A roof window brings light and air into an attic. It is also a hole in the roof, and that is where leaks, condensation, unpermitted works and arguments with the condominium come from. This guide explains the types, why they drip, what permit may be needed, what a manufacturer’s guarantee says and which prices we could confirm. We do not recommend firms.
Updated on 3 November 2026. General information, not a substitute for the town council or a qualified professional.
The essentials
- Cutting a new opening in the roof alters the outside of the building. In our reading of the RJUE, it does not fit the exempt interior works. Ask the council first.
- Apartment building: the roof is a common part, and works that change its appearance need the authorisation of two thirds of the building’s value.
- The manufacturer’s guarantee does not cover poor installation. Whoever installs it answers for it.
- Condensation is not a leak. The VELUX guarantee excludes condensation.
- Price: the VELUX table gives list prices, without VAT. We found no official price for labour.
The types
The VELUX Portugal catalogue (price list of 1 July 2026) shows, among others:
- Opening roof windows, manual, electric or solar: centre-pivot-style tilting (the handle is at the top) and top-hung. They suit roof pitches from 15° to 90°.
- Fixed windows, which only give light.
- Windows for low-pitch roofs (10° to 20°), with their own flashings.
- Balcony window and terrace window, which give access to the outside.
- Domes and zenithal windows for flat or nearly flat roofs.
- VLT 1000 skylights, described in the guarantee as made for uninsulated, unoccupied attics.
- Light tunnels.
We did not find in that catalogue a separate “roof exit” type.
Why they drip
The manufacturer’s documents give three clues.
- Flashings and pitch. The price list sells flashings separately and by roof covering (corrugated tile, flat tile, slate). A flashing wrong for your roof, or a window outside its intended pitch, is a leak waiting for rain.
- Installation. The guarantee excludes defects resulting from installation contrary to the instructions or good practice, or outside the recommended areas.
- Blockages. It also excludes leaks caused by ice, snow or branches. See gutter cleaning.
Condensation: the guarantee says condensation on roof windows, and the water damage that follows, can be a natural result of humidity and temperature differences. If there are only drops on the glass or frame and no ceiling stain after rain, it may be condensation; confirm with a technician. See damp at home: roof or something else and the causes of roof leaks.
Permit: opening a hole in the roof
We read the text of Decreto-Lei n.º 108/2026, which revised the RJUE and has applied since 1 October 2026 (see the permit guide).
- “Alteration works” are those that change the physical or aesthetic characteristics of a building, including the nature and colour of exterior cladding materials, doors and windows included (article 2).
- Interior alterations are exempt only if they do not change the exterior, in particular facades, roofs or coverings (article 6, no. 1, b).
- Under article 4, alteration works need a licence, except those subject to prior communication, such as works in a consolidated urban area that follow the plans and do not increase the height (no. 4, d and e).
In our reading, a new roof window needs a licence or a prior communication, depending on your area. Replacing one with an identical window we could not confirm: it may count as maintenance, and article 6-A only covers replacing frames to improve energy efficiency, with identical geometry and finish. Ask the council for the answer in writing.
For listed buildings, protection zones or listed groups, the minor-works exemption does not apply, except for replacing frames (article 6-A, nos. 1 j and 2). Some councils have their own rules: the Setúbal regulation allows “velux” windows only on roof slopes that do not face the street, in the historic centre (see Roofs in Setúbal). Even for exempt works, tell the council up to five days before the works start (article 80-A).
If you turn the attic into a lived-in room, there are other questions (use and area) that we did not confirm.
Condominium
The roof is a common part (Código Civil, article 1421). Owners may not harm the architectural line or the aesthetic arrangement, and works that change them need the assembly’s authorisation, by a two-thirds majority of the building’s total value (article 1422, nos. 2 and 3). The council licence does not replace this vote. See condominium roof, who pays.
VAT
Labour for renovating or improving a dwelling pays 6% (item 2.27), but materials carry 6% only if they do not exceed 20% of the contract value. Buying only the window pays 23%. We have no Tax Authority ruling on roof windows: see the VAT guide and ask the firm for an invoice with the amounts separated.
Guarantee
The VELUX product guarantee, edition of 1 November 2026, gives 10 years to roof windows (glass included), flashings and installation products, and 2 years to VLT 1000 skylights. The period runs from purchase, with an invoice. It excludes removal and reinstallation, and claims must be made in writing within two months of learning of the defect. The consumer’s legal rights remain; the document cites Decreto-Lei n.º 67/2003 and we did not check whether that is the version in force.
Also ask the installing firm for a written guarantee on the work against leaks. See the works warranty and how to choose a contractor. We found no official certification of roof window installers.
Safety at height
Do not climb up to look at the window or to clean it. The European Agency for Safety and Health at Work (FACTS 49) warns that fragile areas, such as skylights, are not always visible. See work at height.
What it costs
In the VELUX table of 1 July 2026 (prices without VAT), the manual tilting window GGL 2070, with safety glass, costs 324 € to 648 € depending on size (from 55×78 cm to 114×160 cm). Flashings are sold separately: the EDW 1000S costs 107 € to 168 €. These are the manufacturer’s list prices, not what a shop or installer charges, and we have no verified installation price. Windows for the facade, not the roof, are on our sister site JanelaCerta.pt.
What we could not confirm
- The exact status of a roof window under the RJUE, since no official text names it.
- Whether replacing an identical window needs a communication.
- The labour price and prices on private portals (Habitissimo, Zaask): we did not read them.
- The consumer law in force and the current version of article 1422 of the Código Civil.
- Installer certification.
Sources (read on 3 November 2026)
- VELUX Portugal, Price list from 1 July 2026 (types, pitches, flashings, prices without VAT).
- VELUX Portugal, VELUX product guarantee, edition V-P 01.11.2026 (periods, exclusions, condensation).
- Decreto-Lei n.º 108/2026, of 29 May, Diário da República, 1st series, n.º 104, articles 2, 4, 6, 6-A and 80-A (copy of the official text).
- Mapfre, Regime da Propriedade Horizontal, articles 1421 and 1422 (2003 text; confirm the version in force).
- VAT and Setúbal: sources in our guides on VAT and Setúbal, read on 2 and 3 November 2026; FACTS 49 in the work at height guide.