Services to be considered when planning a garage conversion


Existing services

There is always the possibility of encountering problems with existing services and the time to deal with them is usually before any major alteration work such as roof renewal or extending the building. You may find the main house rising main water feed in the garage and consideration must be given to its position in the design of the project. It is possible to move its position a few feet by digging down and either extending the underground pipe or shortening before relocating to its new position.


Many garages have the electrical consumer unit installed on the outside wall close to the electrical meter. If major alteration to either the wall or the roof is to occur then this will run in tandem with the electrical works. If not its worth considering the age of the consumer unit and whether or not to upgrade or even add another phase.

Either way, the job needs a qualified electrician. The first fix is done after major structural work and before any insulating / covering over is carried out. You may need to re-route existing wiring in the case of structural alterations.

In its most basic sense a new lighting circuit is added and a new ring main although it is possible to add the garage to existing circuits.


Pretty much essential regardless of the use, heating can be either electrical or taken from the main central heating system in the main house. If the garage is separate then consideration must be given to the route the pipework takes outside the building. Insulation is required. If the boiler is in the garage, adding extra radiators is a simple job, if not then tapping into existing pipe runs and piping through the wall into the garage is usually the method employed. Certain factors need to be respected such as no more than 3 radiators should come off a 15mm pipe. If you can tap into 22mm pipes so much the better. If the existing system is microbore then consideration must be given to the route the pipework will take back to the manifold which feeds all radiators on the system. A qualified heating engineer will be able to give a good estimate of cost and viability.

Domestic water supply

This depends on the proposed use of the conversion. Utility rooms may require a softened water supply. If there’s already a softener in the house then its got to be piped into the conversion. Cold water can be piped directly from the mains, however, if any mixer valve is to be used and the domestic hot water supply from the main building is ‘gravity fed’ then the cold supply will have to come from the main house header tank. Pipe sizes and routes will need consideration. A good plumber / heating engineer should again be able to advise on cost and viability. In some cases the domestic hot water is combination boiler fed and the route is a simple one so a good diy’er with plumbing knowledge would be able to do the job reasonably easily.

Waste / Drainage

In the event of a wc being installed then a route to an existing soil system is required. In some cases the soil drain runs underneath the garage and it’s a case of digging down to find it, tapping into it and installing an air admittance valve above cistern height in the wc once installed. In the event the soil drain runs parallel to the garage along the outside there may be a soil stack close enough to tap into (the existing one for the main house wc) or it may require digging down to and coupling an inspection chamber to it. The wc soil pipe can then be core drilled though the wall, and piped down to the inspection chamber. The easiest way to couple into an existing underground soil pipe is with the use of either a slip coupling, which allows the coupling to be slid all the way onto the existing pipe then halfway back onto the new section once in place or by the use of flexible rubber couplings which facilitate new 110mm underground pipe to be coupled to larger existing clay pipes.

For sink, basin, bath or shower waste a gulley may be required. This can either be found existing, close enough to pipe into or installed new and piped down to the main soil drain similar to a soil pipe. Modern gulleys have a rodding point built in and an inspection chamber need not be installed for this reason. If there is an existing soil stack close enough to the exit point of the waste pipe through the wall then it may be possible to utilise a ‘strap boss’ and couple the waste into the stack pipe.