Find out what's possible for your home with our architectural design appraisal service

How much can you extend your property?

Our Design Appraisal service provides a comprehensive and meticulous evaluation of a property’s suitability for development, with a focus on the architectural aspect. We define the potential for building extensions while ensuring compliance with planning requirements. The appraisal involves a thorough examination of the site, planning regulations, building regulations, materials, and design solutions.

How it works

Step 01. Book a Design Appraisal
Select your preferred package and get in touch to book your report with us.

Step 02. Kick Off Meeting
Once you book your Design Appraisal, we will invite you to schedule a kick-off meeting with our Architect to confirm your Project Brief, agree the report timeline, and explore some initial ideas for the scheme.

Step 03. Report Production
Our team will produce the report and keep you updated on the progress. See report deliverables here.


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What’s included in the report?

The deliverables depend on the type of report you choose. Generally, the Design Appraisal Report includes:

Site & Context Analysis: This part entails a thorough examination of the site, including any contextual constraints such as the potential impact of the proposed extensions on neighbouring properties.

• Existing Building/s Analysis: This section includes a review of the existing buildings or structures on the site and their suitability for redevelopment or preservation. The insights provided in this section are strictly based on the information available at the time of the report’s production.

• Planning Regulation: This step involves reviewing all relevant planning regulations, including any restrictions or conditions that may impact the development, such as conservation areas, flood risk, and listed buildings.

Materials and Finishes Analysis: This section provides an indication of the most appropriate materials to be used for the development based on the brief and on the planning constraints.

• Sketch Diagrams: This section involves a review of different design options for the proposed Home extensions. The number of options depends from the chosen type of report.

• Massing Studies: this section involves the production of a 3d model showing a schematic bird eye view of the property to better understand the size of the proposed scheme and the impact on the land and surroundings.

• Planning Success Rate: the conclusion section provides a summary of the key findings of the report in a table format, including the Planning Success Rate for each of the presented options. Additionally, each design option will have a list of associated potential planning objections to be considered when preparing the scheme for planning.


Private Residence Design Appraisal

We offer three Design Appraisal packages to provide a service tailored to your needs.


From £ 397 +VAT


  1. Kick-Off Meeting ( 1 hour )
  2. Sketch Plan ( 1 Scheme )
  3. Building Regulation Requirements
  4. Waste Management Plan
  5. Bikes Enclosure Plan


Delivered in 12-20 Working Days

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From £ 597 +VAT


  1. Everything In Basic
  2. Sketch Plan ( Additional Scheme )
  3. Public Transport Study
  4. Floor Risk Study
  5. Listed Building Study
  6. Conservation Area Study
  7. Planning Success Rate
  8. Design Appraisal Review Call ( 1 hour )


Delivered in 12-20 Working Days

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Price on application


  1. Everything in Regular
  2. Sketch 3D model
  3. High Level Cost Estimation
  4. Market Analysis & Comparables
  5. Rental Evaluation
  6. Screenshots from Rightmove
  7. GDV Estimate
  8. Consultants cost estimation


Delivery subject to project size

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"We were so impressed with the Design Appraisal done by WindsorPatania for our home in Cambridge. Thanks to their expertise, my wife and I now have a clear understanding of what extensions are possible. We couldn't be happier with the outcome!"

Philip & Katy — Home Owners, Cambridge

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What is a Design Appraisal?
The Design Appraisal generally includes a professional assessment of a property’s potential for adding new extensions. The purpose of this appraisal is to determine the feasibility of a proposed development scheme by examining various factors, such as planning and building regulations, architectural design and site constraints.

What type of extensions will you take into considerations?
We will look at any type of extension which can add value to your Home, including: loft conversions, dormer extensions, rear extensions, side extensions or basement extensions.

Why do I need a Design Appraisal?
The Design Appraisal provides valuable information to help Home Owners to make informed decisions about the project’s viability and whether to proceed with the next phase of the development. It saves time, helps avoid costly mistakes, assists with vendor negotiation, and supports pre-planning applications. Overall, it is an essential tool for anyone looking to develop ther home.

Is it feasible ( Can you do it )?
When you purchase your Home, it’s very important to go into the deal with complete clarity and confidence that you can do the expected conversion and renovation without much complication. This includes getting the required planning permission. WindsorPatania will help you understand your likelihood of Planning Success.

Is it viable ( Should you do it )?
Just because you can technically do it, doesn’t mean it’s a good decision.
Looking at the masterplan and understanding how many units you can fit in to maximise space, ensure compliance is an important part of extending your Home. We help you understand potential layout options to achieve your ideal down up value.

How much does a Design Appraisal cost?
We offer three levels of Design Appraisal, depending on the level of support you require. You can find the details of what is included in each package by referring to the relevant section on this page.

How long does a Design Appraisal take?
A Design Appraisal takes around 15 working days to produce depending on complexity. If you need it sooner you can request an expedited report for an extra fee to be agreed with WindsorPatania.

When should I get a Design Appraisal if I am planning to buy my future Home?
WindsorPatania always recommends getting a Design Appraisal prior to purchasing your future Home so you can know exactly what you’re buying before actually making the purchase. You can also get it before you make an offer to help with the vendor negotiation process but we recommend mostly doing it on properties that you are seriously considering buying and had an offer accepted.

What if I already own my Home?
If you already own your Home and have plans to extend it, this report is the perfect document to examine the feasibility and viability of your vision before committing to higher consultant fees.

Do you go on site to do a Design Appraisal?
A Design Appraisal does not include an on-site visit. It is a purely desktop research-based assessment that uses sophisticated tools and is designed to be quick and relatively affordable.

What do I need to start a Design Appraisal?
To begin the process, all you need are the details of the land you are considering purchasing or have already purchased.

How do I book a Design Appraisal?
In order to book a Design Appraisal please submit your project details via clicking on the button below.

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