+x multiply.build

Architecture
Simplified

Plans, drawings and planning permission for any building project in London.

80+ projects and growing • From £1,295 • Fixed price

Resources • Updated October 2025

Everything you need to get started

Free tools and expert guides for your London extension

Popular guides

Learn from real London projects

Build Without Planning Permission

Complete guide to Permitted Development rights. Find out what you can build without planning permission in London.

What Does an Extension Cost?

Real costs from 5,000+ London extensions. Ground floor, loft, and side return prices by area.

Side Return Extensions

Everything about side returns. Typical costs £55k-85k, planning rules, and kitchen integration.

Loft Conversions

Complete loft conversion guide. Dormer, hip-to-gable, and mansard costs. Building regs and planning explained.

Rear Extensions

Single and two-storey rear extensions. Costs, size limits, design options, and planning requirements.

Extending a Terraced House

Extension options for terraced houses. Size limits, party walls, side returns, and wrap-around designs.

Building in Conservation Areas

What you need to know about conservation areas. Restricted rights, planning requirements, and costs.

Building Regulations Explained

Understanding building regs for extensions. Structural, fire safety, insulation, and ventilation requirements.

Party Wall Agreements

Everything about the Party Wall Act. When required, the process, costs (£700-1,500), and neighbour disputes.

Two Storey Extensions

Building up. Costs £130k-150k, planning permission, design considerations, and structural requirements.

Extending a Semi-Detached House

Extension options for semi-detached houses. Size limits, rear and side extensions, and loft conversions.

Kitchen Extensions

Creating open-plan kitchens. Bi-fold doors, lighting, costs £75k-120k, and layout options.

How Long Does an Extension Take?

Complete timeline from design to completion. 6-12 months typical. Planning, building regs, and construction stages.

Architect or Online Service?

Honest comparison of traditional architects vs online services. Costs, design quality, and when to use each.

Our Method

From first chat through ready-to-build plans

Read the full guide
Key:
Delivered by us
Delivered by third parties
Swipe left to see the full timeline →
Month 1
Month 2
Month 3
Month 4
Month 5
Month 6
Measured Survey
1 week
Existing drawings
10 working days
Proposed design
2-3 weeks
Planning support
8-10 weeks
CCTV drainage survey
1 week
Structural engineering
10-12 working days
Building regs drawings
3-4 weeks
Party wall notices
1-2 weeks
Building Control Approver's signoff
1 week
Find a builder
4-6 weeks

Project examples

Real projects with real costs.

FAQ

Questions

Contact

Let's talk

Ready to start your extension? Get in touch and we'll take it from there.

Call or WhatsApp

Chat about your ideas or get a quick answer.

+44 7405 920944

Email us

Send us your ideas, photos, or questions.

hello@multiply.build