Acoustic Plasterboard Calculator — Part E Sound Insulation

This calculator estimates quantities for an acoustic board build-up: board counts, resilient bar lengths, acoustic sealant tubes and screw counts, from your wall area and the target you select. It does not demonstrate compliance with Approved Document E (Part E). Compliance with Requirement E1 is shown by pre-completion testing under Regulation 41, or, for new-build houses and buildings containing flats only, by notifying a Robust Detail (AD E para 0.2 and Annex E).

The formula

Boards = (Wall area ÷ 2.88 m²) × Layers × Wastage factor

Resilient bar quantity is calculated from the number of horizontal rows (wall height ÷ bar spacing) multiplied by wall width. Acoustic sealant is an estimate based on the total perimeter length at roughly 15ml per linear metre (a 4–5mm bead) per layer of board — always confirm against your cartridge data sheet, as coverage depends on the bead size you run.

System configurations

Separating walls and floors are judged in the finished building as a field result (DnT,w + Ctr, AD E Table 0.1a), while internal walls to bedrooms are rated by a laboratory figure (Rw, AD E Table 0.2). These are different quantities and there is no arithmetic conversion between them. The only quantified laboratory-to-field allowance in Approved Document E is 4 dB, and it applies to the same quantity measured in a flanking laboratory: 49 dB DnT,w + Ctr there is indicative of 45 dB in the field (para B3.13), and 58 dB L′nT,w there is indicative of 62 dB in the field (para B3.14). Para B3.11 states that it is not possible to demonstrate compliance with Requirement E1 using results from a flanking laboratory.

The dB figures below are the regulatory targets. The build-ups beside them are the quantity basis this calculator prices, not constructions taken from Approved Document E. No AD E separating-wall type uses resilient bars: they appear only in the Section 3 ceiling treatments for separating floors (paras 3.21 and 3.22). Take the actual build-up from a tested system or the relevant Robust Detail.

• Separating wall, target DnT,w + Ctr ≥ 45 dB (AD E Table 0.1a; 43 dB where formed by a material change of use): quantities based on 2 × 12.5mm acoustic board + resilient bar at 600mm
• Separating floor, target DnT,w + Ctr ≥ 45 dB and L′nT,w ≤ 62 dB impact (AD E Table 0.1a): quantities based on 2 × 12.5mm acoustic board + resilient bar at 400mm, plus a mineral wool absorbent layer. AD E ceiling treatments A, B and C all require an absorbent layer of mineral wool filling the ceiling void (paras 3.19, 3.21 and 3.22); treatments B and C specify a single board layer, so two layers here is a conservative quantity basis rather than treatment B as described
• Internal bedroom wall, target Rw ≥ 40 dB laboratory (AD E Table 0.2): quantities based on 2 × 15mm acoustic board + resilient bar at 400mm. Requirement E2 does not apply to an internal wall which contains a door, an internal wall separating an en suite toilet from the associated bedroom, or existing walls and floors in a building subject to a material change of use. Those limits are read wall by wall, not room by room: a bedroom with a door in one wall still has three walls inside E2. This is a laboratory value, and AD E para 0.9 states it is not intended that performance should be verified by testing on site
• Studio (Rw ≈ 55+ dB laboratory, not a regulatory target): quantities based on 3 × 12.5mm acoustic board + resilient bar at 300mm