Should I Move or Extend? The London Homeowner's Decision Guide 2025

The cost of moving to a larger property in London is significantly underestimated by most homeowners. The major transaction costs of a London property purchase include: Stamp Duty Land Tax (SDLT): for a London homeowner buying a larger property as their main residence (selling the existing property at the same time), the SDLT rates in England in 2025 are: 0% on the first £125,000; 2% on £125,001 to £250,000; 5% on £250,001 to £925,000; 10% on £925,001 to £1.5 million; 12% above £1.5 million. For a typical inner-London family home purchase at £900,000 as a main residence sale and simultaneous purchase (not a second home), the SDLT is approximately £32,500. At £1.2 million, the SDLT is approximately £63,750. Estate agent fees (sale of existing property): typically 1-2% + VAT of the sale price. On a £700,000 sale at 1.5% + VAT: £12,600 in estate agent fees. Solicitor/conveyancing fees (sale and purchase): typically £1,500-£4,000 for the sale and £2,000-£5,000 for the purchase, including searches, Land Registry fees, and disbursements. Mortgage arrangement fees: a new mortgage on the larger property may incur arrangement fees of £500-£2,000. Survey costs: homebuyers survey (£400-£600) or full structural survey (£600-£1,500) on the property being purchased. Removal and relocation costs: £1,500-£5,000+ depending on volume and distance. School catchment and family disruption: moving in London often means crossing school catchment boundaries, which can have significant implications for children's schooling — particularly for primary and secondary school-age children. This is not a financial cost, but it is a major consideration for families in London. Total typical transaction costs for a London property move: For a family selling at £700,000 and buying at £900,000 (main residence, not a second home): SDLT: £32,500; estate agent fees (sale): £10,500; conveyancing (sale + purchase): £8,000; survey: £700; removal: £2,500; total transaction costs: approximately £54,200. These transaction costs are incurred immediately and do not add to the home's value — they are the direct cost of the move.

The cost of extending a London home is better understood and more controllable than the cost of moving — the homeowner can design the project to their budget, phase the works, and add exactly the space needed. Key costs for a typical London extension project: Design fees: architect/designer fees for a rear or double-storey extension, planning drawings, technical design, and contract administration: typically 10-15% of the build cost. For a £150,000 extension, design fees are typically £15,000-£22,500. Planning application: £258 for a householder planning application in England. Structural engineering: £500-£2,000 for structural calculations and drawings. Building Regulations: £500-£1,500 in Building Control fees. Party wall surveyor (if required): £700-£1,500 per surveyor (building owner's surveyor + adjoining owner's surveyor if they appoint their own). Build cost: For a London rear extension: single-storey 20 sq m: £50,000-£70,000 all-in (build only, excluding design fees and planning); double-storey 20 sq m/floor (40 sq m total): £80,000-£130,000. For a London loft conversion (dormer, one bed + bathroom): £45,000-£90,000 all-in (build only, excluding design fees). Kitchen renovation (if extending the kitchen space): £15,000-£40,000. Total all-in project cost for a typical London rear extension + kitchen renovation: £80,000-£160,000 for a comprehensive single-storey kitchen extension project, including design, planning, structural, party wall, build, and kitchen fit-out. Hidden costs of extending that homeowners underestimate: temporary accommodation during the works (2-6 months for a major renovation): £2,000-£8,000/month in London rental costs; skip hire and waste disposal: £500-£2,000; temporary storage for furniture: £500-£1,500/month; landscaping to restore the garden after the extension footprint is removed: £2,000-£15,000 depending on the extent of the garden impact.

Extending is almost certainly the better financial decision in the following circumstances: Your existing location is ideal and irreplaceable: in London, where schools, commute routes, social networks, and neighbourhood character vary enormously street by street, an excellent current location is extremely valuable. If the family has a child in a sought-after primary school, a short commute, or a network of friends and neighbours that would be disrupted by moving, the non-financial benefits of staying can outweigh a significant financial cost. The extension creates the exact space needed: if the family needs one additional bedroom, a larger kitchen, or a home office, and the existing house can accommodate those needs within the extension footprint, extending is a precise solution. Moving creates risk — the larger property purchased may have its own deficiencies (a problematic layout, a difficult neighbour, planning constraints). The transaction cost of moving exceeds the cost of the extension: for a London homeowner in a £700,000-£1 million home, the transaction costs of moving (£40,000-£80,000+) are very often comparable to or more expensive than the cost of the extension needed. Spending £70,000 on an extension that adds £80,000+ in value is a significantly better financial outcome than spending £60,000 in transaction costs to move to a house that starts with the larger space already built. You are within a mortgage fixed-rate term: if breaking out of a current mortgage fixed rate early would incur a significant early repayment charge, the timing of a move may be constrained in a way that an extension project is not (the extension can be financed via a further advance without breaking the existing mortgage).

Moving is almost certainly the better financial decision in the following circumstances: The existing property cannot be made to work at any cost: if the existing property is on a very small plot with no scope for a rear extension, or if the maximum achievable extension would still not provide the bedrooms needed, extending is not a solution. The property is already at the top of its street value ceiling: if an extension would cost £100,000 but only add £60,000 in market value (because the property is already at or above the local street ceiling), extending is financial over-capitalisation. Moving to a property that already has the space needed is more efficient. A significantly better location is available at a manageable transaction cost premium: if a school catchment change, a shorter commute, or a significantly better neighbourhood is achievable by moving at a manageable cost premium, the non-financial benefits of the better location may justify the transaction cost. The family needs a specific type of space that cannot be created by extending: some spatial needs (a large garden for young children, a double garage, a specific floor plan) cannot be achieved by extending the current property. If the specific need is tied to a fundamental characteristic of the site that cannot be changed, moving is the only route. Decision framework for the London move vs extend question: For the typical inner-London family, a quick framework: calculate the total transaction cost of moving (SDLT + agent fees + conveyancing + survey + removal); calculate the all-in cost of the extension needed (including design, planning, structural, party wall, build, temporary accommodation, and garden restoration); compare: if the extension cost is significantly less than the moving cost AND the extended property meets the family's long-term needs, extend. If the moving cost is comparable to the extension cost AND a significantly better property or location is available, consider moving.