First Fix and Second Fix Plumbing for New Builds and Renovations
On any building project, the plumbing happens in two visits with a lot going on in between. Getting the first fix right, before the walls are closed up, decides how smoothly everything else goes. This page explains both stages and how to plan them with your builder.
Gas Safe registered 25 years in the trade 12 years running the business
What first fix plumbing covers
First fix is everything that will end up hidden. It happens after the structure is up and before plastering, boarding, screeding or tiling. Typical first fix work includes:
Running hot and cold supply pipes to every outlet
Waste pipes from sinks, basins, baths, showers and toilets to the soil stack
Heating flow and return pipes to radiator positions or underfloor heating manifolds
Concealed shower valves and any in-wall frames for toilets
Gas pipework to the boiler and cooker positions
Pressure testing everything before it is covered
What second fix plumbing covers
Second fix comes once walls and floors are finished and decorated, or nearly so. That is when sanitaryware, taps, radiators, the boiler and controls are connected, the system is filled and flushed, and every joint is checked. It is the stage where the house starts to work, and where mistakes made at first fix become expensive to put right.
Why the order matters
A pipe in the wrong place at first fix might mean a radiator ends up behind a door or a basin waste misses the vanity unit. Moving it later means chasing out new plaster. That is why outlet positions are agreed in writing, or marked on the walls, before the first fix starts.
Pressure testing before covering up is just as important. Once a floor is screeded or a wall is tiled, a weeping joint can only be reached by breaking in.
Working with your builder
On extensions and renovations the plumber is one trade among several. It helps to have a clear programme: when the walls go up, when the electrician is in, when the plasterer starts and when the kitchen and bathroom are due. Chris will tell you how much notice he needs for each stage, and what has to be in place before he can start, such as floor joists being open or a stud wall being built but not boarded.
Extensions and loft conversions
Adding rooms usually means extending the heating and hot water. A bigger house may need more radiator output than the existing boiler can supply, or a hot water arrangement that copes with an extra bathroom. These questions are best answered at the planning stage. Our central heating page covers radiators and controls, and our boiler installation page explains how boiler type affects hot water.
Kitchens and bathrooms
Kitchen and bathroom refits follow the same two-stage pattern on a smaller scale. A new layout often needs the waste and supply pipes moving, and a concealed shower or wall-hung toilet needs its valve or frame fitted at first fix. Our bathroom installations page goes through bathroom planning in more detail.
Underfloor heating in new floors
If a new floor is being laid, it is the ideal time to consider wet underfloor heating, because the pipes go in before the screed. Our underfloor heating page explains when it suits a project.
Talk to us early
The best time to get in touch is before work starts, with drawings if you have them. Call or WhatsApp 07429 632804, or use the quote form. See our services page for everything else we do.
Common questions
First Fix and Second Fix Plumbing FAQs
Clear answers before you arrange a visit.
What is the difference between first fix and second fix plumbing?+
First fix is the hidden pipework installed before walls and floors are finished. Second fix is connecting the fittings, appliances and radiators once the surfaces are done.
How long is the gap between first and second fix?+
It depends on the project. Plastering, drying, tiling and decorating all happen in between, so it can be days on a small job or weeks on a larger one.
Do I need drawings before you can quote?+
They help a great deal. Without them, Chris will need to walk through the layout with you and agree where each outlet goes.
Can you work alongside my builder?+
Yes. A shared programme with clear dates for each stage makes the job run more smoothly for everyone.
Will my existing boiler cope with an extension?+
Sometimes. It depends on the boiler's output, the extra radiators and any new bathrooms. This is worth checking when you plan the work.
