sound resisting details for loft conversions

INFORMATION SHEET 27
SOUND RESISTING DETAILS FOR LOFT CONVERSIONS
Typical Detail
Notes:
(1) Flooring generally T&G Chipboard 21mm or Plywood 18mm or equivalent weight
for T&G pine flooring
(2) Mineral Wool – 100mm thick * lying on existing ceiling (ceiling assumed to be in
good condition if lathe & plaster)
Zone A Second layer of mineral wool. A second layer of mineral wool, to ensure a ‘snug
fit’ is required (50mm will usually suffice) between the soffit of the beam and the
principal layer of mineral wool (see typical detail Zone A overleaf)
Zone B Take T&G boarding fully across to abut with the U/S of the rafter
Ensure mineral wool does NOT touch Sarking felt or tiles – keep clear of these
elements by 50mm minimum.
(3) High performance (Polyisocyanurate) rigid insulation (usually 90mm thickness) or
equivalent.
(4) Battening out to accommodate correct thickness of High performance rigid
Polyisocyanurate) insulation (usually 90mm thickness) or equivalent and ensure a
50mm airflow path above.
(5) 50mm airflow path over insulation.
(6) Fire protection to the steel beam perhaps best achieved using intumescent paint.
(7) To ensure downlighters do not overheat, special plasterboard ‘boxes’ over lights or
alternative acoustic and fire hoods will need to be constructed/provided.

INFORMATION SHEET 27
Typical Details [Zone A]
Sound Insulation 2-storey extensions
Detail of 1 st Floor
Notes:
(1) 21mm Chipboard tongue and grooved flooring (18mm ply)
(2) 100mm Mineral Wool
(3) 12mm Plasterboard e.g. Soundblock by British Gypsum or equal product and Skim