Construction defect · Defects & construction flaws
Window and frame defects: tightness, glazing, drainage in new-builds
How to detect a window or frame defect?
A new window must be airtight and watertight, properly drained, with clear glazing without internal mist, smooth opening without snagging. Test: run your hand around the closed frame to detect drafts, spray water on the outer glazing (tightness test), inspect drainage holes (visible holes at the bottom of the frame), check for mist between the two panes (failed glazing), open and close several times to detect snagging. A poorly shimmed frame creates stresses that crack glazing over time.
Before — compliant
alu frame with visible drains · clear glazing
Drains present · sharp joints · smooth opening
⚠ After — defective
misted glazing · detached mastic
Internal mist · missing drainage · to be reported
Reporting procedure in 4 steps
Outside-joinery defects are frequent in the first year. Chronological documentation is essential to invoke the warranty.
- 1Test each frameHand test for drafts, spray bottle for tightness, drainage check at the bottom, full opening/closing, mist check between panes.
- 2Photograph defectsHD photo with rigid ruler. Plan of the affected window, date, weather. Keep the joiner's delivery slip.
- 3Formal noticeRegistered letter to the contractor and joiner within 90 days. Attach photos, tightness-test video, regulatory references (NBN EN 14351 joinery).
- 4Joinery expert assessmentIndependent joinery expert or thermal engineer in case of dispute. Thermal camera test for thermal bridges. Admissible report · from €380 VAT incl.
Who pays for the repair? Responsibility table
The joiner or approved installer is responsible. The main contractor is jointly liable.
Defect type
Contractor
Owner
Insurance
Misted glazing (internal moisture)
✓ two-year warranty + manufacturer
—
—
Missing drainage
✓ two-year warranty
—
—
Joint draft
✓ two-year warranty
—
—
Joint infiltration
✓ ten-year liability
—
ARI
Glass broken after delivery
—
✓
home insurance
Get an inspection
Independent inspection of your new frames
Thermal test included · admissible report · from €380 VAT incl.
FAQ
Common questions about windows
My double glazing has mist between the two panes. What should I do?
This is an insulating-glazing tightness defect. The argon gas has escaped and moisture has entered. Manufacturer warranty 10 years usually, plus contractor two-year warranty. Report by registered letter.
I feel a draft around my closed window. Is that normal?
No, never. A new frame is airtight. Check the hinge adjustment, compression of the EPDM seal. If the defect persists, report under the two-year warranty.
My aluminium frame drains are visibly missing. Serious?
Very serious. Without drainage, water entering the rebate stagnates and eventually crosses through. Have them drilled immediately (joiner intervention) or demand frame replacement.
My contractor says drafts are normal in the first year. True?
False. New joinery is airtight from installation. EPDM seals do not 'settle' over time. Any draft is a defect reportable under the two-year warranty.
How much does replacing a defective frame cost?
Between €800 and €4,000 VAT incl. per frame depending on dimensions and material (PVC, aluminium, wood). At the joiner's or contractor's expense if installation defect or faulty product.