Loft Insulation by Property Age
Roof construction, timber sizes, and breathability vary dramatically by era. Here is how the insulation approach adapts to your property.
Pre-1920 & Victorian Terraced Homes
*Note: Pre-1920 and Victorian terraces are consolidated here into one unified guide.* Older traditional properties rely on breathable lime mortars and solid brickwork. Roofs were built to breathe freely through slate gaps.
When insulating Victorian or Edwardian lofts, natural sheep wool or breathable mineral wool paired with unblocked eaves airflow prevents trapped moisture from decaying historic roof timbers.
1920 to 1965 Semis & Terraces
Mid-century homes feature standard timber joists and non-breathable roofing felts introduced in the 1950s. Most have 50mm–100mm of old insulation that can be safely topped up to 270mm once eaves airflow baffles are in place.
Post-1965 Modern Homes
Modern timber-truss roofs carry lighter ceiling joists spaced at 600mm centers. Topping up to 300mm or installing raised storage boarding subframes requires care so truss chords are not overloaded or squashed.
Book Era Assessment
Tailored assessment for your property's roof construction.