If you’re reading this, you’ve likely received our letter about a recent Planning Application, or found us through a Google search around the time you submitted a Planning Application.

You’re not alone. Every year, thousands of London homeowners submit planning applications with dreams of improving their homes. What they don’t realize is that planning permission is just the first step in a complex journey that catches many people unprepared.

We’ve guided around 100 homeowners through this exact process since 2019, and we know the questions keeping you up at night.
What if my application is refused? If it’s approved, can I just call a builder to build it? Where can I find a reliable builder? What are all these regulations I keep hearing about? What are these different types of drawings and designers?

This guide answers these questions in plain English. No jargon, no assumptions – just clear information about what you need to know to move forward confidently with your project.

The Six Critical Things Every Homeowner Must Understand

1. Planning Drawings vs Building Drawings – They’re not the same thing

Remember those drawings you submitted with your planning application? They showed what your extension or conversion would look like – its size, shape, and how it fits with your neighbours.
But you can’t actually build from these drawings.

Think of it this way: planning drawings are like showing someone a photo of a cake you want to bake. Building regulations drawings are the actual recipe with exact ingredients, temperatures, and timing.
You need both to create the final product.

What this means for you:

• Planning drawings cost £1,000-£5,000 and take 2-4 weeks to prepare
• Building regulations drawings cost £1,500-£6,000 plus structural engineering (£600-£3,000)
• You’ll need another 4-8 weeks for preparation and 5-8 weeks for approval, if not the whole project duration.
• Starting this process early can save months of delays, in the right hands

🔗 Learn more about the difference between Planning and Building Drawings

2. Principal Designer requirements – you need two different ones

Even experienced builders may not now that according to the latest regulations there are two completely separate “Principal Designer” roles required by law, and they just happen to have the same name but very different responsibilities.
It’s like having two different doctors – one for your general health and one for your teeth. Both are doctors, but they do very different jobs.

The CDM Principal Designer has the duty to plan, manage, monitor and coordinate healt & safety matters in preparation for construction.
Their main role is to identify risks, coordinate the H&S information among consultants, and hand over the H&S information to the Principal Contractor, when there is one, who will then assume the responsibility during construction.
If a CDM Principal Designer is not appointed in writing, the legal responsibility falls automatically on the Client.
If you use more than one contractor (even a builder plus an electrician) independently and manage the project yourself, before the law you may be considered responsible for Principal Contractor duties as well.

The BSA Principal Designer is a new role introduced in 2023 by the Building Safety Act.
This dutyholder is responsible to ensure the design meets all regulations for structure, fire safety, energy efficiency – and in general all the regulations in the Approved Documents from A to O that may apply to the project.
Building Control will demand the BSA Principal Designer to sign off they are satisfied about this compliance, the Client should appoint this role as soon as possible but it is mandatory to have this appointment in place before the project goes into construction.

What this means for you:

• Combined appointment costs typically £2,000-£15,000, depending on project complexity
• This may represent 0.5-2% of your construction budget
• One qualified professional could fulfill both roles
• Appointing them early prevents legal issues and project delays

🔗 Learn more about Principal Designer roles and legal requirements

3. Building Control – the second approval you need

Many homeowners think planning permission means they can start building. This misconception costs thousands in fines and forced rebuilding work every year. Building control is a completely separate approval process that ensures your project is safe and meets all technical standards.

There are two common routes for a Building Control application.

• Building Notice:
  a quicker application for simple projects -e.g. changing a boiler system or doing a certain extent of electrical works-, with no detailed plans needed upfront.
  It’s faster but riskier, as approval relies on inspections during construction and is only available through the local authority.
• Full Plans:
  involves submitting detailed plans for approval before starting work, required for larger or complex projects. It provides formal advance approval, helping to reduce risks during construction, and is handled by the local authority or an approved inspector (private building control).

Think of planning permission as getting approval for what you want to do, while building control checks that you’re doing it safely. It’s like the difference between fixing the date and venue of your wedding… and actually choosing the menu, flowers, guest list, music, etc.

What this means for you:

• Building control fees cost £800-£1,500 for typical extensions
• The process takes 5-8 weeks for approval or the whole duration of the project
• Inspectors visit at key stages (foundations, structure, insulation, completion)
• Without approval, you face £5,000 fines plus £50 daily penalties
• You cannot sell your property without a completion certificate

🔗 What is the role of Building Control and how can you obtain the Completion Certificate

4. After planning approval – the hidden requirements

Congratulations if your planning application is approved!
Before you celebrate, check the decision notice carefully. Most approvals come with planning conditions: specific requirements you must meet before, during, and/or after construction.

These aren’t suggestions. Failing to discharge planning conditions is illegal and can result in enforcement action, including fines and having to tear down completed works.

What this means for you:

• Each application to discharge conditions has a fee but it can group more conditions
• The process takes around 8 weeks per submission
• Often the conditions require information that is part of the Building Drawings
• You must discharge the right conditions at the right stage, some BEFORE starting any work
• Planning permission expires after 3 years with no extensions available
• Smart homeowners start this process immediately after approval

🔗 What are Planning Conditions and how can you discharge them

5. If your planning application is refused, you have options

A planning refusal feels devastating, but it’s often not the end of your project, so don’t give up.
One in three planning appeals succeed, and many refusals can be overcome by addressing the specific concerns raised by the Planning Officers.

You have two main options: appeal the decision or re-design and re-submit.
The choice depends on why you were refused. If the council objects to your design details, a re-design often works better. If they’ve interpreted the planning policies with an angle that is not about right, an appeal might succeed.

With our extensive planning experience we can swiftly review a decision and the design that prompted it, understanding the best next thing to do to help you have the green light for your project.

What this means for you:

• Appeals cost nothing to submit but takes on average 6 months
• Professional support costs £2,000-£20,000 depending on complexity
• Success rates vary dramatically based on the refusal reasons
• There is a specific deadline for each type of application to submit an appeal
• Acting quickly preserves your options

🔗 My application has been refused. Is it REALLY over, now?

6. Construction risks – what could go wrong

Here’s the sobering reality: 91% of construction projects experience delays, and the average project runs 28% over budget. These aren’t random occurrences, they are systematic risks that affect nearly everyone.

Most delays happen after planning approval, during the technical drawing and builder appointment stages. Domestic projects could stall for months after planning and before getting into construction.

Common risks include builders disappearing mid-project, cost overruns from “unexpected” issues such as superficial costing at tender stage, poor contract documents preparation, defective work requiring expensive fixes, insurance claims being rejected, and safety incidents causing project shutdowns.

Homeowners who plan ahead can put together a strong Project Team, avoid the rush, secure better builders, and finish on time and within budget. Wise clients know that in a project expected to cost 100k or more, having a contract administrator -like your architect, if they are proficient- is a small investment that can save you from countless pitfalls, decision paralysis and spiralling costs.

What this means for you:

• Budget an extra 20% for contingencies
• Verify all contractor insurance and references before work starts
• Keep 5-10% retention until defects are fixed
• Review your home insurance for adequate coverage
• Document everything with photos and written records

🔗 Preparing for construction – How to choose the right builder for my project
🔗 Preparing for construction – What is a Contract Administrator and do I need a Project Manager?

A little bit about Tholos Architects

We are a boutique RIBA Chartered Practice led by the same experienced Architect since 2019. As a full-service architectural firm, we can take on your project at any stage – whether you are just gathering ideas before starting your planning application or already have approval and need technical drawings or builder recommendations.

Beyond having extensive experience in planning applications across England, we are passionate about construction and very careful in setting the right framework for the right project.
Our team has technical expertise in verifying plans are buildable and producing building drawings that meet Building Regulations’ standards, including construction details, fire safety, energy efficiency, and material compliance.

We also have Certified Passivehaus Designers to realise projects under the most demanding sustainbility requirements.

Thanks to our long-lasting, successful relationships with various expert consultants, you have access to a high-quality network, convenient rates and fast-track response.
The benefits of working with a multi disciplinary practice without the financial burden.

These include Chartered Structural Engineers, to incorporate structural design and calculations; Health & Safety consultants and Fire Engineers; Energy and HVAC Engineers, for efficient homes and climate control; Heritage and restoration experts, for special projects rooted in history; Financial and Legal advisors; Arboriculturists and Ecologists, to comply with tree preservation and the latest biodiversity regulations; Visual artists, to add an additional layer of greatness and virtual reality to the project of your dreams; and of course reputable construction companies that deliver and care about their reputation.

Our Guarantee to you:

✓ Free, no-obligation consultation – understand your next steps without pressure
✓ Fixed-rate quotes – no hidden costs or surprises
✓ RIBA compliance – highest industry standards and professionalism guaranteed
✓ Director’s involvement – experienced Chartered Architect personally following your project
✓ Client support – no chasing, get a point of contact that actually answers to you

Why Choose a RIBA Chartered Practice?

We’ve seen every mistake – and know how to avoid them

After guiding over 80 projects through planning and construction since 2019, we understand your concerns. You might be thinking: “Can’t I manage this myself?” or “Won’t any architect do?” or “This seems expensive – is it really necessary?”

Here’s what sets a RIBA Chartered Practice apart:

Experience that matters: With a ~70% planning success rate compared to the national average of 33%, we know what works in London and beyond. We’ve navigated refused applications, complex appeals, and challenging site conditions. When surprises arise – and they always do – we’ve likely seen it before.

All services under one roof: We’re not just designers. We are your Principal Designer for both CDM and BSA requirements. We prepare both planning and building regulations/construction drawings. We manage the tender process to find reliable builders. If you want, we’ll supervise construction to ensure quality, up to installing the curtains. One team, one point of contact, no gaps in responsibility.

Fixed prices, no surprises: For 93% of quoted domestic projects we can offer a fixed-fee structure and fix any time-based fee in advance too. No percentage fees that encourage overspending. No hidden extras when complexities arise. You’ll know your professional costs upfront, helping you budget confidently for the entire project.

Your protection is guaranteed: RIBA Chartered status isn’t just letters after our name. It means mandatory insurance, proven competence, and ethical standards enforced by our professional body. If something goes wrong, you have recourse. Can you say the same about unregistered designers?

We limit our workload: We accept only 3 new projects monthly. Why? Because rushing leads to mistakes, and mistakes cost you money. Your project gets the director’s personal attention, not handed to junior staff. When you call, you speak to someone who knows your project intimately.

Our network saves you time: Good builders are booked months ahead. Through our established network, we connect you with reliable, insured contractors who deliver quality work. No more scrolling through online reviews hoping for the best.

The question isn’t whether you need professional help – 91% of projects face delays and 28% budget overruns prove you do. The question is whether you want professionals who see your project as just another job, or a dedicated team committed to your success.

Ready to Move Forward with Confidence?

Your planning decision – whether approved or refused – marks the beginning of your construction journey, not the end. The choices you make now determine whether you join the 91% facing delays and budget overruns, or the successful minority who navigate the process smoothly.

Book your free 30-minute consultation today to discuss your specific situation with our experienced team. We’ll review your planning status, explain your next steps, and provide a clear roadmap forward – with no obligation to proceed.