A guide to mould remediation.

For UK homeowners, tackling mould promptly is essential to prevent respiratory issues and avoid the "sick building syndrome" often associated with poorly ventilated properties. This guide outlines what to expect when hiring a specialist damp proofer or mould remediator to restore your home to a healthy state.

What Does the Work Involve?

• Moisture Survey: Using thermal imaging and moisture meters to locate the source of dampness, such as rising damp, penetrating damp, or condensation.
• Containment: Sealing off the affected area with plastic sheeting and using HEPA air scrubbers to prevent mould spores from spreading to other rooms.
• Physical Removal: Scrubbing non-porous surfaces with antimicrobial cleaners and removing contaminated porous materials like plasterboard or insulation that cannot be salvaged.
• Air Purification: Using "fogging" machines or ozone generators to kill airborne spores and neutralise lingering odours.
• Surface Treatment: Applying fungicidal washes and anti-mould primers to prevent regrowth on treated surfaces.
• Source Rectification: Advising on or installing ventilation improvements, such as PIV (Positive Input Ventilation) systems or humidistat extractor fans.

Typical Costs

Prices generally include VAT and labour. Total costs are heavily influenced by the extent of the infestation, the accessibility of the mould (e.g., inside cavity walls or lofts), and whether structural repairs are needed to stop the original leak or damp source.

How Long Does It Take?

• Minor surface treatment: 3 to 6 hours for a single small room or window area.
• Standard room remediation: 1 to 2 days if plasterboard removal and drying time are required.
• Whole-house decontamination: 3 to 5 days, depending on the level of containment needed.
• Drying out period: If the mould was caused by a major leak, industrial dehumidifiers may need to run for 1 to 2 weeks before redecorating can begin.

DIY or Professional?

Small patches of surface mould (less than 1 square metre) caused by simple condensation can often be handled with a DIY mould spray and improved ventilation. However, if the mould covers a large area, returns frequently, or follows a flood, a professional is required. Professionals have the PPE and industrial-grade HEPA vacuums necessary to handle toxic species like Stachybotrys chartarum (black mould) without cross-contaminating your home.

Note: If you are a tenant, the Landlord and Tenant Act 1985 requires landlords to ensure the property is "fit for human habitation," which includes keeping it free from serious mould growth.

Choosing the Right Tradesperson

• Check Qualifications: Look for PCA (Property Care Association) or BWA (British Woodworking Federation) membership, as these organisations vet damp-proofing specialists.
• Insurance: Ensure they hold valid Public Liability Insurance and Professional Indemnity Insurance.
• Guarantees: Ask if they provide a long-term guarantee for the work, and if it is insurance-backed.
• Red Flags: Be wary of anyone who suggests "just painting over it" with anti-mould paint without first identifying the source of moisture.

• "What is the underlying cause of this mould, and will your treatment stop it from returning?"
• "What containment measures will you use to protect the rest of my house?"
• "Are the chemicals you use safe for pets and children once dry?"

UK Regulations

• Building Regulations Part F: Covers ventilation requirements; any remediation should ensure the property meets these standards to prevent recurrence.
• COSHH: Professionals must adhere to the Control of Substances Hazardous to Health regulations when using industrial biocides.
• Waste Disposal: Mould-contaminated materials should be disposed of as per local council guidelines for hazardous or construction waste.

Common Problems

• Treating the Symptom Only: Wiping away mould without fixing the leaking pipe or poor ventilation ensures it will return within weeks.
• Inadequate Drying: Applying new plaster or paint to a wall that is still internally damp will lead to immediate failure of the finish.
• Using Bleach on Porous Surfaces: Household bleach often only kills surface mould; the water in the bleach can actually penetrate deeper into timber or plaster, feeding the roots (mycelium).
• Lack of Containment: Aggressively scrubbing dry mould without containment can release millions of spores into the air, spreading the problem to other rooms.

Frequently Asked Questions