House extensions in London are everywhere! The eye-watering cost of moving, and the lack of affordable plots in London, mean house extensions (often with associated minor refurbishments to the original house) are by far the most popular building project route we get involved with.

Over the years, we’ve project managed dozens of house extension building projects in London. From loft extensions in Camden and basement extensions in Fulham, to more typical single and double extensions in Twickenham and Ham. We’ve also helped clients who have combined a side return extension with a rear extension, to create what is called a side-return, or wraparound extension. Side-return, or wraparound house extensions are a great way to create extra space and light to create an open-plan kitchen diner in semi-detached homes.

The seemingly unstoppable popularity of house extensions in London however means that the cost of building is at an all time high. Most architects and designer have healthy workloads, and the best builders often have long waiting lists. This means both professions can often pick and choose the work they do, and charge a premium for clients with more difficult projects, or those in a hurry.

Therefore, if you’re wanting to build a house extension in London, it’s now even more important to plan your building project with military precision. Don’t rush the process – think long and hard about what you want to achieve, and how much money you want to spend.

Step 1

Choose your architect or designer wisely. Research the market. Ask family and friends for recommendations. Match your project closely to the skills and scale of the designer. Meet with a number of architects, to make sure you can work together and understand their fees, before you appoint.

Step 2

Brief your architect well. Be open with what you want to achieve, and the money you have available. Talk about how you want to use the space. Outline what problems you might have with the house now, and what ideas you might have for the future. Be open about challenge – it may be that a small extension and re-configuring of the existing space will work better than that big double storey extension you had in mind.

Step 3

Once you’ve got some basic plans, but before you start applying for planning permission or looking for a builder, get an experienced Quantity Surveying company like CLPM to help you double-check that the designs match your budget. CLPM’s cost team can work with you to get an accurate, and very personal estimate of what your building project will cost you. This will also be fully comprehensive and include the elements that your architect may not have allowed for, such as your new kitchen, installing new wooden flooring or refurbishing other parts of the existing house that are affected by adding the extension. While your architect might quote a cost per square as a way of estimating your building costs, these are very inaccurate and often significantly under-estimate the true cost of the works. Labour and materials costs also vary widely – according to your location, and the exact specifications.

Step 4

Once you’ve established that your building plans are affordable, it’s time to get your planning permission. Then it’s time to get your architect to complete your building regulations drawings, and for you to get working on playing your part in producing the full specifications. It’s time to choose all the fixture and fittings you’ll need and to do some serious window shopping – quite literally! Once that’s done, it’s now that the search for a build team should begin in earnest.

Ideally you should have a small  team of independent experts, all of whom work cooperatively. This would be made up of your Architect, your Structural Surveyor, a Quantity Surveying specialist, a Building Project Manager, a Builder and you. For some clients it might also include a Lighting Specialist, Interior Designer or Landscape Designer.

Start by thinking about drawing up a list of possible builders. Do some research in your local area. Ask local family and friends for recommendations – and whether there are any companies to avoid!. Match your project closely to the skills and scale of the building company and pull together a short-list of 6-8 companies.

It’s then best to find and appoint a professional, Quantity Surveying company and an independent Building Project Manager. The Quantity Surveyor is an expert on building costs and building contracts, and is a vital member of the team. It is very unwise to try to save money by skipping this stage, and coordinating the tender and builder appointment process yourself. You are extremely likely to get inaccurate quotations from builders. They will probably quote quite low, but it’s unlikely that they will point out any omissions in your specifications. This is because they will then more than make up for the low quotation when they charge you premium prices for the additional extras that come to light throughout the build. This is the most common way that builders make their profits, and their clients over-spend on their projects!

It therefore makes sense to invest your money in paying for a Quantity Surveying company like CLPM to carry out the competitive tender and contractor appointment on your behalf. This involves our team carrying due diligence on the builder shortlist and establishing whether the companies are interested in tendering for your works. We then brief them face to face and give them a comprehensive tender document to quote against. We also help answer any queries they may have, and chase them to return their tenders within the agreed timescale. This ensures that all tender returns are in the same format, that they do not have any omissions or errors which might lead to the companies putting in additional sums, and means that they are as competitive and accurate as possible.Once we have helped you select your builder we than draw together the building contracts on your behalf.

N.B Getting an independent 3rd party like CLPM to carry out the tender process also means that you will get the lowest prices. It is a little know fact that many architects charge the builders they regularly work with introductory fees. While these fees are not charged to clients directly, this additional cost for the builder is naturally borne by the client indirectly with higher tender returns via the architect’s tender process. Here at CLPM we are 100% independent of both architects and builders, as we do not ask for, nor give, introductory fees so you can be assured that you will always get the lowest tender returns by using us.

Step 5

Appoint an independent Project Manager. Their role is to work with the Quantity Surveyor and coordinate your build team and in effect act as an expert ‘referee’ between you, the client and your builder. They also add an additional construction expert into the mix. The project manager’s role includes helping to spot and resolve any errors or omissions in the architectural plans. He or she also helps to ensure that the clients understand and make the best decisions, in a timely way. He is also there to challenge the quality of the builder’s work and to put pressure on the builder to keep to the agreed build schedule. The project manager also administrates the building contract. This involves making sure that the builder only invoices for completed works, and that any variances are logged and quoted against in a fair way. This ensures that the client only pays the builder the correct amounts. Once the works are completed, the project manager then helps with the snagging and defects stages of the build, and the release of the retained building contract sums.

Are you planning a house extension in London? If so then we’d love to hear from you. Over the years we’ve helped dozens of clients extend their homes in London and we’d love to help you too.

Get in touch to find out how our Quantity Surveying and Building Project Managers can make sure your building project is a success. Call 01923 896550, email info@cl-pm.com or complete a contact form today.

CLPM Project Managers cover London, Bedfordshire, Berkshire, Buckinghamshire, Gloucestershire, Hampshire, Hertfordshire, Oxfordshire, Surrey, and West Sussex. Energy Consultancy and Cost Advice services available across the UK.