than moving a design, and where the tree is protected, a Tree Survey and Arboricultural Impact Assessment with a tree protection plan will be expected with any application. Where a tree shows ageing features, the protection is stronger still.

Flood risk on a constrained plot

Check the flood zone before design. A pool building in Flood Zone 2 or 3 will need a flood risk assessment, and on a small plot the question of whether the building displaces floodwater onto neighbours is a real one rather than a formality.

Surface water flood risk matters as much as river flooding in gardens, because a large impermeable roof and a paved surround change how water moves across a small site. Where the site is within a critical drainage area, the authority may require attenuation even for a householder development.

Where a full application is needed

A full householder application is required where the building exceeds a Class E limit, where the right has been withdrawn by an Article 4 direction, on designated land in the situations the class excludes, where the use is not genuinely incidental, or where the proposal includes anything outside the class such as a significant level change or a separate access.

Even where the building is permitted development, a lawful development certificate for proposed use or development under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm it, and it costs half a planning application fee. On a building of this size and cost, it is worth having before you dig.

PlanScope can draft the supporting documents for the application, with flags where site data is missing, and the drafts should be reviewed before submission. Enter your postcode on PlanScope to see which reports a garden building on your plot is likely to need.

This is general guidance, not legal advice. A lawful development certificate is the only formal way to confirm that works are lawful. 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.