Compare Granny Annexe Builders: How to Choose One 2026

What separates a good annexe builder

Annexes sit at the intersection of planning, building regulations and structural work, so the strongest builders are annexe specialists with a portfolio of completed projects rather than general builders taking on their first. Look for evidence of finished annexes, references you can contact, and a clear understanding of the planning and ancillary-use rules.

Modular vs traditional build

Modular (factory-built) annexes offer a fixed price and fast on-site assembly — often weeks rather than months — but less design flexibility. Traditional brick-and-block builds take longer and carry more variation risk, but match your house and adapt to awkward plots. Choose based on your timescale, budget certainty and how bespoke you need the result to be.

How to compare and choose

1. Shortlist specialists

Prioritise builders with a real track record of completed annexes, not generalists doing their first.

2. Check insurance and warranty

Confirm public liability cover and an insurance-backed structural warranty before any money changes hands.

3. Compare modular vs traditional

Weigh the speed and price certainty of modular against the flexibility of a traditional build.

4. Get three like-for-like quotes

Compare on the same spec, payment schedule and timescale so you judge value, not just price.

Red flags to avoid

Be wary of large upfront deposits, prices well below the rest, no written contract or warranty, and reluctance to provide references or proof of insurance. A trustworthy builder is transparent about staged payments and what is and is not included.

FAQs

Related guides

• How to build a granny annexe
• Do I need planning permission for an annexe?
• Comparison guides
• Is it worth it? Insights