Garden Annex vs Garden Room vs Extension vs Conservatory
Garden Annex vs Garden Room vs Extension vs Conservatory
Should I decide to build a garden room, a garden annex, a conservatory, or an extension?
- For this question, each alternative involves a different approach to expanding a home in the UK, yet each option involves different costs, time to build, required approvals, planning permission, and long-term prospects for a home’s value.
- Some customers need a fast flexible work area, whereas others wish to expand the perimeter of their structures substantially. It is important to understand the distinct characteristics of all the options available.
- To this end, this guide attempts to clarify the most common alternatives available and the pros and cons for customers to consider before setting out on the building process.
Summary
Generally, the most time efficient planning and construction flexible building is the garden room. Annexes and conservatories generally do not provide the same level of construction/ planning efficiency, but garden extensions do provide permanent and integrated building space to the dwelling unit.
| Feature | Garden Room | Garden Annex | Rear Extension | Conservatory |
| Typical use | Office, studio | Living accommodation | Extra room | Sunroom |
| Planning complexity | Low | Medium | High | Medium |
| Installation speed | Very fast | Moderate | Slow | Moderate |
| Cost level | Medium | High | Very high | Medium |
| Insulation quality | High | High | High | Low to medium |
The differences among the structures show the various purposes they serve and indicate what each homeowner aims to accomplish with these structures.
One of the most critical factors homeowners consider the most when deciding to extend their property is the cost involved.
Below are the typical UK cost ranges for the above structures.
| Structure Type | Cost per m² |
| Garden Room | £1,800 – £3,000 |
| Garden Annex | £2,500 – £4,000 |
| Rear Extension | £3,000 – £5,000 |
| Conservatory | £1,500 – £2,500 |
Conservatories are typically the cheapest option, but they are also typically the cheapest option, but they also often provide the lowest insulation performance.
Many factors determine the overall cost of the project, including the size of the overall building, insulation specification, the required utilities and plumbing, the foundations and groundworks, glazing systems and doors, and the high-performance finishes, and flooring.
Garden rooms with high-performance insulation and premium glazing typically fall toward the higher end of the price range, but they provide year-round comfort.
Typical Construction Timelines
The type of building being constructed will greatly influence the timeline.
| Structure | Typical Timeline |
| Garden Room | 8–10 days |
| Garden Annex | 4–8 weeks |
| Conservatory | 2–4 weeks |
| Rear Extension | 3–6 months |
The garden rooms are the fastest of these options because they are built as separate modular structures, whereas the other options include rooms that are integrated into the main building.
Rear extensions involve more complete building work, especially structural, foundation, and planning approval work, all of which can greatly increase the overall work timeline.
For homeowners who would like a garden room or a modular garden office/studio, the garden room is also one of the fastest options.
Contrasting Planning Permission
The planning permission requirements vary from one structure to another.
| Structure | Planning Requirements |
| Garden Room | Often permitted development |
| Garden Annex | Usually requires planning permission |
| Conservatory | Often permitted development |
| Rear Extension | Usually requires planning permission |
According to the developer rights within the UK, the majority of garden rooms and conservatories can be set up without planning permission.
There is one critical rule concerning the height of the building.
Garden rooms that are less than 2.5 m from any boundary will usually not be allowed under the developer rights if they are within 2 m of any boundary.
Laws on construction differ from one local authority to another, so it is best for homeowners to check local laws before starting to build.
Construction Law Differences
Construction laws differ from place to place, but they provide a set of norms on how a building is meant to be designed, constructed, and how it is to be used.
| Structure | Building Regulations |
| Garden Room | Sometimes exempt |
| Garden Annex | Required |
| Rear Extension | Required |
| Conservatory | Often exempt if separated from house |
Building Regulations apply to most rear extensions and annexes because they facilitate permanent living accommodation that is integrated with the main dwelling.
Garden rooms may be exempt from building regulations if they are constructed as a separate detached building used for an office or studio.
Insulation Quality Differences
The comfort that a space provides throughout the year is greatly influenced by the quality of the insulation.
| Structure | Typical Thermal Performance |
| Garden Room | High |
| Garden Annex | High |
| Rear Extension | High |
| Conservatory | Low to medium |
Conservatories of the older designs do not provide comfort in the extreme seasons, as they get too hot in the summer and too cold in the winter.
In contrast, modern insulated garden rooms use advanced construction systems such as structural insulated panels to ensure comfort in the extreme seasons.
This suggests a variety of potential applications, such as:
- Home offices
- Gyms
- Garden studios
- Hobby rooms
Impact on Property Value
Depending on the type, structure, and quality of the build, home improvements can increase a property’s value.
| Structure | Estimated Value Impact |
| Garden Room | 3–7 percent |
| Garden Annex | 5–10 percent |
| Rear Extension | 10–20 percent |
| Conservatory | 2–5 percent |
Rear extensions often provide the largest increase in property value because they permanently expand the internal floor area of the home.
Remote work is here to stay and as a result, garden rooms can improve the value of a home more so than other improvements.
Total Installed Cost Calculator (Concept)
In addition to the base structure price, homeowners can estimate total project costs by considering a number of other factors.
The base structure cost, foundation system, electrical installation, heating or cooling systems, interior finishing, and any planning application fees are typical cost components.
Example Cost Calculation
- Garden room size: 4 m × 3 m
- Estimated base cost: £20,000
- Foundations and groundworks: £2,000
- Electrical installation: £1,200
- Estimated total installed cost: £23,000
These figures provide a rough benchmark and can vary depending on site conditions and specification level.
Time-to-Use Timeline Calculator
Many homeowners want to know how long it will take before they can actually start using the new space.
Stages of a Typical Project Include:
- Design Consultation
- Confirmation of Plans
- Manufacturing/Preparation
- Installation
- Finishing Touches
Example Timeline for a Garden Room
- Design and Prep: 1 – 3 weeks
- Installation: 8 – 10 days
- Total Time: 4 – 5 weeks
Compared to a rear extension which takes months, garden rooms give you usable space quickly.
Which Option is Best?
It truly depends on what your priorities are.
Choose a Garden Room if you want:
- Quick Installation
- A space that is easy to utilize for multiple purposes
- Little planning
- Less disruption during construction
Choose a Garden Annex if you want:
- Accommodations for independent living
- Space for family/guests
Choose a Rear Extension if you want:
- A permanent expansion of the home
- Large living areas that are integrated
Choose a Conservatory if you want:
- A sunroom at a lower cost
- More natural light
Different options serve different needs, ultimately depending on the homeowner’s goals.
What makes garden rooms increasing in popularity?
The construction speed, range of flexible usage, and year-round comfort of garden rooms make them very appealing to many in the UK. The most common uses are:
- Office
- Gym
- Creative Space
- Quiet Work Space
With a focus on remote working, the need for insulated garden rooms is increasing.
Pecasa Garden Rooms
Pecasa creates and commissions personalized garden rooms in North London and throughout the UK, making the outdoors a comfortable place to spend time any time of the year.
Typical features include:
- Insulated structural panels
- Composite or timber cladding
- EPDM roofing systems
- Double-glazed aluminum doors and windows
With the addition of these features, garden rooms will function as insulated rooms separated from the main house, which can be ideal for working, being creative, or just relaxing.
Commonly Asked Questions
Which option is cheapest?
Conservatories tend to be the cheapest and then garden rooms.
Which option adds the most value?
Rear extensions often provide the greatest increase in the value of the property.
Which option is fastest to build?
Garden rooms are usually the quickest option.
Do garden rooms need planning permission?
Provided that they comply with the height and location restrictions, most garden rooms are considered to be within permitted development rights.