Trimble Architects

RIBA Architectural Services

Phone Number: 020 8538 9303

Mobile Number: 07785711635

Are you looking for residential extensions in London? Our RIBA local architect services works throughout Hounslow, Twickenham, Richmond, Kingston Upon Thames, Teddington And Throughout London.

At Trimble Architects Ltd, our projects vary in scale and complexity, as we work across North and South West London and Surrey on refurbishments, house extensions, new builds and change of use. 

We're a leading architectural and structural planning business with a whole host of experienced and qualified architects on board to maximise the fair amount of space and value. 

We aim to assist clients from the first stages of the project right through to the very finish, either in sequence or as isolated steps. For those interested, our services include a wide range of works, such as:

  • Project inception
  • Planning application free consultation and submission
  • Building regulations and calculations
  • Feasibility studies
  • Tender adjudication
  • Contract administration
  • Construction and site supervision
  • Free site surveys

Regardless of how big or small your project is, all teams involved in our fantastic London architecture service can provide you with close guidance and support throughout the entire plan and build process as dedicated project managers. We'll do so for a fixed price that suits your budget.


On-Site Assessment

At Trimble Architects Ltd, our exceptional team of London-based architects have the skills and qualifications to carry out vital on-site assessments for your desired extension throughout London and Surrey. 

Typically, these consultations are hosted by experienced builders, contractors or extension designers, both at the same time, or somebody with both titles. 

An assessment can take up to 2 hours to evaluate each of the necessary limitations on your site, alongside any impartial advice that would help you enhance your project or give you design ideas of what to reconsider for a more seamless transition.

Residential Extensions London

During this inspection, you'll discover the following:

  • Whether or not your extension is achievable
  • How long your extension build will take
  • Whether your specific project needs planning application and how you can obtain it
  • How your project building can best adhere to the regulations of your area
  • You'll gain a rough idea of how much your extension budget will amount to
  • If there are any structural or heat-loss calculations that you need to consider

Planning Permission

Obtaining planning permission for a brand-new extension may initially seem daunting and complicated; however, many amendments have been made in recent years to the rules and regulations. 

As long as you have floor plans and architectural drawings that are thorough, detailed and fit the criteria of your local area from a trusted and qualified professional before applying, you're likely to gain permission. 

With the introduction of permitted development rights, there has been an expansion of the work you can complete on your house without the need for planning office approval. Always remember that if your home or property is located in a conservation area or your home is considered a listed building, you'll need planning permission. It might be a little trickier to obtain it.


Regardless of whether or not you'll require planning permission, you'll most of the time need to gain approval from building control using accurate building regulation drawings that depict the measurements, materials, scale and thorough analysis of the groundworks, drainage and the impact on the environment. 

Contact us today at Trimble Architects Ltd; our professionals will be on the end of the line to provide you with the necessary assistance in completing any planning permission applications or discussing a floor plan that you wish to take to your local council. 

If you have any projects where you are unsure whether or not they would require planning permission, give us a call; we may be able to help with all the answers you require. Otherwise, we suggest contacting your local authorities or planning offices as every location is different!


You should be aware of various types of extensions before starting your project. These are some of the most popular:

Single Extensions


Single-storey house extensions are usually built onto a specific part of your household; whereabouts, one or multiple sides are attached to an area of your building. They include any basement you have and the ground floors.

Single-storeys will always need building control, yet they don't always require planning permission to have built. 

Many single-storey extensions are included under Permitted Development Rights. Yet, it's still paramount to ensure that the extension you build accurately matches and complies with the regulations of your area.

You can turn your single-storey extension into whatever room or use you desire, for example, a home office, dining room, utility room, playroom, new bedrooms for a growing family, guest room, or kitchen extensions. 

There are many options, depending on the size of your extensions, the impact it may have on your neighbours and how your new roof will work alongside your existing property. When installing a one or multiple-storey extension onto your current property, you want to assess other difficulties you could encounter, such as the position of your drainage system, the placement of chimneys and whether you require excavations to complete the job.

Double Extensions


Professional builders have the expertise to install double-storey or multi-storey extensions onto any part of your existing home to add any additional room you desire. 

For example, if you're looking to add another dining room with impressive ceiling height, bedroom or bathroom, we recommend implementing a high-quality double extension.

The complex nature of the build tends to mean that overall costs are much higher than a single-storey house extension. You'll find that this also means your neighbours may experience far more disruptions, as the building work is more extensive. 

Due to its larger scale and much higher value, double-storey house extensions require planning permission from local councils and planning consultants before you can go ahead. It's also helpful to remember that two-storey extensions can only be completed for detached or semi-detached homes with some garden or side plot that allows additional building space. 

It would be pretty challenging to attempt a double-storey extension for terrace houses and create a great deal of disturbance.


Wrap Around Extensions

Wraparound extensions are skillfully created when architects combine rear extensions and side return extensions to form an L-Shape that wraps around the back of your household. 

These will typically involve building a side wall closest to your neighbouring border and moving any rear wall into the rear of your garden to create a much broader L-Shaped house extension. 

Wraparounds are a fantastic choice for those who wish to remodel their entire floors, add further space for a dining room, create a bedroom or guest room, increase kitchens' size, and for living room extensions. They curate and add space, filtering natural light to illuminate the area.

Side Extensions


When you have enough space within your household, a single-storey rear or side extension can change your home's entire outward appearance. 

Such extension ideas include creating open-plan areas that you can utilise as dining, extra living space or combined kitchen area. 

Alongside internal property alterations, for example, to open up a room to your back garden for the family to enjoy and allow more natural light.

With the option of a side extension, you can massively benefit from the additional space it will add to your household. Implementing a more versatile space will make your property more attractive to potential buyers, adding significant value. 

A skillfully designed and constructed side extension will increase the space within your room, and you can utilise the newfound space to reorganise or remodify the interior. We're confident that our architects will work hard and work with you closely to ensure your side extension is well-designed to feel like a natural part of the house.


For those looking to start a new build, change the use or class of your existing building or extend your house by size or number of rooms, you'll likely require planning permission. 

Once you've decided what kind of project you wish to complete, you and your architects can begin filling out a planning application that accurately details the entirety of your building proposal to send to the LPAs (Local Planning Authority). The local council will check the details of your floor plans and any groundwork against the location criteria and building regulations. 

It is a way to ensure that your plans are designed with sensitivity to the neighbouring communities, the local guidelines and the specific area, street or sites. Without such systems, we'd never be able to create communities with uniform buildings with similar forms, functions or designs to completion.

Local planning authorities (LPAs) tend to have guidelines catered to particular locations; for example, London Boroughs will have unique regulations to follow. Most planning councils and authorities tend to take around 6-8 weeks to come to a conclusion on your project.

    How far you can extend without planning permission will differ depending on the type of extension you're looking to create and install.

    Single-Storey Rear Extensions:- For those living in terrace houses or semi-detached homes, you can now extend your build to 6m due to a change of rules in 2020 from the local planning authorities. 

    Those in detached houses can extend their single-storey extensions up to 8m if they ensure they get full planning permission, especially if their property is a maisonette, flat or within a conservation area.

    Side Extensions:- These fall under permitted development and, therefore, cannot extend more than half the original width of your house.

    Side Extensions:- These fall under permitted development and, therefore, cannot extend more than half the original width of your house.

    Double-Storey Extensions:- New rules are gradually being phased into the building control regulations since 2019 to allow homeowners to build their desired extensions onto detached homes without planning permission. Adding two-storey extensions to your household will be much like a loft conversion. It will still involve some paperwork, making the extension process much more straightforward.

    Roof and Loft Extensions:- To complete these extensions without planning permission, you must ensure that the roof space does not exceed 20cm from the eaves or the required volume allowance, which is set at 40m3 for terrace or semi-detached houses and 50m3 on detached homes.

    In receiving an on-site assessment from a planning consultant or discussing your plans with a qualified architect or structural engineer, you'll be able to figure out what you can achieve with your new extension without planning permission.

    Many may believe that due to Permitted Development Rights, regardless of the extension they are taking, they won't require any planning permission; however, this is not always the case.

    On most occasions, you can adjust and improve your home in numerous ways without the need for any planning permission, yet there are still a few instances where local councils and planning consultants restrict you. 

    For example, your permitted development rights do not cover the building of double-storey extensions, flats, large loft conversions, the development of listed buildings, or those in conservation areas. You will need to send your plans to the local authorities and councils, so they can check and approve your desired building plans, even if you meet all the requirements.

    When it comes to a complete planning application, it's paramount to understand the local guidelines of your area and approach the permission process with a complete set of architectural and building regulation drawings and a suitable design. 

    Numerous architectural services across the UK and London will complete your drawings yet do not offer planning advice or submit a full application on your behalf; however, at Trimble, we can complete it all for you to a high quality.

    The difference between planning consultants and extension architects is that planning consultants have plenty of knowledge of the regulations of your local area and what is most suitable, meaning they can play a significant role in gaining planning permission for complex, bespoke extension projects. 

    However, that is ultimately where their job role ends, and when your planning application has been approved or refused, you may be left wondering 'what next?'

    Trimble Architects Ltd understands that planning and building extensions and new builds is a confusing and daunting task, which is why we intend to guide our clients through the entire process. 

    Our specialists have extensive experience in designing and planning; we won't charge to submit your applications or arrange high-standard assessments. It's our job to liaise with your local councils or authorities to ensure your project solutions go ahead and are brought into reality with little to no hassle on your end.

      Building regulations are significant no matter the type of build you want to complete. They are necessary to ensure the safety of those living inside the building and surrounding areas. 

      Unlike planning permission, the building approval means your building not only aesthetically complies but practically complies with the national standards to protect people's livelihood, health, and safety.

      Some actual examples of the aspects of building regulations consist of, are the following:



      Structural Calculations


      Ventilation and Accessibility



      Once you've received planning permission, you must get building regulation drawings submitted and approved before beginning the construction process. Ensure you're not employing odd builders you find for such extensive and risky works. 

      Under the Building Act 1984, local authorities and planning offices have the power to enforce the removal or alteration of non-compliant work. Trimble has various teams of experienced extension builders that can deliver efficient and aesthetically pleasing construction to transform your existing house with new storeys or high-quality extensions.

      Permitted Development Rights are a comprehensive set of rules and policies allowing UK homeowners the freedom to enlarge and extend their homes or properties with pre-approved permission. 

      In acting according to these rights, you consent to extend your house or property to a specific degree more than the norm without going through the planning application process, which can be time-consuming and expensive. 

      Typically, such rights apply to front porches, single-storey or rear extensions, solar panels, skylights for new windows or doors and any outbuildings like greenhouses or sheds. However, you must remember to comply with the existing rules to stay within the bounds of permitted development. 

      There will always be restrictions, especially for double-storey extensions, more extensive loft conversions, listed buildings or those in conservation areas and flats.

      What is the full range of services on offer at Extension Architecture?

      Trimble Architects Ltd offers plenty of new home extensions, including single and double-storey extensions, side and loft extensions, change of use projects, commercial extensions and complete new builds. We consider it our responsibility to take complete care of our clients, from our first on-site assessment to gaining planning permission and building regulation approval to the finished result.

      Trimble services include the following jobs:

      • Design and Planning Drawings
      • Site Survey
      • Submission of Planning Applications
      • Building Regulations and Calculations with our in-house Structural Engineer
      • Project Management
      • Trusted Builders
      • Interior Design
      • Kitchen Showroom
      • Kitchen Supply

      Trimble Architects

      Based in Twickenham

      South West London

      Contact Us

      If you require help and advice from our construction project management consultancy get in touch today. Trimble Architects are based in Twickenham and work across south-west London.

      Get in touch