Celotex Isover

Insulation for Timber Joist Separating Floors

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The primary purpose of a separating floor is to provide acoustic separation for both airborne and impact sound between two adjacent dwellings, thereby improving the acoustic comfort of both dwellings.

The minimum permitted acoustic specifications are defined by Approved Document E (England & Wales) and Section 5 (Scotland), although it is often recommended to improve on this where possible.

One of the methods to demonstrate achieving this is to use Robust Details, alternatively an acoustician can be tasked with verifying the design of a separating floor.

The insulation of choice for timber separating floors is typically a glass mineral wool (GMW) roll or slab. Isover Acoustic Roll (APR 1200) can be installed as part of the separating floor construction between the joists/I-beams and also, depending on the choice of floating floor treatment, between the resilient battens above the sub-deck to provide the level of sound reduction required according to Approved Document E (England & Wales) and Section 5 (Scotland).

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.


Insulation products to consider
Product Name Thickness Range Sizes Lambda BBA
ISOVER Acoustic Partition Roll (APR 1200) 25-100mm Width 2x600mm, Length 9170mm-20000mm NA Tick Icon
ISOVER Acoustic Slab 50-100mm Width 600mm, Length 1200mm NA Tick Icon
ISOVER Unislab 50-140mm Width 400mm or 600mm, Length 1200mm 0.036 W/m.K Tick Icon