I’m planning a loft conversion, rear extension and substantial renovation of a Victorian house in London, and I’m trying to sense-check whether some form of shell-only or hybrid main contractor arrangement is realistic.
By “hybrid”, I mean a builder taking on the main structural/building works and other agreed core items, while I separately procure some specialist packages and selected internal works.
About me
I have a day job, so I cannot be on site full time. I can commit some time to managing the project, but probably not as much as would normally be needed for a pure shell-only/self-managed route.
However, a close friend, who I trust, is a self-employed carpenter and runs a carpentry/renovation business with his business partner. They do not normally operate in my area and they do not have the experience/capacity to take on the whole project, but they do have good experience working on renovation projects. My idea would be for him to take on the elements he is comfortable with and help me coordinate some other packages.
Why I am considering this route
Cost is obviously one factor, but the other reason is that I have already identified a number of packages/trades that I am likely to procure separately, mostly specialist items. These include:
cellar waterproofing/tanking;
potentially cellar dig-out/underpinning, if not within the builder’s scope;
ASHP and UFH throughout the property, by a heating specialist;
windows and steel rear doors;
wood flooring, at least to the ground floor;
kitchen fitting, likely by the kitchen supplier;
solar, batteries and EV charger.
I have also found a plasterer and decorator. My carpenter friend should be able to carry out a lot of internal carpentry and fit-out work, potentially including internal stud walls, plasterboarding, insulation, doors, architraves, skirting, boxing, access panels and similar works, subject of course to agreement with the main contractor and Building Control requirements where relevant.
On electrics, I have found two potential electricians that I would like to use. I understand that electrics probably need to be treated as one coherent package, with one electrician responsible for first fix, second fix, testing and certification.
My reservations
The biggest gap is bathrooms. My carpenter friend is not comfortable fitting bathrooms out, and I am not sure I want to leave bathrooms as something to find a separate trade for later. My instinct is that, even under a hybrid route, I would need the main builder to take responsibility for the bathrooms and associated domestic plumbing.
I would also want the main builder to own certain key items, such as the roof/external envelope, flat roof build-ups/VCL/weathering, main structural works, and ideally the staircase into the loft. I could possibly source a staircase specialist, but I would rather not add another separate package.
Generally, I do not mind that this route will cost me more time (though, as I say, I'd hope my friend can take some of this burden) but I would not want to do it if it prolongs the build by a lot (if it takes me a few extra months, that's fine, but if it takes an extra six months that would be a problem).
What I am trying to work out
I am trying to work out whether it is realistic to find a builder who would be happy to take on a defined main contractor package – structure, shell, roof/envelope, weather-tightness and selected core items such as bathrooms/plumbing – while allowing me to procure some specialist packages and internal works separately.
I would be grateful for views from anyone who has done something similar, or from builders/PMs who have been on the other side of this kind of arrangement.
Thanks in advance.
