Endorsed by Which?

J.M.B Design & Build Ltd

5.0

8 Reviews

Opening Hours
Today - 08:00–19:00
  • Monday 08:00–19:00
  • Tuesday 08:00–19:00
  • Wednesday 08:00–19:00
  • Thursday 08:00–19:00
  • Friday 08:00–19:00
  • Saturday 08:00–19:00
  • Sunday 08:00–19:00

What is a Which? Trusted Traders Hertfordshire Trading Standards Approved Endorsement?

Which? Trusted Traders has partnered with Hertfordshire Trading Standards to create a Hertfordshire Trading Standards Approved endorsement. In addition to our standard trading standards assessment, this trader has had a DBS check and is subject to a Trading Standards intelligence check

About

JMB Design & Build Ltd is an established building firm operating in Hertfordshire, London and the surrounding counties.

From renovations, extensions, loft and garage conversions to a new build, our team of skilled craftsmen utilise their combined decades of experience to ensure all projects are completed to the highest possible standard, tailored to each client's needs.

What we do

  • Building construction contractors

    • Basement conversion
    • Building construction management
    • Porches
    • Swimming pool construction
  • Builders

    • Building services
    • Conservatories
    • Extensions
    • Garage conversions
    • Loft conversions
    • Log cabins and homes
    • Porches
    • Guttering repair services
    • Plastering
  • Property refurbishment contractors

Customer reviews

Why you can trust these reviews

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100% of the reviews we publish have been through our stringent moderation process.

5.0
8 reviews
Customer Service
5.0
Quality
5.0
Value
5.0
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Highly recommend James and his team
Customer Service
Quality
Value
I am so happy that we found James because this was the first time I had ever done any building work on a home and we did a lot (a ground floor extension, all rooms renovated including the kitchen and bathrooms)! James never once made us feel like we were anything other than important to him or that we were in any way a pain for asking many questions, or stressing (which I am very good at)! When there were any unexpected costs, such as the cost of moving a water main that we didn't know existed, we got told how much it would be before his team carried out that unexpected work. The quality of work is great, because we lived at the house while the work was carried out, and I was even working from home the whole time, James had to be very flexible with what he could do and when to accommodate us. A special acknowledgement to Owen and Nash who both spent a lot of time with us but also to all of those who worked for James during the period we were having work done as they were all very professional and friendly. I would not hesitate for one minute in recommending JMB Design and Build.
Customer in Greater London Posted on 03/03/2026 , work completed 02/03/2026
Loft Extension 25/26
Customer Service
Quality
Value
Really happy with our loft extension from JMB Design & Build. We had great support from James throughout the whole process, especially dealing with building control. There was also a clear point of contact at our house throughout so that myself and my partner could check in on progress and be made aware of any issues - thanks to Connor for this. Would recommend.
Customer in Hertfordshire Posted on 03/03/2026 , work completed 20/02/2026
The 6th star!
Customer Service
Quality
Value
Our work started in August 2024 and anyone who’s had a project of such size will know that it’s very nerve-wracking before it begins. The first day work started the team arrived and straight away one of James’s guys (Dan) said to me was “Don’t worry, it’ll all be ok…we’re going to make your house look amazing.” It may seem trivial but little things like that mean a lot and put us at ease. Every single day the JMB team were on time, cracking on with the work. Clean and punctual seem to be the values with which they work. Even with a sudden family bereavement in the first week and a funeral to attend to we were confident in leaving our keys with them as they were so understanding and just carried on with the work to alleviate any stress on us. It’s little things like this which have meant so much. The quality of work itself is outstanding. The attention to detail and care taken in every aspect to not only deliver the best results but also minimise any disruption to us as we were living in the house whilst this work was carried out was amazing. We’d met other builders who told us they don’t do site visits very often and that wasn’t very encouraging as having the owner checking up on this is integral. Fortunately James was a regular presence at our house to check on the work being done, check on his team and also check in on us. Any miscellaneous bits that popped which incurred extra work and costs, James took upon himself to handle and take the stress of us which was so welcomed.
Customer in Greater London Posted on 26/03/2025 , work completed 26/03/2025
Highly recommend JMB
Customer Service
Quality
Value
I recently used JMB for a salon build and they had truly exceeded my expectations. From the very beginning, their professionalism and attention to detail was 10/10. Throughout the process, their communication was top notch and I would highly recommend if you are looking for reliable, trustworthy builders.
Customer in Hertfordshire Posted on 19/01/2025 , work completed 01/01/2025
Endorsement Reference
Customer Service
Quality
Value
Renovation of a bungalow including inside and knocking down a bedroom made out of a garage and putting up a side extension.
Which? Trusted Traders Consumer Posted on 19/08/2024 , work completed 01/03/2024
Endorsement Reference
Customer Service
Quality
Value
JMB was the principal contractor for a new build bungalow
Which? Trusted Traders Consumer Posted on 19/08/2024 , work completed 26/06/2024
Endorsement Reference
Customer Service
Quality
Value
JMB completed a loft conversion at our property. All work done within the budget. My wife was pregnant so quite a stressful ordeal, but JMB made the experience very easy for us.
Which? Trusted Traders Consumer Posted on 19/08/2024 , work completed 29/05/2024
Endorsement Reference
Customer Service
Quality
Value
We had a double storey, side extension to our house. As part of the extension, we also needed to have work done internally, not just to the new extension but also to some of the existing rooms within our house. We were looking for a building firm that would be able complete all the work, not just the physical building work but also other areas such as electrical, plumbing, roofing, carpentry, kitchen installation & internal decorating. JMB Design & Build was able to offer us this full end to end service and we found them very professional & knowledgeable throughout the entire process. As part of the various pre planning meetings we had, James talked us through the process, made us feel at ease and was always on hand to answer any questions that we had. When the work did start, we were very impressed with the professionalism & quality of work of all the JMB team that worked on our extension. They treated our house with the upmost respect, like it was their own and kept it as tidy as possible throughout the entire project. As with any large extension of this kind, we did encounter some problems e.g. heavy rain, leaking roof & strong winds but James & his team were always on hand to review and find the best solutions. We are so happy with our new, extended house and we are very grateful to James & all his team at JMB for making our extension a reality.
Which? Trusted Traders Consumer Posted on 19/08/2024 , work completed 28/09/2023