Dormer cost 2026: the complete overview

Anyone who only looks at the bottom line of a quote will never understand why one bid is €1,800 apart from another. A dormer price is not a single number; it is the sum of six fixed items, each subject to quality and execution choices. If you know these six items, you immediately recognise which quote is complete and which has a hole somewhere.

Item one is the prefab element or build kit. With prefab manufacturers this is 40 to 50 percent of the total price and covers the complete shell: frames, glazing, insulation, sheathing, gutter and exterior cladding. A 3-metre prefab in PVC starts at €3,000 factory price; in timber at the same size it runs to €4,500. Traditional on-site builds skip this item, but their labour items in item two are correspondingly higher.

Item two is installation and crane work. Installing a prefab averages €1,400 to €2,200 in labour, including a half-day crane (€450-€700), two to three installers and all connections to the existing roof. With traditional builds this scales to €3,500-€5,500 because three to five days are spent on site. A narrow street, overhanging trees or a deep back garden can add €300-€800 for a larger crane or a street closure with a traffic controller.

Item three is insulation and frames. Standard delivery is R-value 4.5 with HR++ glazing; that is in the base price. Choosing R 6.3 (required for energy-label targets) or triple glazing costs €400-€900 more. Timber frames add €600-€1,200 over standard PVC. Aluminium is exotic in dormers and adds another €800-€1,500; in practice rarely chosen because the added value is limited.

Item four is interior and exterior finishing. Standard interior delivery is one layer of plasterboard ready for paint or wallpaper. Having the installer paint, plaster, fit skirting and install power outlets adds €800-€1,800 depending on width and finish level. Exterior is standard white; non-standard colours, wood-look foil or cedar cladding cost €400-€1,500 extra.

Item five is lead, zinc and trim work. Technically the most underestimated item: this is where leaks ten years from now are prevented. Quality leadwork (lead 25, machine-dressed onto a substrate) costs €400-€800 on a 3-metre dormer. Zinc valleys and bottom trim add €200-€400. Companies that economise here deliver leaks within 5-8 years; the quote must specify lead 25 minimum plus named zincwork.

Item six is permit and extras. Municipal fees for an environment permit run between €300 and €700 in 2026, depending on town and project size. A structural engineer's calculation (often required above 4 metres) costs €350-€600. Non-physical items like architect consultation for aesthetics review (€500-€1,000) and construction supervision add up on front facades and listed buildings.

With virtually every comparison of three quotes for identical sizes we see a spread of €1,500 to €2,500. Sometimes it comes down to contractor margins, but in 80 percent of cases the specification explains the gap. It is tempting to take the cheapest, but without laying the specs side by side you do not know if you are comparing apples to pears.

The most common differences that explain more than half of the price spread: R 4.5 insulation (base) versus R 6.3 (€500-€800 difference), HR++ glazing versus triple glass (€350-€700 difference), standard colour versus custom-painted (€400-€800), interior finishing included or excluded (€800-€1,500), and lead 25 versus cheaper lead 20 on connections (€200-€350, major lifespan impact).

On top of that: one contractor itemises municipal fees, another bundles them in an 'all-in package'. Anyone who does not see this item explicitly listed often gets a meerwerk (extra-work) invoice afterwards. Always ask: 'Are the environment permit, structural engineer's calculation and municipal fees in this quote, or do they come on top?' An honest contractor answers within ten seconds.

A second layer of spread sits in warranty and service terms. A quote of €6,500 with 5 years installation warranty and 10 years on the element competes with a quote of €5,900 with 2 years installation warranty and no lead warranty. The €600 gap earns itself back on the first real leak or complaint. Always make warranty part of the price comparison, not just the build itself.

The figure on the installer's quote is rarely the total you end up spending. We see an average of 10 to 15 percent in extras that fall outside the dormer build but are needed to make the space usable. Putting them in the budget upfront prevents surprises mid-project.

Electrical inside the new space costs €500 to €1,200. This covers wall outlets, a switch, possible data connections and a new circuit in the consumer unit if capacity demands it. A dormer without power is practically unusable as bedroom or study; always include this item.

Floor and wall finishing inside: the installer usually delivers only the bare wall with plasterboard ready. Painting, papering, underfloor heating or laminate flooring and skirting costs €800 to €1,800 for an average dormer space. DIY can halve that, but materials still count.

Window treatments are never supplied by the installer. Curtains, pleated blinds or sunshading for a dormer costs €300 to €800 per window unit, depending on quality and operation. With triple-glass dormers facing south, sunshading is more than a wish: the space becomes unbearable in summer otherwise.

External insurance and disruption: during construction your house is briefly vulnerable. A cheap temporary insurance (€50-€150) covers damage from rain or burglary during an open roof. Ask your own buildings insurer how long an 'open roof' is still covered; many policies cap at 48 hours. Beyond that, cover may lapse.

Step one: determine your size. Not what you want, but what fits your roof and what the house calls for. Use the per-width pages (2 to 6 metres) to see realistic prices per size. Do not budget from dream figures in adverts; those start at the narrowest size in basic spec.

Step two: decide front or rear. Front almost always means a permit, an aesthetics review and 10-20 percent higher price due to visibility and stricter execution. Rear more often falls under permit-free and offers a wider palette of material and colour freedoms.

Step three: pick a material. PVC is cheaper upfront, timber more expensive but longer-lived. Polyester (white gelcoat shell) sits between them. See the material pages for an honest lifecycle cost comparison.

Step four: request at least three quotes and demand uniform specifications. Give every contractor the exact same sizes, insulation package, glazing and finish level. Only then are the quotes substantively comparable. Without uniformity you are comparing incomparable offers.

Step five: add 10-15 percent for extras and reserve 5 percent for contingencies. A dormer project rarely runs exactly to budget; a small reserve prevents mid-project stress.

Not every upgrade is wasted money. Some upgrades demonstrably pay back in comfort, energy or resale value. Three choices are almost always worth their premium.

A higher R-value (from 4.5 to 6.3) costs €500-€800 more, but reduces heat loss through the dormer by about a third. With average heating use this saves €80-€120 per year; payback 6-9 years, lifespan 30+ years. In gas-to-heat-pump transitions, higher insulation is even a precondition for a viable heat pump.

Triple glazing costs €350-€700 more than HR++ and gives a noticeable comfort difference on north- or west-facing windows: less cold downdraft, no condensation, better sound damping. For the Randstad: triple glass against traffic noise is almost always worth the premium.

An extra window (from 2 to 3 window units on a 3-metre) costs €400-€700 more, but significantly improves light and visibility. WOZ uplift is higher than standard, and sale ads can highlight 'extra light'. A simple long-term living-comfort winner.