How is an old metal roof repaired?

1. Inspection

• the main surface: surface rust, pinholes, sagging sheets,
• the seams: open, cracked, badly soldered,
• the details: chimney, valleys, penetrations, eaves and verge,
• the substrate: from the loft, look for stains on the boarding and damp spots,
• ventilation: if moisture builds up under the sheet, it corrodes from below.

2. Assessment

3. Coatings

For pre-painted sheet, Ruukki recommends renewing the coating once the aesthetic warranty has expired: scrape off loose material, remove rust, wash, let it dry, repair damaged spots with primer and apply at least two top coats. Plain galvanised steel is treated in a similar way with paint intended for zinc. Titanium-zinc and copper are not normally painted.

4. Permission and heritage

Under Section 18(5)(a) of Building Act No. 25/2025 Coll., repairing and replacing a roof covering needs no notification; a notification is needed for a listed cultural monument and for work that could affect the appearance of the building from public space. In a heritage area you need a decision from the regional monuments board (krajský pamiatkový úrad) before altering the building (Section 32(5) of Act No. 49/2002 Coll.) – this applies, for example, to changing the colour or material of the roof covering.

5. Cost

Repairs are often charged by the hour – Numiq (14 May 2026) gives €20–40 per hour excl. VAT; installing a standing seam roof is €25–65 per m² excl. VAT, materials not included.