Otät ångspärr (leaky vapour barrier)
The vapour barrier (ångspärr) is the plastic sheeting that prevents damp indoor air from penetrating into walls and ceilings. If it leaks, warm, moist air seeps into the structure, condenses against cold surfaces, and can over time cause moisture damage and microbial growth from the inside. The damage builds up slowly, often over several winters.
What it means in practice
The inspector has seen a seam that isn't taped, a hole from an electrical or ventilation penetration, or sheeting that ends in the middle of a surface — often near roof trusses, an attic hatch, or around a bathroom. Sometimes it's only an indication: condensation on the inside of a window, discolouration in a corner, or an elevated reading above the insulation. A leaky vapour barrier does not mean the house has damage today. It means the moisture transport the structure is designed to stop is partly ongoing, and that the effect builds up over winter seasons rather than days. The remedy is usually cheap when you're inside the structure anyway and expensive when you're not — so the price tag depends more on whether the surface layer needs to be torn out than on the sealing itself. A common and reasonable plan is to fix it when the room in question is next renovated.
How serious is it?
Plan for 1–3 yearsRarely urgent, but shouldn't be forgotten — the damage builds up slowly and only becomes expensive once the structure has already been affected.
- How large the leak is and where it's located — around wet rooms and kitchens the moisture load is highest.
- Whether there are already signs of condensation or growth in the structure.
- Whether the surface layer is going to be renovated within a few years anyway, in which case the fix becomes nearly free.
What does it cost to fix?
SEK 3,000–15,000 for an accessible structure; SEK 40,000–120,000 if a wall or ceiling has to be opened up.
Ranges are AI estimates for a typical Swedish house — not quotes.
Frequently asked questions
Does a leaky vapour barrier have to be fixed right away?
Usually not. It's a slow process, but it should be fixed the next time the room is renovated — or sooner if there are already signs of moisture in the structure.
Can I see for myself whether the vapour barrier is leaking?
Rarely — it's behind plasterboard or panelling. Signs include condensation, drafts around electrical outlets, and discoloured corners. Thermography or an air-tightness test gives more reliable answers.
How much does it affect heating costs?
A leaky vapour barrier usually also means air leakage, which can account for a few percent of energy use — but the moisture risk is the bigger reason to fix it.
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