Installing a roof window in an existing roof: 2026 price and finishing

indekscen.pl editorial team · published 30 September 2026 · prices according to the 5 October 2026 index

A roofer typically charges PLN 1,000 in labour to install one roof window (usually PLN 1,000 ‑ 1,200), excluding the cost of the window. In an existing roof, the price may be closer to the upper limit, up to PLN 1,600, because an opening must be cut through the roofing and battens. Finishing the reveals inside with plasterboard is a separate expense of around PLN 750.

Installing a window in an existing roof is the simplest way to bring more daylight into a loft or attic. Labour quotes can vary severalfold, however, because installation in a prepared opening is very different from cutting a new one in a sheet-metal or tiled roof. We break down the cost using roofers’ price lists and construction articles collected by indekscen.pl.

How much does it cost to install a roof window in an existing roof?

According to 5 sources collected by indekscen.pl, labour for installing a roof window in an existing roof most often costs PLN 1,000 per window, with typical quotes ranging from PLN 1,000 ‑ 1,200. The lowest rates, starting at PLN 250, are for straightforward installation in a prepared opening. The highest, up to PLN 1,600, are for installation involving cutting an opening and fitting flashing in a complex roof.

The price of roof window installation usually includes fitting the window, installing the sealing flashing (in some quotes) and basic sealing. It excludes the window itself, shutters or blinds, strengthening or altering the roof structure, and plastering around the inside of the window.

How much does it cost to install a roof window in a sheet-metal roof?

Installing a roof window in a sheet-metal roof usually costs towards the upper end of the PLN 1,000 ‑ 1,200 range because the metal must be cut and sealed precisely to prevent leaks around the profiling. High-profile trapezoidal sheeting requires the most work, as standard flashing does not always fit and the roofer must adapt the metalwork on site.

Comparison of roofing types:

Roof covering	Installation difficulty	What to expect
Metal roof tiles	medium	flashing for profiled roofing, labour around PLN 1,000
Trapezoidal sheeting	high	customised metalwork, closer to PLN 1,600
Clay or concrete tiles	medium	removing and cutting tiles around the window
Standing-seam sheet metal	high	sheet-metal finishing around the window
Roofing felt, bitumen shingles	low to medium	flashing for flat roofing

It is worth inspecting the sheet metal at the same time. If the roof needs refreshing, see how much painting a sheet-metal roof costs, as it makes sense to schedule roof work at the same time.

What determines the cost of installing a roof window in an old roof?

The cost of installing a roof window in an old roof depends primarily on whether the window fits between the rafters. If the spacing is too narrow, a trimmer must be installed, which involves cutting a rafter and transferring the load to the adjacent ones. This is carpentry work and is priced separately.

Factors that increase the cost:

1. Rafter spacing and any required alteration or reinforcement of the structure.
2. Type of roofing and the condition of the battens, membrane and insulation beneath it.
3. Roof pitch and access: scaffolding for a tall building costs extra.
4. Flashing and accessories: sealing flashing, apron and thermal insulation around the frame.
5. Travel outside the town or city, charged separately in some quotes.
6. Disposal of the old window when replacing it.

How much does labour for finishing a roof window cost?

Finishing the inside of a roof window with plasterboard costs around PLN 750 per window in price lists. This is separate from installing the window: it includes forming the reveals, filling and fitting corner beads, and is often done by a different team from the roofer. For plastering around ordinary windows, companies charge per linear metre, around 51 PLN/linear metre.

The bottom reveal of a roof window should be vertical and the top reveal horizontal. This allows more light into the room and lets warm air flow across the pane. It is also important to maintain continuous insulation and a vapour barrier around the frame, as this area is particularly vulnerable to thermal bridges and condensation.

How much does a roof window with installation cost?

The price of a roof window with installation consists of the cost of the window, flashing and labour. Our index only provides the median labour cost: PLN 1,000 per window. The price of the window itself depends on its size (the most popular sizes are 78×118 and 78×140 cm), frame material, glazing and opening mechanism, so always ask for a quote itemising the window, flashing and installation.

Example labour costs for several windows:

Median and typical range from public price lists, as at 5 October 2026. Each price includes a source and quotation on the service page.

Scope	Labour
Installation of 1 window	PLN 1,000 ‑ 1,200
Installation of 2 windows	around PLN 2,000
Installation of 3 windows	around PLN 3,000
Internal plasterboard finishing of 1 window	around PLN 750
Installation of an external shutter	around PLN 300 per unit

When several windows are installed, roofers often offer a lower rate per window because scaffolding and travel are shared. We cover replacing ordinary windows in houses and flats in our article window replacement in a block of flats: price.

How long does it take to install a roof window?

Installing one roof window in an existing roof usually takes from a few hours to one day, including the flashing and sealing. The sequence of work is as follows:

1. Marking the window’s position between the rafters and checking the installation height.
2. Cutting an opening in the roofing, battens and membrane.
3. Fitting the frame on mounting brackets and levelling it.
4. Installing the flashing, apron and other metalwork, and connecting the membrane to the window.
5. Closing the opening from the inside, followed by internal finishing at a later date.

Internal plasterboard finishing takes another day and is often carried out by a different team. If a rafter must be cut and a trimmer installed, the carpentry extends the installation by several hours.

Velux or Fakro: does the brand affect the installation price?

The brand of roof window has little effect on the installation price: labour rates for Velux, Fakro and Roto are similar, usually PLN 1,000 ‑ 1,200 per window. Differences concern the price of the window itself, available sizes, flashing and accessories. The flashing should be the same brand as the window and suitable for the type of roofing, as it is crucial to keeping the installation watertight.

When choosing a window, consider its thermal transmittance, the position of the handle (at the bottom or top of the sash), and whether it has a trickle vent. In an attic that becomes very hot in summer, it is worth planning for an external shutter or awning from the outset.

How can you avoid overpaying for roof-window installation?

• Ask for an itemised quote covering the window, flashing, labour, internal finishing and any carpentry work.
• Check the rafter spacing before buying the window and choose a width that avoids cutting the structure.
• Ask about travel and scaffolding, as some quotes charge for them separately.
• Schedule installation for a dry day. An open roof in the rain risks flooding the attic.
• Ask about the guarantee on the watertightness of the installation, not just the window itself.

You can find more prices for roofing work, including soffit installation, on the blog, and installation rates in the installations and energy category. We show the median from several sources and the typical range, so you can immediately see whether a roofer’s quote is reasonable.

„Koszt robocizny dekarza: Od 500 do 1500 zł za sztukę (zależnie od stopnia skomplikowania konstrukcji dachowej).”

EnergetycznyProjekt.pl, 2026-06, source

„w niektórych przypadkach ceny montażu okien zaczynają się już od 250 zł, w innych przypadkach mogą sięgać do ok. 1000 zł.”

ExtraDach.pl, source

„Średni koszt montażu okna dachowego waha się od 500 do 1500 zł, a cena samego okna zależy od wielu czynników, takich jak rodzaj, rozmiar i materiał.”

Budujemy.eu, 2025-10, source

„Standardowy montaż jednego okna z kołnierzem to najczęściej 800–1600 zł, a dojazd poza miasto bywa doliczany jako 50–200 zł.”

Zleca.pl, 2026, source

The prices in this article come from public price lists published by roofing companies and from construction articles. On the how much does roof-window installation cost page, each price has a source, date and verbatim quotation.

Frequently asked questions

How much does a roofer charge to install a roof window?

Dekarz bierze za wstawienie jednego okna dachowego najczęściej PLN 1,000 samej robocizny, typowo PLN 1,000 ‑ 1,200. Okno, kołnierz i obróbka wewnętrzna są zwykle liczone osobno.

How much does it cost to install a Fakro roof window?

Montaż okna Fakro kosztuje tyle co montaż okien innych marek, bo robocizna zależy od dachu, nie od producenta: zwykle PLN 1,000 ‑ 1,200 za sztukę. Różnice wynikają z ceny samego okna i kołnierza.

How much does removing and installing a roof window cost?

Wymiana starego okna dachowego na nowe w tym samym otworze to zwykle robocizna z przedziału PLN 1,000 ‑ 1,200, czasem z dopłatą za utylizację starego okna. Jeśli nowe okno ma inny rozmiar, koszt rośnie o przeróbkę otworu.

Can a roof window be installed in winter?

Tak, jeśli jest sucho i nie pada śnieg, bo dach jest otwarty tylko przez kilka godzin. Niska temperatura utrudnia jednak pracę z blachą i materiałami uszczelniającymi, dlatego dekarze wolą okres od wiosny do jesieni, a cena robocizny, zwykle PLN 1,000 ‑ 1,200, się nie zmienia.

Is planning permission required to install a roof window?

W domu jednorodzinnym zwykle nie jest potrzebne pozwolenie na budowę, ale przy ingerencji w konstrukcję dachu, w budynku wielorodzinnym albo zabytkowym zasady są inne. Przed pracami zapytaj w starostwie lub urzędzie miasta, czy potrzebne jest zgłoszenie.

Translation of the original Polish article dated 30 September 2026. Quotations from price lists are in Polish, as published by the companies. Read the original in Polish.

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