Loft Condensation — what's actually going on

Damp timbers, black mould on rafters or water droplets on the underside of the felt.

Common causes

Bathroom or kitchen extract venting straight into the loft
Eaves and ridge ventilation blocked by insulation or sagged felt
Old bitumen felt instead of breathable membrane
Recently upgraded insulation pushed tight against the eaves

How we fix it

Rule out an actual leak first with a proper inspection
Fit over-fascia vents or tile vents to restore airflow
Re-route any extract ducts to vent outside through the soffit
Recommend a breathable membrane upgrade at the next re-roof

Loft Condensation by area

Locally specific notes for loft condensation across the towns and neighbourhoods we cover.

Loft Condensation in HamptonTW12 Loft Condensation in RichmondTW9

Our guides on this

Condensation and poor loft ventilation

If the damp appears in cold, still weather rather than during rain, is spread widely across the underside of the roof, and shows as droplets or frost on the felt and nail points, it is condensation. The fix is ventilation at the eaves and high level, not roof repairs.

Loft condensation: ventilation, not leaks

Damp loft timbers, mould on the underlay and drips in cold weather with no rain are the classic condensation picture. Chasing it as a leak wastes money.

Breathable membrane vs vapour control layer

A breathable roof membrane sits beneath the external covering and sheds water while allowing water vapour to pass out. A vapour-control layer sits on the warm side of insulation and limits moist indoor air entering the roof build-up. They do different jobs and one is not a substitute for the other.