Renovating an existing dormer
An old dormer can often get a second life for €2,000-€5,000 instead of €7,000+ for replacement. But only if the structure is sound. When renovation pays and when demolition and new-build is smarter — covered here.
- Renovation cost range
- €2,000-€5,000
- Replacement cost range
- €7,000-€13,000
- Renovation extra life
- 15-20 years
- Replacement extra life
- 30-40 years
- Pre-inspection cost
- €150-€350 building survey
When renovation pays
On a structurally sound dormer (no rot, intact load structure) with dated frames, yellowed panels or low insulation.
Single-to-HR++ glazing (€800-€1,500), new PVC cladding over timber (€1,800-€3,500), or full frame replacement (€1,500-€2,800) are realistic moves that buy 15-20 more years.
When replacement is better
On rot in the structure, leaks affecting load beams, dated sizes (1.5-2 m) where you could gain space, or if insulation is below R 3.
Full replacement is cost-effective and gives 30-40 new years plus better energy performance. A replaced dormer with R 6+ can save €200-€400/yr in heating — payback 15-20 years on insulation alone.
Possible renovation interventions
Painting timber (€500-€1,200): every 6-8 years, +6-8 years life. Frame replacement (€1,500-€2,800): timber > PVC or HR++ > triple. Add interior insulation (€600-€1,200) — watch moisture balance.
Lead replacement (€400-€900) if existing lead is weathered. EPDM cover replacement (€800-€1,500). Full cladding renewal (zinc, panel, PVC) (€2,000-€4,000).
5-minute decision matrix
Step 1: visual check — rot visible in cheeks, fascia or interior beam? Yes → replace. Step 2: building survey (€150-€350) for borderline cases.
Step 3: calculate — renovation cost > 60% of new? → replacement is better long-term. Step 4: high energy bill? → replacement with R 6+ pays back fast. Step 5: just cosmetic with no insulation concern? → renovation suffices.
FAQ
- Do I need a permit for renovation?
- On same size and only maintenance: no. On size change or major look change (e.g. different material): possibly yes. Check with municipality.
- How do I know if my dormer has rot?
- Visually soft spots, screwdriver test (sinks in = rot), dark discolouration around fixings, moisture damage on interior cladding.
- What about asbestos in old dormers?
- Dormers <1994 may contain asbestos in sheathing or board. Asbestos inventory mandatory before demolition (€350-€600); removal by certified firm €1,500-€3,500.
- What warranty on renovation?
- 2-5 years on workmanship, 10-20 years on new components (factory warranty on frames, glass).
- Does renovation help at sale?
- Yes, a tidy dormer affects 3-8% of sale price. A very dated dormer can dissuade buyers; renovating or replacing offers certainty.