Quick answer
Clean a composite door with warm water, a small amount of mild washing-up liquid and a soft microfibre cloth, working top to bottom and rinsing thoroughly. Avoid bleach, solvents and abrasive scourers, which can damage the gel-coat finish and seals. Quarterly cleaning suits most homes, monthly nearer the Cornish coast.
Overview
Composite doors are easy to keep clean with the right routine. Warm water, mild detergent, soft microfibre. Never use bleach, solvent, abrasive scourers or aggressive pressure washers.
Symptoms
- General dirt build-up.
Common causes
- Traffic, weather, salt air.
The correct basic cleaning routine
Fill a bucket with warm, not hot, water and add a small squeeze of mild washing-up liquid. Using a soft microfibre cloth or sponge, wash the door from top to bottom, letting gravity work with you rather than dragging dirty water back up over a section you've already cleaned.
Rinse with a separate cloth or a light hose spray to remove any soap residue, since leftover detergent film can attract dust and look streaky once dry. Finish by drying with a clean, dry microfibre cloth, which also gives you a good opportunity to spot any marks, stains or early wear you might otherwise miss.
- Warm water and a drop of washing-up liquid.
- Soft microfibre cloth, top to bottom.
- Rinse thoroughly to remove soap residue.
- Dry with a clean microfibre cloth.
Why the basic routine is genuinely enough for most doors
It's tempting to think a tougher problem needs a stronger product, but GRP composite doors are specifically engineered to resist staining and weathering on their own, which means most day-to-day dirt, dust and light salt film respond perfectly well to this mild routine. Reaching straight for a stronger cleaner on a door that just needs its regular wash is unnecessary and, over time, can do more harm than the dirt itself.
Save dedicated composite door cleaners and treatments for genuinely stubborn marks, algae, or salt build-up that doesn't shift with the basic routine, rather than using them as your default weekly clean.
What to never use on a composite door
Bleach is the single biggest thing to avoid. It's a common household go-to for outdoor grime and mould, but it can degrade the gel-coat finish over repeated use and damages rubber seals around the glazing and door edge faster than normal weathering would, which can then let moisture in.
Solvents, including things like nail varnish remover or strong household degreasers, can affect the gel-coat's sheen and shouldn't be used except in the very specific, limited case of a small dampened cloth for hardened adhesive residue. Abrasive scourers, scouring pads and anything with visible grit will create fine scratching across the surface that catches dirt more easily on every future clean.
- No bleach, ever.
- No solvents beyond a small dampened cloth for specific residue.
- No abrasive scourers, scouring pads or gritty cleaners.
- No aggressive pressure washing directly at seals.
How often to clean in a Cornish setting
For an inland Cornwall property away from direct sea exposure, cleaning every three months keeps a composite door looking good and prevents dirt and salt building to a level that needs stronger treatment. That's roughly a quarterly routine, easy enough to tie to a seasonal changeover.
For coastal properties, particularly anywhere within a mile or so of open sea where salt spray is a regular feature of the local weather, monthly cleaning is the more realistic schedule. Salt film builds up faster than most people expect in genuinely exposed spots, and letting it sit longer between cleans means it's had more opportunity to interact with UV exposure and accelerate dulling.
Cleaning glazed panels and hardware alongside the door
While you're cleaning the main GRP panels, it's worth giving glazed inserts a separate pass with a proper glass cleaner rather than washing-up liquid, which can leave streaks on glass even though it's fine on the surrounding GRP. A non-ammonia glass cleaner is the safer choice near any rubber glazing seals.
Handles, letterboxes and knockers benefit from their own quick wipe with a soft cloth, and for anything showing tarnish, a metal-appropriate polish rather than the general door cleaner, since hardware finishes (chrome, brass, matt black) each respond differently to cleaning products.
Cleaning routines for holiday lets between changeovers
For a holiday let, a quick wipe-down at each changeover, even just a damp cloth over the handle area and any visible marks, keeps the door looking presentable for arriving guests without needing a full clean every single week. Building this into a changeover checklist, alongside the quarterly or monthly deeper clean, covers both the day-to-day appearance and the longer-term maintenance.
It's also a useful moment to spot anything that's changed since the last visit, a new stain, a scratch, or hardware starting to feel loose, catching small issues while they're still easy and cheap to address rather than after a season of guest turnover.
When cleaning alone isn't enough
If a proper clean using the routine above doesn't restore the appearance you'd expect, particularly if the whole door looks dull and chalky rather than just dirty in specific spots, that's usually a sign you're looking at UV fade or general wear rather than dirt, and a wax treatment or full restoration is the next sensible step rather than a stronger cleaning product.
Does routine cleaning affect the guarantee, one way or the other
Regular cleaning with warm water and a mild, non-abrasive detergent has no negative effect on the colour-fastness guarantee, and in practice it is one of the few things a homeowner can do that actively supports a stronger guarantee position, since it removes the salt and grime that accelerate UV damage. Neglecting cleaning entirely will not void a guarantee outright, but it can make it harder to distinguish genuine pigment fade from years of accumulated surface grime during any future assessment.
Keeping a simple record of your cleaning routine, even just a note of roughly how often you wash the door, can be useful if you ever need to demonstrate reasonable care as part of a guarantee conversation.
A seasonal cleaning calendar for Cornish conditions
Coastal properties generally need more frequent cleaning than inland homes, since salt spray settles on surfaces even without visible rain, gradually building a fine film that dulls the finish if left. A practical calendar is a full wash every four to six weeks through spring and summer, moving to every three to four weeks through autumn and winter when storms throw salt spray further inland.
Properties directly on the seafront or within a few hundred metres of exposed coastline may need weekly attention during stormy periods, since the salt loading in those conditions is considerably higher than a standard coastal calendar accounts for.
- General coastal homes: wash every four to six weeks in spring and summer.
- Autumn and winter: increase to every three to four weeks with more storms.
- Seafront or highly exposed properties: weekly checks during stormy spells.
Why north- and south-facing doors need slightly different cleaning
South-facing doors accumulate more sun-baked salt residue that can become slightly stubborn if left too long between washes, so a slightly warmer water temperature and a touch more detergent helps lift it without needing to scrub. North-facing doors are more prone to a slightly greasy, damp film from reduced drying time, which responds better to a soft brush worked gently into any textured panel detail rather than a cloth alone.
If your property has doors facing both directions, it is worth treating them as two separate routines rather than assuming one approach suits both equally well.
Cleaning around holiday-let changeovers
For holiday lets, the front and back doors take far more contact through a season than an equivalent door on an owner-occupied home, from luggage, dogs, sandy feet and simple handling by a rotating cast of guests. Building a quick door wipe-down into the standard changeover cleaning checklist, alongside the usual work inside the property, keeps the door looking presentable for every arrival photo and review, not just an occasional deep clean.
It also spreads the workload more evenly across the season rather than needing one big restorative clean at the end of summer once marks have had months to set in.
How we assess cleaning needs during a visit
When we look at a door that a customer feels is simply dirty rather than damaged, we check whether marks lift with a basic warm water test, note the orientation and likely exposure, and look at whether the existing cleaning routine matches what the property's position actually needs. Quite often the fix is simply adjusting frequency rather than finding a stronger product.
Where a customer has been using the wrong type of product, we will explain plainly what to switch to and why, since most cleaning problems we see come down to either too little attention or the wrong product rather than a fault with the door itself.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Washing-up liquid and microfibre cloths | Under £10 | Covers most regular cleaning for a year |
| Non-abrasive composite door cleaner | £8-£15 | For occasional stubborn marks |
| Professional deep clean | £45-£75 | For a thorough seasonal service |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- For a deep restoration.
Prevention
- Clean every 3 months, more often near the coast.
