Trimble Architects

RIBA Architectural Services

Phone Number: 020 8538 9303

Mobile Number: 07785711635

Are you looking for a home extensions architect  in London? Our Twickenham based RIBA chartered architect offers a complete service for planning and extending your home or business. Contact us to discuss loft conversion architect services for Hounslow, Twickenham, Richmond, Kingston Upon Thames, Teddington and South London.

Extension Architecture Services London

Trimble Architects is a London-based architecture service with a group of talented designers and project architects who have completed extensions, rear-extensions, conversions and planning applications throughout the local and surrounding areas.  

We have plenty of pride in our extensive portfolio and the exciting, innovative projects we have accomplished in our many years as a trusted establishment.

Extension Services We Offer

Trimble Architects have plenty of years of experience in the new build and extension industry, delivering a vast range of designing, building and observing services.  

We'll perform works, project management, and contract administration and deliver double, flat and single-storey conversions, two-storey extensions, dining room and kitchen designs and even basement extensions for residential and commercial properties.  Whether you have a semi-detached house or terraced house, we'll be here to help create your dream home.  

Our fantastic South-West London, Muswell Hill architects, can help you transform your household into your dream aesthetic.  We are always available to contact if you wish to discuss your questions with professional teams or arrange a face-to-face meeting to draw up some initial plans and assess your chosen site. 

How much does an architect cost for an extension UK?

Firstly, decide on your budget; how much would you like to spend on this extension?  

Perhaps remember architects can assist you in saving money on the overall costs when it comes to building extensions, as many can get substantial discounts on trade materials.  However, we encourage you to bear in mind any contingency issues, so getting your builders to state if their quote includes VAT is significant. 

You'll want to ask your planning consultant or architect for a rough idea of the costs of building your extension.  For example, an estimate of rear or loft extensions could come to £50K; however, that price may not include rendering, wiring or interior fixing.  

It's best to contact our Trimble architects or local architect's near you to compare prices and get the best quote for your project. 


Planning to develop a complex house extension can be a difficult task. However, we primarily encourage you to take your time and ask yourself all of the following questions to ensure you cover all essential basis before contacting builders, architects, interior designers or contractors. 

What's Your Budget?

One of the most significant and fundamental questions you need to ask yourself is your budget; it is also one of the first questions architects pose to their clients.

At Trimble, we advise that you call in your architects or contractors and come up with a sufficient sum of money to spend on your new build or extension; at this stage, it doesn't have to be exact, but a close estimate will be good enough.

You'll want to ensure that you include all extending extras, such as the costs of your planning application and the architect fees. Many builders and architects in the field often provide a quote including VAT, so you may have to add 20% onto the final price. 

Costs can gradually creep up on any house extension as homeowners begin to add new materials or new features, so it's best to create a budget you can collectively stick with. 

What Do You Want To Achieve?

Before rushing ahead all guns blazing and hiring architects, you'll want first to establish what you want to achieve with your new build or house extension design.  

Are you in search of a brand-new living area that your friends and family can thoroughly enjoy all year round, a home office to keep up with the work-from-home job you acquired in the lockdown or an extra bedroom to welcome in a little one?  

Whatever you wish to use your new extension project for, make sure you have it in mind when creating plans with your architect, as this will help determine the style of alteration you wish to make.

How Long Will It Take?

It's best to be aware that even professional builders can't build house extensions overnight.  It can often take weeks or months to receive full planning permission and building regulation drawings approval. You must be patient and warn those that live or work close by of the building work going on as it may cause interruption or upheaval to their daily life.

When you choose to complete such new-build work, you must factor in family events, holidays, garden parties, and other previously planned occasions.  These are events where you will likely need your back garden or the entire house without disruptions from builders, loud noises from tools, or even experiencing technical issues. Plan your home renovation as far ahead as possible so that you can skilfully plot fun events around it.


You don't always require planning permission for your architectural designs to proceed with your building project or property type alteration, for example, single-storey extensions, first floor and ground floor extensions, some sunrooms, en-suites and loft conversions. These are referred to as permitted developments. 

However, whilst this can be the case, we don't believe you should plough ahead with your plans; professionals would prefer you check your local building regulations and all the requirements with a local planning authority or consultant.  

You could also ask your architect as they are likely to be educated on the local standards to garner a perfect solution. 


You don't always need an architect; however, we would fiercely urge you to utilise the help and talents of a skilled professional when planning and designing your extension or new build.  

Larger projects, for example, external home extensions and loft conversions, are not something we'd advise that you attempt to DIY.  

Big-scale projects have often gone wrong, even when someone relatively skilled in DIY projects has attempted them.  

You may think it will be cheaper to complete the job yourself; however, the job will be too big to take on yourself and ultimately, if it goes wrong, it'll be even more expensive to have remedied.  

Architects can offer incredibly detailed 3D planning drawings that you may not be able to create even with similar technologies. They have been thoroughly trained in the art and engineering of structural properties. 

We considerably push you to invest in the services provided by experts and architects when deciding to make significant alterations to your building or home.  

Plenty of the planning application process must include plans curated and drawn up by qualified architects, designers, structural engineers, and other consultants.  

Planning councils may be more inclined to deny you permission to proceed with your project if you do not have a detailed drawing done by someone in the field.  

You mustn't forget to factor the architect and potential engineer into your final overall costs when drawing up your budget. 


Assessing whether your neighbours will be impacted due to your extension or major alterations is an incredibly significant factor to consider. Do you frequently enjoy a friendly conversation over the party wall on a summer's day?

If this is the case, it may be upsetting for your neighbour to hear that you'll extend or alter your property. Your new build could even potentially damage their existing wall, and you must make them aware and get their permission to do so. 

Doing so will allow you to avoid legal disputes in the future, which is beneficial for keeping relations with your neighbours, the surrounding community and those tenants/new owners whom you may sell the home or property in the future.

You don't want to be an inconsiderate neighbour, so you must be conscious of the social aspect that comes with it. If they are an elderly neighbour that you communicate with regularly, it could impact their quality of life if you were to build walls between you.  

If they have a large garden, your extension may prevent any natural light from being let in so that they can relax in the summer and grow plants and flowers.  

Consider the construction process as well; it could disrupt a lot for your neighbours; for example, they may not be able to complete specific tasks, especially any essential gardening. It's best to make them aware as soon as physically possible, with the dates of when work is commencing.

Contact your local architects if you face any major issues when discussing your new build or extension. 

They may be able to help you with the best way to present them with the information or could get you into contact with the best solicitors or arbitrators if the problems excel into legal disputes.


For those with a commercial property or residential home that is a graded or listed building or perhaps located in a conservation area, you may face incredibly stringent controls and restrictions that dictate the kinds of alterations you can make on your building, if any.

It can sometimes be difficult to tell whether you are situated in a conservation area. It may not be a specific landmark or tourist area that many visit or walk to, like a nature reserve.  If you struggle to search it up online, we highly recommend checking your address with your local council or perhaps asking them upfront; they may have enough knowledge to tell you there and then.  

Suppose your location has some environmental or historical significance. It can be challenging to achieve permission to carry out extensions on the property to completion, and you may be asked to search for new spaces.  We deliver our services across South-West and East London and have plenty of knowledge of the area, give us a call if you are curious about the significance of your location.

Trimble Architects

Based in Twickenham

South West London

Call 020 8538 9303 to discuss your requirements.

RIBA LOCAL ARCHITECT SERVICESHounslow, Twickenham, Richmond, Kingston Upon Thames, Teddington
 ARCHITECT Hounslow, Twickenham, Richmond, Kingston Upon Thames, Teddington

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If you require a home extensions architect get it touch today. We offer RIBA chartered architectural services throughout Hounslow, Twickenham, Richmond, Kingston Upon Thames, Teddington and South London. We look forward to hearing from you!

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