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House Extension in Chelmsford
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M.Marriott Construction - "Transforming houses into homes"

House Extensions

Single Storey, Double Storey & Wraparound House Extensions & Porch's in Chelmsford and Essex. 

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If your house is too small for your growing family or needs, you need more space for entertainment or work, building an extension to your house is a perfect alternative to moving to a new home.  It is a less expensive option to moving to get the extra space that you need.

Increasing the size of your house with an extension is an excellent way to add value and space to your property. Whether you’re looking for new bedrooms, bathrooms, or a home office or playroom, you can quickly increase the size of your house with an extension.

We will collaborate with you to create a space that is tailored to your needs. We will create an interior and exterior for your house extension that complements the aesthetics of your current house, as well as your outdoor space.

When you work with us, you'll get a fixed price. We promise to respect your home and keep it clean, provide a superior service, and deliver your house extension project on budget. We understand that this is more than just a construction project — it's your home.

18 Years of House Extension Building 

Mark has been building house extensions for home owners in and around Chelmsford for 18 years, starting out with a small family building company, Mark went out on his own 5 years ago to specialise in his preferred projects - to discuss your project and get a free quote please get in touch today.  

Mark Marriott House Extensions Chelmsford

How Much Does a House Extension Cost?

You’re thinking about building an extension to your house. This kind of big project can seem pretty intimidating, and it’s easy to get overwhelmed with all the rules and regulations involved. To make things easier, it’s a good idea to think about how much it’s going to cost before you start.


Here we’ll cover: 


  • House extension costs

  • What are the factors that determine the cost of building an extension

  • What are the steps to adding an extension

  • How to hire an extension builder


If you want to extend your home, but you are unsure of where to start, you should keep reading or get in touch for a free quote


House Extension Costs: 

The cost of an house extension depends on a number of factors, including its size and complexity. Smaller, simpler projects tend to be the most affordable. The following are common types of house extensions and their costs, from budget to mid-range and high end in Chelmsford & Essex, the closer to London the more expensive as access, charges and higher material costs increase the overall costs:

Single-Storey House Extensions           

Budget: £1,000 - £1,600 Per SQM,  Mid Range £1,700 - £2,000 Per SQM,  High-End £2,200 - £4,000 Per SQM, 

Time Required  8 - 10 Weeks


Double-Storey House Extensions         

Budget: £1,200 - £1,900 Per SQM,  Mid Range £2,000 - £2,200 Per SQM,  High-End £2,300 - £4,000+ Per SQM, 

Time Required  12 - 16 Weeks

Wraparound House Extensions             

Budget: £1,500 - £1,900 Per SQM,  Mid Range £1,900 - £2,200 Per SQM,  High-End £2,200 - £2,500+ Per SQM, 

Time Required  12 - 16 Weeks

The above house extension costs relate to the shell construction and do not include the fixtures and fittings.

What are the factors that determine the cost of building a house extension:


When building a house extension, it’s important to know the exact costs. There are several factors that can contribute. The cost per square metre of construction is already very high with materials and skilled labour at a premium so the additional factors need to be considered.


Design & Planning Costs: 


When building a house extension you must consider the cost of the architect and potentially a structural engineer. Getting the required planning permission (if needed), building regs approval, and party wall agreements will also factor in. All of these things take time and money.


House Extension Dimensions:


The bigger the size of your house extension the higher your cost will be. Additionally, the materials used will have a major impact – brick, render cladding the amount of glass – will affect your price.


All buildings need a solid foundation, and that foundation is a hidden part of the total cost. If you're building on uneven ground, it may be more expensive than if you're building on something flat. Building around or diverting drains, underpinning, piling over strip foundations or excessively deep strip foundations due to nearby trees can all have knock-on cost implications for your project. 


Trees are a serious matter when it comes to House Extensions. When you are thinking about any kind of extension, it's vital to consider trees. There are many kinds of protected trees that could be affected by your work. If you cut down, alter or remove a protected tree illegally, you could end up in hot water. Nearby trees on your or your neighbours property will also impact foundation depths and systems.  

The Site Constraints:

If you have an unusual or complex site you may face additional costs, the soil type can affect the foundation system required, drains and services (gas, electric & water) can take surprising routes across properties and may need moving or upgrading at your expense. Access to your site and the space available may impact your builders schedule and an often overlooked cost is the knock-on effects of the new work on the existing interior, new flooring, plastering to walls and ceilings and decorating to the adjoining rooms are certainly likely requirements and should be considered from the start.    

Windows, Doors & Bi-Folds:

There are a staggering number of options when it comes to glazing and openings, Aluminium Bi-Folds and Lanterns are impressive and can make a house extension but can also dramatically push up the price over uPVC windows and French Doors. Discuss these options early with your architect so your building quotes are like for like. 

Fixtures and Fittings:

If you’re happy with standard finishes, you can keep your costs low. A lengthy list of extras can sometimes add up and lead to a costly renovation. As briefly mentioned above with kitchen and bathroom extensions, it’s all the little extras that can sometimes add up and lead to a hefty bill. If you’re happy with simply painted walls, carpet or laminated wood floors you can keep costs down. Luxurious touches such as bespoke flooring or tiling and fitted joinery can add a unique look to your house extension but will make it more expensive.

Home Insurance:

If you are planning to undertake a building project, call your home insurance provider. They may need to adjust your cover and premiums.

Initial House Extension Steps:

The process of adding a house extension to your home can be complicated. Here are some steps for you to consider:

Rough House Extension Costs: To work out the cost of your extension, you need to multiply length x width x number of stories x the cost ranges above. 

Planning Permission Requirements: You might not need planning permission. But you will definitely need building regulation approval. The good news is that you can speak to your local building control officer and find out about specific ground conditions in your area. That way, you’ll be able to know how deep your foundation should be before getting quotes from builders.

Architectural Drawings: Before you get quotes for your house extension, finalise the plans with your architect. Otherwise you will have different builders quoting different jobs. You want to get the drawings down to the last detail — the number and locations of switches and sockets and other features to get like-for-like, comparable quotations.

Selecting Your House Extension Builder:

When you're searching for a house extension builder, you should get 3 to 5 estimates. That way, you can see what the market rate is and who you like the most. 

Don’t confuse an estimate with a quote. If you're hiring a tradesperson, surveyor, or architect, they might give you an estimate on the first visit. If they seem like they're going to be a good fit for your job, then you should ask for a detailed quote so you can get the precise costs. 

To avoid being taken advantage of, you should have a family member or friend accompany you to any meetings. You’ll have somebody to verify any pricing, time frames, and personalities. More importantly, having someone by your side will ease your stress. No honest builder would ever pressure you into anything.

When you’re looking for a contractor, you can ask your friends, neighbours and relatives if they have any recommendations. Ideally someone who can tell you about their experience with the builder, and if they’d hire them again. 

What questions to ask your house extension builder: 

Before you begin any work, ask for a detailed quote. Verbal agreements are never a good idea. It's important to have everything in writing, especially when the job is big and expensive. A quote takes the guesswork out of an agreement. You know exactly what you’ll get, when you’ll get it, and for how much.

Like interviewing job candidates, when you’re hiring a house extension builder, it’s good to find out their experience and whether or not they’ve built something like the structure you’re wanting for your home extension. Even if you have a brilliant recommendation from a friend or neighbour, if the contractor is unfamiliar with what you want, they might not be the best fit for you. Look at the finished product. Ask for photos and videos of the contractor’s past projects to make sure you know exactly what you’re getting.

When you hire a house extension builder, make sure they have insurance that covers both themselves and you. This will protect you both financially in case of any trouble while they’re working. It will also help you avoid cowboy builders, who may not bother to get insured and will become irritated if pressed on the issue.

Free Quote For Your House Extension Project

To discuss your House Extension, Garage Conversion, Summer House or General Building project please get in touch.

Service Areas:

Chelmsford and surrounding areas in Essex.

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© 2022 by M.Marriott Construction Limited. House Extension, Garage Conversion, Summer House & General Building in Chelmsford & Essex. VAT Number 377248561. Company Number 13324525 Registered in England.  Registered Office Address: Bennachie, Buxton Road, Coggeshall, Essex CO6 1QR

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