House Extensions St Albans

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Do you need more space in your family home?

We are St Albans house extensions leading experts.

Struggling To Find A Reliable Builder For Your House Extension?

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14+ Years of outstanding building work in St Albans

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Fully Customisable

Custom built to your unique requirements.

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5* Reviews

More than 90% of our work comes from recommendations.

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Why Choose Us
For House Extensions In St Albans?

CJ Smiths is a great choice for those St Albans residents looking to extend their home.  We have over 14 years of experience in the building industry and stand proudly as the premium builders of St Albans City.

Our reputation in the local community is unmatched, and we are proud of our many 5-star reviews. Our team are highly skilled individuals with extensive experience and a genuine passion for what their work.

We operate as a family-run business. We take pride in the fact that 90% of our work comes from recommendations. For your next project, choose Cjsmiths and experience the difference.

Building up into the loft can also be a great way to add space to your home. Cjsmiths are the top rated loft conversions specialists. Please check out our service page to find out more.


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Benefits Of Extending Your House

If you want to increase the space in your home without relocating, then an extension may be a great choice. They can also raise the value of your property and provide the necessary extra space.


Planning Permission Advice

We can help you with your application and the process of securing permission.

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We offer custom payment plans to suit your budget and needs.


Complete Project Management

We will manage your extension project, ensuring it runs smoothly.



We aim to ensure you are completely satisfied with your new extension.




Different Types of Residential Extensions

These extension types below will showcase what CJ Smiths is capable of building for you.

Single Storey House Extension

One of the most popular types of extension is a single-storey, often seen as a kitchen extension. These extensions are often built on the side or rear of the house. This utilises the unused garden space and gains valuable kitchen space. French doors and bifold doors are often used to invite natural light in.

Two Storey Extension

Double storey extensions cost more than a single storey but can be budget efficient. With the average cost per square metre being lower on the double storey. This is because foundation and roofing costs are similar for both types. They can gain the family home an extra bedroom and a larger hosting area downstairs. Increasing the value of the property.

Rear Extension

With a high likelihood of planning permission approval and minimal disruption to neighbours. Rear extensions are a prevalent type of home extension in the UK. By extending your property out into your garden space, You can create a large open plan living area and kitchen.

Side Extension

Like the rear extension, a side home extension can be single or double storey. But if you don't have much garden space and have unused space on either side of your home. A side extension can be a great option to extend your family home. A prevalent use of this extension is to add an extra bedroom or increase kitchen and bathroom space.

Wrap Around Extension

A wrap around extension is an L shape extension that is at the back of the property. It is a combination of the popular side and rear extension. And can be either single or double storey, depending on the budget. By adding extra property space on the rear and side, the possibilities are endless when it comes to design.

Side Return Extension

This type of extension is similar to the rear as it's built onto the back of the house. But the aim of this extension is to make use of the wasted space called the " Side return ". This is the small alleyway that runs along the side of your house. With this extension, you can gain space without losing any of the garden.

Over Structure Extension

This type of extension uses the existing property footprint to build upon. The most common type is building a small extension above the garage. Where you can create an extra bedroom for the house or a comfortable office space. This allows extra living room without taking any of the existing ground level space away.



How Much Is A House Extension

Typically the cost of an extension will be cheaper than moving to a bigger home. If you love the home you live in, they are a great option. Prices can vary depending on factors such as size, complexity and design.

On average Single Storey, extensions range from £1600-£2600 per square meter. Double Storey extension prices range from £1700-£2800 per square meter. 

For us to be able to provide you with an accurate quote, we would need to come and see your project.

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Get Inspired

We are the leading experts in home extensions. To see our gallery and gather some inspiration. Please see our Projects page.

Milvus Road

This beautiful St Albans extension increased the light and kitchen space. We installed a new pathway around the house and an impressive patio. This increased the property's curb appeal and functionality.

Hatfield Road

Space is a growing need we all face. The installation of a single-storey rear extension to the house increased the space downstairs. Allowing our Hatfield Road clients to expand the kitchen area and increase natural light.

Eagle Way

Cjsmiths managed this project and all the building work involved from start to finish. We are very proud of the result. We completed an oversized rear ground floor extension for our Eagle Way clients. 


Client Testimony

What Our Clients Say About Us?

Feel free to read more about what our previous clients have said about us designing and building their vision.

HK Buono
HK Buono
Had my garden renovation nicely done. Staff are attentive, sincere, efficient and knowledgeable. Able to answer to all my doubts and give constructive advice when facing contingent issues. They also clean up the place at the end of the project, no follow up cleaning needed. One good builder with integrity, knowledge, expertise and efficiency. Will definitely call them up for my next project. Highly recommended.
Deepak Anand
Deepak Anand
Assigning Craig to manage our life long dream of creating a big kitchen/living room (90sqm) was one of the best decisions we ever made. We got in touch with Craig 1 year in advance of works commencing and from the get go Craig scheduled an initial meeting to discuss our plans. Leaving the meeting Craig gave us new ideas and put no pressure on signing and was happy to work around us. Having visited several existing projects and received great customer feedback, we knew Craig was the builder for us as the quality of work was just exemplary. Craig saved us 5K by urging us to allow him to project manage the build and true to his word, he was on onsite multiple times per day, making sure everything was perfect. Along the way, we did encounter some problems, due to the existing condition of the garden but Craig always had a plan to work around them and not change designs with little or no change in cost. Craigs team are highly skilled, clean and respectful. They always tidied and locked up at the end of each day which left us worry free. One great trait about Craig; he treats his jobs like his own home and if he’s not happy with it, the project does not move to the next stage. It is no wonder he is respected in St Albans as a 5star builder. We will 100% be onboarding Craig again to do our 2nd story and driveway in the future. A big thankyou to Craig and his excellent team.
Hannah Franco
Hannah Franco
Craig and his guys did some work in our garden for us and completely transformed it. We couldn’t be happier with the quality of work. The guys working for Craig were polite, punctual and respectful. I will be going back to Craig for our next house project.
Siddika Walji
Siddika Walji
Thanks Craig for creating a beautiful outbuilding at the back of our garden. It looks stunning!
Rebecca Hopkins
Rebecca Hopkins
In the last couple of years we have used CJ Smiths to build us a house from scratch and also to completely renovate and extend our current home. We have been absolutely delighted with the service we have received and have recommended CJ Smiths to many friends and family. Craig and all of his team are professional, friendly and trustworthy and my family have always been pleased to have them working in our home. They are extremely tidy and mindful when working in a home with children, so we’ve never had to worry about any sharp edges/power tools being left around for little people to find! We have also never had to worry about builder’s bad language around the kids as they are all family men and are a pleasure to have around. The jobs have always been finished to a high standard and Craig is completely transparent when it comes to timings, costs, payment schedules and any delays that might crop up due to unforeseen circumstances like weather etc. The team works quickly and efficiently and you will actually miss them when they’re gone!!! Especially Terry the chippie who is completely wonderful and will even make a fuss of your dog and let it out for you if you need him to! 100% recommend CJ Smiths to anyone!
Natalie Atkins
Natalie Atkins
We have used Craig and his team for 3 home-renovation projects now, the last of which being July 2022 - we are looking forward to the team completing a 2-storey side extension for us later this year. - Trustworthy This is number one for us. They do what they say when they say they will do it and at the price agreed. Additional costs were extras added on / changed by us during the project. - Friendly Craig and his team have all been friendly and a pleasure to have in the property. They are polite and respectful and we are comfortable with them (especially as we have young children around). - Tidy The team tidy up at the end of each day and leave tools safely out the way. - Quality Work completed by Craig, his team & contractors has been to a high standard and where there has been a snag list, minor issues have been addressed promptly. -Communication Craig is available to us throughout each project by WhatsApp or phone. It helps having a central person to coordinate with all parties.
Robert Quinn
Robert Quinn
Highly recommended… We recently used CJ Smiths for an extension and full house renovation. From the first meeting, to completing the project, we found Craig and his team absolutely faultless. The project was on time but for unavoidable weather delays. There were also no surprises from a budget perspective. Anything that required an “extra” or a design change was met with a pragmatic response and always a mutually agreeable way of resolving - refreshing in a world where most things are viewed as a problem. Nothing was too much hassle for the CJ Smiths team, who always went above and beyond to ensure we were kept informed of every small change or decision that needed to be made. We even mildly miss the busy house when everyone was on site. A huge thank you to the entire CJ Smiths team - we are delighted with the end result and would highly recommend them to anyone embarking on a renovation.
Philip Tam
Philip Tam
CJ Smiths is a great choice for anyone looking for quality workmanship and friendly service. They pay attention to every detail and deliver excellent results. Their prices are also very reasonable for the value they provide. I was very satisfied with their work and would highly recommend them to anyone. CJ Smiths is the best in the business! 👍🏼
dale Anthony
dale Anthony
Great service - very reliable friendly builders! We had our garden room built in St Albans by Cjsmiths, we found that the level of advice and service was a cut above the builders we have used in the past. During the planning phase, they answered all of our concerns and together we were able to plan and create the perfect space we wanted. The team were very polite and respectful during the build, cleaning up the site daily and treating our home and garden like it was their own! We are incredibly happy with the final result, it was completed on time and to a very high standard. We highly recommend Cjsmiths to anyone looking for builders in St Albans! Thanks
Ryan Smith
Ryan Smith
Outstanding job! Craig and his team completed an loft conversion for us at the beginning of this year and we couldn't be happier. We were so impressed by his level of professionalism from the very start. He managed our expectations and gave us a realistic timeline for the loft conversion to be completed, which ended up being very close to his estimate. We highly recommend C J Smiths for anyone looking for a loft conversion or building work in general. We will definitely be using C J Smiths again in the future. Great job!
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Frequently Asked Questions About House Extensions

If you have any questions that are not covered in the FAQ section, please don’t hesitate to send us an email. We are always ready to help you out!

A: Typically, we aim to complete your home extension in 14-18 weeks. This allows 8-10 weeks for the main construction work. And a further 6-8 weeks for all the essential finishing touches and facilities to be installed.

A: Yes, it is reported that a single-storey extension can add around 5-8% value to a home. But this may vary depending on the extension’s size, style and finish.

A: On average, it takes about 5-8 weeks to prepare and submit the plans. After that, it usually takes another 8 weeks for them to be processed and approved.

A: The current rules and regulations state that a semi-detached house under permitted development can be extended by up to 3 meters. This will increase to 6 meters under prior approval. You could extend your home further with local authority approval.

A: We get booked up far in advance, so we advise customers to contact us as soon as possible to get their project quoted and planned in.

A: Yes, of course. As part of our service, when we quote your project, we advise on the best type of extension and design. We have a valuable list of contacts and work closely with our architect and the local building authority in the Hertfordshire areas.

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