If you’ve ever been around a building site or watched your own home rise from the ground up, you’ve probably heard the term “first fix.” It’s one of those phrases contractors throw around like everyone was born understanding it. But for most homeowners, renovators, or curious minds, the question remains: what does first fix actually include?
Let’s break it down together—not in a jargon-heavy, head-scratching way, but in a straight-talking guide you can use whether you’re planning a new build, managing a renovation, or simply trying not to look confused next time your builder mentions it.
1. What Exactly is First Fix?
The first fix refers to all the foundational work that happens before walls are plastered and floors are finished. Think of it as the skeleton and arteries of a house—the structure, wiring, and pipework that need to be in place before you can start making things pretty.
In construction, the process is often broken into two stages:
- First fix – structural, hidden work (framing, wiring, plumbing, heating runs, etc.).
- Second fix – visible finishing touches (sockets, taps, doors, skirting boards, etc.).
I once heard a builder describe it perfectly: “First fix is everything you want working but never want to see.” And that’s spot on.
2. Structural Carpentry in First Fix
Carpenters play a huge role in first fix. Before you even dream of hanging that gorgeous oak door, they’ve already been sweating over:
- Stud walls and partitions – these are the non-load-bearing walls that divide up your rooms. Without them, your “four-bedroom house” would just be one giant hall.
- Floor joists and stairs – those solid structures you’ll walk on and climb every day. If they’re not right now, you’ll be hearing squeaks and rattles for years.
- Roof structures – rafters, trusses, and supports that create the roof shape.
A stat worth knowing: according to the UK House Building Federation, around 15–20% of first fix time is spent on carpentry alone, because mistakes here are the most expensive to fix later.
Personal note? I once lived in a flat where the builder cut corners on floor joists during first fix. Every step across the living room sounded like a haunted house creak. Trust me, you really want this part done right.
3. Electrical Wiring During First Fix
When it comes to electrics, first fix is all about laying the groundwork for future power and lighting. Once plastering is done, you can’t exactly rip open the wall without tears (and bills).
What’s included:
- Running cables for sockets, lights, and switches.
- Wiring circuits for appliances (oven, boiler, extractor fans).
- Setting back boxes for sockets and switches.
- Routing cabling for internet and data points.
Did you know the average UK home today uses 25% more electricity than it did 30 years ago? (Energy Saving Trust, 2022). That’s why good planning here is crucial. Imagine realizing you need more sockets in your home office after plastering—it’s like wishing for more chocolate chips after the cookies are baked.
4. Plumbing in First Fix
Water is life—but in construction, it’s also a nightmare if not handled early. First fix plumbing ensures water supply and waste systems are neatly tucked away before walls close in.
Key plumbing jobs:
- Pipework installation for hot and cold water.
- Heating system pipework (radiators, underfloor heating).
- Waste pipes for sinks, toilets, showers, and baths.
- Ventilation ducts for bathrooms and kitchens.
On average, plumbers spend 10–15% of the total project time during the first fix. They basically map your house like a hidden network of veins.
Quick anecdote: I once visited a house where the builder had forgotten to leave pipe access for the upstairs bathroom sink. The result? They had to cut into a newly plastered wall two weeks later. The homeowner nearly cried watching fresh plaster crumble. Moral of the story: plumbing first fix = check twice, plaster once.
5. Heating and Ventilation Systems
While plumbing handles the water, heating engineers set up the warmth. In modern homes, this often includes:
- Boiler connections and pipe runs.
- Radiator connections (before the actual radiators are fitted).
- Underfloor heating pipes embedded in concrete or screed.
- Ventilation ducts for extractor fans or whole-house ventilation systems.
Considering that heating accounts for 55% of household energy bills (UK Department for Energy Security, 2023), getting it right at first fix is a money-saver in the long run.
Pro tip: always ask your installer to future-proof. For example, even if you don’t want underfloor heating now, they can install pipe loops for later without much extra hassle.
6. Windows, Doors, and Openings
First fix carpentry also covers the frames of windows and doors. Not the shiny glass or painted finish yet, but the bare bones that will hold them.
Why is this important?
- Proper frames prevent draughts and leaks later.
- Poor alignment now means sticking doors and rattling windows forever.
- They set the exact openings for plastering and finishes.
I remember a friend’s renovation where the door frames weren’t square during first fix. By the time the second fix came, none of the doors would shut properly. They had to plane each door edge individually—a nightmare and a cost bomb.
7. Insulation and Soundproofing
Yes, insulation sneaks into the first fix too. This is when builders tuck in:
- Wall insulation (between stud walls or external cavities).
- Floor insulation (especially for underfloor heating).
- Acoustic insulation (to stop you hearing your teenager’s drum kit at 2am).
Stats to note: Proper insulation can cut energy bills by up to 20% annually (Energy Saving Trust, 2023). And trust me, once you’ve lived in a drafty old house, you’ll never underestimate this step again.
8. Fire Safety Installations
Fire safety measures are often overlooked in first fix discussions, but they’re critical. This includes:
- Smoke detector cabling.
- Heat sensors in kitchens.
- Sprinkler systems (in some modern builds).
- Fire-rated partitions and doors where required.
Personal anecdote: During my cousin’s loft conversion, the builder initially skipped installing a wired smoke alarm system at first fix. It was only flagged during inspection. Imagine the chaos of rewiring the loft after plastering—it’s like unwrapping and rewrapping a giant present, only with more swearing.
9. External Works in First Fix
Depending on the project, some external works also fall under first fix. These can include:
- Drainage systems around the property.
- External pipework.
- Ducting for utilities (gas, electricity, water mains).
Why it matters: You can’t move into a house if your drains aren’t connected—simple as that. Builders usually tackle this while the ground is still open, so it blends into first fix timelines.
10. Inspections and Approvals
Before plasterboard goes up, inspectors (building control officers or similar) will want to sign off on the work. They check:
- Electrical cabling meets safety standards.
- Plumbing systems are correctly installed.
- Structural framing follows regulations.
Skipping inspection is like baking a cake without tasting the batter—you might be in for a nasty surprise later.
11. Timeline of First Fix
How long does first fix take? It depends on project size, but here are some averages:
- Small extension – 2 to 4 weeks.
- New-build 3-bedroom house – 6 to 8 weeks.
- Large custom home – 3 to 6 months.
A survey by NHBC (National House Building Council) found that first fix makes up around 30–40% of the entire build time. It’s the slow but steady foundation that everything else relies on.
12. Why First Fix is So Crucial
Here’s the truth: mistakes in first fix are the most painful to fix later. If your light switch is in the wrong place, it’s not just annoying—it could mean ripping open a finished wall.
Think of it like cooking. First fix is chopping your onions, prepping your ingredients, and getting your pans ready. If you forget the garlic at this stage, you’re either making a bland dish or starting over.
The golden rule? Plan, plan, and plan again. Walk through the house in your mind: where do you want to plug in your phone? Where will your sofa go? Where will you need a radiator? Answering these now saves regret later.
13. Cost of First Fix
On average in the UK:
- First fix carpentry – £2,000 to £5,000 (depending on size).
- First fix plumbing – £3,000 to £6,000.
- First fix electrics – £2,000 to £4,500.
Altogether, you’re looking at £15,000–£25,000 for a standard 3-bed new build (RICS cost data, 2023).
Sure, it’s not the glamorous spending (no one brags about their hidden pipework), but it’s the backbone of your home.
14. Common Mistakes to Avoid
From my own experience and stories I’ve heard, here are the biggest pitfalls during first fix:
- Not planning socket locations carefully. (You’ll regret that single plug in the living room).
- Skipping extra cable runs. Tech moves fast—better to future-proof.
- Poor pipe insulation. Leads to frozen pipes in winter.
- Forgetting ventilation. Hello, damp walls.
- Misaligned door frames. The squeaky nightmare.
15. How to Prepare as a Homeowner
Even if you’re not swinging the hammer, you play a role. Here’s what you should do:
- Walk the site with your builder before first fix finishes.
- Bring masking tape and mark where you want sockets, switches, and radiators.
- Double-check bathroom layouts (nothing worse than realizing the toilet clashes with the door swing).
- Ask questions. Don’t worry about sounding clueless—better now than later.
I once drew my entire living room layout in chalk on the floor before first fix finished. The electrician thanked me because it saved him hours of guessing where the TV would go.
Conclusion
So, what does first fix include? In short: everything structural, hidden, and essential before walls close up. Carpentry, wiring, plumbing, heating, insulation, and safety measures—it’s the invisible backbone of your home.
Get this stage right, and second fix will glide smoothly. Get it wrong, and you’ll be haunted by creaks, leaks, and misplaced sockets for years.
The secret? Plan ahead, double-check, and never rush. First fix isn’t glamorous, but it’s the quiet hero of every home build.
FAQs
1. What does first fix include?
First fix covers all the hidden structural and mechanical work—carpentry, wiring, plumbing, heating pipework, insulation, and fire safety installations—done before plastering and finishing.
2. How long does first fix take?
Anywhere from 2 weeks for small projects to 6 months for large homes. A typical new-build 3-bedroom house takes around 6–8 weeks.
3. Is first fix more expensive than second fix?
Generally yes, because it involves structural and mechanical work. First fix often accounts for 60–70% of trade labor costs.
4. Can changes be made after first fix?
Technically yes, but it’s costly. Moving a socket or pipe after plastering means ripping walls open. Best to plan carefully beforehand.
5. Who is involved in first fix?
Carpenters, electricians, plumbers, heating engineers, ventilation specialists, and sometimes inspectors for approvals.