Construction on Site Ltd is a building company based in Harrow with over fifteen years of experience in the industry.  We are a team of experienced construction professionals, offering a full range of building services for domestic and commercial clients.  Our work includes kitchen and bathroom installations, extensions, loft conversions, plumbing, gas services, boilers, smart controls, electrics, roofing and landscaping.  We are dedicated to every project so that you can have peace of mind and the reassurance that our work is completed to the highest standards.  From small scale renovation projects, to house extensions and large scale refurbishments, we will work closely with you to realise your vision.  We work hard to uphold our reputation and provide high-quality workmanship and excellent customer care.  We have many satisfied customers who return to us with further projects and recommend us.  We serve the North West London area, Hertfordshire and Buckinghamshire.

Some of the building services we offer:



Renovations and refurbishments



Loft conversions

Plumbing & gas work

Central heating

Click here to see our Google Reviews

Contact us:


[email protected]

Trades offered

Garage Buildings/Garage Doors
Builder general
Loft conversions
Bathroom tiling
Bathroom fitter
Wet rooms
Bedroom fitter
Bedroom design
Brick work
Windows, Doors and Conservatories
Velux windows
Wooden/Timber/Sash windows
Window fitter
Bifold doors
Carpenter and Joiner
General carpentry
Dormer / Roof windows
Flat Roofing
Roofing general
Kitchen worktops
Bespoke kitchens
Kitchen installation
Kitchen design
Kitchen tiling

Case studies

Existing 1 bedroom flat-we achieved 2 bedroom flat with great garden design(landscaping)!

  • 14 Oct 2021
  • Harrow

Loft and height headroom adjustment!

  • 08 Aug 2020
  • North Harrow

See more case studies

Customer testimonials

28 Jul 2022

Construction on Site came to us via recommendation. Our request was an awkward one as it was to pick up and remedy the work of a previous shoddy builder. Having assessed the previous works and the remedial works required, Cosmin and his team just got on without fuss and did what was needed, working quickly, tidily and to schedule, enabling us to get our build back on track. What a fantastic team we have found here and who we hope to bring back to help with next stages. Highly recommend without hesitation. - Greally-Totteridge


15 Jul 2022

Every task I asked for to be done was completed to a high, professional standard. Cos offered me technical advice regarding our kitchen and bathroom. He and his team worked very hard on completing the works and overall we are very happy with our new kitchen and bathroom. Very courteous and reliable people. Work was done on time with minimal disruption in our home and I could fully trust Cos that all works would be done to the highest quality. Highly recommend Cos and his team - V Johnson


25 Mar 2022

Highly recommend Construction on Site Ltd. They offered a wonderful, friendly and honest service which was refreshing. We required all plumbing checked and connected, boiler to be installed and heating tested. We were informed at every stage what work was being carried out, shown any issues discovered and offered solutions to the problems. The team were professional and caring in the work carried out and I would not hesitate to use them again. - Bhavik


20 Feb 2022

We have been using this builder for a number years for multiple projects. Always reliable - K furniture company ltd

North Harrow