First Fix vs Second Fix Plumbing UK — What Each Stage Covers and How to Price Plumbing in New Builds and Renovations (2026)

Why first fix and second fix are two separate jobs

On any new build or renovation involving structural work, a plumber will visit the site at least twice at completely different stages of the build programme. These two visits — first fix and second fix — are not just different tasks. They are different contracts, different payment milestones and different site conditions. Treating them as one job is how plumbers end up out of pocket.

First fix happens before plastering or screed is laid. The plumber runs all the pipework through floors, walls and ceiling voids — hot and cold supply, waste runs, heating flow and return, soil stack connections. None of the sanitary ware or radiators go in yet. Everything is hidden when the plasterer finishes.

Second fix happens after plastering and decoration are complete. The plumber returns to connect the sanitary ware, fit taps, hang radiators, commission the boiler, test the system and issue the relevant sign-off documentation. The gap between the two visits can be anywhere from two weeks to three months depending on the build programme.

Quoting them separately matters for three reasons. First, if the first fix is priced accurately but the second fix scope changes (the client adds an en-suite, upgrades to a freestanding bath), you are protected — the second fix quote reflects the actual work. Second, separate payment milestones make cash flow manageable on longer builds. Third, if there is a delay between stages — a common occurrence — there is no ambiguity about what you have been paid for and what remains outstanding.

First fix plumbing: complete scope checklist

First fix plumbing covers everything installed before the walls are boarded, plastered or screeded. The key rule: if it will be hidden by the finish, it is first fix. Here is a full scope checklist for a standard residential new build or whole-house renovation:

Supply pipework

• 22mm hot and cold mains supply runs from meter/stopcock to cylinder or combi boiler
• 15mm branch pipes from main runs to each bathroom, kitchen and utility position
• Pipework in timber or concrete floors (sleeved through joists or laid in screed)
• Isolation valves at each appliance/sanitary ware position
• Cold water storage tank connections if required (e.g. vented system)

Heating pipework

• 22mm or 28mm flow and return main circuits from boiler position
• 15mm branch pipes to each radiator position
• Underfloor heating manifold position roughed in (with flow/return connections to manifold)
• Cylinder connections for system boilers (flow, return, DHW primary)
• Boiler flue position and gas supply pipe roughed in (run to position, not connected)

Waste and drainage

• Soil stack installation (110mm UPVC, internal or external)
• WC soil connection at correct height and angle from stack
• Branch waste pipes for basin, bath and shower trap positions (40mm)
• Washing machine and dishwasher standpipes/waste connections to gulley or stack
• Kitchen sink waste run
• Gully connections at ground level where required

Bathroom-specific first fix

• Bath trap position and waste outlet through floor
• Shower tray waste position (wet room or tray drainage)
• WC soil connection (stubbed out to finished floor level)
• Basin supply stubs (hot and cold, with isolators)

Everything must be in position and tested before the plasterer arrives. Screed dates in particular are unforgiving — underfloor heating pipework is pressure tested before screed is poured and cannot be moved afterwards.

Second fix plumbing: complete scope checklist

Second fix is where the job becomes visible. The pipework is now hidden and the plumber installs all the sanitary ware, appliances and heating equipment, then commissions and tests the full system. Scope includes:

Sanitary ware and bathrooms

• Bath installation (set in position, waste connected, overflow fitted)
• Shower tray and enclosure (or wet room former)
• Basin installation (pedestal, wall-hung or vanity unit)
• WC pan and cistern connection (close-coupled or back-to-wall)
• Taps fitted and connected — monobloc, pillar or wall-mounted
• Shower valves, thermostatic cartridges and heads fitted
• Bath/basin wastes and traps connected

Heating

• Radiators hung and connected (lockshield one end, TRV the other)
• Boiler installation and connection (gas, water, flue, condensate)
• Hot water cylinder connection and wiring to motorised valves
• Filling, flushing and balancing the system
• Underfloor heating manifold valve settings and system balancing
• Programmer/thermostat installation and commissioning

Kitchen and utility

• Kitchen sink installation and waste connection
• Dishwasher supply and waste connection
• Washing machine supply and standpipe connection
• Fridge/freezer water supply if required (ice maker, chilled water)

Testing, commissioning and sign-off

• Full system leak test (visual check under pressure for minimum 1 hour)
• Boiler commissioning and Benchmark completion certificate
• Gas Safe notification if gas connections are made
• Handover to client — how to use controls, isolate supply, bleed radiators

First and second fix plumbing prices 2026 (labour only)

All figures below are labour only. Materials are quoted separately (see the next section). London and South East rates typically run 20–30% above these figures. Prices assume reasonable access and standard construction — timber frame, block-and-beam or traditional brick cavity with accessible joist voids.

The wide range on a full 3-bed first fix reflects property size, number of bathrooms, soil stack position and floor type. A 3-bed terrace with a single bathroom and a combi boiler will sit toward the lower end. A 3-bed detached with two bathrooms, an en-suite, underfloor heating throughout and a system boiler with cylinder will be toward the top — or beyond it.

What drives the price up or down

Several factors push a plumbing first fix significantly above or below the base range:

• Number of bathrooms and en-suites. Each wet room adds a soil stack connection, branch waste pipes and a full set of supply stubs. A three-bathroom house is not far off double the labour of a one-bathroom house on first fix.
• Soil stack position. A single internal stack with short branch runs is fastest. Multiple stacks, long horizontal waste runs or awkward falls (particularly on extensions) add significant time. Waste pipes must fall at 1:40 to 1:80 — if the floor layout does not allow it, boxing or structural changes are needed.
• Floor type. Timber joists are the easiest — pipes clip to the underside or pass through notched joists. Solid concrete floors require chasing or surface routing before screed. Underfloor heating on a solid floor adds manifold positioning, a complete pipe loop per room and a pressure test before pour.
• Pipework material. Most plumbers use plastic push-fit (Speedfit, Hep2O) for speed and cost on first fix supply runs. Copper is still preferred by some builders for visible sections and heating pipework. Copper costs more in both materials and labour time. On a large new build, the choice matters.
• Distance from boiler or cylinder. Heating pipework is significantly more expensive when the property is large or the boiler position is awkward. Every extra metre of 22mm flow and return adds to the materials bill and the time on site.
• Access to routes. A new build with open walls and accessible floor voids is far quicker to first fix than a renovation where original floorboards must be lifted and relaid, or where pipe routes have to be chased through solid walls.

Materials: what plumbers supply and how to mark them up

On new build and renovation plumbing, the standard practice is for the plumber to supply all pipework and fittings, and for the client to supply sanitary ware. This split is important for both parties.

The plumber supplies pipework and fittings because the choice of pipe system (push-fit vs copper, brand, diameter) directly affects the speed and quality of the first fix. It is not practical for a client to source the right combination of pipe runs, bends, clips and isolation valves — the plumber has trade accounts and knows what they need.

Sanitary ware is the opposite. Baths, toilets, basins, taps, showers and shower enclosures are design choices that the client makes on finish and budget. The plumber does not want to be responsible for sourcing a £2,000 freestanding bath or a bespoke shower tray. Clients supply these items to site, and the plumber fits them.

Marking up materials: Standard practice is to add 15–20% to the trade cost of all pipework, fittings and ancillaries supplied. This markup covers your time ordering, collecting, loading and managing materials — it is not just profit. On a full 3-bed first fix, materials (pipe, fittings, waste pipe, soil pipe, clips, sealant, isolation valves) might total £600–£1,200 at trade. At a 15% markup, that is an additional £90–£180 on top of trade cost. Always show materials as a separate line on your quote — it is transparent and easier to adjust if spec changes.

What to show on the quote: List main material categories (supply pipework, waste and soil pipe, heating pipework, fittings and valves) with approximate quantities and a lump sum per category at your marked-up price. Do not itemise every elbow and clip — it creates unnecessary arguments. But do make clear that sanitary ware is client-supplied and that pricing assumes standard-spec materials (e.g. plastic push-fit supply, plastic waste, UPVC soil stack).

Payment terms for new build and renovation plumbing

New build and renovation plumbing jobs are high-value and long-duration. Without clear payment milestones, you risk carrying significant materials cost and labour time before you see any money. The industry standard structure that protects plumbers is:

• 30% on first fix completion. Payable when all pipework is in position, pressure tested and signed off before plastering begins. This covers most of your materials cost and the first site visit labour.
• 30% on second fix start. Payable at the point you return to site — before you commit further labour time. This payment covers any sanitary ware delivery co-ordination, your return mobilisation and materials for the second stage.
• 40% on commissioning and sign-off. Final payment due on practical completion — system tested, boiler commissioned, Benchmark certificate complete, Gas Safe notification issued if applicable, and client signed off.

On jobs with main contractors (builders or developers), expect 30-day payment terms rather than immediate payment. This is standard in the industry but should be reflected in your cash flow — do not plan to pay your materials supplier from this job until 30 days after each milestone. Domestic self-build clients often pay within a few days, particularly when they are on-site and can see the progress.

Always confirm payment terms in writing before starting. A brief one-page subcontract or quote acceptance email with payment milestones spelled out protects both parties and removes any ambiguity when it comes time to invoice.

Pressure testing pipework and snagging

Pressure testing is non-negotiable on any new build or renovation where pipework will be hidden by the finish. If a joint fails inside a wall or under a screed floor, the remedial cost is enormous — the plumber is liable. Testing before boarding and plastering is how you protect yourself.

How to pressure test copper and plastic supply pipework: Cap off all outlets, connect a pressure gauge and hand pump, pressurise the system to 1.5 times working pressure (typically 9–10 bar for mains pressure systems). Leave under pressure for a minimum of 1 hour with no drop permitted. On larger systems, 24 hours is better practice. Photograph the gauge reading at the start and end of the test.

Underfloor heating pipework: Polythene UFH pipe is pressure tested before screed is poured and must remain pressurised during the screeding process — the screed contractor needs to work around live, pressurised pipework. Standard test: pressurise to 6 bar, leave for 24 hours. Document the reading. Many UFH systems require a written pressure test certificate before the screed contractor will proceed.

Waste and soil pipework: Tested visually with a temporary water fill — block all outlets, fill the waste runs and observe for leaks at joints and connections. No pressure gauge is used on gravity waste systems.

Documentation: Keep a simple written or photographic record of every pressure test — system tested, date, test pressure, duration, result, and your name. This is your evidence if a defect claim arises after completion. Some main contractors require a formal pressure test certificate as part of the handover pack.

Snagging at second fix: Before handing over, do your own snagging pass. Check every joint under pressure with a damp cloth. Check all taps and valves open and close cleanly. Confirm all TRVs operate. Flush the system and check the filter. Bleed every radiator. These ten minutes save a return visit.

Renovation and new build plumbing: your highest-value work

New build and renovation plumbing generates the highest job values in any plumbing business. A full 3-bed first and second fix with boiler installation, a cylinder and two bathrooms can easily reach £8,000–£15,000 in combined labour and materials — compared to £150–£300 for a tap replacement or £400–£700 for a bathroom radiator swap.

The challenge is that this type of work does not come from the same channels as emergency call-outs. Builder referrals, repeat clients from previous renovations, and local property developers are the most common sources. Google Ads targeting “plumber new build” or “renovation plumber [town]” can also deliver high-quality enquiries — but only if you know that those enquiries are converting into jobs, and at what cost.

Tracking which marketing source generates your renovation and new build enquiries — and which of those enquiries convert to booked jobs — lets you focus investment on the channels that actually win this type of work. A job worth £10,000 in revenue justifies a very different marketing budget than a £200 call-out.