If your planning application has been approved, congratulations! That is a big milestone for your project. But before you start ordering materials or calling a builder, there is one more layer of approval you absolutely need to understand: Building Control. 

It’s not optional. It’s not a formality. And if you ignore it, you could face delays, fines, or even have to undo completed building work.

Let’s explain what Building Control is, how it works, and what it takes to get that all-important Completion Certificate at the end of your project. 

WHAT IS BUILDING CONTROL? 

Building Control is a legal process that checks if your building work meets national technical standards known as the Building Regulations. 

Where planning permission decides what you’re allowed to build (in terms of design, size, use, etc.), Building Control ensures how it’s built. Is it safe, stable, energy efficient, and fit for use?

This covers everything from: 

• Structural stability 
• Fire safety and escape routes 
• Thermal insulation and ventilation 

• Drainage and Sanitary water supply
• Damp-proofing and ventilation
• Electrical standards 

• Accessibility
• Sound proofing
• Conservation of power and energy performance

So even if your design has been approved by the planning department, you can’t legally build without notifying Building Control how the work will be done, what materials will be used and performance levels will be achieved.

What Are My Options? 

There are two main routes to apply for Building Control approval, and which one is best depends on the extent your project. 

1. Full Plans Application 

This is the most common route for extensions, conversions, lofts, structural works, and of course new builds. 

• You or your designer submit detailed technical drawings before work starts (and a Principal Designer has to confirm their conformity)
• The drawings are checked and commented by Building Control
• Inspections take place during construction to ensure the build follows the plans 
• You receive a Completion Certificate if the works have been completed in line with the requirements.

✅ Best for larger or more complex projects
✅ Reduces risk of mistakes, delays, or work needing to be redone
✅ Can be handled by a private inspector or the local authority 

2. Building Notice Application 

This is quicker and simpler, but only suitable for small, low-risk works. These may include replacing windows, changing a boiler, rewiring the electrics. 

• No detailed drawings are submitted upfront 
• You notify the local authority at least 2 working days before starting 
• Inspections may happen during the works
• Approval is based entirely on what the inspector sees on site or gas/electrical certificates provided by the qualified competent trade.

🚫 Not suitable for extensions or structural changes
🚫 Only available through your local council, not private inspectors
🚫 Higher risk if your builder isn’t experienced with regulations 

Do I Have to Use the Council? 

No, you can choose between: 

• Local Authority Building Control – your local council’s in-house team 
• Approved Inspectors – private companies registered to carry out Building Control services

Both options are legally valid. The key difference is that: 

• Local authorities have enforcement power, but can be slower and more rigid 
• Approved inspectors are often faster and more responsive, but carry a cost (and can’t issue formal notices, they inform the council instead) 

At Tholos Architects, we generally work with trusted Approved Inspectors for most of our clients, but we also have experience with some Councils’ Building Control department, more suitable for some (e.g. listed buildings or certain conservation areas). 

How Much Does It Cost? 

Building Control fees vary depending on: 

• The size of your project 
• The total cost of the work 
• Whether you choose Full Plans or a Building Notice 
• Whether you use the council or an approved inspector 

But for most domestic extensions and internal conversions, the cost can sit between: 

💷 £800 – £1,500 for the entire process (including inspections) 

This is a necessary and unavoidable cost of doing building works legally. 

What Is a Completion Certificate and Why Does It Matter? 

Once your project is finished and passes all inspections, Building Control will issue a Completion Certificate. 

This is your legal proof that the work: 

• Meets current Building Regulations 
• Was carried out to a safe and acceptable standard 
• Is signed off by an official authority 

You’ll need this certificate to: 

• Sell your property in the future 
• Remortgage or release equity 
• Make an insurance claim 
• Avoid some enforcement action from the council 

No Completion Certificate = potential legal and financial problems. 

Common Misunderstandings 

Let’s clear up a few things we hear all the time: 

“I have planning permission isn’t that enough?”
No, planning permission and Building Control are two totally separate approvals. 

“My builder says they’ve done this before, do I really need Building Control?”
Yes, even experienced builders make mistakes or skip steps. And without inspections and a certificate of completion, you are legally exposed. 

“Can I do this later?”
No, you must apply before work starts, and inspections must happen at key stages. Doing it backwards may lead to very expensive risks, including having to remove and re-do some works and may be refused.

When Should I Start the Process? 

We recommend to start preparing for the Building Control process as soon as your planning permission is granted, rather than in a rush before commencing construction. 

Why? 

• It takes time to prepare the detailed drawings and structural calculations 
• Approvals can take 5–8 weeks (or longer in busy seasons) 
• You need a clear set of plans and specifications  to give your builder 
• It avoids delays or mistakes later on 

How Can I Make It Simple? 

The easiest way is to work with an architectural team that can: 

• Prepare your technical drawings to Building Regs standards 
• Coordinate structural calculations and energy reports 
• Submit and manage your application 
• Liaise with inspectors and contractors during the build 
• Help you get your Completion Certificate without hassle 

At Tholos Architects, we have helped dozens of homeowners (and businesses) get through this process smoothly. We know what Building Control wants to see, and we make sure your project is safe, compliant, and fully approved. 

Need Help? We’re Here to Talk 

Whether you’re just starting or already have planning permission, we can help you prepare the documents and handle the approval process from start to finish. 

📞 Book a free 30-minute consultation
We’ll explain exactly what you need for Building Control and how to avoid costly mistakes – no pressure, no obligation.