The dos and don’ts of planning a home extension
Here, RIBA-chartered Architect George Omalianakis from architect firm GOAStudio offers professional advice, tips and key insights to guide you through the process of adding an extension to your home.
Article written for i-Build magazine by George Omalianakis, GOAStudio London residential architecture.
There is a lot to consider when you start planning how to add an extension to your home. You will need to appoint a team of design professionals to advise you and you will reply on their skills, knowledge and experience at the start. Then you will need to appoint a team of contractors who will build your extension.
Luckily the project process is broken down in stages, which means that you will not need to make all the decisions at once. Pretty soon you will get used to the pace of things and the step-by-step approach that is required so that everything is done and considered in the right order.
Below Chartered architect George Omalianakis, RIBA from GOAStudio architects offers professional advice, tips, and key insights to guide you throughout this process.
Design matters – What do I want and how can I achieve it?
Remember, B comes before D but not before A – You need a Brief before you start with the Design process because you need to know in advance about what you hope to achieve and what your budget is for your home project. However you will not be able to finalise your Brief before you have Appointed an Architect to Advise on the overall feasibility of your project which will then inform your Brief and help you make a final decision on how best to proceed.
DO design from inside out – start with by thinking of the internal spaces and how they work for you, including the existing spaces next to the new extension. Adding an extension means that everything else changes too and you will need to tweak things to ensure that everything, new and old, works together in harmony and to your needs.
Garden is a stage – the chances are that 98% of the time you will be inside your home looking out. There will not be too many times that you will sit at the back of the garden to admire a particular gutter detail the architect did for your extension. The garden will most definitely be your focal point, what will visually surround any internal space you will create. For this reason DO allow part of your budget and creativity to extend to your garden area and DO ask for the help of a landscape architect or garden designer to achieve this.
DO balance the living and bedroom areas across the property – you can potentially extend your home by going up, down, to the side, to the rear, sometimes to the front, one a single storey or two storeys. And you will have particular requirements for a larger kitchen, for another bedroom, or for additional family space. Your home will be able to accommodate one or more of these extensions however DO ensure that you keep a balance between the number of bedrooms you add, the amount of living space available, and the amount of garden left once you are done with extending your home.
DO think long term with the choice of materials and the associated plumbing, wiring, heating and insulation you can add to your home – you will probably have one chance, one opportunity, to upgrade the fabric and systems of your home. When you start planning your extension consider what other upgrades you would like to do and how your budget could stretch to cover for these additional works. The time you will add the extension will be the most perfect, convenient and cost-effective, time to add a few more things to your project Brief that will pay massively off longer term.
DO consider the roof profile of your extension – you might not have too much choice when it comes to the roof profile of a mansard or loft extension, and that’s fine. However the design of your roof might be the single design item that can define the most the character of your extension, create an wow factor internally and externally, and help you zone the functions (kitchen, dining, living) of your home in a sensible and proportionate way that will feel just right.
Approval matters – What approval will I need for my home project?
For your home extension project you are likely to need one or all of the following approvals:
1. Planning – Full planning, or a Householder application, or a Permitted Development application, or Listed Building Consent depending on the type of your property (house or flat), on the type of the works you would like to carry out, and where you are in the country. This is an approval you need to obtain from your local authority and remember that there is a number of different applications under the umbrella name of “planning”. DO ask your architect and your local planning authority to advise you on which application you need to submit for your project.
2. Building Regulations – This approval is in regards to a number of technical and structural standards that need to be met to ensure safety and compliance, this includes fire safety, thermal insulation, sound insulation, and structural considerations. You DO NOT need to have detailed knowledge of any of these matters but you DO need to make the right appointments (typically an architect or technician or technologist and a structural engineer) for knowledgeable professionals to prepare this information on your behalf.
3. Party Walls – if you DO works near a shared wall, floor or ceiling then the Party Walls Act might become relevant to your home project. This means that you will need to engage with the neighbours under the Act and satisfy them that the works will not affect their property. DO contact a Party Wall Surveyor who will give you all the advice you will need.
4. Freeholder approval – if you own the Leasehold of the property or if you own a share of the Freehold then you will need this approval from anyone with a Freehold interest to your property. DO check the relevant terms in your Lease or share of Freeholder agreement and DO ask a solicitor to advise you on the process you will need to follow. This process is specific to you and the particulars of your agreement.
5. Water authority – if you do an extension near or over any public drains in your garden then you will need to obtain the relevant approval from your local water authority. DO appoint a CCTV drain survey company to survey and map the private and public drains around your home. DO send this information to your local water authority who will advise you on whether you need to apply or not, and how you need to go about it.
DO apply and DO obtain in advance all the approvals you need for your project.
DO NOT take chances because this will cost you later in money and time.
Money matters | How much will it cost and how much can I do with my budget?
You DO need a shopping list of project requirements before you can possibly have a realistic and reliable estimate of costs for your home project. No builder, architect or quantity surveyor will be able to tell you how much your extension will cost before they have a list of design, technical and structural information to price.
DO start with a budget though and DO decide how much you are comfortable with spending for your project. In fact this is a much better starting point when you start planning your home project. Your budget will determine what you can do and what you will not be able to do and ultimately you will have to cut your cloth accordingly during the design development stage.
BE prepared for the possibility that your project requirements and your budget are not compatible and that something has to give in this case. You can set of priorities for the budget to cover and then stick to these priorities for your project. Or alternatively you can re-think the budget, decide that some things are too important to leave out, and magic something happen to increase the budget accordingly if this is possible at all.
Also, BE prepared to discover that the project is not feasible in a way that you find satisfying. In this case you might abort the project or postpone it for a few years down the line when you will be able to spend more.
Cost control is a process and there is a secret to it – DO NOT wait to get costings at the end of the design development process and after you have obtained all the required approvals. Because at that point it will be too late to discover that the cost of the works is substantially above your budget.
Instead DO prepare some initial design proposals and DO get some very rough cost estimates from a builder or a quantity surveyor. If the estimates are roughly in like with your budget then great, you can now proceed with developing the proposals further and make the planning submission to the Council.
DO the same once you have prepared the required technical and structural information for the Building Regulations submission. Is the new estimate still in line with your budget? Brilliant and you can now proceed with making your final decisions on finishes and electrical before sending the information out to the Contractors to tender for detailed quotes.
This way you ensure that any detailed quotes from the builders will be around your budget and that any variations will be manageable.
Time matters – How long will it all take?
DO NOT be overly optimistic about how long things might take, the chances are that everything will take a bit longer than expected. Often this is due to fault of no one in particular. And often enough this is due to “unknown unknowns” that you only discover later in the day.
Which means that you should ALWAYS have a contingency plan and be ready for when things overrun. You often read that you should have a contingency when it comes to costs. Well, similarly the trick is that at the start of your project you also have a contingency plan when it comes to time and this will take a lot of stress out of the whole process.
Generally speaking it takes around 4-6 months to go through the design development phase and to obtain all necessary approvals before your builder is able to start on site.
DO invest time and energy and focus during the design development stage – this will pay off massively down the line and it is during the design development stage when the magic happens and when everything takes shape. What you want to achieve is a solid outline plan that responds to what you and your family needs. This is a really valuable investment of time and once you have come up with this initial plan you can speed up the rest of the process to develop this plan accordingly if you have to.
DO invest effort and time in selecting builders – no good contractor sits around waiting for your call ready to start with your project this coming Monday. In fact the opposite is true and most builders book jobs well in advance. Check their references, visit their sites (tip: a clean and organised building site is a sign of good management skills), see how you get on with them and if possible be prepared to wait for the right builder until they are available to start your project.
Construction matters – What are the key things to know during the construction stage?
DO have a written and robust contract with your builder – in an event of a dispute you will not be able to rely on the memory of what was said, who said it, and when it was said. A lack of a robust contract is an actual recipe for disaster and problems down the line. A fair contract will keep things straight-forward during the construction stage and a written contract, and the clarity it provides to all parties, will give you peace of mind and it really is priceless as a safety net at all times.
BE specific and clear with your builder about what you need – the contractor is not a friend. Sometimes working relationships, and ultimately projects too, fail because of lack of boundaries and lack of clear roles and lack of clear communication. The same thing can happen in a relationship between a homeowner and a contractor and over familiarity might not the best approach when there are might be site issues to be resolved and some difficult discussions to be had at some point.
BE friendly with your builder at all times – you are a team and you work together for a common goal. A building project is always a collaboration between the homeowner, the design professionals and the construction team. Chemistry is important and remember that every single member of this hastily-put-together-band-of-people will be very proud of the outcome when your home project is complete.
DO agree a payment schedule with your builder in advance – typically it should include 4-5no. stage payments, the first payment should not be more than around 20%, and to include a retention fee (typically around 5%) that is not paid until every single piece of work has been completed, including any snagging items.
BOROUGH SPECIFIC ARCHITECT AND PLANNING GUIDES FOR YOUR HOME PROJECT
Your local Council will have in place design and planning requirements for your home project and you will need to obtain planning approval for a wide range of extensions and alterations to your property.
When you get in touch we will offer you detailed advice about what is likely that your Council will approve and in the meantime we have prepared the following architectural and planning guides that include extracts of the relevant planning policy and examples of our projects in our Borough.
Barnet architects | Planning and design homeowner guide, Camden residential architect and planning guide, Enfield residential architect and planning guide, Hackney residential architect and planning guide, Hammersmith Fulham residential architect and planning guide, Haringey architects | Planning and design homeowner guide and planning guide, Islington residential architect and planning guide, Kensington and Chelsea Conservation architects, residential and planning guide, Lambeth residential architect and planning guide, Lewisham residential architect and planning guide, Newham residential architect and planning guide, Tower Hamlets residential architect and planning guide, Waltham Forest residential architect and planning guide, Wandsworth residential architect and planning guide, Westminster residential architect and planning guide
HOME DESIGN – Find ideas for your project.
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We provide architectural services for residential projects in the following London Boroughs:
Barnet, Camden, Enfield, Hackney, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Lambeth, Lewisham, Newham, Tower Hamlets, Waltham Forest, Wandsworth, Westminster
We specialise in
- Greener homes
- Retrofit and energy efficiency for older and traditional buildings
- Conservation areas
- Listed Buildings
- Homeowner architectural services
- Property developments architectural services
GOAStudio London residential architecture limited.
86-90 Paul Street, EC2A 4NE, Hackney
Chestnut Avenue South, E17 9EJ, Waltham Forest
t: 0203 984 3005
