Materials for sheet-metal roofing products
The material decides how long the flashing will last, what it will look like in ten years and what it must never be combined with on the roof. For each material we give only figures we can back up with a source.
- Sheet
- Materials
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- 22 items
- Type
- information guide
Overview
| Material | Thickness (KJG gutter) | Expansion, mm/m per 10 K | Gutter, girth 333, € per m excl. VAT | Price index |
|---|---|---|---|---|
| galvanised steel | 0.55 mm | 0.12 | 4.20 | 1.0 × |
| pre-painted galvanised steel | 0.55 mm | 0.12 | 7.93 | 1.9 × |
| pre-painted aluminium | 0.70 mm | 0.24 | 8.70 | 2.1 × |
| stainless steel AISI 304 | 0.50 mm | not given | 12.02 | 2.9 × |
| titanium-zinc | 0.65 mm | 0.22 | 13.49 | 3.2 × |
| copper | 0.55 mm | 0.17 | 45.59 | 10.9 × |
Prices: KJG a.s., recommended retail prices, price list from 11 August 2026, checked 14 October 2026. Expansion: KJG, installation guide 2025; for titanium-zinc RHEINZINK gives the same figure, 2.2 mm/(m · 100 K). Our sources contain no figure for stainless steel, so we do not give one.
Galvanised steel
Steel sheet with a zinc coating on both sides (in Slovak pozinkovaný plech, or pozink for short). With the designation Z275 under EN 10346 that means 275 g of zinc per m² in total on both sides, typically about 20 µm per side. Zinc protects the steel twice over – as a barrier, and by sacrificing itself where the coating is damaged.
Service life depends on the environment. ISO 9223 gives these first-year corrosion rates for zinc:
| Category (ISO 9223) | Typical environment | Zinc, µm per year | 20 µm coating lasts roughly |
|---|---|---|---|
| C2 | countryside, small towns, low pollution | 0.1–0.7 | 29 years or more |
| C3 | towns, moderate pollution | 0.7–2.1 | 9–29 years |
| C4 | industry, salt | 2.1–4.2 | 5–9 years |
The last column is our own simple calculation (thickness ÷ rate). The standard points out that first-year rates cannot simply be extrapolated into the future; long-term corrosion tends to be slower. Treat it as a comparison of environments, not a guarantee.
Pre-painted steel
Galvanised steel sheet with an organic coating (polyester, matt polyester, thicker finishes such as Pural) – in Slovakia often called lakoplast. The paint protects the zinc, so the service life is longer and the colour matches the roof. Manufacturers give warranties on pre-painted rainwater systems: Ruukki 30 years on the GreenCoat RWS Pro rainwater system (warranty certificate 09/2026; half the periods above 900 m above sea level), and Lindab up to 30 years on its Elite range rainwater system according to the table in its warranty certificate. The warranty depends on conditions – for example no cutting with an angle grinder, no contact with copper and a minimum gutter fall.
Weak points: cut edges, scratches and swarf. They are repaired with the manufacturer’s paint.
Aluminium
Light and rustproof; in sheet-metal work it is used pre-painted – for window sills, gutters, trims and roofing. It has the highest thermal expansion of the metals discussed here (0.24 mm/m per 10 K), which has to be respected in piece lengths and expansion joints. It must not be below copper. Our sources contain no verified figure for the service life of aluminium flashings.
Titanium-zinc
An alloy of high-purity zinc (99.995%) with additions of copper and titanium, made to EN 988. In air it forms a protective patina of basic zinc carbonate. KJG supplies titanium-zinc in thicknesses of 0.65 / 0.70 / 0.80 mm.
Service life: in its technical recommendations (March 2024) VMZINC gives a service life of 100 years for roofs and facades and more than 50 years for gutters; it gives the average corrosion rate of rolled zinc today as about 1 µm per year.
Watch out for: copper above zinc (RHEINZINK: “problematic”), acidic run-off from unprotected bitumen membranes and some membranes (PVC, ECB), and moisture from the underside without ventilation. Joints are soldered.
Copper
A premium metal with a characteristic patina – it turns brown first, and after some years may turn green. Building sheet is Cu-DHP to EN 1172. In its environmental product declaration Aurubis gives a reference service life of more than 100 years.
Copper is the most expensive (a gutter costs ~11 times as much as galvanised steel) and brings one fundamental restriction: water running off copper must not flow onto zinc, titanium-zinc, galvanised steel or aluminium. It dissolves them. The other way round – titanium-zinc above copper – RHEINZINK permits, as long as the metals do not touch.
Stainless steel
Corrosion-resistant steel, in sheet-metal work most often AISI 304. A KJG stainless gutter (0.50 mm) costs €12.02 per m excl. VAT. Stainless steel is used for chimney cowls, fixings and clips, and where a very durable gutter is wanted. RHEINZINK lists stainless steel as harmless in combination with titanium-zinc; take care with permanent contact with aluminium. Our sources contain no verified figure for the service life of stainless-steel flashings.
Galvanic compatibility
| Water runs from ↓ onto → | galvanised / pre-painted | titanium-zinc | aluminium | copper | stainless steel |
|---|---|---|---|---|---|
| copper | ✕ no | ✕ no | ✕ no | ✓ yes | – not assessed |
| titanium-zinc | ✓ yes | ✓ yes | ✓ yes | ✓ yes, no contact | ✓ yes |
| aluminium | ✓ yes | ✓ yes | ✓ yes | – not assessed | – not assessed |
| stainless steel | ✓ yes | ✓ yes | ! caution | – not assessed | ✓ yes |
| galvanised / pre-painted | ✓ yes | ✓ yes | ✓ yes | – not assessed | – not assessed |
Sources: RHEINZINK (copper above zinc problematic; aluminium, stainless steel, galvanised steel and lead above zinc harmless; zinc above copper permissible without contact), VMZINC (run-off from copper onto zinc ruled out, unalloyed steel unsuitable), Lysaght per AS/NZS 2179.1 (run-off from copper onto aluminium and galvanised surfaces ruled out; stainless steel with aluminium only in mild environments), Lindab (no contact with copper). Combinations marked “not assessed” are not clearly covered by our sources. Interactive version: material comparison.
Technical sources
The sources this sheet draws on. We checked prices and values from standards on the date shown; for prices, whatever the source currently states always applies. Sources marked “in Slovak” or “in Czech” are only available in that language.
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