House Extensions

Looking for a builder for your home extension?

Extension Builders in South East London, Central London & Beyond

Transforming your home with an extension is an excellent way to make more room for you and your loved ones.

Whether it’s a bigger kitchen, an extra bedroom, another bathroom, a bigger living space, side return or a combination, P&A have years of experience in planning, managing and completing brilliant extensions with care and attention to detail.

Whatever your goals for your house extension, P&A can help you find the best options for your project at competitive costs and great value for money.

At P&A we draw on years of experience in designing, building and renovating homes.

We can work with you on:

  • Single or multiple-storey extensions
  • Architect’s extension drawings
  • Quantity surveying and costs
  • Extension planning permission
  • Building regulations
  • Extension building project management

We know what it takes to build a great extension for your home, and we work closely with our team to ensure we make your project a success. We have the technical knowledge to convey exactly what you need to every member of the team to bring your ideas into reality.

Home Extension: Where Do I Start?

Extending your home is a popular way to increase space and add value to your property. With the hassle and costs of moving house – from legal fees to stamp duty – the reasons to stay put and improve your existing home soon mount up. But where do you start?

Tips on starting your home extension

Whether you’re thinking of a garage extension, side extension, double or single storey rear extension, there is much to consider as you embark on an improvement project to expand your home. To help get you started, we take it from the top with pointers on planning rules, building regulations, through to handling the neighbours and finding a builder.

Will your plans add value?

As with any big home improvement project, it’s worth sense-checking your plans before you dive in. Unless money is no object, it’s worth speaking to a good local estate agent who can give a view on whether your plan would add value to your home. They should also be able to give you an indication of how much it would increase the value by, which may help inform your budgeting for the project. Our guide to home renovation costs can also help with budgeting.

Permitted development and planning permission

You can undertake some extension projects without the need for planning permission, referred to as your “permitted development rights”.

Under the rules, a rear wall of a detached home can be extended by 8m to the rear if it is a single storey property, and 3m if it is double storey. This is reduced to 6m in a semi or terraced house.

There are also height restrictions: a single storey extension not being higher than 4m in height to the ridge and the eaves, and ridge heights of any extension not being higher than the existing property. And double storey extensions mustn’t be closer than 7m to the rear boundary.

There are other conditions that must be met. For example, if the extension is more than half the area of land around the original house, you will need planning permission. Extensions must be built with similar materials to the existing property. Find out whether or not plans fall under the permitted development guidelines.

Different planning rules may also apply if your home is in a Conservation Area, and for any renovations to a Listed Property you will need to obtain listed building consent.

Sometimes difficulties arise getting planning permission. Problems getting planning permission? Find a local Planning Consultant to help you.

Building Regulations

Regardless of whether or not planning permission is required, any renovation project must comply with building regulations. You’ll need to ensure whoever carries out the work can either self-certify the work they do (for example, FENSA accredited window fitters, Gas Safe registered gas engineers and NICEIC registered electricians and so on) or will liaise with the local Building Control Officers at your council to have their work certified. If the requirements aren’t met, you could be served with a notice to take the extension down and will have trouble when it comes to selling your home without the relevant Building Regulations certificates.

Your Insurance Provider

Before starting the project it’s important that you contact your home and contents insurance provider to let them know of your plans. The extension will likely increase the rebuild cost of your house – which insurers take into account when pricing premiums – while any building work could put the property at risk of damage. If you don’t let your insurer know and there’s a problem with the property at some point you may find your policy is void. Your insurer will let you know if your current policy will cover the new extension. You may find your premiums increase. If for some reason they are unable to cover the property now, you’ll need to find a new provider before your cover is cancelled.

You should also check that any builder working on your property has professional indemnity insurance to cover the costs should something go wrong.


If you own the leasehold – rather than freehold – to your property, you’ll want to check the details of your lease to ensure you have the right to make alterations, usually subject to approval from the freeholder. Get in touch sooner rather than later with your freeholder about your plans, as there may be additional costs involved to obtain their approval and sign-off. See when to approach your freeholder about your extension plans,

Your Neighbours

Building projects can be a major cause of disputes between neighbours. If planning permission is required, your neighbours will be consulted by the local planning authority, but before a letter lands on their mat, it’s a good idea to let them know about your plans well in advance, particularly if the works may cause disruption.

Party Wall Act

A party wall is the shared wall, usually between a terrace or semi-detached house, and divides the homes of two separate owners. It also includes garden walls built over a boundary and excavations close to a neighbour’s property (within three or six meters, depending on the depth of the new foundations).

Party Wall Agreements between neighbours are most commonly needed for loft conversions and extensions which require the insertion of steel supports, a damp proof course and/or digging of new foundations.
Read our guide about your responsibilities under the Party Wall Act and let us help you find a local party wall surveyor

Finding an Architect

Depending on the scale of the project, you may wish to involve an architect. There’s no law saying you need to use an architect, even for large renovations and builds, but some people find it easier to have a professional draw up the designs. Using an architect will generally mean you’ll get a better end result, however their fees are usually around 15%, so you’ll need to factor this into your budget.

Read our guide on appointing an architect and search architects in your area with our Find an Architect service.

How to brief an architect

When you meet your architect, it’s important you give as much detail as possible on what you want from the project, your timings, how and when you intend to pay them and what penalties will be in place if deadlines are missed. The architect will then send you a detailed appointment letter along with a contract to sign.

Obtaining structural engineer calculations

A structural engineer can also provide technical drawings and calculations which can be used to seek Building Regulation approval and will then be used by your building contractor and/or architect during the renovation work.

Find a structural engineer near you today.

Choosing a Builder

How to compare tradesmen
The key to any successful home improvement project is professional, reliable trusted tradesmen. Online review sites are a good place to start when comparing builders and other contractors. We’ve partnered with Checkatrade because of their vetting and review service.

Find and compare rated local builders to undertake your extension now

Getting Quotes

As with any service it’s always a good idea to shop around. We’d always recommend getting at least three quotes from three different contractors for the work. You’ll usually need to ask at least five firms to get three quotes. Find out how to invite contractors to tender for the work.

Setting a Budget

When setting a budget for your job start by making a list of everything you would like included (bear in mind the cost of a two story extension is not that different to a single story structure as most of the cost is in the foundations). Compare your quotes item by item and when pricing services and materials always check the VAT is included in the costs. guide to home renovation costs Read our for an idea of what you may need to pay.

You will also need to work out the best way of funding the cost of your home improvement project. Re-mortgaging or a home improvement loan? Read our guide on options for financing your home improvement project Common questions asked – What is contingency sum on a large construction project?

Side Notes

A contingency sum is an amount of money, usually expressed as a percentage, included in the project budget to allow for the unknown or unresolved aspects of a design. It is usual for the initial allowance to be as much as 25% to 30%.

How much contingency should a small building project have?

Most construction projects use a rate of 5%-15% from the total budget to determine contingency. Typically, that will cover any extra costs that might come up. However, it is often a bad idea to use a rate less than that, depending on the scale of the project.

TIPS -When planning your construction project, establishing a budget is one of the first steps in planning a successful project. Setting a plan for where to spend the money, and budgeting for all the work takes both attentions to detail and a complete scope of the project. However, there is often unforeseen issues, or items that come up where additional work will be needed. This is where a contingency budget becomes critical.

Preliminary Costs

(or ‘prelims’) may appear in tender documents, providing a description of a project that allows the contractor to assess costs which, whilst they do not form a part of any of the package of works required by the contract, are required by the method and circumstances of the works. In short, Preliminaries relate to the cost-significant items required by the method and particular circumstances under which the work is to be carried out, and those costs concerned with the whole of the works rather than just Work Sections. These costs may either be ‘one-off’ fixed costs, such as the cost of bringing to site and erecting site accommodation (and subsequent removal) or time-related, such as the heating, skips,labouer ,Plant , lighting and maintenance/Management cost for that accommodation.


Project Example - House Extensions - Extension Builders in South East London, Central London & Beyond
Project Example - House Extensions - Extension Builders in South East London, Central London & Beyond
Project Example - House Extensions - Extension Builders in South East London, Central London & Beyond


Having renovated our entire property over the last year we have had lots of experience with different tradesmen. P&A properties stand out by a mile as being the best we’ve hired. Their communication is excellent, their pricing is transparent and fair and they really know what they’re doing. The finish of the build is great and we felt in safe hands throughout. No ask was too big for Paul and Alison and we would have no hesitation at all in recommending them to anyone who asks. We fully intend to engage them again on future projects.


Paul, Alison and team did a great job redecorating three of our bedrooms. They were always on time, were responsive to comments and achieved a great finish. Would definitely work with them again in the future.


Looking for a builder for your home extension?

Extension Builders in South East London, Central London & Beyond

Contact us today for a free consultation about your building or renovation project

Call us on 01689 812942 or email us at

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