SCDF lets owners paint the walls, ceiling and door of a household shelter. It does not allow plaster or wall tiles on the inside walls, drilling deeper than 50mm, or changes to the vents, and at least 25% of the two vent openings must stay uncovered. Dry everything before it goes in, let air through, and get help if the mould keeps returning.
Household shelters are a common place for mould in HDB flats: a closed room, little moving air and stored things that bring damp in. This guide sets out what SCDF's rules let you do about it, and when to call for help. It is a short guide for a specific room, not a replacement for SCDF's own requirements.
Why household shelters get musty
SCDF describes the shelter as a room with strengthened walls, floor and ceiling, two ventilation sleeve openings and a light protective steel door. The door is designed to give an airtight closure, and each vent sleeve is 125mm across. With the door shut, very little air moves.
Mould needs moisture: the US EPA notes that no type of mould grows without it. A shelter used as a store room often holds things that bring damp in, such as luggage after a trip, camping gear or cardboard boxes. Still air plus damp items is how the musty smell starts.
What SCDF allows
Clause 7.2 of SCDF's Technical Requirements for Household Shelters 2023 lists what owners may do. For mould, these matter:
- Painting the walls, ceiling and door. Do not paint over the door notice, locking bolts or door seal. Strip the old paint on the door and frame before repainting, and let new paint dry completely before closing the door, or the door and rubber gasket can stick to the frame.
- Painting the vent plates, outside face only.
- Drilling up to 50mm deep into the inside walls and ceiling for inserts and removable screws. Shelves, cabinets and other fixtures on the inside walls must be removed by the owner within 48 hours when notified.
- Removable vent covers, as long as at least 25% of the total area of the two openings stays uncovered for ventilation in peacetime.
What SCDF does not allow
- Wall tiles, rock stone finish, cement sand finish or gypsum plastering on the inside faces of the walls. You cannot tile or plaster over a mouldy wall.
- Cornices, or power driven nails into the inside walls.
- Hacking, or drilling beyond the clause 7.2 limits.
- Changes to the door, or tampering with the vent openings, plates, bolts and nuts.
- Painting the inner face of the vent plate, the vent sleeves, the rubber gaskets or the bolts.
- Covering up or removing the door notice.
SCDF also expects owners to keep the door and vent sleeves working smoothly and free of rust.
Cleaning a small patch safely
The US EPA's home guidance is to scrub mould off hard surfaces with detergent and water, then dry the surface completely. Prop the door open for fresh air, but clean the visible mould before you switch on a fan, so the fan does not spread it, as the EPA's flood cleanup guidance advises. Wear gloves and goggles; the EPA also suggests an N95 respirator. Never mix bleach with a cleaner that contains ammonia.
The EPA treats a patch smaller than about 10 square feet, roughly 0.9 square metres, as a job most people can handle. Do not paint over mould: clean and dry the surface first, because paint over mould is likely to peel.
Airing and storage habits
- Open the door on dry days and, once any visible mould has been cleaned off, use a fan to move air through.
- Keep both vent openings clear where you can. More open area lets more air through.
- Put nothing inside until it is fully dry. The EPA advises drying damp items within 24 to 48 hours.
- Swap cardboard boxes for sealed plastic boxes. Utah State University Extension lists cardboard boxes among the places booklice live, wherever mould can grow.
- Leave a gap between stored items and the walls so air can reach them.
- Choose free standing racks over shelves screwed into the walls. They need no drilling.
When to call for mould treatment
Get help when the growth returns after cleaning, covers more than a small patch, comes with tiny pale insects, or the smell stays after the room is emptied and aired. A stain that spreads from one point can point to a leak, which needs fixing first. Our guide to finding hidden mould behind a musty smell shows how to track down growth you cannot see.
Four Solutions treats household shelters as part of its HDB mould removal service. The team inspects with moisture meters to find the cause, removes the mould with professional biocide instead of painting over it, and applies anti mould protection where suitable. Send a photo of the shelter walls, ceiling and door on WhatsApp, and say what is stored inside.
Message Four Solutions on WhatsApp with photos of the shelter.
Sources: SCDF Technical Requirements for Household Shelters 2023, clauses 4.1, 5.1, 6.4 and 7.2, and SCDF's page on types of shelter; the US EPA's A Brief Guide to Mold, Moisture and Your Home and flood cleanup guidance; Utah State University Extension on booklice. The EPA and USU pages are United States general guidance. Checked 10 October 2026.
Household shelter mould FAQs
Can I use anti mould paint inside my household shelter?
SCDF allows painting of the walls, ceiling and door and does not name a paint type. Clean and dry the surface first, keep paint off the door notice, bolts, seal and vent parts, and let it dry fully before closing the door.
Can I plaster or tile over mould in the shelter?
No. SCDF does not permit wall tiles, cement sand finish or gypsum plastering on the inside walls. Remove the mould and deal with the damp instead.
Can I cover the vents to keep out dust or insects?
Only with removable finishes, leaving at least 25% of the two openings uncovered in peacetime. If the room smells musty, keep them clear.