Acoustic Design: Designing for Calm

 A quiet look at how sound shapes the way we learn, teach, and feel in schools.

Considering acoustic treatment:
1 Acoustic ceiling panels
2 High level acoustic wall panels
3 Cork and felt lined display boards
4  Sound proofing from outside activities

The Spaces That Talk Back at Us

We all know the rooms.
The ones where the noise just… hangs.
Where staff raise their voices without realising.
Where concentration dips by mid-morning—and tension quietly rises.

Sometimes, it’s not the behaviour that’s the issue.
It’s the acoustics.

Why Sound Matters More Than We Think

Sound affects more than hearing.
It affects attention, memory, regulation, and physical stress levels.
In schools—especially busy urban ones—acoustic quality can change the whole tempo of the day.

For staff:

• Constant background noise increases cognitive load

• Voice strain is common (and exhausting)

• Poor acoustics make behaviour management harder than it needs to be

For students:

• Processing language in a reverberant room can increase anxiety and reduce engagement

• For neurodiverse learners, the impact can be overwhelming

The Department for Education sets minimum standards in BB93.
But many buildings, especially older ones don’t meet them—and often refurbishments don’t prioritise them.
And yet the difference can be felt within days of making changes.

According to Sharon Baker, an acoustics expert at Ecophon:

• A standard classroom might have a reverberation time of 1.2 seconds—resulting in echo and elevated ambient noise.

• Teachers may need to speak over the background, which can strain vocal cords and cause long-term issues.

• Classrooms with ceilings higher than 2.8m are more prone to echo.

• If the back row of desks is more than 9m from the teacher, speech intelligibility drops dramatically.

• Noise from corridors, playgrounds or adjacent rooms can interfere with focus unless sound insulation is considered.

• For pupils with hearing loss, visual impairments, autism, ADHD or EAL needs, greater sound absorption is essential. A reverberation time of 0.4 seconds is typically recommended.

What Can Be Done (Without a Major Overhaul)

This isn’t about spending a fortune or gutting classrooms.
It’s about small interventions, well placed.

Some practical strategies we’ve seen work well:

• Acoustic ceiling panels in high-ceiling classrooms to reduce echo without compromising sense of space

• High-level wall panels on front or rear walls, where display space isn't needed

• Swapping hard surfaces for soft ones: felt-lined cork display boards, carpet and underlay, beanbags or soft furnishings in reading corners

• Soundproofing from outside sources where necessary

• Rethinking zoning: avoid placing quiet workrooms next to echoey corridors

• Designing in sound absorption, not just adding furniture

These aren’t just tricks. They’re thoughtful responses to how people experience sound.

Acoustic performance can even be assessed using a smartphone decibel app. If the classroom regularly peaks above 65dB during lessons, it may benefit from acoustic treatment.

Typical costs for acoustic interventions range between £2,500 to £3,500 + VAT, adjusted for inflation from 2013 estimates.

Listening is Part of Design

At DesignBox, we don’t come in with fixed answers.
We listen—to your staff, your students, your site.
Sometimes what’s needed is a tweak. Sometimes it’s a sequence of improvements, phased over time.
But always, the goal is the same: to make the space work with your school—not against it.

Want to Explore This in Your Context?

If there’s a space in your school that feels “off” acoustically—and you’re not sure where to start—feel free to get in touch.

Book an enquiry call
We’ll ask a few questions, listen carefully, and help you think through what’s possible.
No pressure. No jargon. Just thoughtful support.

Thanks

Phil

DesignBox Architecture Ltd

Listening with design—so schools can flourish.

What Does a Home Extension Really Cost? A Complete Guide for Homeowners

If you’ve ever tried to work out the cost of a home extension or renovation project, you’ll know how confusing and opaque it can feel. “How much will it cost?” often gets a vague “Well… it depends.”

So let’s break the fog.

This post is your no-nonsense breakdown of typical costs, based on projects in Southwest London — including building work, professional fees, consent charges, and everything in between.

👉 Book a free discovery call to get early clarity and support on your next steps.

1. Building Costs

This is the price of the construction work itself — what your builder will quote for labour, materials, and subcontractors.

Project Type	Typical Build Cost (per m², ex VAT)
Rear Extension	£1,800 – £3,500
Loft Conversion	£1,500 – £2,500
Interior Refurbishment	£500 – £1,600

	Item     Typical Range (ex VAT) New Kitchen     £10,000 – £50,000 + Each New Bathroom / Shower Room     £5,000 – £15,000 +

These ranges depend on the complexity of installation, number of units, layout changes, plumbing, lighting, finishes, and appliances. High-end projects or bespoke cabinetry can push the upper limits — while budget solutions (like flat-pack ranges) can keep things lean.

To estimate your overall build cost:

• Multiply your project area by the rates above

• Add in any kitchen, bathroom or joinery items

Then multiply by 1.6 to allow for VAT, design fees and contingency.

2. Design Fees (Architect + Consultants)

These are approximate fees for the professionals helping you design and manage your project.

Service	Typical Cost (ex VAT)	VAT	Total (Inc VAT)
Architect – Planning Design & Application	£2,000	£400	£2,400
Architect – Thames Water Drawings	£500	£100	£600
Architect – Building Regs Drawings	£1,200	£240	£1,440
Architect – Tender Pack for Builders	£1,800–£3,000	£360–£600	£2,160–£3,600
Interior Design (Optional)	£1,000	£200	£1,200
Architect - Site Monitoring (per10 hrs.)	£1,000	£200	£1,200
Structural Engineer (Steel calcs, drawings)	£2,000	£400	£2,400
Measured Survey	£600 – £1,500	£120 – £300	£720 – £1,800

Tip: fees can scale with complexity — your architect can advise on scope and what's necessary.

3. Consent Fees (Statutory Applications)

Some of these are fixed by law or external bodies — but all are essential to getting your project off the ground (legally!).

Consent	Budget Cost (ex VAT)	VAT	Total (Inc VAT)
Planning Application (Householder)	£206	£0	£206
Lawful Development Certificate (optional)	£103	£0	£103
Building Control Fee (based on £150k build)	£900	£180	£1,080
Thames Water Build Over Agreement	£286	£57.20	£343.20
CCTV Drainage Survey & Report	£330	£66	£396
Party Wall Surveyor (per neighbour)	£1,200	£240	£1,440
CDM Principal Designer Role	£1,000	£200	£1,200

4. Other Project Costs

Item	Cost
Freeholder Consent (if developing a flat)	£TBA
Insurance for Construction Works	£300 – £600		- Usually provided by specialist brokers
Solicitor's Fees (if required)	£TBA

Ballpark Example

Here’s a rough total for a 40m² single-storey rear extension, mid-spec:

• Build Cost: £2,500/m² × 40m² = £100,000 + VAT = £120,000

• Design + Professional Fees = £12,000–£16,000

• Consents + Surveys = £4,000–£6,000

• Contingency (10%) = £12,000

• VAT (20%)

• TOTAL = £177,600 – £184,800 (give or take)

Why Transparency Matters

One of the biggest myths in residential projects is that all these costs go to “the architect.” In reality, your architect helps you orchestrate these moving parts — but many of the fees go to other specialists, regulatory bodies, and third-party consultants.

That’s why we break everything down clearly for our clients — so they can make informed decisions, plan ahead, and avoid costly surprises.

Ready to Explore Your Ideas?

If you’re thinking about a home extension or renovation and want to understand what it could cost — let’s chat.

👉 Book a free discovery call to get early clarity and support on your next steps.

Thinking of a Home Extension or Renovation? Here’s What You Need to Know

Building work is rarely straightforward. Even a standard home extension can involve up to five statutory consents. Managing these properly is key to keeping projects on time and on budget.

That’s why we offer a free Zoom consultation for homeowners — to help you understand the process before you commit to your project.

👉 Book a free discovery call here to talk through your ideas and get a clearer picture of what’s involved.

Whether you’re dreaming of a light-filled kitchen extension, a loft with a view, or rethinking your entire layout, carrying out private residential refurbishments and extensions is a big undertaking. It’s costly, time-consuming, and often stressful. The construction industry is complex and fragmented, and without the right guidance, projects can quickly become overwhelming.

A good architect helps untangle all of this — ensuring your vision is realised with fewer surprises, better coordination, and more confidence.

The Three Phases of a Successful Home Project

We divide the project process into three clear stages, aligned with the RIBA Plan of Work:

1. Design Stage (RIBA Stages 0–3)

Here we work together to define your brief and develop a design that reflects your needs, aspirations and budget. This includes everything from initial concept sketches to submitting your Planning Application and acting as your ‘agent’ through the planning process.

2. Detail Stage (RIBA Stages 3–4)

We help with preparation of the technical drawings and documents needed for Building Control and other approvals, and for your builder to price the works accurately.

3. Construction Stage (RIBA Stages 4–6)

This includes working with you on the appointment of your builder, coordinating site works, and ensuring all compliance is met through to the completion of your.

The 5 Key Statutory Consents (That Often Catch People Out)

Depending on your project, the following consents might be required:

1. Planning Permission

Most extensions and lofts will require formal planning approval. Even if your proposals fall under Permitted Development, we recommend a Certificate of Lawfulness is applied for instead, to ensure the Council agrees. Getting the application right the first time is key to avoiding delays later.

2. Building Control Approval

Most projects will also require Building Regulations approval. A ‘Full Plans’ submission is recommended to catch design or compliance issues before works start on site.

3. Thames Water Build Over Agreement

If your project is within 3 metres of a shared sewer, you’ll need permission from Thames Water. This usually involves:

• A CCTV drainage survey and report
• Architectural or design drawings of your proposals for Thames Water approval
• A formal application

4. CDM Health & Safety Compliance

Under the Construction (Design and Management) Regulations 2015, sets out criteria requiring most domestic projects to require a ‘Principal Designer’ to coordinate the health and safety aspects of your project during the design and construction stages. 

5. Party Wall Awards

If your works affect a shared wall, boundary, or nearby structure, you’ll likely need to serve Party Wall notices to your neighbours. If they ‘dissent’, you’ll need a Party Wall Award with each relevant neighbour from a party wall surveyor.

Important to note - As the homeowner, you’re legally required to have someone act on your behalf to manage Building Control and Health & Safety design compliance (known as CDM). These are two separate roles, but confusingly, both are called “Principal Designer.”

Your architect can take on both roles — but only if they’re appointed through to the end of the project. If not, someone else needs to step in. This could be your contractor, but make sure they have the right Professional Indemnity Insurance to cover it.

Yes, it’s confusing. Yes, it’s fragmented. That’s why it helps to have someone experienced by your side. 

+ Additional Consent for Leaseholders: Freeholder Consent

If you own a leasehold property, you’ll almost certainly need formal written consent from your freeholder before carrying out any alterations — including extensions, loft conversions, or internal reconfigurations.

This is not a statutory planning consent, but it is a legal requirement under the terms of your lease. Failing to get it can cause problems down the line, especially if you plan to remortgage or sell.

Key points:

• It usually involves a formal application with drawings

• Some freeholders charge fees for reviewing or granting consent

• It’s advised to check the lease early — some leases prohibit certain alterations outright

Top tip: If you’re a leaseholder, speak to your freeholder before submitting a planning application. It can save time, money, and legal hassle.

Budgeting Your Project: Two Ways to Look at It

Method 1 – Budget-first:

1. Start with your available capital
2. Then deduct the following:
   
• 10% for contingency
• 15% for fees and surveys
• 20% for VAT on construction
3. The remainder is your construction budget before VAT - and this is the figure that most builders will give you.

Method 2 – Cost-first:

1. Estimate build costs:
   
• Rear extension: £1,800–£3,500/m² + VAT
• Loft conversion: £1,500–£2,500/m² + VAT
• Interior refurb: £500–£1,600/m² + VAT
• New kitchen £10,000–£50,000 + VAT
• Each new bathroom or shower room £5,000–£15,000 + VAT
2. Multiply total area by these rates and add kitchen, bathrooms and shower rooms as required
3. Multiply the result by a factor of 1.6 to cover fees + VAT + contingency

Whichever method you use, it’s essential to understand your total capital expenditure before diving into detailed design.

Other Services That May Be Required

Depending on complexity, your project might also need:

• A measured survey
• Structural engineer (for steel design, calcs & drawings)
• Specialist supplier’s information: Drawings and specifications from specialists contributing to the design and construction of your project
• Quantity Surveyor: For managing costs on larger/complex jobs
• Interior design, visuals, and VR: Optional, but powerful for decision-making

Typical Timelines

Here’s a guideline summary of typical time requirements for each step of your project.  It might easily take between 6 and 9 months to progress from the start of a design to being ready to start work on site.

• Design Stage: 1-2 months
• Planning Permission Process: 3 months including time for ‘validation’ and decision 
• Detailing for Building Control and Tender Pack for Builders: 1-2 months
• Confirming a price with a builder and scheduling in the start of construction: 1-2 months+++
• Construction: 3-18 months be pending on the size and scope of the project

Top tip: Start speaking to builders early. Their availability often dictates your start date more than anything else!

A Little Known Item…Your Insurance!

Before construction begins, make sure you have the right insurance. Check your builder has the appropriate insurance cover but this will not cover everything, so it is highly recommended you have your own.  Some policies can be extended to cover home renovations, or you can take out a specific contract works policy. Your architect or builder can advise.

Final Thoughts

Your home is likely your most valuable asset — financially and emotionally. Extending or renovating it should be exciting, not overwhelming. Having a qualified, experienced architect by your side not only improves outcomes but saves time, stress and costly mistakes.

If you’re thinking about making changes to your home and want to understand the process properly:

👉 Book a free discovery call here to talk through your ideas and get a clearer picture of what’s involved.

Good luck with your project, and enjoy the process.

Thanks for reading

Phil

DesignBox Architecture

Designing Supportive Environments

This is a summary of our working approach to architectural design in education.  It focuses on how to support both client and stakeholders involved in the project, including the students, teachers, staff, the maintenance team and parents etc.  Thoughtful design can shape environments that positively support everyone's experience, by considering physical, procedural, and mental / well-being issues.  Designing for supportive environments can help reduce stress related absences in schools, allowing greater support of the school towards the individual and in turn, the individual to support the school.  

Defining Design

Effective design goes far beyond addressing the immediate requirements of the client (i.e. answering the “what is needed” question).  It must consider the broader group of stakeholders; effectively every group of people who engage with the school.  Each group engages with the environment differently, so the design should reflect those diverse needs. In practice, this involves consulting with all relevant stakeholders to determine how the spaces should work for everyone, and how the operational dynamic of the whole should work.

There are three essential aspects to consider in any design project:

Physical Design:

This includes the tangible elements of the project; how the materials, space, light, and ergonomics should work.  It’s the part that everyone sees and enjoys.  It is often the part of the project that has the “wow” factor.   While this is often the easiest to achieve, it's also the area that usually consumes most of the budget.

Designing with care for the physical elements is crucial, as it sets the foundation for how people experience the space.

Processes and Procedures:

This is often harder to quantify because it involves the dynamics of how people work within the space.  Workplace roles and responsibilities change over time, so designing with flexibility is key.  Spaces should accommodate shifting working conditions, evolving technologies, and the personal dynamics of the people using them.

Making room for adaptability helps to ensure that a building can continue to function well as its occupants and their  working needs change.

Mental Wellness:

It is essential that design also contributes to a sense of mental well-being.  Spaces and their layout should work to help reduce stress and anxiety, while fostering a feeling of safety and comfort.  This is the most difficult to define because it can be heavily influenced by workplace dynamics, individual characters and changes in working procedures.

Acknowledging this, well-designed spaces can alleviate some of the tension that arises from challenging working environments and heavy workloads.  By creating an environment that feels safe and uplifting, design can contribute to lower stress levels.

Artbox - A School Art Studio Extension

As a case study of holistic design is the Artbox, Art Studio Extension for a State Primary School in South-West London used design to address physical, procedural, and wellness needs within tight budget constraints.

Physical Design Response:

With limited funds, the focus was on creating a spacious room with ample diffused natural light, rather than expensive finishes or intricate details.  Physically, the priority was to create a space that was fun to work in, flexible for a range of art activities, and be durable. 

Supporting Processes:

The design ensured minimal disruption to the existing school layout.  It included a dedicated art studio, an adjacent art store, and a one-to-one teaching space. This created a neat, efficient space that supported both teaching and creative processes.

A Place to De-stress:

The ArtBox became the go-to for students and teachers to visit, as it offered a quiet, uplifting atmosphere separated from the rest of the school. It provided a place where kids could escape their regular routines and engage in hands-on creativity, fostering both mental relaxation and educational growth.

Holistic Design Considerations

Designing supportive environments is especially relevant in places like schools, where stress levels can be high. Teachers often experience significant and unrelenting levels of stress, which can lead to absences and serious health conditions.   Although design cannot resolve all workplace tensions, it can help mitigate stress in a coordinated approach with the school to manage stress levels at work, by creating spaces that promote positive interactions and help limit difficult working situations between people.

For example, when designing, consideration to factors like good acoustics, lighting and ventilation, connections with nature, access to outdoor spaces, and opportunities for physical activity can help. These elements can all contribute to a healthier, more supportive environment.

This might not sound new or helpful, and after all most of the points listed in the diagram above are standard design considerations, but it is all in the approach.  By focusing on the people and interactions of individuals and groups, rather than just the functionality of the building, design can be managed to deliver a product which looks good, functions efficiently for everyone and is supportive.   

The Design and Delivery Process

So in addition to design, the detailing and delivery of a project is just as important.  For this to happen effectively, the right people need to be involved.  It's a similar approach to being effective in design; having the right consultants and experts involved in the process, will help achieve the required results.  

Although we work to the Royal Institute of British Architect's (RIBA) 'Plan of Work', for the purposes of discussing projects with our clients, we find it is easier to think of the sequence in terms of 'Design', 'Detail' and 'Delivery'.  This helps us to keeping a focus on the people-centric project balance of physical design, processes and procedures, and mental wellness throughout each stage.   

How We Can Help You

For schools or educational establishments considering upgrades to their facilities whilst grappling with tight budgets, designs for improvements can still go hand in hand with enhancing procedural and wellness outcomes. So, let us talk to you se see how we can help. From the Head to the troubled Teacher, if your education facilities are not performing as they should, contact us to see how we might help.  

By considering the needs of all stakeholders, we can create environments that are not only functional but are also supportive, promoting well-being and productivity for all who use them.

In conclusion, designing supportive environments means considering more than just the physical space. By addressing processes, procedures, and mental wellness, we can create spaces that help foster better working relationships improve personal well-being, and reduce stress-related illnesses in the work-place.  

We Help to Make Your Neighbours Jealous

The DesignBox Architecture Process

Hi, I'm Phil at DesignBox Architecture.  We're based in South-West London, and we help make your neighbours jealous.  

You know how life is fast paced and demanding? And when you do have down-time, you don't enjoy your home the way you'd like.  I can help make your home be the place you've always dreamed of.  

If you want to explore this, the process is simple. We have a quick thirty-minute zoom in which I find out about you, your home and your aspirations etc. Then I set out a proposal outlining ideas, next steps and costs.  If you’d like to take it further, we schedule a visit to your home to dive into design.  

There are only so many film nights, Christmases and evenings with friends over for dinner.  

My clients are comfortable with a home they enjoy and which supports them.  Day after day they share experiences and build memories.  All because they made their place work for them.  

You can book a call on this link:

https://calendly.com/designbox-architecture/designbox-meeting

Would you like to chat?