Common dormer mistakes
The pitfalls that cause leaks, complaints and arguments about warranty. Read this before you sign anything — and before you decide a problem is 'just bad luck'.
Mindset
Most mistakes are made on paper
A surprising share of dormer problems start before any tool is touched: vague quotes, unclear warranty, missing permit work. Catching them on paper is much cheaper than catching them on the roof.
Top mistakes
What to actively avoid
During the build
Install-day warning signs
Checklist
Mistake-prevention checklist
Checklist
Run through this before you sign
- 01Compared at least three quotes per line item.
- 02Read the warranty document, not just the brochure.
- 03Confirmed the permit status with the council, not the salesperson.
- 04Checked reviews on more than one platform.
- 05Confirmed the company has its own fitters or a fixed crew.
- 06Confirmed the install plan, including a same-day waterproof plan.
- 07Agreed handover protocol with snag list.
- 08Agreed aftercare contact and response time.
Read next
Related guides
Quick answers
Frequently asked questions
FAQ
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01What is the most common dormer mistake?
Comparing quotes only on the total price. It hides large differences in insulation, frames, glazing and warranty that come back to bite later.
02How do I tell if a leak is the company's fault?
Leaks within the warranty period from junctions, lead flashing or seams are almost always install issues, not 'weather'. Document with photos and request a written response.
03What if my dormer feels cold despite 'good insulation'?
Usually a thermal bridge at the junction, an air leak around frames, or a missing vapour barrier — not the insulation thickness itself.
04Can a bad install be fixed without removing the dormer?
Some issues (lead flashing, ventilation, interior finish) can be reworked. Structural and insulation issues often cannot, which is why up-front checks matter.
Conclusie
Most expensive dormer problems are predictable. The list above is short, the checks are quick, and they save thousands. Do them before you sign — not after.