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Extensionplanner.co.uk – Turning houses into dream homes logo

Extensionplanner.co.uk – Turning houses into dream homes

Brighton, Brighton and Hove, West Sussex

5 hires on Bark
Extensionplanner.co.uk – Turning houses into dream homes logo

Extensionplanner.co.uk – Turning houses into dream homes

Brighton, Brighton and Hove, West Sussex

5 hires on Bark


Extension Planner is a Sussex-based extension design specialist run by Lizzie and Peter Smith.

We work across the counties of Sussex, Surrey, Kent and Hampshire, and specialise in helping our clients take an idea for making their homes bigger, work out the best way to do it, and help them get planning permission.


Reviews (15)

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20 June 2020

Peter was extremely helpful from his first visit onwards, suggesting home improvements that hadn’t occurred to us, whilst also keeping costs in mind to stop us going wild. Very professional and clearly draws on a lot of experience as he takes a project on. Highly recommend! More...

12 June 2020

It was such a blessing to have Peter’s experience and insight to hand - he was adept at translating our requirements, and at the same time brought lots of interesting and useful ideas to the table. The planning application process was seamless, as due to Peter’s knowledge we were able to submit plans that were right first time - he handled the paperwork and made the application so much easier than I imagined it could be. We could not be happier with the service we received. More...

9 June 2020

We approached Peter as we were looking to extend our home, a major concern for us was that a similar plan to extend in the same area by a previous owner had met a number of objections and was subsequently refused by planning. We met with Peter who took the time to understand what we were looking to achieve and our concerns around the impact on the neighbours and planning. He came up with a design which met our requirements, addressed the concerns of the neighbours, and was granted planning permission on the first application. Very impressed with the service and would definitely recommend to others. More...

Thanks Rory. It was a most interesting project and we are delighted to have been able to help - that makes 12/12 with Horsham council in the last year!

20 November 2019

We’ve really enjoyed working with Peter at Extension Planner. It’s been a very collaborative and open-minded process, resulting in a set of plans we are excited about and will hopefully be approved by planning.

Thanks Jill, As you know the planning went through seamlessly with some very positive comments from the planning officers - they loved your living roof!

19 August 2019

Really helpful friendly people. The design it’s self was so much better than I imagined it could be. Super please with the results and definitely fully recommend
Thanks so much again 😊

Thank you Claire it was a delight working with you!

15 August 2019

Peter achieved what we hoped for our planning approval and would recommend highly

I wasn't sure if we would get it through, but the arguments we put clearly won the day!

20 June 2019

Peter from Extension Planner has a wealth of knowledge about the local planning system, really listened to what we were trying to achieve and was very flexible in working with us to submit plans for our kitchen extension. We're expecting approval next week! More...

Thank you Mary, we look forward to seeing your fantastic new kitchen!

7 June 2019

I would very much recommend working with Peter as he took the stress and worry out of our hands completely from the moment we contacted him. He was very flexible and fit his visit around our schedule. He spent time listening to our ideas and he made some valuable suggestions. We opted for Peter to submit our plans to remove the hassle of dealing with planning services. He kept is well informed at all stages of the process and the work was quickly submitted to planning. The whole process took less than 2 weeks and felt effortless. More...

Thank you Kath. It was a real pleasure working with you!

7 June 2019

Highly recommend Peter Smith. Very reliable and answered queries even at Weekends. Had great patience with my suggestions, and came up with amazing ideas for my whole house and garage renovation.

Thank you Pamela & John - one of the most exciting and enjoyable projects (and clients!) we've worked with. Hope the build goes as smoothly!

9 May 2019

Outstanding service. They really know their way around the regs and nuances of different local authorities' planning needs. Great people to work with and delivered an outstanding result More...

Thank YOU Philip. It was certainly an unusual and interesting brief, and we were really pleased you asked us to deliver it for you.

7 March 2019

I've worked on two projects with Peter & Lizzie now and been deeply impressed with their ability to come up with answers to tricky problems at very short notice. Lizzie has an eye for detail in the way things looks that is outstanding, and Peter produces plans that are clear, easy to understand and to a very much higher standard than many of the large and costly architect firms we have worked with in the past.

I'd recommend them to anyone looking to expend or update their house sympathetically and to a high quality.

Very kind Alan - As you know we generally never recommend nay suppliers, but in your case we're happy to make an exception!

7 March 2019

We couldn't believe how tricky it is to get permission in a conservation area, but despite all the obstacles, Peter & Lizzie pulled it off, and we ended up getting not just one, but two excellent extensions. They are thoroughly professional, extremely helpful and full of good ideas. A pleasure to work with them. More...

Thank you Mike. Getting anything substantial in the SDNP is always going to be a challenge, and we were delighted that we could find a solution that worked for both you and them

7 March 2019

A really great experience- We had a lot of different things we wanted to do, but not the budget, so getting the planning permission at the outset meant that we could work through the different aspects of the job over time, without having to worry about going back to the council each time we wanted to do the next bit. It meant we had one less thing to worry about.

As designers we really could not have found anyone better

Thank you Paddy. It was a really interesting project - as you guessed we love traditional houses and its great to find a client that wants to bring out the best in them as well as preserve heritage

7 March 2019

We had a particularly complex project - a thatched house conservation area, so needed a designer that could very tactfully design a major extension - we added around 50% of the footprint! . Peter & Lizzie were fabulous to work with. They really do know their stuff and we got lots of great ideas, as well as a seamless planning permission. More...

Thank you Paul. This was our first thatched house, so seeing it in Country Life was a huge plus for us. May you enjoy it for many years.

7 March 2019

We found them to be very knowledgeable and helpful to work with. They brought an air of calm and confidence tot he proceedings, despite the complexity of the build. Whenever we spoke we learned something useful, and when we needed advice, they were always there. More...

Thank You Roger. It was a good fun project as well as complex, and we hope you will be equally delighted with the final results when it is finished.


We have got a number of successful plans through for garage conversions, including adding a room above, relocating a garage and redesigning frontages.

Generally the first thing you need to check out is the local authority planning guidance. Depending on where you are you may be refused on the principle that you cannot afford to lose off street parking. If you can demonstrate that there won't be a loss of parking, perhaps through having a large off-street parking area, then you might be able to get it through.

You also need to consider the impact on the street scene and other properties. These are very important

First off is making sure it is suitable, with in structure and planning terms. Then we go for planning permission, which involves drawing up a full set of plans, working with the local planning policies and interacting with the planning and conservation officers as needed.

A lot of local authorities are very short staffed in planning, so welcome applications that they can deal with easily. This means lots of attention to detail, making sure everything marries up and that all the correct documentation is completed. We do all this as part of our service.

Once you have permission, you then find a builder, preferably two or three, and get quotes for the job. It's important to find a builder you get on with, because all birds are stressful, and you need to be confident they will have your interests in mind!

There are lots of builders that specialise in small jobs. They will bring in specialist subcontractors, like electricians, plumbers and decorators, to finish the job, and provide an element of project management - making sure all the materials arrive on time and that you don't have days where you are paying people with not much to do!

A lot depends on the way it has been built. Any loft can be converted, but you must again abide by the local authority's policies. In some areas, like Brighton, the Council is actively against more loft conversions facing the road. Arguing precedent doesn't cut much ice, as they have amended their structure plans to stop them in some areas, especially those where there are conservation policies.

If it is a pre-1950's house, conversion is normally a lot simpler as these were built with pitched, rather than truss roof construction . We need to survey the property to check how it has been put together to advise, as this could have a dramatic effect on the cost.

As with any build, the first stage is planning, then you go through the builder selection process, and the deep joy that is building regulations.

Building regulations have traditionally been carried out under a building notice. This minimises the need for detail drawings, although we do produce these if needed, and instead relies on the building inspector being happy that it is being put to gather properly. Any structural item, like RSJs, or structural Oak Beams, will need calculations. We can recommend Structural Engineers, or an online service for simple linear loads, such as when a room is being opened up.

Every property is different, as are the owners, but they all share one thing - a desire to turn their property into a dream home. We share that desire and love being able to give a client the basis they need to achieve their perfect home.

It really is the perfect job - we get to meet friendly people who want to make the best out of their properties and help them turn houses into dream homes.

We started out doing it for ourselves after having a number of architects and designers come to visit us when we were starting out on the refurbishment and extension trail thirty odd years ago. We found that most didn't want to share ideas until we signed up to an expensive contract - often costing over £5k. Having learnt about building design and construction as part of training to be a Chartered Surveyor, we already had the skills required to do the plan drawing and application process, so developed our own ideas and did it ourselves.

Since then we have either redeveloped or new-built around 50 individual properties on our own account, and helped many more people turn their ideas into practical extensions. At one stage we ran a 20-person professional consultancy, but having semi-retired, we now focus in extension planning.

Over the years we had many people asking us 'who was your architect' about our own properties, and when we told them, they asked us to do plans and designs for them. After a while, it struck us that there was business opportunity, so we launched the website about ten years ago and have been keeping busy ever since.

We always try to work with our clients to give them the perfect result.
Our approach is service-led, so we make sure that you are never outside your comfort zone
We have huge knowledge of extending and modifying properties, both as designers and having done several builds of our own
We offer exceptionally good value - all our prices are based on fixed price menus, and we don't charge 'extras' just to move a wall on a plan
We're nice people to do business with!


A complete service to help you redesign your home by extending and making the best use of existing spaces. THis includes all the elements you need Including: Planning Permission Plan Drawing Building measurement Construction guidance Planning consultancy

After preparing plans we provide a one-stop-shop service to manage the planning application process which includes: Dealing with local authority Creating appropriate statutory plans Submitting all plans and documents to Planning Authority preparing Design Heritage and Access Statements Arranging public adverts ( if needed) Monitoring progress Dealing with any Local Authority queries We provide this service for £700.00 plus disbursements, e.g. planning fees, statutory MPs advert costs etc.

This is the basic service you need or any planning application and builder quotes. It includes Measuring up the property to provide an accurate base Drawing before and after floor plans and elevations to 1:100 or 1:50 as needed Ensuring the plans comply with planning authority requirements We provide this service for £1545