How to insulate a parapet on an EPS-insulated roof

Trace the concrete from the interior towards the top and outer face of the parapet. Adding insulation in the middle of the roof does little for a continuous path at its edge. For complex junctions a heat-flow calculation can identify both the local heat loss and the internal surface temperature.

Boards in the roof field must resist compression and limit deformation over time. On a vertical face the fixing method and the bond to the finish become important. Two EPS boards with the same declared thermal conductivity can therefore suit different parts of the junction.

Where the outer face is part of an external thermal insulation composite system, check the boards, adhesive, reinforced base coat and finish against the system specification. Tensile strength perpendicular to the faces (TR) is one selection criterion. White, graphite and lower-water-absorption boards all require protection against water at the parapet head.

Specify how the roof waterproofing turns up the vertical face and how its upper edge is secured and sealed. Set the height relative to the finished build-up. A terrace, a ballasted roof and an exposed technical roof may have different finished levels and different system requirements.

The membrane system may require an angle fillet or corner reinforcement at the change of plane. Keep exposed EPS away from flames and incompatible solvents during installation. If additional insulation raises an existing roof, measure the remaining upstand height before ordering materials and revise the junction if necessary.

The coping must direct rainwater to the intended side and protect the layers beneath. Detail falls, edge terminations and watertight joints. Allow the metal to expand without tearing its joints, and provide a stable fixing base so that tightening the coping does not crush the EPS.

Check wind actions at the roof edge, where suction may exceed that in the roof field. Trace the load from the coping fixings into a suitable substrate. A thin facing alone may offer insufficient anchorage. Seal penetrations through protective layers so that the fixings do not admit water.

The wall, membrane and metal coping can move by different amounts. Allow for the movements specified in the design, particularly at corners and along long runs. Thermal expansion can damage a rigid joint even when the EPS grade and thickness are appropriate.

Fit adjacent boards closely at ordinary junctions. At a structural movement joint, retain the designed movement capacity rather than packing the gap with rigid offcuts. The detail must maintain thermal protection and watertightness while accommodating movement at that specific location.

Before fitting the final cover, measure the EPS and inspect its junction with the façade insulation and all corner pieces. Check the fixing substrate and the membrane termination while they are visible. Photographs with a scale will help identify concealed layers during later maintenance.

EPS board manufacturers include Termo Organika, Arsanit, Paneltech and Genderka. Select the appropriate board for each face once the roof-to-wall section is complete. The drawing gives the sizes and thicknesses needed and reduces the risk of narrow offcuts leaving the coping unsupported or the insulation discontinuous.