Pricing for House Extensions

Prices for Architectural Design Services

House Extension Cost

A house extension project is a significant commitment requiring patience and a certain amount of funds. This event rarely happens more than once or twice in a person’s lifetime so it’s only natural that you may feel cautious about choosing the right professionals to use for your project. We are mindful about the stress and importance of the decisions a homeowner must take on the journey from the initial thought to the finished building.  

The extraordinary nature of these projects is the reason why our Ecclesall Design team is focused on providing clarity on the steps involved in the whole process and the relevant factors that determine the fees we quote for the services we provide. The costs of the architectural design stage will be only a small proportion of the overall project budget that includes construction costs. However, the right decision at this stage is essential to get the high quality and attentive, effective service you need to ensure the best possible result for your house extension.

As part of our service proposal we offer 3 packages to choose between for house extension projects. They reflect different types of drawings and the included services. The image on the left sets out key features for each package. Please also read our ‘2D and 3D Drawings for House Extensions’ page to learn more about the different types of drawings; our team will be happy to advise on which package would best suit your project.

The architectural design service is the first step in the whole extension project, and we feel it’s our responsibility to share our knowledge of the process to provide you the confidence and ability to understand the steps ahead. For this reason, we have prepared a House Extension Project Process Scheme explaining the important steps that are required to lead your project from the initial enquiry to the building process.

In this page we are going to look in more detail at the fees that are involved to turn your ideas into architectural design drawings and achieve planning permission and building regulation approval. We will explain the factors that determine our fees and give an indication of the other professionals and authorities whose fees should be considered. Also, we will provide some advice and information related to construction costs and choosing the right builder.

What Our Architectural Service Fees Are Based On

Our fees are largely based on the time we allocate for our team to do the necessary work on your project, based on our experience of similar projects. The two main aspects informing the scope of the work involved are (1) the complexity of existing property and (2) the brief for the proposed house extension and any other works.

The planning and building control authorities in the majority of cases require a full set of not only the proposed house extension plans and elevations but also drawings of the existing building. This enables them to assess the proposed alterations to the property and make the informed judgement required to provide the various approvals and certificates. This means that even a relatively small extension project requires drawings of the whole existing property. The complexity of the existing property is one of the two aspects that determine the time required for each project and this includes variation in terrain and the density of the urban surroundings as well as the level of detail in the architecture of the existing building. Each of these elements contribute to the amount of time required to provide a set of existing drawings.

The second element that determines the fees we charge for our architectural services is the extent of the intended alterations to the property. The size, type and style of the extension determines the amount of work required to reach an outstanding design and then achieve planning permission or a lawful development certificate. Larger extensions come with more possible alternative designs; unique features or materials take time to research with suppliers so we can give creative and informed advice to our clients.

House extensions can range from just adding a porch to double-storey wrap-around extensions and loft conversions with major internal remodelling on each floor. So, it is evident that the time and effort required on our part to find the best design options and then negotiate with local authorities to get their support can be significantly different depending on the proposed extension. We take care to listen to our clients’ needs and then provide informed service proposals only after researching and assessing the complexity of the existing property as well as the proposed project.


Architectural Design Services - Ecclesall Design
Architectural Design Buildings - Ecclesall Design

Building Costs

The cost of construction takes the greatest share of the overall project budget. Therefore, choosing the right offer from the builder is crucial. Our project management is designed to provide assistance in this latest stage of the project and represent the interests of the client. As part of this we offer advice on the builders’ quotes to help you make the right choice.

The established way of forming a contract for the building work is via an agreed fixed price with the builder prior to construction – this makes the quoting stage even more important. A professional detailed quote can prevent any misunderstanding occurring during the construction process and help you budget accordingly for remaining aspects such as flooring after the construction work is complete.

The price quoted by the builder can depend on many factors such as the type of the company, how busy the builder is at the time, how urgently the building work has to be carried out, and the exact items included in the quote. More standard design extensions are usually fully covered in the builder’s quote but it’s worth getting separate quotes from manufacturers or suppliers for more bespoke architectural features such as green or glazed roofs, wide-span glazed doors, special heating systems, feature materials etc.

The building process is often challenging but it’s always exciting to see the design from the drawings becoming your real-life home. The Ecclesall Design team is always excited to see it happen too and we are always willing to clarify our designs or give our client advice along the way. Please check out our Project Management page if you would be interested in our services and support throughout the building process.

Achieving Planning Permission Lawful Development Certificate - Ecclesall Design

Payment Schedule

Our fees are split into staged payments to reflect the commitment and progress made on the project at certain points. This fee schedule consists of 4 payments splitting the total amount into parts of 10%-30%-45%-15% payable at key stages of the process. This method fairly balances the value for you, our client, with the payment for the time our team spends.

The first payment of 10% is the project engagement deposit, with the second payment of 30% of the overall fee due when the building measurement takes place. This is the time when we carry out the site visit and survey the existing building and its surroundings. Also, this meeting is an opportunity to clarify your ideas and expectations for the proposed extension. After this meeting we will start work on the initial set of architectural design drawings which will contain not only the ‘existing’ drawings but also a range of options for the proposed extension.

The third payment of 45% is due once we meet to present the initial drawings. This meeting is one of the most significant parts of the process – it’s the time when we show you our ideas then together we explore the different options for your proposed extension. Our team will discuss various pros and cons of each suggestion so you can make the informed decisions that best suit your needs. Often this includes interesting ideas that were not initially thought about. At this stage we encourage clients to take as much time as needed to select the best way forward.

The fourth and final payment of the remaining 15% is due when the required rounds of amendments are done and the drawings are ready. This is the stage when the drawings can be used for the desired purpose: achieving planning permission or a lawful development certificate, moving to the next stage for building regulations approval, making investment decisions, consulting estate agents and mortgage advisors about changes in property value. This is the point when drawings become an asset and an instrument to achieve further stages of the project.

Third Party Payments

There are other fees involved in getting your project ready for the construction stage. These could be separated into two main groups: fees charged by local authorities and fees for the services of other professionals involved in the process. These fees are independent from the ones payable to our company and are necessary to ensure your project reaches the building stage with required permissions, certificates and reports.

The first group contains the fees payable to the local authorities. The planning pre-application enquiry fee is charged by a local planning department to assess your project proposals and provide feedback or recommend any changes required. Fees for planning and lawful development certificate applications are also payable to the planning authority. The building regulation detail application fee is payable to the local authority building control department or private building control company. These fees are fixed but can vary between different councils. We can advise you on this matter once you get in touch.

The second group of payments include the ones payable to individual professionals whose input is required in the process. Some of them are required for almost all the extension projects (e.g. a structural engineer) while others are needed only in certain circumstances or if local authorities require it (e.g. energy assessor, topographical surveyor, planning consultant etc). These professionals are independent from our company and their fees can vary. A client is always welcome to shop around and select their preferred professional. We can provide and advise on the quoting process if required.

Construction Stage Architectural Design - Ecclesall Design
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