Internal walls & partitions

EI90 fire-rated partition using dry construction

Last updated: 14 October 2026

EI 90 is a certified assembly, not a single board: W112 system, maximum height, sequence of works, 10 inspection points and the errors that invalidate the test.

The system at a glance

Solutions & Applications · Dry Construction

The theory is simple — EI 90 is a certified system, not a single board. The difficult part is the next step: how do you verify that what has been built is indeed the certified assembly? This page serves as the manual for installation and inspection.

ARGYNET LAB · YouTube Short · 37″Watch the solution in 37 seconds→

What does EI 90 mean?

Letter	Criterion	What is tested
E	Integrity	Flames or hot gases do not pass through cracks or openings
I	Thermal insulation	The unexposed side does not exceed the temperature rise limit
90	Minutes	The period during which both criteria are met

Firstly: which system are you looking for?

Partition systems are codified. The logic is consistent and aids in specification:

System	Layout	Typical scope
W111	Single frame, one layer of boarding per side	Partitions with no fire resistance requirement or with a low
W112	Single frame, double layer per side — 4 boards per m²	The standard solution for EI 90 · good sound insulation
W113	Single frame, triple layer	Higher indices, greater heights
W115	Double, independent framework	Where sound insulation is just as critical as fire resistance

The same EI 90 rating can be achieved using more than one configuration. The choice is determined by the other requirements: partition height, required sound insulation, available thickness and support loads.

ARGYNET Note

Ask for the classification report — and read exactly what has been tested. It is the document that turns a claim into evidence, and contains the parameters that must not be altered:

type and thickness of board per layer; number of layers per side; cross-section and thickness of the studs; centre-to-centre distance between studs; type, density and thickness of insulation; length and pitch of screws; method of jointing; maximum permissible height.

The practical conclusion regarding the tender: every ‘equivalent’ substitute is checked against this list. A steel stud of lesser thickness, mineral wool of lower density or a wider screw spacing are not commercial details — they are test parameters. At ARGYNET, we supply the system complete with its documentation and the materials specified therein.

Height is a constraint, not a desire

Each certified assembly has a maximum permissible height, which is determined by the cross-section of the stud, the thickness of the steel and the centre-to-centre distance. When the height of the space exceeds this, the available options are as follows:

Spacing of studs — from 62.5 to 41.7 or 31.25 cm.
Larger profile cross-section — CW 75 or CW 100 instead of CW 50.
Greater steel thickness in the profile.
Double studs at specific locations.

None of these are decided on site. They all stem from the system tables — and alter the quantity take-off.

The scope of works

Marking the position of the partition on the floor and ceiling — from slab to slab, not up to the suspended ceiling.
Track membrane beneath tracks and perimeter profiles — before fixing, not afterwards.
UW tracks on floors and ceilings, with fixings suitable for the substrate and at the system’s pitch.
CW studs at the axial spacing of the arrangement, with free play at the upper end to allow movement of the slab.
First layer of fire-rated board on one side, with the joints resting on a stud.
Meshes and reinforcements within the framework — before the second side is closed.
A1 mineral wool across the entire width and height, at the test density, without voids and without compression.
Second layer with joints offset from those in the first layer — on both sides. Screws of a specific length per layer.
Joint filling with Uniflott or Fugenfüller and tape, in layers — including the joints in the inner layer.
Sealing of perimeters, joints and penetrations using certified materials. Inspection hatches of the same class as the wall.

The ten points of supervision

The inspection takes place in two stages, and the first is the crucial one — because afterwards, nothing is visible.

Before closing the second side

Point	What is checked
Axial distance between studs	Measurement, not estimation — in accordance with the report’s provisions
Cross-section and profile thickness	Markings on the profile
Track membrane	Continuous, beneath all perimeter profiles
Mineral wool filling	Complete, with no gaps at the edges or around boxes
Density of insulation	Packaging labelling — A1 and test density
Reinforcement of supports	On the furniture layout plan

After cladding

Point	What is checked
Joint displacement	The joints in the second layer do not coincide with those in the first
Screws	Length per layer and pitch; slightly indented heads, no paper tears
Crossings	Sealed with certified material — not with ordinary foam
Upper end	A seal that allows the slab to move without creating a gap

ARGYNET Note

Take a photograph of the wall before it is closed up. It is the cheapest form of compliance documentation available, and the only one you will have left. Once the second side is in place, no one can verify the spacing of the studs, the density of the mineral wool or the completeness of the infill — without opening up the wall.

What is documented: the framework with a tape measure resting against the studs, the markings on the insulation packaging, the filling along the length, the points of penetrations and the top termination. Five photographs per partition, filed under the room code.

Factors that invalidate EI 90

Point	Why	Correct
The partition stops at the suspended ceiling	Above the suspended ceiling, the void is continuous throughout the entire floor	Continuity from slab to slab
Back-to-back sockets	Vulnerable to fire and sound	Displacement and, where required, certified gaskets
Unsealed penetrations	Standard foam is not a fire barrier	Waterproofing systems in the corresponding category
Shared visitor reception	The opening becomes the weak link	Compartment of the same class, e.g. F-TEC F90 in an EI 90 wall

When the requirement is A1, not EI

This is a separate requirement and is often specified in conjunction with the other. Where the design specifies a non-combustible surface — and not merely the fire resistance of a structural element — standard fire-rated plasterboard is not sufficient: its surface is made of paper.

Class A1 fireboard, such as Knauf FIREBOARD, is used there, with glass fibre mesh instead of paper. Typical applications: cladding in assembly spaces, protection of metal structures, shafts and high-risk areas.