Mould & Damp Remediation — Chemical Dilution & Dwell Time Reference Card

← Back to Module 7

Mould Remediation — Chemical Dilution & Dwell Time Reference Card

CCMTec Academy  |  Professional Certificate Resource  |  Version 1.0 — August 2026

Always check the current product SDS and label before use. Dilution ratios and dwell times given here are general professional guidance only. Manufacturer instructions take precedence. Never mix chemicals unless specifically directed by the manufacturer.
Section 1 — Dilution Quick Reference
RTU = Ready To Use (no dilution required). All ratios are product:water unless stated otherwise. Use clean cold or warm water unless the SDS specifies otherwise.
Chemical Type Typical Use Dilution Ratio Application Method Notes
Fungicidal mould spray (RTU) Surface mould treatment, Levels 1–2 RTU — no dilution Trigger spray Shake well before use. Do not dilute.
Fungicidal concentrate (general) Surface mould treatment, Levels 2–3 1:10 to 1:20 Trigger spray / pump sprayer Check SDS; higher dilution for maintenance, lower for active mould
Biocidal mould remover (concentrate) Active mould, Levels 2–4 1:5 to 1:10 Pump sprayer / brush application Wear full PPE. Ventilate area. Do not use on porous stone.
Quaternary ammonium compound (QAC) Disinfection post-removal 1:100 to 1:200 Spray / mop / wipe Effective against bacteria and some fungi. Check spectrum of activity.
Hydrogen peroxide (3–6%) Surface mould, colour-safe option RTU (3%) or dilute 6% to 3% (1:1 with water) Spray / sponge Test on hidden area first. Avoid on metals. Light-sensitive — store in dark.
Sodium hypochlorite (bleach) Non-porous surfaces only 1:10 (1 part bleach : 9 parts water) Spray / wipe Never mix with ammonia or acids. Corrosive. Not suitable for porous substrates. Ventilate well.
Encapsulant / mould barrier coat Post-remediation sealing RTU or as per manufacturer Brush / roller / spray Apply only to clean, dry, treated surfaces. Allow biocide to fully dry first.
 
Section 2 — Dwell Time Reference
Dwell time = the period the chemical must remain wet on the surface to achieve the stated efficacy. Do not wipe off or rinse before dwell time is complete unless the SDS requires it.
Chemical Type Minimum Dwell Time Optimal Dwell Time Max Before Reapplication Notes
Fungicidal mould spray (RTU) 5 minutes 10–15 minutes 30 minutes Reapply if surface dries before dwell time is complete
Fungicidal concentrate (diluted) 10 minutes 15–20 minutes 45 minutes Keep surface visibly wet throughout dwell period
Biocidal mould remover 15 minutes 20–30 minutes 60 minutes For severe contamination, a second application after removal may be required
QAC disinfectant 5 minutes 10 minutes 30 minutes Organic matter reduces efficacy — clean surface before applying
Hydrogen peroxide (3%) 10 minutes 15–20 minutes 30 minutes Will bubble on contact with organic matter — this is normal
Sodium hypochlorite (diluted) 5 minutes 10 minutes 20 minutes Rinse with clean water after dwell on food-contact or skin-contact surfaces
 
Section 3 — Dilution Calculation Guide
Target Volume Ratio 1:5 Ratio 1:10 Ratio 1:20 Ratio 1:100
500 ml 83 ml product + 417 ml water 45 ml product + 455 ml water 24 ml product + 476 ml water 5 ml product + 495 ml water
1 litre 167 ml product + 833 ml water 91 ml product + 909 ml water 48 ml product + 952 ml water 10 ml product + 990 ml water
5 litres 833 ml product + 4.17 L water 455 ml product + 4.55 L water 238 ml product + 4.76 L water 50 ml product + 4.95 L water
10 litres 1.67 L product + 8.33 L water 909 ml product + 9.09 L water 476 ml product + 9.52 L water 100 ml product + 9.9 L water
Formula: Product volume = Target volume ÷ (ratio + 1). Water volume = Target volume − Product volume.
 
Section 4 — Substrate Compatibility Guide
Substrate Fungicidal Spray Bleach Solution H²O² QAC Notes
Painted plaster / plasterboard ✓ Caution ✓ ✓ Bleach may strip paint. Test first.
Bare plaster / masonry ✓ ✗ ✓ ✓ Bleach does not penetrate porous surfaces effectively
Timber (untreated) ✓ ✗ Caution ✓ Bleach damages timber fibres. H²O² may lighten wood.
Ceramic tiles / grout ✓ ✓ ✓ ✓ All suitable. Grout may need repeat treatment.
Silicone sealant Caution Caution Caution Caution Mould often grows within sealant — removal and replacement usually required
Metal surfaces ✓ Caution ✗ ✓ Bleach and H²O² can corrode metals. Rinse promptly if used.
Fabric / soft furnishings Caution ✗ Caution Caution Test on hidden area. Heavily contaminated soft furnishings should be disposed of.
Waste disposal: Diluted chemical solutions must be disposed of in accordance with local authority guidance and the product SDS. Do not pour concentrated chemicals down drains without dilution and authorisation.
CCMTec Academy  |  Mould & Damp Remediation Professional Certificate  |  Chemical Dilution & Dwell Time Reference Card v1.0 — August 2026
This document is provided for professional development purposes only. Always follow current manufacturer SDS instructions.  |  www.ccmtec.co.uk

Use your browser’s Print function and select “Save as PDF”. Set paper size to A4 portrait, margins to minimum.