London Home Extension Experts | Add £50k+ Property Value
We design your dream home extension with fixed pricing, planning approval guarantee, and full architectural plans - with complete peace of mind.
Trusted by 100+ London homeowners
June Offer
Limited Time
Free survey (£250)
💎Typical Value Added
*Based on typical London property values
Select Your Project Type
Choose the option that best matches your needs
Ground
From £1,295
Design service fee
First Floor
From £1,795
Design service fee
Loft
From £1,595
Design service fee
Renovation
From £1,295
Design service fee
New Build
From £2,495
Design service fee
"Multiply transformed our cramped terrace into a stunning family home. The fixed-price guarantee gave us complete peace of mind, and they delivered exactly on time."
Sarah & James Mitchell
Clapham, London
+£65k
value added
"The planning approval guarantee was essential for us. Our complex loft conversion got approved first time, and we now have two beautiful bedrooms."
David Chen
Islington, London
+£35k
value added
"From quote to completion drawings in 4 months. The quality of architectural plans exceeded our expectations, and our builder said they were the best he'd worked with."
Emma Thompson
Wandsworth, London
+£50k
value added
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Step-by-step guide to
your extension journey
From concept to completion, our streamlined process guides you through every step of your home extension journey.
Frequently Asked
Questions
Find quick answers below. If you don't see your question, feel free to reach out via the Contact section.
Our fixed-price design service starts from £1,295 for architectural plans and planning application. The total construction cost varies but typical projects are: Rear Extension £45-80k, Loft Conversion £30-50k, First Floor Extension £60-100k. Use our free calculator for instant pricing based on your specific project.
100% Money-Back Guarantee. If your planning application gets rejected due to our design, we refund your full fee. We have a 100% success rate because we pre-assess every project and only take on projects we're confident will get approval. Book a free consultation to discuss your project's feasibility.
From initial quote to construction-ready plans: 4-6 months typically. Breakdown: Design & Planning Application (6-8 weeks), Council Review (8-10 weeks), Building Regulations & Final Plans (4-6 weeks). We manage the entire process and keep you updated weekly. Start your free quote today.
Extensions typically add significant value to properties, but the exact amount depends on various market factors including location, property type, and local demand. Based on our experience with 100+ completed projects, well-designed extensions often add more value than they cost. We provide a property value assessment as part of our service to help you understand the potential financial impact. Get your value assessment.
Everything you need for construction-ready plans: Measured survey, architectural design, planning application, structural calculations coordination, building regulations drawings, and project management. No hidden fees. Only exclusions are council fees (£200-500) and optional extras you choose. See full breakdown in our instant quote.
We provide construction-ready plans that any builder can use. We can also introduce you to our network of vetted builders who regularly work with our plans and offer competitive pricing. Optional service: We can help manage the tender process to get you the best price from multiple builders.
Minor changes are included in our fixed price. Major scope changes (like adding a floor or doubling the size) may require a fee adjustment, which we'll quote transparently before proceeding. We include 2 rounds of revisions to ensure you're completely happy with the design before planning submission.
Free feasibility check included. Before you pay anything, we assess your project against planning policies, permitted development rights, and local restrictions. If we identify any major issues, we'll advise alternative solutions or recommend not proceeding. Start your free assessment.
Ready to Add £50k+ to
Your Property Value?
Join 100+ London homeowners who've successfully increased their property value with our guaranteed fixed-price service.
Get Your Free Quote in 2 Minutes
Get instant pricing for your extension with our smart calculator. No personal details required until you're ready to proceed.
Email Our Experts
Have specific questions? Email us directly and we'll respond within 2 hours during business days.
hello@multiply.buildBook Free Consultation
Get expert advice on your project. Free 15-minute consultation to discuss your vision and get initial guidance.