Issues and repairs | BRANZ Maintaining My Home

Timber board or plywood ceilings – black staining of timber

Listed under: Interior, insulation, timber and wood-based, plywood, health and safety, stains, timber, ceilings, moisture, condensation, leaks, mould, mould health and safety

ceiling uninsulated, insulation has shifted or is poorly insulated. Remove old insulation and install new insulation within the roof space , following the guidance on this page
reduce internal moisture levels:

avoid using unflued gas heaters and avoid drying laundry inside
opening windows fully for at least 10 minutes every day (in bathrooms immediately after the bathroom has been used for showers or baths) is recommended to remove the initial heavy concentration of moisture. This can make a difference to indoor air quality and moisture levels
ensure installed ventilation systems are used
where there is no extract ventilation, add a rangehood over the kitchen stove and an exhaust vent near the shower in the bathroom, both vented to remove moisture to outside the house
add an acrylic dome to open-topped showers to contain the moisture within the shower enclosure

wash or steam clean the ceiling in conjunction with a fungicidal cleaner to remove mould/mildew. Allow to dry thoroughly. Sand lightly to provide a clean smooth surface and recoat.

identify and repair the source of the moisture
For many ‘leaks’ the actual cause of the moisture is damp air from living spaces migrating into the roof space, condensing on the colder roofing. This drips back down on to the insulation and ceiling giving the appearance of a roof leak. In these cases, first deal with the internal moisture within the living spaces. If the problem persists, contact a specialist to advise on the installation of some roof space vents at the eaves and the ridge
For a roof leak the precise location of the leak may be difficult to find, or there may be multiple leaks. Call a registered building surveyor to investigate and recommend solutions. If the leak is likely to be in a pipe rather than cladding or flashings, call a licensed plumber to locate and make the repair
if the leak has resulted in thermal insulation above the ceiling becoming wet, the effectiveness of the insulation is lost. Once the leak has been repaired, remove the wet insulation, allow the space to dry and replace with new insulation