How to Get Rid of Mould in a Rented Flat Before Moving Out
Mould sits in an awkward grey area between "tenant cleanliness issue" and "landlord damp problem". What matters at checkout is what's visible — and whether you can show you dealt with it properly. Clean what you can, document what you can't, and leave the property dry, ventilated, and inspection-ready.
Why Mould Matters So Much at End of Tenancy
Mould is a "high impact" inspection issue because it's easy to spot, easy to photograph, usually seen as preventable, and linked to hygiene and ventilation. If a landlord sees mould at checkout, they'll often assume the tenant didn't look after the property — even if the real cause is structural damp.
And once a landlord proposes deductions, your deposit return timeline slows down — the 10-day return rule only applies after both sides agree on the amount. So mould isn't just a cleaning issue. It's a deposit risk.
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Tenancies with cleaning-related deposit deductionsGrey
Area — tenant vs landlord responsibility depends on cause#1
Trigger for 'property not returned in clean condition' flagsWhat Causes Mould in Rented Flats
Mould is caused by excess moisture. Understanding the source matters — because it determines who's responsible and how you should handle it at checkout.
Condensation (most common)
Warm air hits a cold surface and turns into water droplets. Triggered by shower steam, cooking without extractors, drying clothes indoors, and not opening windows. Usually appears on window frames, bathroom ceilings, behind furniture, and in bedroom corners.
Penetrating damp
Water enters through the building fabric — leaking roofs, cracked external walls, broken guttering, or damaged brickwork. Appears as damp patches that grow over time, often on external walls.
Rising damp
Moisture rises from the ground through walls due to poor or failed damp-proofing. Usually appears at the bottom of ground-floor walls with a distinctive tidemark pattern.
Is This Mould Your Responsibility?
The key question every tenant asks — and the honest answer is: it depends on the cause. Use the checker below to understand where responsibility likely sits for your specific situation.
Is This Mould Your Responsibility?
Answer a few questions about the mould in your property to understand where responsibility likely sits — and what to do about it. This isn't legal advice, but it highlights the key factors.
Where is the mould?
Bathroom ceiling or around shower/bath
Window frames or corners near windows
External wall or corner (bedroom/living room)
Under sink or around pipes
Bottom of walls (ground floor)
Where Inspectors Look for Mould
Mould in these areas is extremely common in London rentals and will almost always be treated as a cleaning failure unless addressed before checkout.
Mould Hotspots Inventory Clerks Check
Tap each room to see the exact spots inspectors look at — and the areas tenants most often miss.
Bathroom
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Ceiling mould spots (corners especially)
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Mould around extractor fan
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Mould in grout lines between tiles
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Mouldy silicone sealant around bath/shower
Windows (all rooms)
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Black mould on rubber seals
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Mould on frames (especially bottom corners)
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Mould in corners of glazing units
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Condensation staining on sills
Bedrooms & Living Areas
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Behind wardrobes against external walls
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Behind sofas pushed against walls
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External wall corners (especially north-facing)
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Near skirting boards on ground floor
Kitchen
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Behind washing machine
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Under sink cupboard
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Behind fridge
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Around extractor hood area
Before You Start: Safety First
Mould cleaning is usually safe if it's small surface growth, but don't be reckless.
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Wear rubber gloves
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Wear a mask (especially if scraping)
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Open windows while cleaning
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Work in a well-ventilated area
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Mix bleach with other cleaning chemicals
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Scrub dry mould without dampening first (spreads spores)
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Ignore large patches — document and report instead
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Work in a closed room without ventilation
If mould is severe — large patches, strong smell, spreading across multiple rooms — it may be a bigger damp issue. In that case, document it thoroughly and report to your landlord rather than aggressively scrubbing.
How to Remove Mould — Room by Room
Bathroom Ceiling Mould
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Ventilate the room — open the window and turn on the extractor fan
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Spray mould remover or diluted white vinegar onto affected areas
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Leave for 10–15 minutes to break down the mould
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Wipe with a damp cloth — don't scrub dry mould (it spreads spores)
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Dry the surface fully
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Tip: If you clean it and the mould returns within days, that suggests a ventilation problem rather than a cleaning issue. Document the recurrence — it strengthens your position in a deposit dispute.
Silicone Sealant (The Black Stuff That Won't Budge)
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Apply a thick mould remover gel directly onto the silicone line — gel clings better than spray
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Leave for several hours or overnight for heavy staining
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Rinse thoroughly and inspect the result
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If staining persists after two treatments, consider replacing the sealant entirely
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Worth knowing: Replacing silicone sealant is cheap (under £10 in materials) and straightforward. It's often less costly and more effective than repeated cleaning — and definitely cheaper than a landlord deduction.
Grout Lines
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Apply mould spray or vinegar solution to affected grout
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Scrub with an old toothbrush — work along the grout line, not across it
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Rinse thoroughly
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Dry completely — trapped moisture in grout causes rapid regrowth
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Tip: If grout has turned permanently dark, it may be stained rather than actively mouldy. But inspectors often don't distinguish — they record "dirty grout". So it's worth tackling. This is also flagged during limescale inspections since both issues appear in the same areas.
Window Frames and Seals
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Spray vinegar or mould remover onto frames and rubber seals
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Leave 5–10 minutes
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Wipe with a microfibre cloth
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Use cotton buds or a toothbrush for corners and seal edges
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Dry completely — if you leave moisture, mould returns quickly
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Tip: Window mould is probably the most common mould issue in London rentals. Single-glazed properties are worst hit because the cold glass creates heavy condensation. If your windows are single-glazed, mention this context if your landlord raises the issue.
Behind Furniture (The One That Catches Tenants Out)
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Pull wardrobes, sofas, and beds away from walls — especially external walls
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Photograph what you find BEFORE cleaning (this is important)
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Clean surface mould with vinegar or mould spray
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Let the wall dry fully before repositioning or leaving
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Key distinction: If the wall is wet, flaky, bubbling, or smells strongly damp, that's not a cleaning issue — it's a building problem. Clean lightly, but focus on documenting the evidence. This is your strongest defence against deductions.
Under-Sink Cupboards
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Empty the cupboard completely
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Check for active leaks around pipes and connections
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Clean mould with vinegar or mould remover
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Leave the cupboard door open to dry fully
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Tip: If you find an active leak, document it with photos and notify your landlord immediately in writing. Mould caused by a plumbing leak is the landlord's responsibility — not yours.
What NOT to Do
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Don't paint over mould. Landlords and inspectors can usually tell. It often peels, looks suspicious, and the mould returns without moisture being addressed. You'll likely lose deposit money anyway.
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Don't use bleach on porous surfaces. Bleach removes visible staining but doesn't kill mould roots inside porous material like plaster. It's fine for tiles and silicone, but less effective on walls.
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Don't ignore mould and hope it's 'wear and tear'. Mould is not normally treated as fair wear and tear if it appears as preventable surface growth. If you leave it, it will likely be flagged — and it becomes an easy claim for a landlord.
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Don't aggressively scrub damp walls. If the wall itself is wet or the paint is bubbling, aggressive cleaning can make it look worse. Clean lightly and focus on documenting the underlying issue.
The Move-Out Strategy That Actually Protects Your Deposit
The best approach to mould at checkout is a combination of cleaning and evidence-building. Here's the sequence that gives you the strongest position:
Take photos BEFORE cleaning
If mould is clearly linked to damp patches or leaks, photograph it first. This evidence shows the cause — and separates a building defect from a tenant cleaning failure.
Clean what you reasonably can
Surface mould on tiles, silicone, grout, window frames, and ceilings should be removed. You're expected to return the property in clean condition, and visible mould undermines that regardless of cause.
Take photos AFTER cleaning
Show you made the effort. Before-and-after pairs demonstrate good faith, which matters in deposit disputes.
Record a video walkthrough
Walk through bathrooms and window areas on camera. Video captures context that photos don't — like ventilation, wall condition, and the overall state of the room.
Attend the checkout inspection if possible
If mould is mentioned during the walkthrough, you can explain what you did and point out any underlying damp issue. Being present gives you the chance to add context that a report alone won't capture. See our tenant rights guide for more on attending inspections.
When DIY Isn't Enough
If mould is extensive or has been there for months, it may need professional-grade cleaning — or it may be beyond cleaning entirely.
Signs DIY won't be enough
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Mould returns within days of cleaning
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Strong damp or musty smell throughout
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Walls feel wet to the touch
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Paint is bubbling, flaking, or peeling
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Mould has spread across multiple rooms
At that point, it becomes less about cleaning and more about moisture management — which is a structural issue. But for move-out purposes, you still want to remove as much surface mould as possible and document any building-level damp.
Mould is one of those issues that can undermine an otherwise perfect end of tenancy clean. You might have spotless floors, a clean kitchen, and a deep-cleaned oven — but if the bathroom has mouldy sealant or the window frames have black mould, the checkout report may still say "property not returned in clean condition". That's enough for a deposit deduction.
Mould Removal Checklist
Work through each item before handing back keys. Photograph as you go.
Bathroom ceiling corners checked and cleaned
Silicone sealant around bath/shower — mould removed or sealant replaced
Grout lines scrubbed and dried
Window frames and seals — mould removed, surfaces dried
Behind furniture checked (wardrobes, sofas, beds against external walls)
Under-sink cupboard cleaned and checked for leaks
Behind washing machine and fridge checked
Any damp corners near skirting boards addressed
Before-and-after photos taken of all affected areas
Any structural damp reported to landlord in writing
Bottom Line
Clean surface mould before checkout — it's expected regardless of cause
Document everything — before-and-after photos are your strongest deposit protection
If it's structural damp, report it in writing — that shifts responsibility to the landlord
Don't paint over it, don't ignore it, and don't assume it's 'just wear and tear'
Professional End of Tenancy Cleaning
Our end of tenancy cleaning covers bathroom mould, sealant treatment, window frames, and all the areas inventory clerks check. 72-hour re-clean guarantee included.
Deni is a seasoned professional with over 10 years of experience in content marketing and vast knowledge in the cleaning business. He specializes in creating engaging content that drives growth and builds brand identity. Passionate about innovation, Deni believes in delivering value through impactful messaging and providing value to readers in a concise and comprehensive manner.
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