Extensions Q&A's

How long does a single storey extension take to build?

The time required to build a single-storey extension depends on several factors, including size, complexity, materials, site conditions, and whether planning permission is needed. However, here’s a general breakdown of the timeline:

1. Planning & Preparation (4-8 weeks)

• Architectural Drawings & Design (2-4 weeks) – If needed, an architect or designer will create the plans.

• Planning Permission (if required) (8-10 weeks) – Most single-storey extensions fall under permitted development, but if planning is needed, it adds time.

• Building Regulations Approval (2-4 weeks) – Either through Full Plans Submission or Building Notice.

2. Groundworks & Foundations (2-4 weeks)

• Site Preparation & Excavation (1 week)

• Laying Foundations & Concrete Curing (1-2 weeks)

• Drainage Work & Floor Slab (1 week)

3. Structural Work (4-6 weeks)

• Walls, Steel Beams & Roof Structure (2-4 weeks) – Time varies based on materials (brick, block, timber, steel).

• Windows & Doors Installation (1-2 weeks)

4. Internal Work & Finishing (4-8 weeks)

• Electrics, Plumbing & Heating (2-3 weeks)

• Plastering & Insulation (1-2 weeks)

• Flooring, Tiling & Painting (2-3 weeks)

• Final Touches & Snagging (1-2 weeks)

Total Estimated Build Time: 10-16 weeks (3-4 months)

If unforeseen delays occur (bad weather, material shortages, or changes to plans), it could extend to 5-6 months.

Can you live in a house during an extension?

Yes, you can live in a house during an extension, but it depends on the scope of work, layout, and level of disruption. Here’s what you need to consider:

1. Type of Extension & Impact on Living Areas

• Rear or Side Extensions – Usually manageable if the main living spaces (kitchen, bedrooms, bathrooms) remain accessible.

• Wraparound Extensions – More disruptive, especially if structural work affects multiple walls.

• Kitchen Extensions – Difficult if the kitchen is out of use for weeks; you may need a temporary cooking setup.

• Garage Conversions – Least disruptive if the garage is separate.

2. Key Considerations

• Noise & Dust – Construction work will be noisy, and dust will spread. Sealing off work areas with plastic sheets can help.

• Safety Concerns – Open foundations, structural changes, and power tools pose risks, especially if you have kids or pets.

• Heating & Water Supply – If plumbing or heating is affected, ensure temporary solutions are in place.

• Access to Essentials – If the bathroom or kitchen is out of order, temporary alternatives or staying elsewhere might be necessary.

• Electricity & Power Cuts – Builders may need to cut power at times, so plan for backup arrangements.

3. Strategies to Make It Easier

• Create a Livable Zone – Designate an area of your home as a dust-free, comfortable space.

• Plan for Temporary Cooking & Washing – A small portable cooker, microwave, and kettle can help if the kitchen is out of use.

• Talk to Your Builders – A clear schedule helps you plan around the most disruptive phases.

• Consider Moving Out Temporarily – If work affects bedrooms or bathrooms for an extended period, staying with family or renting short-term accommodation might be more comfortable.

Verdict

✅ You can stay if the disruption is minimal and you can access essential rooms.🚧 If major structural work affects key living areas, moving out temporarily may be the best option.

How long does it take to lay foundations for an extension?

The time it takes to lay foundations for an extension typically ranges from 2 to 4 weeks, depending on various factors. Here’s a breakdown of what affects the timeframe:

1. Site Preparation & Excavation (2-5 days)

• Clearing the site, removing debris, and preparing access for machinery.

• Digging trenches to the required depth (typically 600mm-1m deep, but deeper for unstable ground).

• Time can be extended if tree roots, old foundations, or unexpected underground utilities are found.

2. Foundation Type & Installation

• Shallow strip foundations (most common) – 1-2 days

• Deep trench fill foundations (for weaker soil) – 3-4 days

• Pile foundations (for unstable ground or close to trees) – 1-2 weeks

3. Inspection & Approval (1-3 days)

• A building control officer (from local authority or private inspector) must approve the depth and structure before concrete is poured.

4. Concrete Pouring & Curing (3-7 days)

• Concrete is poured and left to cure and harden. Most builders allow at least 3 days before loading, but full strength takes up to 28 days.

• Work on brickwork can often start after a week, depending on the project.

5. Additional Groundwork (Optional) (3-7 days)

• Drainage and damp-proofing installation.

• Levelling and preparing for floor slab.

Total Time: 2 to 4 weeks

• Simple, straightforward ground conditions: 2 weeks.

• Challenging ground, bad weather, or deeper foundations: 3-4 weeks.

How long does it take to build a 2 story extension?

Building a two-storey extension typically takes 4 to 6 months, but the exact timeline depends on factors such as size, complexity, weather, and material availability. Here’s a general breakdown of the process:

1. Planning & Preparation (6-12 weeks)

• Architectural Design & Drawings (2-4 weeks)

• Planning Permission (if required) (8-10 weeks) – Many two-storey extensions require planning approval.

• Building Regulations Approval (2-4 weeks)

• Party Wall Agreements (if applicable) (4-6 weeks) – If the extension affects shared walls.

2. Groundworks & Foundations (3-5 weeks)

• Site Preparation & Excavation (1 week) – Clearing, setting out, and digging trenches.

• Foundation Construction (1-3 weeks) – Pouring concrete and allowing curing time.

• Drainage & Damp-Proofing (1 week)

3. Structural Build (6-10 weeks)

• Ground Floor Construction (2-3 weeks) – Laying the floor slab, brickwork, or steel frame.

• First Floor & Roof Structure (2-4 weeks) – Installing walls, beams, and roof trusses.

• Roof Covering & Waterproofing (2-3 weeks) – Installing tiles, insulation, and weatherproofing.

4. Internal Work (6-10 weeks)

• First Fix Electrics, Plumbing & Heating (2-4 weeks) – Installing wiring, pipes, and heating systems.

• Plastering & Insulation (2-3 weeks)

• Second Fix (Floors, Fixtures, Doors, Windows) (2-3 weeks)

• Final Decorating & Snagging (1-2 weeks)

Total Estimated Build Time: 4 to 6 Months

• Straightforward builds with minimal disruption: 4 months

• Complex builds requiring structural work, steel beams, or custom designs: 5-6 months

• Delays due to weather, planning, or material shortages: 6+ months

What is the cost of a single storey extension?

The cost of a single-storey extension in the UK varies depending on size, materials, location, and level of finish. On average, expect to pay between £1,500 – £3,000 per square metre. Below is a breakdown of estimated costs:

1. Basic Cost Estimates

Size	Basic Finish (£1,500/sqm)	Mid-Range (£2,000/sqm)	High-End (£3,000+/sqm)
15 sqm (Small)	£22,500 - £30,000	£30,000 - £45,000	£45,000+
25 sqm (Medium)	£37,500 - £50,000	£50,000 - £75,000	£75,000+
40 sqm (Large)	£60,000 - £80,000	£80,000 - £120,000	£120,000+

🔹 Basic – Simple build, uPVC windows, standard materials.🔹 Mid-Range – Bi-fold doors, underfloor heating, modern finishes.🔹 High-End – Bespoke glazing, premium materials, smart home tech.

2. Breakdown of Costs

Category	Estimated Cost
Architect Fees	£2,000 - £5,000
Planning Permission (if needed)	£206
Structural Engineer	£500 - £2,000
Building Control Fees	£500 - £1,500
Foundations & Groundwork	£5,000 - £15,000
Walls, Roof & Structure	£10,000 - £30,000
Windows & Doors	£3,000 - £15,000
Electrics & Plumbing	£2,000 - £10,000
Plastering & Insulation	£2,500 - £7,000
Kitchen/Bathroom (if included)	£5,000 - £20,000
Flooring & Finishing	£3,000 - £10,000

3. Additional Costs to Consider

• Demolition & Site Preparation – If existing structures need removing, add £2,000 - £5,000.

• Party Wall Agreement – If needed, £1,000 - £3,000.

• Garden & Landscaping – Could add £2,000 - £10,000.

• Temporary Accommodation – If moving out is required, factor in extra costs.

4. Cost-Saving Tips

✅ Stick to a simple design – Complex shapes, large glazing, and custom features increase costs.✅ Use standard materials – Off-the-shelf options are cheaper than bespoke designs.✅ Do some work yourself – Painting and decorating can save on labour costs.✅ Get multiple quotes – Prices vary by contractor, so compare at least 3 quotes.

Can a Neighbour stop you building an extension?

Yes, a neighbour can potentially stop or delay your extension, but only under specific circumstances. Here’s what you need to know:

1. Planning Permission Objections

If your extension requires planning permission, your neighbour has the right to object.🔹 How they can object: They can submit concerns to the local council during the public consultation period (usually 21 days).🔹 Valid reasons to object:

• Loss of light (Right to Light)

• Overlooking/privacy issues

• Overdevelopment of the property

• Out of character with the neighbourhood

• Noise or disruption concerns

  
  

  🔹 Invalid reasons (Council is unlikely to consider):

• Loss of view

• Personal dislikes

• Potential impact on property value

👉 What happens? If the council agrees with the objections, they might reject the application or require modifications.

2. Permitted Development Rights

If your extension falls under permitted development (e.g., a single-storey extension within size limits), neighbours cannot stop it, but they can raise concerns under the Neighbour Consultation Scheme (for larger extensions).

• The local authority can refuse under specific reasons, such as loss of amenity.

3. Party Wall Act (1996)

If your extension involves building on or near a shared boundary, you may need a Party Wall Agreement.

• You must notify your neighbour in writing at least 2 months before work starts.

• If they refuse to agree, you’ll need a party wall surveyor, which can delay your project by weeks or months.

4. Right to Light

If your extension significantly reduces the amount of natural light to your neighbour’s windows, they could take legal action.

• If proven, they might be able to stop the build or claim compensation.

5. Restrictive Covenants

Your property deeds may have legal restrictions preventing extensions.

• If an old covenant exists (e.g., requiring permission from a previous landowner or estate), neighbours may enforce it.

6. Disruptive Construction Issues

Neighbours can also complain to the council if:

• Noise & Working Hours – Builders must follow local regulations (usually 8 AM – 6 PM on weekdays).

• Blocked Access or Damage – If work causes obstruction or damage, legal action could be taken.

• Health & Safety Concerns – If scaffolding, dust, or machinery poses a risk.

Can They Stop It?

🚧 Yes, if:

• Planning objections are upheld.

• A party wall dispute arises.

• Right to light is breached.

• A restrictive covenant exists.

✅ No, if:

• The extension falls under permitted development.

• Their objection is not based on planning laws.

Do I need permission to build an extension?

Whether you need permission to build an extension depends on the size, location, and design of your project. Here’s a breakdown:

1. Permitted Development Rights (No Planning Permission Needed) ✅

You can build a single-storey extension under Permitted Development if you meet these rules:

Single-Storey Extension Rules:

• Rear Extension:

  • Up to 3m deep (terraced/semi-detached)

  • Up to 4m deep (detached house)

  • Can be up to 6m (terraced/semi) or 8m (detached) under Neighbour Consultation Scheme

• Height:

  • Max 4m high (pitched roof) or 3m if within 2m of boundary

• Side Extension:

  • Max half the width of the original house

  • Max height 4m

• Materials:

  • Must be similar to the existing house

• No building forward of the front elevation

👉 Larger extensions (up to 8m) require the Prior Approval Neighbour Consultation Scheme. If neighbours object, the council may review the plan.

Two-Storey Extension Rules:

• Rear only (not side)

• Max depth 3m

• Max height 7m (not taller than existing house)

• At least 7m from the rear boundary

• No balconies, terraces, or verandas

• Roof pitch must match existing house

🚨 If any of these limits are exceeded, you need full planning permission! 🚨

2. When Planning Permission is Needed 🏗️

You will need full planning permission if:

• Your extension is larger than permitted development limits.

• The house is listed or in a conservation area.

• The extension covers more than 50% of the original land around your house.

• You plan to build a wraparound extension.

• The extension significantly changes the appearance of the house.

How Long Does It Take?

• Permitted Development: No approval needed.

• Larger Extensions (Neighbour Consultation Scheme): 42 days (6 weeks).

• Full Planning Permission: 8-10 weeks.

3. Building Regulations Approval (Always Needed)

Even if Planning Permission isn’t required, Building Regulations Approval is mandatory for: ✅ Foundations✅ Structure (walls, roof, beams)✅ Insulation✅ Drainage✅ Electrical & Plumbing work

You can apply through:

• Building Notice (quicker for small extensions)

• Full Plans Application (detailed approval in advance)

4. Other Considerations

• Party Wall Agreement – Needed if building near a shared boundary.

• Right to Light – If blocking neighbour’s windows, legal issues may arise.

• Restrictive Covenants – Your house deeds may have limits on extending.

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Final Answer: Do You Need Permission?

✅ No planning permission needed if within permitted development rules.

🚧 Yes, planning permission required if exceeding size limits, in a protected area, or making major structural changes.