Approved Document ‘E’ Section 5 includes the following examples of internal wall constructions that meet the laboratory values in Table 5: (Internal wall type D) Aircrete block wall, plaster or plasterboard finish on both sides.

- for plaster finish, minimum surface mass, including finish 90kg/m
- for plasterboard finish, minimum surface mass, including finish 75kg/m
- all joints well sealed

100mm Aircrete blockwork walls with lightweight plaster and 75mm Aircrete blockwork walls with plasterboard provide the necessary mass or have been tested to demonstrate compliance with the appropriate Rw value.

BBA have certified that these constructions are also suitable where the partitions abut any masonry separating wall specified in Approved Document E or BBA certified masonry separating wall.

For internal floors the following Aircrete beam and block floor construction can meet the requirement of Regulation E2 and Section 0 Table 2 of Approved Document E for internal floors.

• 100 mm thick minimum 440 kg/m3 density Aircrete infill blocks laid between 150 mm deep inverted T Precast concrete floor beams at maximum 620 mm centres finished with a minimum 40 mm sand: cement screed and a 12.5 mm plasterboard ceiling.

4.2.11 Robust Detail Constructions for aircrete masonry
Following representations from the Home Builders Federation (HBF), the house-building industry was invited to develop an alternative to pre-completion sound testing, called "robust details", for new build separating walls and floors for houses and flats - the principle being that robust details would provide consistently good performance eliminating the need for pre-completion sound testing.

The introduction of pre-completion sound testing in new homes was postponed until July 2004 to allow time for a robust details scheme to be implemented in the event that ministerial approval was given.

In January 2004 the Government announced that they would allow robust details to be used as an alternative to pre-completion sound testing as a means of satisfying Part E of the Building Regulations. This took effect from 1st July 2004 to coincide with the introduction of pre-completion sound testing.

A robust detail, for Part E of the Building Regulations, is a separating wall or floor construction, which has been assessed and approved by Robust Details Limited. In order to be approved, each robust detail must be:

• Capable of consistently exceeding the performance standards given in Approved Document E to the Building Regulations for England and Wales (see Table 2) by having, in the case of walls, a mean value of not less than 50dB and no individual test result lower than 47dB.
• Practical to construct on site
• Reasonably tolerant to workmanship.


Each robust detail has its own sitework checklist that are designed to help builders to ensure that building work is carried out exactly in accordance with the robust detail specifications.

Further information is given on www.robustdetails.com

There are currently 2 Robust Details for aircrete separating walls notated as followings:

• E-WM-6 (traditional mortar).
• E-WM-7 (thin layer mortar).


Each construction consists of the following

• Two leaves of 100mm minimum Aircrete block
• Block density of 600 to 800kg/m3
• Minimum cavity width 75mm
• Gypsum-based board (nominal 8kg/m2) mounted on dabs on cement:sand render (nominal 8mm) with scratch finish
• Render mix must not be stronger than 1:1:6
• External flanking wall to have an inner leaf of 100mm (min) aircrete block (450 to 800kg/m3) and an internal finish of 13mm plaster or nominal 8kg/m2 gypsum based board.
• Separating and flanking walls to be tooth or tied together.


This construction has not been assessed as a separating wall when it acts as a flanking wall to separating floors, but in this case only the separating floor has to be pre-completion tested.

Aircrete flanking walls can also be used in conjunction with other types of concrete block separating walls given in the ‘Handbook’ to robust details.

Solutions exist for 100mm minimum aircrete flanking walls to separating floors. At the time of publication there are two floors under the Robust Details guidance, which are acceptable with aircrete flanking leaves. These are designated details E-FC-3 and E-FC-4. Advice should be sought from the manufacturer or from Robust Details Limited to obtain the latest constructions available.