Frequently Asked Questions

House extension costs in London typically range from £50,000 to £200,000+, depending on size, specification, and location. As a rough guide:

• Single-storey rear extension: from £50,000
• Double-storey extension: £80,000 - £150,000
• Wraparound extension: £100,000+

Every project is unique. For a detailed breakdown, see our house extension cost guide, or get a quote tailored to your property.

Loft conversions in London typically cost between £45,000 and £120,000. The main types and their starting costs are:

• Velux / rooflight conversion: from £35,000
• Rear dormer conversion: from £45,000
• L-shaped dormer: from £55,000
• Mansard conversion: from £70,000

Read our full loft conversion cost guide for more detail.

Yes. We offer a completely free, no-obligation consultation and site visit. After assessing your project requirements, we provide a detailed written quotation with a full cost breakdown so you know exactly what to expect — no hidden costs or surprises.

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We use stage payments tied to project milestones. A typical payment schedule looks like this:

• 10% deposit to secure your start date
• Stage payments at key milestones (foundations, superstructure, first fix, second fix)
• Final retention released after snagging and completion

This approach protects both parties and ensures work is completed to the agreed standard before each payment is made.

Many single-storey rear extensions fall under Permitted Development (PD) rights and do not require a formal planning application. However, you will need full planning permission if:

• Your property is in a conservation area or is a listed building
• The extension exceeds PD size limits
• Your PD rights have been removed by the local authority
• You live in a flat or maisonette

We assess this during your free consultation and handle all planning applications on your behalf. Read our detailed guide on planning permission for house extensions in London.

A party wall agreement is a legal notice and agreement between you and your neighbours, required under the Party Wall etc. Act 1996. You need one when building work involves:

• Work on a shared boundary wall
• Building a new wall on or near the boundary
• Excavating near a neighbouring property's foundations

We guide you through the entire process and can recommend experienced party wall surveyors. See our party wall agreement cost guide for more information.

Yes. We manage the full building regulations process, including:

• Preparing and submitting applications to building control
• Arranging inspections at each stage of the build
• Obtaining final sign-off and completion certificates

You do not need to deal with building control directly — we handle everything on your behalf.

Standard householder planning applications typically take 8 weeks for a decision. Major applications can take up to 13 weeks. We recommend starting the planning process as early as possible to avoid delays to your build programme.

If you need a Lawful Development Certificate (to confirm PD rights), this usually takes 8 weeks as well.

A typical house extension takes 12 to 20 weeks from start to completion. As a guide:

• Single-storey rear extension: 12-16 weeks
• Double-storey extension: 16-20 weeks
• Wraparound extension: 16-22 weeks

Timescales can vary based on complexity, weather, and specification. Read our detailed guide on how long a house extension takes.

Most loft conversions take 8 to 14 weeks depending on the type:

• Velux conversion: 6-8 weeks
• Rear dormer: 8-12 weeks
• Mansard conversion: 12-14 weeks

Loft conversions are one of the least disruptive types of building work, as most work takes place above the existing living space.

Our process has four clear stages:

1. Free consultation & site visit — We visit your property, discuss your vision, and provide a detailed written quotation.
2. Design & approvals — We coordinate architects, structural engineers, planning applications, building regulations, and party wall agreements.
3. The build — A dedicated project manager oversees the construction, with regular updates and quality checks throughout.
4. Handover — Final snagging inspection, completion certificates, warranty documentation, and a clean, finished space ready to enjoy.

We work closely with a network of trusted architects and can manage the full design process on your behalf. Whether you already have architectural plans or need to start from scratch, we ensure designs are:

• Buildable and structurally sound
• Compliant with planning and building regulations
• Cost-effective and within your budget

If you already have an architect, we are happy to work directly with them.

We cover all London boroughs, from East London (our home base in Wanstead) through North, South, and West London. Our teams regularly work in areas including:

• Hampstead, Highgate, Muswell Hill, Islington
• Kensington, Chelsea, Notting Hill, Fulham
• Wimbledon, Richmond, Putney, Wandsworth
• Wanstead, South Woodford, Chingford, Buckhurst Hill

See our full list of areas we cover.

Yes. Alstruct Ltd holds independently verified accreditations and insurance:

• CHAS Elite — the highest level of health & safety accreditation
• Constructionline Gold — verified contractor credentials
• Federation of Master Builders (FMB) — vetted member
• £10 million public liability insurance
• Full employer's liability cover

These accreditations mean you can be confident that your project is in safe, professional hands.

In most cases, yes. For extensions and loft conversions, homeowners can usually remain in the property throughout the build. We take care to:

• Seal off the work area from your living space
• Minimise dust, noise, and disruption
• Maintain safe access to your home at all times

For full house renovations or projects involving major structural work across the whole property, temporary relocation may be advisable for comfort and safety. We discuss this honestly during the consultation stage.