Ask "are polytunnels allowed on allotments?" in any plot-holders' forum and you will get a dozen confident answers that contradict each other. The reason runs simple. No single national rule exists. Polytunnel allotment rules are set in two layers: the council that leases the land, and then the site committee or association that runs your patch. What sails through on one site can be refused on the next street over.
Below, you will find how those two layers work, the sizes that tend to get approved, why committees restrict tall film tunnels in the first place, and the rigid lower-profile structures that usually pass where a polytunnel does not. No invented statistics, no claim of a blanket ban. Just the rules as they read, plus exactly where to check the ones that apply to your own plot before you spend a penny on a frame.
Are polytunnels allowed on UK allotments?
Usually yes, with written permission first. Most sites permit polytunnels but cap the size, and some ban them for sightline, wind or community reasons. There is no national rule: each council lease sets conditions, then your individual site committee sets its own. Always check your tenancy agreement before you buy anything.
The National Allotment Society does not impose a universal structure-size rule. Its general view is that sheds under 12 sq m and greenhouses under 15 sq m, without foundations or service connections, should not need local-authority approval. Treat that as a starting point, not a guarantee. Your site can be stricter, and many are.
The two layers you are dealing with
- The council lease sets the legal conditions for the whole site, including what counts as a permitted structure and any planning triggers.
- The site committee or association then interprets and tightens those conditions for your plot, often via a written structure application. Rules around structures rank among the most variable and most contested on any allotment site.
Because volunteers who live alongside the plots run that second layer, it tends to hold the real limits. A committee that has had three torn covers blow across the path in a wet winter writes tighter rules than the council ever did.
Do I need permission to put up a polytunnel?
Almost always, yes. The standard process runs as a written structure application to your committee or the council allotments office, approved before you erect anything. Friern Barnet, for example, asks plot-holders to complete a Structure Application Form and receive back an approved copy signed by a committee member. Bristol asks you to contact the Allotments Office for permission first.
Skip that step and you risk being told to take the tunnel down at your own cost. The application is also where size caps, siting rules and material rules get spelled out for your specific site, so it doubles as the answer to most of the questions a plot-holder asks.
The "two structures" pattern
A common committee rule caps each plot at two structures: one shed, plus either one greenhouse or one polytunnel, never both. Friern Barnet sets a maximum of two structures. Birmingham and Woodley both run the shed-plus-one rule. If you already have a shed and a greenhouse, a polytunnel may simply not be permitted, whatever its size.
What size polytunnel is allowed on an allotment?
It depends entirely on your site, and the figures vary widely. There is no standard limit. The examples below are real caps from named sites, included to show the range, not a norm you can apply anywhere. Only your own tenancy agreement binds your plot.
| Site (example only) | Polytunnel cap | Greenhouse cap |
|---|---|---|
| Friern Barnet Central | 2 m high × 2.5 m wide × 4.6 m long | Counts toward the two-structure limit |
| Horfield & District | 12 sq m (14.3 sq yd) | 5 sq m (about 6 ft × 8 ft) |
| Common committee restriction | 8 ft width limit | Varies by site |
Notice how widely those differ. One site measures the whole envelope in metres, another caps floor area, a third polices width alone. Read your own rules rather than borrowing a neighbour's.
Planning permission is a separate question
Site rules and planning law run on separate tracks. For a domestic or allotment polytunnel, planning permission is generally not required unless the structure is over 3 m high, sits within 2 m of a boundary while over 2.5 m high, stands forward of the house frontage, or covers more than 50 per cent of the surrounding area. On most allotments the site committee's cap bites long before the planning thresholds do, so the committee rule is what you plan around.
Why do allotment sites restrict polytunnels?
Restrictions come down to four practical worries: height blocking light, wind tearing covers, glass breakage and the look of the site. None of these reflect a dislike of polytunnels. They come down to keeping a shared space workable for everyone who pays rent on it.
Height and sightlines
A tall structure can cast shade onto a neighbour's beds or an adjacent private garden, which generates complaints. Committees often require structures sited to the rear of the plot, away from paths and boundaries. Birmingham, for instance, asks for a gap of at least 60 cm (2 ft) from a private-garden boundary. Both committees and planning officers watch height most closely of all.
Wind and torn covers
Film stretched over a frame stays light and large, which makes it a sail. When a cover tears in high wind it scatters litter and a hazard across neighbouring plots, and the rules usually require prompt repair or replacement. Sites that have spent a winter chasing flapping, shredded covers across the paths tend to write the tightest polytunnel clauses of all.
Glass and appearance
- Some sites require greenhouse glazing to be polycarbonate or plastic and ban glass outright as a breakage hazard. Horfield states glazing must be polycarbonate or plastic, with glass not allowed because it shatters dangerously if broken.
- Associations also limit numbers and sizes openly, to avoid too many structures, which they say can create problems within the community and for residents living near the plots.
Where do I check the rules for my plot?
Two places, in this order: your tenancy agreement, then your site committee. The agreement should state what you are allowed to have. If anything is unclear, ask the allotment provider you pay rent to. The RHS and the National Allotment Society are the recognised bodies for general guidance, and allotment law itself differs between England, Scotland and Wales.
A five-minute read of your own agreement settles more arguments than any forum thread. If it caps structures at two, or bans glass, or sets a width limit, that is your answer regardless of what a site three streets away allows. Where the wording reads vague, get the committee's view in writing first.
What passes where a polytunnel does not?
Where a tall film tunnel is restricted, a rigid, lower-profile, glass-free structure often meets the same site rules. The two that come up most are a compact polycarbonate greenhouse and a low close-arch structure. Both keep height down, both avoid glass, and both remove the torn-cover problem that worries committees.
A compact polycarbonate greenhouse
A small footprint fits inside common size caps. A 6 ft × 4 ft greenhouse measures roughly 1.92 m × 1.32 m, about 2.3 to 2.5 sq m of growing space, comfortably under the 5 sq m greenhouse cap in the Horfield example. Polycarbonate also satisfies the common "no glass" rule and resists shattering. It transmits around 83 per cent of light against roughly 90 per cent for glass, a modest trade-off for a real safety and compliance gain.
If you are weighing the glazing decision, our guide to polycarbonate versus glass for a UK greenhouse covers the light, safety and longevity differences in full. For sizing your plot, what size greenhouse do I need walks through footprint against growing ambition.
A low, rigid arch instead of a tall tunnel
Height gates approval for both committees and planning, so a structure that keeps its profile down clears the rules more easily than a tall film tunnel. A close-arch rigid frame holds a low silhouette while still giving walk-in or duck-in cover, depending on the model you choose.
A maintenance argument runs alongside it. A polytunnel cover typically carries only a 4 to 5 year UV warranty and lasts around 5 to 10 years before it needs replacing. That adds a recurring cost and a recurring torn-cover compliance risk that a rigid panel avoids. For a fuller look at the rigid options, our polytunnel versus polycarbonate greenhouse comparison sets out the trade-offs side by side.
Ventilation still matters, whatever you build
A rigid structure needs airflow as much as a tunnel does. The RHS rule of thumb for greenhouse roof vents is to size them to about 15 to 20 per cent of the floor area, ideally on both sides of the ridge. At a 1 sq m vent per 5 sq m of floor, you get roughly one full air change every two minutes. For a polytunnel, leaving about a 5 cm (2 in) gap above the doors keeps a little air moving end to end without a ground-level draught.
If your site allows a rigid structure, our SteelRoot galvanised steel arch greenhouse is one honest option to weigh: a low close-arch frame in galvanised steel with twin-wall polycarbonate glazing, no glass to fall foul of a site ban. It is one route, not a recommendation over any other. The advice in this guide works whatever greenhouse you end up buying, and your tenancy agreement still comes first. Delivery is typically 1 to 2 weeks, free to the UK mainland.
Polytunnel or rigid structure: which fits the rules?
Use this as a quick read against your own site rules, then confirm with your committee. A polytunnel can still be the right choice on a site that allows it at the size you need. Match the structure to the rules you actually have, not to the rules you wish you had.
| Factor | Tall film polytunnel | Low rigid greenhouse / close arch |
|---|---|---|
| Height/sightline rules | Often the sticking point | Lower profile, easier to site |
| Glass bans | Not affected (film, not glass) | Met by polycarbonate glazing |
| Wind and torn covers | Recurring cover-tear risk | Rigid panels, no cover to tear |
| Cover replacement | Every 5 to 10 years | Panels, no scheduled re-cover |
| Cost to enter | Lower upfront | Higher upfront, fewer recurring costs |
One honest note on our own range. We do not sell mini or patio bench units. The smallest NORDIC is an 8 ft × 6 ft walk-in, a proper small greenhouse rather than a tiny shelf structure, for plot-holders who want a walk-in and have the room for one within their site rules.
What to do before you buy
Read your tenancy agreement today and note three figures: the structure limit, any height or width cap, and whether glass is banned. Then send your committee one email describing exactly what you plan to put up and where, and get the approval in writing. Those two steps, done before you spend a penny, separate an approved structure from one you are told to dismantle in March. If your site caps a polytunnel at 8 ft wide or 2 m high, a low rigid greenhouse under 5 sq m is usually the structure that clears the rule.
If your site allows a rigid structure, our polycarbonate polytunnel buyer’s guide covers what to look for.
