How to Write a Specification for Building Work

Anyone who’s ever been near a building site knows this: drawings only get you so far. They’re good for showing shapes and spaces, yes, but they don’t tell you what’s under the skin. They don’t tell you which brick, which screw, which tile. That job belongs to the construction specifications.

And here’s the thing—without them, you’re asking for trouble. Builders guess, clients assume, and somewhere in between, the budget suffers. I’ve seen it happen.

Why Specifications Matter in Building Work

A good specification is basically the rule book. It says what’s expected, what standard, what code, and sometimes even how long it should last. Without that, you leave room for argument.

Here’s a simple example. I once saw a plan with “tiles” marked on the floor. That was it. No word on whether they were ceramic or porcelain, no mention of slip resistance. The builder just picked whatever he thought “looked right.” The client wasn’t happy. Cue delay, cost, and finger-pointing.

That’s why many people now rely on specification writing services or even bring in an architectural specification writer. It’s cheaper to get it right on paper than to fix mistakes on site.

Understanding the Types of Specifications

Not all specs are written the same way. You’ll usually see three types floating around:

• Performance specifications – the result is what matters, like “roof must achieve U-value X.”

• Prescriptive specifications – these give exact instructions, “use 50mm PIR insulation with foil facing.”

• Proprietary specifications – this is when a specific brand or product gets named.

In practice, most projects end up being a mix. Energy efficiency tends to be performance-based, while fire safety? Usually prescriptive.

Step 1: Define the Scope of Work

First things first: figure out what the specification is covering. Is it a new house, a warehouse, or a tricky refurbishment? That scope sets the tone. You’ll also want to set performance requirements—thermal performance, fire safety, acoustics.

A master spec template can be a handy framework, but please, don’t just copy-paste. Every building has its own quirks. What worked for one project can create chaos on another.

Step 2: Break the Work into Sections

Specifications read easier in chunks. That’s why the NBS specification is so widely used in the UK. It sorts work into neat categories:

• Site prep (demolition, groundworks).

• Substructure (foundations, damp-proofing).

• Superstructure (walls, floors, roofs).

• Finishes (plaster, paint, flooring).

• Services (electrical, plumbing, HVAC).

It’s not just tidy—it’s practical. Contractors can price each part and tackle it in order. Less overlap, fewer surprises.

Step 3: Be Precise and Avoid Ambiguity

Here’s where many specs go wrong. They use words like “high quality” or “durable.” What do those actually mean? To one person, “durable” might mean 10 years; to another, 2.

Try this instead:

• ❌ Weak: Provide durable cladding.

• ✅ Clear: Provide aluminium rainscreen panels, 3mm thick, polyester powder-coated, 25-year warranty, installed in line with BS EN 13501.

That second line? No debate. Everyone knows what’s expected.

Step 4: Coordinate with Drawings

Drawings and specifications need to tell the same story. If a drawing says “timber windows” and the spec says “aluminium,” which one wins? Builders hate that kind of conflict—it slows jobs down.

That’s why teams now often use BIM specification tools. They link written requirements directly to the model, so when something changes, everything updates together. Less chance for errors, more chance the builder actually has the right information.

Step 5: Refer to Standards and Codes

A strong specification leans on standards. Why? Because they stop arguments. If you write “concrete to BS EN 206,” nobody has to guess what mix is acceptable. Same with fire doors tested to BS 476 or EN 1634—you don’t leave wiggle room.

Codes and standards give your words teeth.

Step 6: Keep the Language Simple

Now, this is important. A specification might be technical, but it doesn’t need to be unreadable. You’re not writing a novel. You’re writing instructions.

Think about the person reading it—it might be a site manager who just wants to know what to order tomorrow. Keep sentences short. Keep them plain. Save the jargon for the lawyers.

Step 7: Review and Update

Here’s a truth: specifications are never final. Buildings change as they’re designed, as products go out of stock, as new regulations land. A spec that’s not updated is just a trap waiting to spring.

That’s why systems like master spec or the NBS specification are useful. They let you track revisions and issue new versions clearly. No one should be working off old notes.

Common Pitfalls to Avoid

• Over-specifying – adding unnecessary detail, driving up cost.

• Under-specifying – leaving gaps, leading to poor results.

• Copy-paste mistakes – reusing text that doesn’t fit the project.

• Conflicts with drawings – the classic cause of site arguments.

The Role of Professionals

Some projects are small enough that an architect can draft the spec themselves. But on larger, more complex jobs, a specialist is often worth their fee. An architectural specification writer brings not just technical know-how but also an understanding of contracts and compliance.

Dedicated specification writing services also keep documents clear and consistent, which makes tendering smoother. Contractors like clarity—it means fewer assumptions, more accurate pricing.

Conclusion

A specification isn’t just a piece of paper—it’s the backbone of a building project. The best construction specifications are clear, specific, and written in plain language.

Whether you lean on a master spec, follow the NBS specification, or work with a BIM specification system, the key is to treat it as a live document. Keep it updated, keep it aligned with drawings, and use it to set expectations right from the start.

At SpecStudio, we’ve seen how much smoother projects run with well-written specs. Done properly, they save time, money, and plenty of headaches.

Read This Blog: What Are Specifications in Building Construction?