Can EPS insulation be laid on a profiled steel roof deck?

Only part of the board rests directly on the steel. Between the flanges, the EPS spans a gap. Boards of the same thickness can therefore behave differently on two deck profiles. The description ‘roof insulation’ tells you little about the permissible unsupported width.

Look in the roof system documents for the minimum thickness of the bottom layer, the direction of laying and the permitted deck geometry. Where these are unspecified, obtain an assessment from the designer and system supplier. Verify any proposal to replace a thick board with two thinner layers across an open trough.

Provide stable bearing and set out joints to suit the layer arrangement. A poorly supported corner can break under a worker’s foot. A membrane laid afterwards cannot repair that support. Lay out a trial area to check dimensions and joint offsets. If the proposed deck changes, check the bearing width again. Profiles of equal depth can have different upper flange widths.

The corrugations make sealing at walls, rooflights and penetrations more difficult. Select the vapour control layer for the indoor humidity and the roof construction. Identify the layer that provides airtightness as well. Restricting vapour diffusion and stopping moist air leakage are separate functions.

An open end or an unsealed penetration can admit moist indoor air even when the membrane covers the entire roof field. Detail connections at perimeters, equipment bases and services. When laying the EPS, protect completed laps and seals from damage.

Wind loads vary across the roof. Corners and perimeter strips may need a different fastening pattern from the central area. Account for the deck, roof covering, insulation layers and fastener performance. The appropriate number of fasteners per square metre depends on the particular building and roof zone.

Choose fasteners for the steel type, sheet thickness and total build-up. Overtightening can indent the insulation, while inadequate engagement reduces pull-out resistance. Inspect the fixing positions and installation as work progresses. Defects become harder to locate and correct once the roof is closed.

The board documents may state reaction-to-fire class E. To establish the roof’s performance, check the scope of the classification for the assembly, including steel deck, insulation, protective layers, roof covering and fastenings.

A layer that contributes little to thermal resistance may serve an important protective function in a tested assembly. Removing it, changing a material or reducing its thickness may fall outside the documented configuration. Check thermal, structural and fire requirements together when considering a change.

Set out storage areas and access routes before laying the covering. Pallets, installation equipment and workers impose local loads that differ from the weight of the finished roof. Where temporary walkways are needed to distribute pressure, determine their supports before work starts.

EPS suppliers include swisspor, Paneltech, Neotherm and Arsanit. Define the requirements for the actual deck profile and roof assembly before selecting a supplier. Identify the exact boards in the order and check the delivery against the design. Substitutions need assessment for the same build-up.