Extending your home – what you need to do

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Extending your home can be a great way to add space and value.

Here’s our step by step guide to what you need to do to make sure it is a success.

The feasibility stage

  • Review the need and validity of doing it. Sometimes an extension is not the answer to your problem. A well designed extension can be great but it’s true to say that it is rarely as good as a purpose designed and built house of that size. Moving might be a better option, but of course that could be unaffordable. One pitfall to be wary of is over-development; this could be creating a property too big for it’s plot or of a size or value that nobody will buy because its not in an area where those kinds of buyers are looking.
  • Review your constraints and priorities. The project management triangle is Time : Cost : Quality. You cannot alter one without affecting the other two. Which one is your priority? Set your budget, timescale and what you want.
  • Budget. Establish what funds you have or will have available. Not only for the construction work, but also for contingency to deal with unforeseen work or problems, the various fees and the complete fitting out including carpets, appliances and furniture. Most people don’t stop to think about the future cost too; how much it will cost to maintain. Use this to define the scope of what you can afford to do.
  • Research. Look at similar extensions locally. These give you an idea of what was achievable and was permitted by planners. Check for local precedents and limitations. A good place to see this is the local authority website planning section where you have access to view previous planning applications, look at the actual plans and even the planners reports, commentary and objections. You must also look at the Planning Portal website where there are guides on what you can do within permitted development (automatic planning permission) and what you have to apply for planning permission for.
  • Regulatory constraints. There are many things that could constrain what you can do or require an additional consent. Is the building Listed? Bear in mind Listings can be national (Grade I, II or II*) or local (on a list as the council themselves have deemed). Is it in a Conservation Area? Would excavation be required an area of Special Archaeological Interest? Your plans could also need to take account of environmental issues, so search for known or likely Tree Preservation Orders, habitats of bats, badgers or newts, SSI’s or other ecological constraints. We can help with this if you don’t know where to start, optionally as part of our Design and Drawing Service.
  • Sketch your plan. Now you can begin to sketch out what you want within these constraints as a basis for developing a design. We can do this optionally as part of our Design and Drawing Service.
  • Speak to neighbours. Talk to neighbours who may be affected by your plans. You can get a good idea if there will be resistance or objection. You don’t have to but it gives you an opportunity to modify your plans to ease these issues. This is more important where full planning permission is required.
  • Consider the impact. Review what this means for you personally and as a family. Financially, can you only just afford it? What if it there are problems or extra work discovered? Delays? Can you move out for the work, live with relatives or afford rent on top? Will you live in half a house with a building site and contractors coming in and out all day? What if you have no useable kitchen or bathroom? Do you have to pay for storage of furniture or possessions? It will take longer than you think. It will be noisy, dirty and stressful. Home life and privacy will be impacted. Neighbours may be impacted too which can cause difficulties. Not everything will go according to plan.

The outline design and planning stage

  • Planning drawings. You’ll need plans and other drawings for confirming the design, assessing regulatory requirements, making a planning application or confirming permitted development. The planning drawings are about the overall plan, size, shape, appearance and impact. More detailed technical drawings are needed later for building regulations consent and for contractors to quote with and then to use to build from. We provide planning drawings and advice, see our Design and Drawing Service.
  • Planning permission. Virtually all extensions require planning permission, but some within certain limits have an automatic permission granted called “Permitted Development”. Other extensions and changes outside the allowed limits have to go through a full planning application. Anyone can do a planning application, but it can be much easier and smoother to have us do it for you. We can do this optionally as part of our Design and Drawing Service.
  • Listed Building Consent. If the subject house or area has historic status such as listing or is close to some, or in a conservation area then a listed building or other consent might also be required. This is usually done in tandem with the planning application process and again we can deal with that optionally as part of our Design and Drawing Service.
  • CDM – Construction Design and Management Regulations 2015 – design stage. As part of our Design and Drawing Service we would advise you what needs to be done to comply with these design safety regulations and carry out the required duties with you.

The detailed design stage

  • Construction drawings. Detailed technical drawings are needed for building regulations consent and for contractors to quote with and then to use to build from. We provide this service, see our Design and Drawing Service. We can also find and liaise with trusted qualified structural engineers who design the structural parts required, such as beams and foundations.
  • Specifications. Written specifications can be relatively simple and added to construction drawings or for more complex projects they can be a detailed separate document. On larger schemes there might be separate schedules listing every door, windows, and finishes such as paint or tiling and where each apply.
  • Building Regulations. Whether a planning application was required or not, a building regulations application is almost always required. Planning deals with the look and impact of the building, but building regulations deal with the technical details and compliance of the construction work itself. The detailed drawings are submitted to building control and a conditional ‘plans approval’ consent is given showing that the work looks good on paper. We can do this optionally as part of our Design and Drawing Service. The building control officers will detail which stages of work they want to come and check during the build. A building regulations certificate of compliance is only given after the last satisfactory inspection.
  • Licence to build over a sewer. If the planned building is close to sewers, you will need to also get a licence from the water authority. This involves submitting satisfactory drawings and paying a fee but can take many weeks to obtain. Again we can deal with that on your behalf.
  • Party Wall Etc. Act 1996. Building on or close to a boundary or doing work to a shared wall is likely to come under the control of the ‘Party Wall’ Act. This is quite complex and nuanced, and involves significant fees, obligations and liabilities, so it is best to get good advice in how to approach it. We provide party wall services separately.
  • Scaffold licences or access licences. For some sections of work you may need access on adjoining land. This might be covered by the party wall act or sometimes has to be negotiated separately. We can advise on this and provide the services required separately.
  • CDM – Construction Design and Management Regulations 2015 – detailed design stage. Further duties apply here. As part of our Design and Drawing Service we would advise you what needs to be done to comply with these design safety regulations and carry out the required duties with you.

The tender stage

  • Contractor competitive tendering. You should never take a single tender price or quote for a job. Always compare at least three quotes. You should ensure that each contractor prices for the same work; this is where detailed drawings and specifications come into play – if not one contractor may price for low quality build or materials and another for high quality and they cannot be properly compared. Make clear the terms you will use; a written contract is a must. Contractors should be found from approved lists and recommendation; view their work and speak to past clients if possible. Deal with established, reputable and traceable companies. Ensure they have insurances.
  • Special packages – kitchens/bathrooms direct. You may have decided on a particular brand of kitchen or bathroom either for purchasing materials direct or full install by the specialist; make sure that you make this clear to tendering contractors and everyone understands the interface between areas of work and who is responsible for what, particularly plumbing and electrics. Also be wary of delays caused by one contractor impacting the other and resulting in extra costs.

The works stage

  • Written contract. Always use a written contract to appoint contractors. There are several simply laid out domestic consumer contracts available from organisations such as the Joint Contracts Tribunal, NEC, the Chartered Institute of Building and the Federation of Master Builders. Most contracts set up stage payments. Avoid any payment up front, unless you are sure its for items which have had to be ordered and that those items are formally your property even if not yet delivered. If a contractor has inadequate cash flow to fund the works they should probably be avoided.
  • CDM – Construction Design and Management Regulations 2015 – construction stage. The next stage of duties apply here. For domestic clients, these duties would usually fall to your appointed contractor.
  • Management, monitoring and checking. This is a key area overlooked by many. Leaving the contractor to simply get on with it is going to go badly. Some clients have done this and then found they are stuck with poor quality, defects, part completed work and often ruined neighbour relationships. If you cannot regularly monitor, check the work and control contractors conduct you should appoint a project manager or surveyor to do that for you. We provide this service on commercial and public sector projects only.
  • Building Regulations. The building control officers will detail which stages of work they want to come and check during the build. A building regulations certificate of compliance is only given after the last satisfactory inspection.
  • Handover documentation, manuals, warranties and certificates. Ensure the contractor hands over all the documentation, manuals, warranties and certificates required for the new work.
  • Defects. Using a written contract as above will give some protection about defects that arise. Many have an option for retention of a small percentage of money for a period of months which is only paid when the contractor has sorted out any defects arising. The contractor may have either a six year or twelve year legal liability for materials and workmanship, but no money is held for that time and some may go out of business or be wound up so choose an established company which you think will be around for some time.