Orangeries
Masonry piers, a lantern roof and a proper perimeter, which is what separates an orangery from a conservatory.
Fig. 01
An orangery is an extension with a lot of glass in it. A conservatory is a glazed box attached to the house. They look similar in a brochure and they are not the same building, because one is built to full Building Regulations and the other is usually built to avoid them. This page explains where the line sits and what it costs to be on the right side of it.
What an orangery actually is
Masonry piers, a substantial insulated roof around a central lantern, and a floor built like the rest of the house.
The name comes from the eighteenth century, when a heated masonry building with tall windows was where you kept citrus trees through an English winter. The modern version keeps three features of that original: solid corners, a mostly solid roof, and a glazed centre to the ceiling.
In construction terms an orangery has brick or blockwork piers at the corners and between the glazed bays, carrying the roof load down to foundations. Between the piers sit windows or doors. The roof is a flat or shallow insulated deck, usually 600mm to 900mm wide all the way round, and the middle of it is opened up for a lantern. Inside, that perimeter is finished as a plastered ceiling with a deep upstand around the lantern opening, which is what gives an orangery its particular look from below.
Underneath, the floor is a proper insulated slab with a damp proof membrane, not a thin screed laid on the old patio. The walls are cavity construction with insulation, or an insulated timber frame behind brick. The glazing is the same specification you would put in any other extension.
Everything on that list is what a house is made of. An orangery is a room of the house that happens to have a glass ceiling, and every rule that applies to a room of the house applies to it.
Orangery, conservatory or glazed extension
Three different buildings, three different prices, and only one of them is right for any given household.
A conservatory is a light structure, usually on a dwarf wall, with a fully glazed or polycarbonate roof and slim frames. It is quick to build, it is the cheapest of the three by a wide margin, and if it is genuinely separated from the house and separately heated it sits outside most of the Building Regulations. It is also the one that is too hot in July and too cold in January, because there is very little material between you and the weather.
An orangery is a masonry extension with a glazed lantern. It is built to the same standards as any other extension, it holds its temperature, and it costs two to three times what a conservatory of the same size costs.
A glazed extension is a conventional single storey extension with large sliding or folding doors and rooflights, and no lantern. It is often the better answer where the roof has to run under a first floor window, or where the house is modern and a lantern would look applied rather than built in.
| Conservatory | Orangery | Glazed extension | |
|---|---|---|---|
| Roof | Fully glazed or polycarbonate | Insulated perimeter deck with a lantern | Insulated deck with rooflights |
| Structure | Frames on a dwarf wall | Masonry piers on foundations | Cavity walls on foundations |
| Building Regulations | Often exempt if separated | Always applies | Always applies |
| Usable in February | With difficulty | Yes | Yes |
| Counts as floor area on a sale | Generally not | Yes | Yes |
Will you need planning permission?
Four questions, an honest answer, and nothing sent anywhere. This runs entirely in your browser.
What are you extending?
Permitted development rights for extensions apply to houses. Flats and maisonettes are a different route entirely.
Is the property listed?
Listed building consent is a separate decision from planning permission, and work without it is a criminal offence rather than a planning irregularity.
Has the house been extended before?
Depth is measured from the ORIGINAL rear wall, so a previous owner's extension has already used part of your allowance. This catches almost everybody.
Is it in a conservation area?
Colchester has a number of them, including the historic core, the Dutch Quarter, part of Lexden and several village centres. The boundaries rarely follow the roads you would expect.
Answer the four questions for an indication
Whatever the answer, Building Regulations approval is always needed. We check the planning history, the designation and the deeds on your address before anyone draws anything, because it decides the design rather than the other way round.
This is an indication based on four questions, not advice on your property. Planning rules change and the position depends on your specific address, its planning history and its designation.
Why the difference is legal rather than decorative
The exemption is real, it is conditional, and the conditions are the whole argument.
A conservatory can be exempt from most of the Building Regulations, and the exemption itself is short. It has to be at ground level. Its floor area must not exceed thirty square metres, so exactly thirty is inside it. And where it is glazed, the glazing and any doors near floor level have to meet the safety requirements of Part K. That is all of it. A second rule sits alongside and does the work everybody credits to the first: the energy efficiency requirements stay off the structure only while it is separated from the house by external quality walls, doors or windows, meaning the doors between the kitchen and the conservatory have to be the sort you would fit on an outside wall and they have to stay there, and only while the house heating system has not been run into it. Heat it on its own controls and that holds.
Take out that door set so the kitchen opens straight into the glazed room, and the protection is gone. What you now have is a badly insulated extension that was never approved, and the whole house is heating a space with a glass roof.
An orangery makes no attempt at any of this. It is a full extension, it is notifiable, and it is inspected. We notify Colchester City Council Building Control and it is signed off and we see the job through to the point where Building Control issue your completion certificate.
The commonest problem we are called to. A conservatory built ten or fifteen years ago under the exemption, with the separating doors removed at some point since. It is not illegal to live with, but it shows up when the house is sold, it makes the room cold, and putting it right generally means rebuilding the roof rather than adding a radiator.
Planning permission and permitted development
An orangery is treated as a rear extension. The same limits apply, and the same measurement catches people out.
Most orangeries fall under permitted development, which means permission has already been granted in general terms provided the work stays within a set of national conditions. Depth is measured from the original rear wall of the house, meaning as built, or as it stood in 1948 for anything older. If a previous owner added a utility room in the nineties, that depth is already spent and it counts against you.
Detached houses are allowed to go deeper than semi detached and terraced houses. Both can go further under the Larger Home Extension prior approval route, where you notify the council, the council writes to the adjoining neighbours, and if someone objects within the consultation period the council decides whether the impact is acceptable. That route runs to 42 days.
Overall height is capped for a single storey rear extension, and there is a lower cap on eaves height where any part comes within two metres of a boundary. On a semi with a fence close to the flank, that limit is frequently what determines the design, because the perimeter roof and the lantern above it both have to fit under it. A lantern that looks right on paper can be the thing that pushes the design out of permitted development.
There is also a limit on how much of the land around the original house can be covered by buildings. Sheds and previous extensions count towards it, and so does a conservatory, because a conservatory is measured under the same rules.
Want this checked on your actual address?
Planning history, designation and deeds. We look at all three before anyone draws anything, and it costs you nothing.
Conservation areas, listed buildings and the deeds
Four separate restrictions, each of which can apply on its own.
In a conservation area permitted development is restricted rather than removed, and the details that go with an orangery, particularly cladding and side extensions, generally lose their permitted status. Colchester has several conservation areas, including parts of the historic centre, Lexden and a number of the surrounding villages.
An Article 4 direction removes permitted development rights for a defined area or for a specific type of work. Where one is in place, work that would be permitted anywhere else needs a full application.
On a listed building, listed building consent is needed separately for anything affecting its special interest, in addition to whatever planning permission the work requires. A lantern on a listed house is a difficult proposition and is decided case by case. It is not a conversation to have after the materials are ordered.
Finally, restrictive covenants on the title are private law. Newer estates around Stanway and Myland often carry them. The council will not check them and planning permission does not override them, but a neighbour or a management company can still enforce one.
Where the work is clearly permitted development, apply for a Lawful Development Certificate anyway. It costs a fraction of a planning fee and it is the document that answers a buyer’s solicitor in ten years’ time. Without one you are relying on somebody’s memory.
These limits change from time to time and how they apply depends on the property. Treat this as an explanation of the system rather than confirmation of what you can build. We check the position on your address before anything is drawn.
The lantern roof and how it is held up
The lantern is the reason for the room, and it is a structural component before it is a feature.
A lantern sits in an opening formed in the flat roof deck. That opening has to be trimmed, which means the joists or beams around it carry the load that the missing middle would have taken, plus the weight of the lantern and its glass. On anything wider than a couple of metres that is a steel or an engineered timber, sized by the structural engineer rather than guessed at on site.
The load then travels through the perimeter roof into a ring beam over the piers, and down through the piers themselves. Piers concentrate load in a way a continuous wall does not, so the foundation beneath each one has to be capable of taking it. That is a design decision at the start, not something to discover when the brickwork is up.
The upstand around the lantern opening matters more than people expect. It has to be insulated as thoroughly as the rest of the roof, because it is a ring of structure sitting between a warm room and a cold sky. Get it wrong and you have a cold line running around the ceiling that collects condensation and eventually mould, in the most visible place in the room.
Lanterns come in aluminium, timber, or timber with an aluminium outer face. Aluminium gives slimmer bars for the same span. Timber suits period houses. Either is fine when the thermal break is properly designed, and neither is fine when it is not.
The same wall, before and after
Drag to reveal. A real job in the Colchester area, photographed as it went. No staging and no borrowed images.
During
Finished
The glazing, and why a cheap lantern is the regret
The lantern is the one item on the job where saving two thousand pounds is felt every day.
Ask for the U-value of the whole lantern, not the centre pane figure for the glass. The centre pane number is always the flattering one, because it ignores the bars, the frame and the perimeter, which is where a lantern loses most of its heat. A good lantern and a poor one can show similar glass figures and behave completely differently.
The units themselves want a soft coat low emissivity layer, a warm edge spacer rather than aluminium, and an inert gas fill. On a glazed roof the outer pane is normally toughened and the inner laminated, so that a failure overhead stays in place rather than coming down.
The other half is water. A lantern has to drain, and the good ones have positive drainage channels in the bars that take condensation and any wind driven water out to the outside face. Cheap lanterns rely on the seals alone, and seals age. The complaint that follows is usually described as a leak when it is condensation running off the bars.
Then there is the noise. Rain on a slim glazed lantern set into an insulated deck is a pleasant sound. Rain on a large polycarbonate roof is not.
If you are comparing quotations, ask each builder for the lantern make up in writing: the overall U-value including frame, the glass specification, whether the outer pane has a solar control coating, and whether it includes an opening vent. Two prices with a five thousand pound gap are usually two different roofs.
Part L, and the glass budget
There is a limit on how much of an extension can be glass, and an orangery is designed around it.
Part L limits the total area of windows, doors and rooflights in an extension to a proportion of its floor area, with an allowance added for any existing openings in the wall you are covering over. A typical orangery, with glazed bays between the piers and a lantern above, gets close to that limit and sometimes exceeds it.
Exceeding it is allowed, but not for free. You then have to demonstrate that the extension performs as well overall as a compliant one would, which is done by calculation and paid for by improving something else: better glazing units, more insulation in the roof and floor, or a smaller solid wall build up with a higher performing insulation. That is a design decision with a price attached, and it is settled before the drawings are finished rather than argued about later.
This is also where the perimeter roof earns its place. Because an orangery has 600mm or more of well insulated deck all the way round, it has real thermal fabric to trade against the glass in the middle. A conservatory has none, which is precisely why it needs the exemption instead of compliance.
The floor is the quiet part of the same calculation. Insulation under a slab is cheap while the ground is open and impossible to add afterwards. On a room with a glass ceiling it is worth going beyond the minimum.
Five things you can check yourself.
Trust on a building job should be verifiable, not asserted. Every one of these can be confirmed without taking our word for it.
-
01
Real company
Essex Probuild Ltd, company 15979928, registered in West Bergholt. Checkable on Companies House in a minute.
-
02
Real cover
£2m public liability cover in place. Evidence available on request rather than a badge on a website.
-
03
Real reviews
4.6 out of 5 on Google from 10 reviews, shown as they were left. We do not curate them.
-
04
Real photographs
Every project image on this site is a job we built. No stock, and no fabricated before shots.
-
05
Real accountability
We notify Colchester City Council Building Control and manage the inspections through to your completion certificate.
The July problem, which no regulation will catch for you
Overheating is the defining practical risk in a highly glazed room, and it is designed out rather than fixed later.
Approved Document O covers overheating in new dwellings and does not apply to an extension of an existing house, so nothing in the regulations will stop you building a room you cannot sit in. The physics does not care about that exemption. A south or west facing lantern over an open plan kitchen will take a large amount of solar gain on a July afternoon, and glass overhead collects far more of it than a vertical window of the same area.
Three things actually work. The first is solar control glass in the lantern, chosen by its g-value, which is the proportion of solar energy it lets through. A neutral solar control coating on the outer pane cuts that substantially with very little change in how the light looks. It costs a few hundred pounds more at the point of order and it is the single most effective decision available.
The second is ventilation at high level. Hot air collects at the top of the room, so an opening vent in the lantern itself, ideally one that can be operated remotely and closes on a rain sensor, lets it out. Opening a door at floor level does very little on its own.
The third is orientation. A north facing orangery can take as much glass as you can justify, because the light is even and it never bakes. On a south west elevation the honest advice is a smaller lantern, deeper perimeter roof and better glass.
Blinds are a comfort measure, not a solution. Fitted inside the glass, the heat is already in the room.
Heating, and whether it works in February
This is the whole reason for building an orangery instead of a conservatory.
The test of any glazed room is a wet Tuesday in February. A conservatory fails it, which is why so many of them are used for storing bicycles by their third winter. An orangery passes it, because it has insulated walls, an insulated roof around the lantern, an insulated floor and a heating system connected to the house.
Underfloor heating suits an orangery better than radiators for two practical reasons. The floor is being built from scratch, so the pipework and the insulation go in as part of the slab at no extra disruption. And there is very little solid wall to put a radiator on, because the space between the piers is glass. Underfloor also warms the surface people actually stand on, which matters in a room with a lot of cold glass overhead.
It works best under tile or stone, and it is a slow responding system, so it wants a programmable thermostat and its own zone rather than being run off the hall.
The wider point is the existing boiler. Adding twenty five square metres of heated space increases the load on a system that was sized for the house as it was. On an older boiler that is worth checking rather than assuming, and it is a question we raise early because the answer occasionally changes the budget.
What might it cost?
A realistic range rather than a single number, with what it excludes shown as prominently as what it includes.
£44k to £60k
- VAT
- Kitchen and appliances
- Flooring
- Decoration
- Drawings and calculations
- Planning and Building Control fees
- Party wall surveyor
- Service diversions
Indicative only. The biggest variable around Colchester is foundation depth, because most of the ground is shrinkable clay and mature trees are common. We price the job after seeing it.
Get a real price
Foundations, Essex clay, trees and drainage
The most expensive variable on the job is invisible until somebody digs.
The ground around Colchester is mostly shrinkable clay. It swells when it takes on water and shrinks when it dries, and near the surface that seasonal movement is significant. A foundation founded inside that zone moves while the house, founded deeper, does not, and the extension cracks away from it. On an open site with no trees nearby the usual answer is a trench fill foundation around 900mm deep, though the exact figure depends on the plasticity of the clay.
Mature trees change the arithmetic entirely. An oak, poplar, willow or elm draws a large volume of water out of the ground across a summer, and its zone of influence extends well beyond the canopy. Depth is then set by species, mature height and distance, and can reach two and a half metres or more, or move to piles with a suspended slab. Removing the tree is not a shortcut: ground dried for decades takes that water back and swells, and heave does more damage than settlement.
Piers make this sharper than on a normal extension, because the roof load arrives at the foundation in concentrated points rather than spread along a wall.
On drainage, if the orangery is built over or within three metres of a public sewer you need a build over agreement from Anglian Water, which is a separate application with its own timescale and may require a survey of the drain. Private drains still have to comply with Part H, and an inspection chamber inside the new footprint is either moved or fitted with a sealed double sealed cover with access maintained.
The opening into the house
Whether you knock through, and how far, is a bigger decision on an orangery than on any other extension.
Removing the old rear wall is what makes the new room part of the house rather than a room you visit. That wall carries floor joists and often roof load, so it goes into a steel beam bearing onto padstones, sized by the structural engineer, with the masonry below the bearings checked and strengthened where it is not adequate.
The judgement call is different here. Some households genuinely want a separate room: somewhere warm and quiet away from the kitchen noise, with doors that shut. Keeping a door set is a legitimate choice rather than a compromise, and on an orangery it costs you nothing in compliance terms because the room is built to full standards either way.
What we would not do is keep the doors while building to conservatory standards, and then take them out a year later. That is the sequence that produces the cold, unapproved room described earlier.
If you are opening up fully, think about where the boiler flue, the soil stack and the kitchen extract currently run, because all three tend to be on the wall that is coming out.
Get a real number, not a range.
We come out, look at the ground, the access and the structure, and price the job we have actually seen. The survey and the quotation are free.
What an orangery costs
A range with its basis stated, because a single figure from someone who has not seen the house is worthless.
Costs move with materials, labour and specification, so treat this as indicative at the review date at the foot of this page rather than as a quotation.
As a broad guide, an orangery on reasonable ground with decent access runs £2,800 to £3,800 per square metre. That is above a plain single storey extension, and the difference is the lantern, the extra glazing, the pier and ring beam structure and the higher standard of finish that a room like this usually gets. Difficult access, deep foundations near a protected tree, a large lantern or a high specification push above the range.
The price normally includes: setting out, excavation and foundations to the depth the ground requires, drainage connections, the slab with insulation and damp proof membrane, piers and cavity walls, the ring beam and roof structure, the insulated warm deck roof and its covering, the lantern and the glazed bays, plastering including the lantern upstand, electrics and heating to a standard specification, and making good where the new work meets the old.
It normally excludes: VAT, kitchen units and appliances, floor finish, decoration, professional fees for drawings and structural calculations, planning and Building Control fees, the Anglian Water build over fee where one applies, party wall surveyor fees if a neighbour dissents, landscaping, and anything genuinely unforeseeable found once the ground is open.
How long it takes
Roughly two months of paperwork you can overlap, then ten to sixteen weeks on site.
Before anything starts, a householder planning application has a statutory determination period of eight weeks from validation, prior approval runs to 42 days, and Building Regulations full plans approval runs alongside. A build over agreement adds its own period. These overlap and we run them in parallel where we can, but the front end is realistically two months and sometimes more.
On site, an orangery commonly runs ten to sixteen weeks from breaking ground. It is a little longer than a plain extension of the same size, for two reasons. The lantern and the glazed bays are made to measure from a survey taken once the openings exist, which is a lead time of several weeks in the middle of the programme. And the plastering and the perimeter ceiling detail take longer than a flat ceiling does.
The disruptive phase is the beginning, while the ground is open and the opening into the house is formed. Once the shell is weathertight it becomes much more tolerable. The day the back wall comes out is planned with you rather than announced.
Fig. 01
What actually happens, in order
Three of these eight stages happen before anybody digs anything. Get the order wrong and you pay to redo work.
-
Survey
We look at the ground, the trees, the access, the existing structure and where the drains actually run.
-
Drawings
A technician produces existing and proposed plans and elevations to a standard the council will accept.
-
Permissions
Permitted development, prior approval or a full application. We submit it and handle the correspondence.
-
Structure
The engineer calculates the beams, the padstones and the foundation depth for your ground.
-
Groundworks
Dig, concrete and drainage. The messiest phase and the one that decides whether the rest stands still.
-
Structure up
Walls, steel into the opening, roof on, windows and doors in. The day the back wall comes out is planned with you.
-
Fit out
First fix, plaster, second fix. From here it stops being a building site and starts being a room.
-
Certificate
Final inspection and your Building Control completion certificate. Keep it with the deeds.
Which Colchester houses suit an orangery
It sits better on some house types than others, and it is worth being honest about which.
The best fit is a detached or semi detached house from the 1930s to the 1970s with a decent garden and a wide rear elevation. Lexden, Prettygate, Shrub End, Highwoods, West Bergholt and the villages north of the city are full of them. There is width for the piers to read properly, room for the roof to sit well below the first floor windows, and garden enough that the room does not fill the plot.
Period houses in the historic centre and the New Town streets are harder. Narrow terraces do not have the width for a symmetrical orangery, and a side return with rooflights is usually the better and cheaper answer. Conservation area status often settles it.
On modern estate houses around Stanway and Myland, the constraints are usually the plot rather than the design: shallow gardens, close boundaries and the eaves limit within two metres of a fence.
Village properties around Dedham, Boxted, Wivenhoe and the Colne villages are frequently good candidates, with the caveat that conservation area and listed status are common and need checking first.
Questions we get asked
Can my existing conservatory be converted into an orangery?
Sometimes, and it depends entirely on the base. If the dwarf wall and the footings were built properly and are deep enough for the clay, you can occasionally build up from them, form piers, and put a new insulated roof and lantern on. More often the original footings were shallow, because they were built as a conservatory and nothing more was required. Then it is a rebuild, and paying twice is the outcome. We dig a trial hole and look before anyone gives you a number.
Is a conservatory ever the better answer?
Yes. If the budget is fifteen thousand rather than fifty, if you want somewhere to sit out from April to October, and if you are content to keep the separating doors and treat it as an outside room, a good conservatory does that job honestly and cheaply. So does a garden room, if the space does not have to touch the house. The mistake is buying a conservatory while expecting an orangery. If you need the space to work in February, no amount of specification will get a fully glazed roof there.
Will an orangery count towards the floor area of the house?
An orangery is built as habitable space to full Building Regulations, so it is generally measured as part of the house, and it will have a completion certificate to show for it. An exempt conservatory generally is not. We would not build one on that basis alone, but it is a real difference between the two.
Do I need an architect?
Not necessarily. For a straightforward orangery a competent architectural technician produces drawings that are adequate for planning and for building from, at a fraction of the cost. An architect earns their fee on a listed building or where the design problem is genuinely difficult. We are builders, and we will tell you honestly which of those your job is.
How we do it
One contract, one contact, and the paperwork is our problem.
Our team has 25+ years in the trade and comes out. The first visit is a survey rather than a sales call: the ground, the trees, the access, the drains, the orientation of the rear elevation and what you actually want the room to do in winter.
Most people who call us already have drawings and permission and want a builder to price the work and build it. That is the ordinary job here, and we are glad to work to somebody else’s plans. Where the drawings do not exist yet, we bring in the technician who draws it and the structural engineer who calculates the beams and the pier loads, we manage the planning route, we notify Colchester City Council Building Control, and we run the trades as main contractor. Probuild Extensions Colchester is the extensions arm of Essex Probuild Ltd, company 15979928. We carry £2m public liability cover, and the work is built to current Building Regulations and we see the job through to the point where Building Control issue your completion certificate.
We are based in West Bergholt, about three miles north west of Colchester, and we work across the city and roughly thirty miles around. The survey and the quotation cost nothing and there is no pressure afterwards.
Last reviewed August 2026. Planning rules and Building Regulations change, and your property may differ, so treat this as a guide rather than advice on your specific job.