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What I Charge to Design a House Extension in the UK

Updated: Jun 6


How much do I charge?



I write this blog about the reality of altering and extending private homes because that’s what I do in my day job. And in my day job, one of the most important decisions I ever made was to publish my fees on my website. This gets the whole messy discussion of, what it costs to hire an architect, off the table. My fees are public and I don't negotiate. A potential client, looking at my website, can either take it or leave it.


In this post I am going to discuss how my fees are structured. What a client gets for their money, what’s included and what is not included.

modern house extension UK
I designed this house extension outside Edinburgh in 2019

At the end of the post I will use this house extension project, which I finished in 2020, as an example of how much I charge. If you want a real world example, of fees, for a house extension in the UK, this is it.


But first, a bit of background.

Architects in the UK do not use fee scales and can structure their fees any way they see fit. I am unusual among my professional colleagues by making my fees public. But the fee structure which I use is fairly standard. Many people expect architects to use percentage fees but reports indicate this method is increasingly rare in the UK. Many Architects I know use some combination of fixed price and hourly charges when calculating fees, and I am the same. It's important to appreciate that hiring me isn't like buying something in a shop. Where an individual item has a single price. I know that might sound obvious but I have lost count of the number of times people have called me asking “How much will the drawings cost?”

I could write an entire post about why that is the wrong way to look at it but, put simply, if you are thinking about hiring an Architect, for your house extension project, keep in mind that this is a process, not a product. And that process has several stages. It might sound odd but you don't hire me to do drawings. Sure, drawings will happen, but that isn't what you are paying for. Whether you realise it or not, you are paying for my independent judgment, training, experience and skills, as well as access to my network. Because the best designers work with the best builders, suppliers and consultants.

Now, back the process. The Royal Institute of British Architects publish a document called the Plan of Work. This divides the process, from the fist phone call you make to an Architect, to inspecting the building long after construction has finished, into eight stages. Personally, I find that some of these stages overlap so, for my own projects, I divide the process into six stages. These are;

The Feasibility study

Where I survey the existing house and then draw up options for the project,

Planning application

This is self explanatory. I make the application for planning permission and deal with any negotiations the planning department require.


Building warrant

Again I make the application for a building standards approval to the local council and coordinate the design with the structural engineers and sometimes also an energy consultant.


Pre-construction

This is where we tender or negotiate a price with contractors.


Construction

Where I draw up a contact between the builder and the client and then I administer that contract. I inspect the site once per week and deal with any variations to time or money that arise during construction.

And finally, the post-construction stage.

This is where I carry out a final inspection of the work, commonly known as snagging. And I also deal with any issues the building standards officer may have following their own inspection.


I charge fixed price fees for every stage expect the first one, the feasibly study. I charge by the hour for that stage because I don't know how many times a client might ask me to revise the drawings, before they are happy with them. Any business which commits to fixed price fees must be careful to describe their services in such a way that it limits the amount of time spent on the task. Otherwise that business will loose money and go bust. In my case, for example, my fee for the planning application stage does not include dealing with an appeal in the event the application is refused.

My fee for the construction stage, is set at a fixed amount per week. Therefore if the project is delayed I wont lose money. In many cases, if a project is running smoothly, I wont need to inspect the site every week and I don't charge the client if that happens.

I should also point out that I don't offer project management services. What I am doing is more correctly called contract management. I don't supervise the contractor, I inspect their work. A project manager would be on site every day, ordering material, hiring people and arranging the sequence of work. For my size of project that role is carried out by the main contractor.

I mentioned earlier that I publish my fees on my practice website. Im not going to link to that, because Real Life Architecture isn't about promoting my regular business. Instead, I have posted a screenshot below.

Architects Fee Scale UK
This is my Architects Fee Scale for House Extensions (2023)

You can see from the fee scale that the six stages are listed left to right. But the fees vary according to construction cost. Essentially, the bigger and more complex the job, the higher my fees. I increased my fees at the beginning of this 2022 because I could see inflation would be a very big deal going forward. Plus there is still a lot of demand for my services.

Now, I suspect there will be some people who think my fees are way too high and others might think I am not charging enough. I made a video a few months back showing how the median architects salary in the UK is the same as the median salary for a secondary school teacher. I don’t have anything against teachers, my mum was one for forty years, and I have now friends who are teachers, but it surprises people to learn about the equivalent salaries. They assume Architects should earn far more. I think the main reason we don’t is because, as a profession, we often don’t value our time properly.

My income fluctuates every year but I typically earn twice as much as the median architects salary, so I must be doing something right. It's also worth point out that I work alone and don't employ staff, so it doesn’t take much to keep me busy. In 2021 I took on just six projects and in 2022 I took on five and in 2023 so far I have taken on four. To put that in perspective I get about one enquiry per week, so I have to set a minimum size of project I am willing to take on, otherwise I will be overwhelmed.




At the moment I set that minimum project size at £150k. In truth it should be about £250k and I may increase this in the near future. They are my fees, for my business, and I’m not trying to suggest other Architects should adopt them or homeowners should pay more across the board. I should also say that I am not VAT registered and in recent years its been a struggle to keep my turnover below the £85k threshold. As problems go, it might seem like a nice one to have but I am seriously concerned that getting VAT registered would negatively impact my business. I often get asked by potential cleans to confirm my VAT status, so I can only assume it matters to them. All my clients are homeowners and would not be able to write off the VAT on my fees, so I would become 20% more expense if I was registered.

So, let’s look at a real project and I will talk though how much I would charge for this job if it were built today.

modern house extension UK
A bright, modern house extension

patio doors open to a patio
I love how the open plan space flows onto the patio and towards the garden

I am using this project as an example because we did very little work inside the existing house, this was almost entirely about the house extension, so it works very well when discussing architect fees. In 2022 this project would be in the £300 - £400k bracket. It cost less back in 2020 because inflation has taken off since it was built. I have also increased my architect fees and the figures I am quoting here reflect what I would charge for this project today.

The feasibility study for this job took me 28 hours back in 2019 and today I would charge £90 per hour for this, so that stage would cost £2,520. I issue invoices monthly, along with a timesheet until the feasibility study is complete. At this point I always advise people to get a realistic cost for their job before we go any further. There is no point getting planning permission for a design if it is beyond the budget. Back in 2019 I regularly carried out cost estimates of my own but, due to rampant inflation in the UK construction industry, I have since stopped offering estimates.

For the pre-construction stage I draw up a document called, a scope of works. It lists every element of the project, so it can be priced individually by the contractor. I can then use that same breakdown to put a value on the work done at any point during construction. In this project we were able to competitively tender between four contractors but, these days, builders are very busy and highly unlikely to agree to a competitive tender. In this situation I still create a scope of works but we now carry out what is called direct negotiation. I introduce my client to a number of suitable builders and they choose one to work with. I charge £3,500 for the pre-construction stage and issue my invoice when the scope of works is first issued to the contractor for pricing.

For the planning application stage I charge £4,000 and issue the invoice the day the application is lodged. In this project we were very lucky, there were no neighbour objections and the planning officer only asked to confirm the design and colour of the new windows. Other projects of mine have had significant issues and drawn out planning applications. Every application is different and none of them are certain to be approved.

For the building warrant stage I charge £6,000 and, just like the planning stage, I issue the invoice the day the application is lodged. A lot of detail goes into a building warrant application and, on this job I worked with a structural engineer and an energy consultant to create a full construction package. Most homeowners are obsessed with the planning application process but far more time goes into the building warrant application, so the fee is much higher.

feature window construction drawings
Construction drawings showing how to build the feature window

It's worth noting that I finished the tender negations with our contractors at this stage as well. Once we had a full contraction package, the builder could accurately price the job. When construction starts I usually inspect the site once per week and charge £350 per week for this. I write minutes of the meeting and issue payment valuations at least once per month, but sometimes fortnightly, if the contractor needs the cash flow.


I also deal with any technical issues that arise during construction. In this project the plan was to keep the existing external walls and drop the new steel frame design into that shell. We discovered during the job that some of those walls were not stable and had to be taken down and re-built. I dealt with the costs and timescale issues for that.

modern house extension under construction
Under construction, notice how the steel and timber beams are shaped to help form the thin edge of the cantilever roof

I also ensured the steel frame design was correct and organised the deign and measurements for the aluminium glazing. Despite the number of construction drawings, the contractor still had a long list of questions that needed to be answered, so I was fully occupied during this stage.


Construction on this job was massively impacted by the first Covid lockdown but, in total a job like this lasting 20 weeks at £350 per week would cost £7,000 and I issue invoice monthly.


The final stage is post-construction. This involves snagging the work and dealing with the building standards officers inspection. Its worth pointing out that I don't provide this service unless I was also involved during construction. The reason is that if I wasn’t on site regularly while the job was being built, the number of issues to revolve at the end of the job could be huge. I charge £1,100 for this service and I issue my invoice when I lodge the application for completion certificate to the local building standards department.


If you are considering extending your home in the UK, I offer online consultations to help you work out what is feaisble and explain how to find the right local architect for your project.


If anyone watching is tempted to write in the comments that they paid way less money for the drawings on their house extension, think before you post. Was your house extension the same size, construction cost and quality as this one and did your designer provide the same services I did throughout the project. If so, we’ll done, you got a bargain.


I justify my fees based purely on supply and demand. But I could also justify them in terms of value added. My services give people something that isn't easy to buy on the open market, a bespoke, contemporary home. I often work on older properties that are listed or in conservation areas, and regular push the boundaries of what is possible. A number of my previous projects have been sold for well above the asking price, and the estate agents marketed them as designed by an award winning Architect. When I say my services add value, I don't mean it in a woolly, abstract sense. I mean it in terms of cold, hard cash. My designs have sold for a premium on the open market.

modern house extension on a historic property
zinc clad house extension at the rear of a 200 year old property

This project was shortlisted for a Scottish Design Award in 2021 and its also got a seven page spread in this months Homes and Interiors Scotland magazine. Im not saying all this to show off, I’m saying it to give the average UK homeowner some context. If you are looking for an Architect to design your house extension, fees will vary. If you hire a young architect, who just stated working for themselves, their fees may be less than mine. If you hire a firm with an office and staff, they will charge more, plus VAT. If your property is in London you will pay more than anywhere else in the UK and if your property is in a remote, rural location, the number of local Architects will be limited, and that will impact the fees they charge.


I want any discussion in the comments to be civil and constructive. Money and property are topics that make a lot of people very uncomfortable but my own experience shows that putting this information in the public domain makes it easier. I don’t know if it changes anything but it does avoid awkward conversations and it certainly helps manage my clients expectations.




















Link to architect fees for a house extension - https://www.instagram.com/p/ChuHF0jsbdt/?igshid=YmMyMTA2M2Y%3D




I built house extension in the UK in 2020. How much would my architect fees be for this house extension if I designed it today. Ive recently made a full length video about this, there is a link pinned in the comments.


I divide my architect fees into six stages.


I charge by the hour for the first stage, the feasibility study. Because I don't know how many times a client will ask me to change the drawings before they are happy with the design. For the all other stages, I charge a fixed price fee.


The feasibility study for this job took me 28 hours, at £90 per hour that stage would cost £2,520.


For the planning application stage I deal with any negations the planning departments require. I charge a fixed price fee of £4,000


For the building warrant stage I work with a structural engineer and produce detailed drawings. I charge a fixed price fee of £6,000


For the pre-construction stage I prepare a scope of works and tender the job to contractors. I charge a fixed price fee of £3,500


During construction I charge £350 per week to carry out contract administration. This project took 20 weeks to build, so that would cost £7,000


The final stage is post-construction. This involves snagging the work and dealing with the building standards officers inspection. I charge £1,100


For full details see the video linked in the description and comments.






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