Why is my composite door cracking, blistering or peeling?
Telling a surface fault from a delamination, why dark doors on south-facing walls fail first, and how to make a warranty claim that is actually accepted.
- Difficulty
- beginner
- Time
- 25 min
- Read
- 4 min
- Safety
- caution
Short answer
Press the affected area. If it flexes or sounds hollow, the skin has separated from the core and that is a manufacturing failure, not wear — photograph it, note the door's age and claim under the guarantee. Surface crazing and colour fading are usually cosmetic and are almost never covered.
Composite doors are a skin bonded to a core. When they fail, they nearly always fail at that bond, and nearly always on the elevation that gets the most sun. Understanding which of the three failure patterns you have decides whether this is a repair, a claim or something to live with, and the answer is usually a claim if the door is under its guarantee period.
Safety
Step by step
- Look at where the fault is.Faults concentrated on the sunny face, near the bottom rail or around a letterplate or glazed aperture tell you what is happening. Sun drives heat into the skin and the core behind it; cut-outs let water in at unsealed edges; the bottom rail sits in standing water.
- Press and tap the area.A skin still bonded to its core feels solid and sounds dull. One that has separated flexes under thumb pressure and sounds hollow when tapped. That single test separates a cosmetic fault from a structural one.
- Check the edges and the cut-outs.Run a fingernail round the letterplate, the spy hole, the handle and any glazed panel. Composite skins are usually sealed at the factory and re-cut on site by installers. An unsealed site cut is where water gets into the core and it is the single most common origin.
- Check whether the door is bowing as well.Hold a straightedge or a taut string along the face. A dark door on a south or west wall can bow measurably in summer. Bowing and delamination often go together because both are driven by heat and by the differential movement between skin and core.
- Find the guarantee and its terms.Composite doors typically carry a guarantee measured in years, often longer on the slab than on the hardware or the colour. Find the original invoice, the installer's paperwork and any FENSA or equivalent certificate, which also proves the installation date.
- Photograph properly before contacting anyone.The whole door in context showing the elevation, then the fault close up with something for scale, then the compass direction the door faces and the paperwork. Photographs taken later, after somebody has attempted a repair, are worth much less.
- Report it to the installer first.Your contract is with whoever supplied and fitted it, not with the factory. Report in writing, describe the fault factually, ask for an inspection and keep the correspondence. Escalate to the manufacturer only if the installer has ceased trading.
- Do not attempt a cosmetic repair before the inspection.Filling, gluing or painting a delaminated skin will very often be treated as evidence that the fault was altered or worsened. Make it watertight temporarily with tape if you must, and say so.
- Deal with a genuinely small, isolated fault.A small chip that does not extend to the core can be sealed with an exterior-grade flexible filler and touched in. Accept that a colour match on a moulded composite skin is approximate at best, and that this is a holding action.
If it doesn't work
The skin has lifted at the bottom corner
Cause: Water tracking up the core from a threshold that holds water, or an unsealed bottom edge — Fix: Guarantee claim. In the meantime, check the threshold drains and that nothing is holding water against the door foot.
Fine cracking across the whole face
Cause: UV degradation of the surface layer, usually on an older door on a sunny elevation — Fix: Cosmetic and rarely covered. Some composite skins accept a specialist exterior coating, but check with the manufacturer before painting anything — it can void what remains of the guarantee.
The colour has faded unevenly
Cause: Sun exposure, and often a dark colour on a south-facing door — Fix: Usually excluded from guarantees, which typically permit a degree of fade. Worth reading the exact wording before assuming.
Blistering around the letterplate
Cause: A site-cut aperture that was never sealed — Fix: Guarantee claim against the installer, since it is a workmanship fault rather than a product one.
Questions people ask
Can a delaminated composite door be repaired?
Not reliably. Once the bond between skin and core has failed there is no way to restore it in situ, and the standard remedy is a replacement slab. That is why the guarantee route matters.
Does a dark door really fail faster?
Dark colours on sunny elevations run substantially hotter, and heat drives both bowing and bond failure. Reputable suppliers restrict some dark colours to particular orientations for exactly this reason.
Can I paint a composite door?
Some can be coated with the right products and some cannot, and doing it may affect the guarantee. Ask the manufacturer in writing before starting.