House Extensions

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.

​

Groundworks: 

​

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:

​

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.