Why Do Extension Quotes Vary So Much for the Same Job?

If you're a homeowner in Solihull or elsewhere in the UK considering extending your property, you've probably noticed one thing straight away: extension quotes can differ dramatically, even when you think you're requesting the same work. Why does that happen? Why can one builder’s quote be £20,000 higher than another's for what sounds like an identical project? This variation can be baffling — and frustrating https://dlf-ne.org/how-much-does-a-30-sqm-extension-cost-in-the-west-midlands/ — but understanding the reasons behind it will help you make smarter decisions and avoid nasty surprises.

Drawing on twelve years of experience managing and estimating UK residential extensions, plus up-to-date insights from reliable sources like the Office for National Statistics (ONS), Checkatrade, and MyJobQuote, this guide breaks down the main causes of quote variation. We’ll also focus on Solihull’s local market quirks, planning considerations, and what homeowners often forget to budget for—so you can compare “like for like” and decide whether to move or extend.

The Solihull Price Gap Is Driving "Extend, Not Move" Decisions

Recent statistics from the ONS, particularly their May 2026 local house price breakdowns, reveal a significant gap between the cost of moving to a larger home and extending your existing property within Solihull. The average house price in Solihull remains high and has risen steadily, while the cost of an extension, when budgeted properly, tends to be Hop over to this website less than the combined expense of stamp duty, estate agent fees, solicitors’ fees, and other moving costs.

Cost Aspect Average Cost in Solihull (£) Notes Stamp Duty (for £400,000 property) £15,000 Varies by property value Estate Agent Fees £8,000 ~1.5%-2% of sale price Solicitor Fees £1,500 Legal costs for buying/selling Typical Two-Storey Extension £40,000 - £70,000 Depending on size and specification

Given that moving involves considerable paperwork, transaction fees, and stress with relatively little guarantee of net space gained or favourable property features, many homeowners in Solihull are weighing up the cost-benefit of extending instead. Understanding your project’s real costs upfront is therefore crucial.

Why Extension Quotes Vary: Specs, Specs, Specs

When you ask for quotes, one of the biggest reasons for wildly different prices is that builders and contractors often assume different specifications—sometimes without making this clear. This includes everything from materials to insulation levels, foundation depth, interior finishes, and building methods.

Verbal Brief vs Drawings: The Devil’s in the Detail

In many cases, quotes start from an initial verbal brief rather than detailed drawings or plans. This creates the proverbial "apples vs oranges" problem. A builder quoting off just your conversation might exclude things later asked for, or price conservatively to cover unknowns. Another using basic sketches or computer-generated plans will price based on more defined information, often including structural elements and finer specification.

Always insist on quotes based on a detailed, written scope of work, ideally accompanied by accurate architectural drawings or at least detailed sketches. This allows for a proper "compare like for like" exercise when you get multiple quotes.

Single-Storey vs Two-Storey Extensions: A Size and Complexity Factor

Extension type and size heavily influence costs. Single-storey extensions generally come cheaper per square metre than two-storey builds due to the complexity of foundations, structural loads, and potentially increased planning requirements.

Extension Type Average Cost per m² (£) Typical Features Single-Storey £1,500 - £2,500 Open-plan rooms, kitchen/diners, garden access Two-Storey £2,000 - £3,500 Additional bedrooms, bathrooms, higher structural needs

This cost per square metre should always be sanity-checked against your quotes to flag unrealistic estimates or underquoting that can lead to expensive change orders later.

Planning Permission and Permitted Development: Don’t Assume You’re Free to Build

Many homeowners forget how planning and local conservation constraints can impact their extension costs. For instance, Solihull properties within certain zones or conservation areas may have restrictions limiting height, footprint, or external appearance.

Using tools like the Solihull Council pre-application enquiry service is a wise first step. Here’s why:

• Pre-application advice reduces delays and unexpected redesign costs.
• Planning application vs permitted development: Knowing which route applies avoids the costly mistake of starting work without permission.
• Time is money: Planning refusals mean reworking quotes, redesigns, and possible legal challenges.

Quotes should reflect any additional work required to meet planning conditions, comply with building regs, or provide more expensive materials to conform with local aesthetics.

Moving Costs Add Up, but Don’t Add Space

Often homeowners who receive high extension quotes consider moving instead. But moving carries many hidden expenses that don’t increase living space but impact finances significantly:

• Stamp Duty: Banding starts at £125,000, but jumps rapidly for higher-priced homes. In Solihull’s rising market, this can be tens of thousands of pounds.
• Estate agent fees: Typically 1.5%-3% of the sale price.
• Solicitor fees and surveys: Legal fees for buying and selling, including mortgage valuations and surveys.
• Removal costs and time off work.

Compare these to the cost per square metre of extending, and you often find that spending £50,000 on a two-storey extension yields more space and keeps you in the school catchment or local amenities you love.

What People Forget to Budget For

Experienced homeowners often overlook these costs in their initial budgets, which can cause quote variations and worries later:

• VAT Inclusion—Not all builders specify if their quote includes VAT (20%), which inflates final costs significantly.
• Contingency Fund—Industry-standard recommends adding 10-15% contingency for unforeseen issues, like foundation surprises or design changes.
• Professional Fees—Architects, structural engineers, party wall agreements, and planning fees add thousands.
• Landscaping and External Works—Paths, drainage, fences, and garden restorations are often omitted.
• Temporary Accommodation—If you must move out temporarily, factor in this cost.

How to Get Quotes That Are Truly Comparable

To avoid the headache of wildly different quotes, here’s a checklist informed by years of project management and estimation experience:

1. Prepare Detailed Drawings and Written Specs: If needed, hire an architect or designer to produce clear plans.
2. Check Planning Constraints Early: Use the Solihull Council pre-application enquiry and confirm permitted development rights.
3. Request VAT-Inclusive Quotes: Make sure quotes explicitly state whether VAT is included.
4. Include a Contingency: Publicly declare you expect a 10-15% contingency in budgets.
5. Ask for Breakdown by Trade and Material: Helps spot what is or isn’t included.
6. Get Multiple Quotes: Use platforms like Checkatrade or MyJobQuote to find vetted professionals.
7. Compare Costs Per Square Metre: Use industry benchmarks to sanity-check prices.
8. Discuss Verbal Briefs into Written Confirmations: Avoid relying on memory or vague descriptions.

In Summary

The wide variance in extension quotes comes down to differing assumptions about specification, scope, planning constraints, and hidden costs. Especially in Solihull, where the local house price gap encourages extending rather than moving, understanding these nuances can save you tens of thousands.

Remember, comparing quotes without detailed drawings and specifications is like comparing apples and oranges. Use the available council pre-application tools, clarify VAT and contingency in quotes, and don’t forget to factor in professional fees and planning nuances. This way, you can confidently decide on the best route for your home improvement journey.

If you’d like more tailored advice or help interpreting quotes, you can reach out via the comments or visit the Checkatrade and MyJobQuote directories to connect with local trusted experts.