# Sandwich panel roof: types, thicknesses, advantages, disadvantages and what to ask in the quote

> What a sandwich panel is, the three types (ribbed, tile-look, timber-faced), thicknesses and data-sheet values, rain noise, fire, pitch, supports, portal prices and what we could not confirm.

- Page: https://telhadoseguro.pt/en/guides/sandwich-panel-roof
- Language: English
- Updated: 2026-11-03

## Summary

- A sandwich panel is two steel sheets with insulation between them (PIR, PUR or mineral wool) and weighs 10 to 13 kg/m² in the PIR-cored data sheets we read.
- Thermal transmittance (Up) falls from 0.73 W/(m².K) at 30 mm to 0.23 at 100 mm, in one Portuguese manufacturer's data sheet.
- Ask for the reaction-to-fire class in the document for the thickness you buy: the declarations of performance we read say "N.D.".
- Swapping tile for panel is not an "identical exterior finish": ask the council. Prices are from portals, not checked officially.

Sandwich panel, "sandwich sheet" or "sandwich tile": increasingly asked for on outbuildings, garages and to replace old roofs. We read manufacturer data sheets, the law and price portals. We do not name brands or firms.

*Updated 3 November 2026. General information, not a substitute for a technician's design.*

## The essentials

- **It is a "sandwich":** two steel sheets with insulation between them (PIR, PUR or mineral wool). It covers and insulates in one piece.
- **It is light:** 10 to 13 kg/m² in the data sheets for PIR-cored sheet.
- **Weak points:** rain noise, badly sealed joints, and fire, which depends on the core.
- **Swapping tile for panel is not an "identical exterior finish".** Ask the council (see the [permit guide](https://telhadoseguro.pt/en/guides/roof-works-permit-2026)).
- **Get in writing** the core, thickness, declaration of performance, minimum pitch and distance between supports.

## What it is and what it is made of

In the data sheet of a Portuguese manufacturer (Alaço, 20 November 2023), the five-rib panel has a 0.5 mm outer sheet, a 0.4 mm inner sheet, a PIR core of 42 kg/m³ and thicknesses from 30 to 100 mm.

- **PIR** (polyisocyanurate): the core in the Portuguese data sheets we read, with a conductivity of 0.023 W/(m.K) (Alaço declaration of performance, 18/10/2024).
- **PUR** (polyurethane): Ruukki said in 2015 that it stopped making it and moved to PIR, after an amendment to standard EN 14509 meant to strengthen fire safety.
- **Mineral wool:** on Ruukki's page, the roof panel with wool has reaction to fire A2-s1,d0 and the PIR one, B-s2,d0.

## Three types that get mixed up

1. **Ribbed profile.** Minimum pitch of 7% for the five-rib model (10% if there is an overlap).
2. **Tile-look.** The same brand's CTELHA model has a Portuguese-tile relief, 40 or 60 mm, and a recommended minimum pitch of 12%.
3. **Timber-faced, to lay tiles on top.** Onduline (data sheet of June 2026) has a particleboard top face, PIR of 50, 65 or 75 mm and a lower face of your choice (OSB, boarding, plasterboard). It weighs 18 to 26 kg/m².

## Thicknesses: what the data sheets say

| Thickness (mm) | 30 | 40 | 50 | 60 | 80 | 100 |
|---|---|---|---|---|---|---|
| Up, W/(m².K) | 0.73 | 0.56 | 0.45 | 0.38 | 0.28 | 0.23 |
| Weight, kg/m² | 10.0 | 10.4 | 10.8 | 11.2 | 12.0 | 12.8 |

Up is the thermal value the data sheet gives for the panel: the lower, the better. Portaria n.º 138-I/2021 sets maximums of 0.40, 0.35 and 0.30 by climate zone (see the [insulation guide](https://telhadoseguro.pt/en/guides/roof-insulation)). We could not confirm whether your pitched roof counts for those values, or the zone of your municipality.

## Advantages

- **Light and quick to fit**, say Habitissimo and Zaask. A Portuguese "lusa" tile weighs 3 to 4 kg and takes 10 to 14 per m²: 30 to 56 kg/m² (our calculation, from the [tiles guide](https://telhadoseguro.pt/en/guides/roof-tiles-by-climate)).
- **Pieces up to 17.3 m** (Alaço): fewer joints.

## Disadvantages

- **Rain noise.** An Austrian study on timber roofs (Holzforschung Austria, June 2025) says rain can raise noise levels, especially in lightweight structures with a metal roof, and that the roof covering weighs most. We found no measurements of panels sold in Portugal.
- **Damp at the joints.** Kingspan's installation guide mentions a factory-applied anti-condensation tape and recommends a vapour tape or sealant where indoor humidity is above normal. Ridge, eaves and overlaps get sealing tapes: see the [leak causes](https://telhadoseguro.pt/en/guides/roof-leak-causes).
- **Heat.** The same guide says small dents in the sheet, from thermal deformation, are unavoidable, and suggests larger washers. Alaço's data sheet gives its span tables for colour group I (ECCS recommendations): ask whether they hold for your colour.
- **Walking on it.** Kingspan allows walking on a fixed, dry panel for inspections, not for regular use, and never in rain, snow or ice. See [work at height](https://telhadoseguro.pt/en/guides/work-at-height-roof).

## Fire

Commission Delegated Regulation (EU) 2016/364 defines the Euroclasses from A1 to F, with s1 to s3 (smoke) and d0 to d2 (burning droplets). Alaço gives B-s1,d0 in the data sheets of both models. **But the declarations of performance for 30 and 40 mm (October 2024) write "N.D." for reaction to fire.** Ask for the class in the document for the thickness you will buy.

Portaria n.º 135/2020 (article 10) requires the outer covering of pitched roofs to be at least C-s2,d0 (no. 12). Next to openings facing the roof of another building or block, no. 6 asks for A1 in a 4 m strip. We could not confirm how this applies to a whole panel.

## Pitch, supports and fixing

- **Pitch:** 7%, 10% or 12%, depending on the model.
- **Supports:** Alaço asks for a minimum width of 40 mm at end supports and 60 mm at intermediate ones, with maximum deflection L/200. For 40 mm on a single span, it gives 3.12 m at a load of 1.0 kN/m² and 2.40 m at 1.6 kN/m². The load (snow, wind) is for the designer.
- **Timber-faced panel:** Onduline allows up to 1.25 m between centres, 83.3 cm with 50 mm PIR and 62.5 cm with plasterboard.
- **Fixing:** a clip on the upper rib (Alaço). Kingspan (September 2024) says 3 fixings per support are generally enough in windy zones and 2 elsewhere, in stainless steel, with the number calculated.

## Permit

Ask the council first. In Braga, the municipal code treats changing asbestos-cement to sandwich panel as a work of minor urban relevance (see [Braga](https://telhadoseguro.pt/en/roof-repair/braga)); in Setúbal's historic centre, corrugated sheet is not accepted in place of tile. If the old roof is asbestos-cement, see the [asbestos guide](https://telhadoseguro.pt/en/guides/asbestos-roof-law-removal).

## Price

Portal figures, **not checked officially**. Habitissimo (10 June 2026): average of 80 €/m² (60 to 100) in one section and 65 €/m² (30 to 100) in another; PIR 55 to 150; tile-look about 15.5. Zaask (undated): average of 60 €/m² (30 to 100); tile-look 11.50 to 25 €/m², without saying whether labour is included. Neither states VAT. See [how much a roof costs](https://telhadoseguro.pt/en/guides/roof-cost-per-m2) and [VAT](https://telhadoseguro.pt/en/guides/roof-works-vat).

## Maintenance

Check joints, flashings, screws, scratches in the paint and [gutters](https://telhadoseguro.pt/en/guides/gutter-cleaning). Ask the maker for the maintenance guide for the model (Paroc has one).

## What to ask in the quote

1. Model, core and thicknesses.
2. Declaration of performance (EN 14509) with the fire class.
3. The model's minimum pitch and your roof's pitch.
4. Distance between supports and load calculation.
5. Fixings: type, number, material.
6. Joints, flashings and tapes included.
7. Ceiling or lining underneath, for rain.
8. A written [warranty](https://telhadoseguro.pt/en/guides/roof-works-warranty).

## What we could not confirm

- **An official price.** Only private portals.
- **The declared fire class** (the declarations say "N.D.").
- **Measured rain noise** of panels sold in Portugal.
- **Service life.** Habitissimo says "at least 25 years", with no source.
- **Changes** to Portaria 135/2020 and to the October 2026 RJUE after the texts we read.

## Sources (read on 3 November 2026)

- Onduline, [Ondutherm Óptima H19 data sheet](https://pt.onduline.com/sites/onduline_pt/files/2026-06/ft_ondutherm_otima_h19_0.pdf), 06/2026. Alaço, [C5-1000 data sheet](https://media.adeo.com/media/4588508/media.pdf) and [CTELHA-1000](https://media.adeo.com/media/4587972/media.pdf), 20/11/2023; declarations of performance [C5-1000, 30 mm](https://media.adeo.com/media/4588884/media.pdf) and [CTELHA-1000, 40 mm](https://media.adeo.com/media/4588065/media.pdf), 18/10/2024. In Portuguese.
- Kingspan, [KS1000 RW design and installation guide](https://a.storyblok.com/f/293586193989128/9490782/4679284e24/kingspan-rw-roof-design-and-installation-guide-nordics-en.pdf), 09/2024, and [installation guide](https://a.storyblok.com/f/293586193989128/6350114/283bdf9829/kingspan-installation-guide-en-ceu.pdf), PDF of 2019.
- Ruukki, [news of 22/06/2015](https://www.ruukki.com/roofing/news/22-06-2015-ruukki-is-adjusting-its-sandwich-panel-portfolio-to-meet-the-standard) and [roof panels](https://www.ruukki.com/building-envelopes/products/roof-structure/sandwich-panels-for-roofs). Paroc, [installation guide](https://a.storyblok.com/f/293586193989128/674131/31e636bb57/paroc-ps-sandwich-panels-installation-guide-int.pdf), 03/2022.
- Regulamento Delegado (UE) 2016/364, [OJ L 68, 15/03/2016](https://prociv.gov.pt/media/yhob1etk/celex_32016r0364_pt_txt.pdf) (Portuguese copy). Portaria n.º 135/2020 of 2 June, [Diário da República n.º 107](https://diariodarepublica.pt/dr/detalhe/portaria/135-2020-134991810), article 10 (read in a [copy](https://www.aiccopn.pt/wp-content/uploads/2021/11/0000200214.pdf)). In Portuguese.
- Habitissimo, [Instalação de painel sandwich](https://www.habitissimo.pt/orcamentos/instalacao-de-painel-sandwich), 10/06/2026. Zaask, [Painéis sandwich](https://www.zaask.pt/quanto-custa/paineis-sandwich), undated. In Portuguese.
- Stenitzer et al., [Rainfall sound insulation of roofs](https://dael.euracoustics.org/confs/fa2025/data/articles/000725.pdf), Forum Acusticum, 2025.

## FAQ

### What minimum pitch does a sandwich panel roof need?

It depends on the model. In Alaço's data sheets (20/11/2023): 7% for the five-rib panel (10% if there is an overlap) and 12% for the tile-look one.

### What reaction to fire does the panel have?

Alaço's data sheet gives B-s1,d0, but the declarations of performance for 30 and 40 mm (18/10/2024) write "N.D.". Ruukki gives A2-s1,d0 for mineral wool and B-s2,d0 for PIR. Portaria n.º 135/2020, article 10, no. 12, asks the outer covering of pitched roofs for at least C-s2,d0.

### Is a sandwich panel roof noisy in the rain?

It can be. A Holzforschung Austria study (Forum Acusticum, 2025) says rain can raise noise levels, especially in lightweight structures with a metal roof. We found no measurements of panels sold in Portugal.

### How much does a sandwich panel roof cost?

There is no official price. Habitissimo (10/06/2026) gives averages of 80 and 65 €/m² in different sections and Zaask, undated, 60 €/m². These are portal figures, not checked officially.

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Source: https://telhadoseguro.pt/en/guides/sandwich-panel-roof. Independent information, not legal or tax advice.