Tapered Roof Board TR/ALU

Tapered Insulation for Mechanically Fixed, Single Ply Waterproofing Systems

Xtratherm TR/ALU is a high performance Polyisocyanurate Tapered Roof Insulation with vapour tight aluminium foil facings suitable for use with single ply membranes. TR/ALU is part of the comprehensive range of Xtratherm’s high performance tapered roof boards providing total solutions for tapered roof projects.

Xtratherm TR/ALU tapered insulation should be laid over a separate vapour control layer. The requirements for this vapour control layer should be assessed in accordance with BS6229 1982. Typically a 1000 gauge polythene should be used with all joints lapped and sealed.

The joints should be butted and care taken to ensure that all joints are supported by the deck. Mechanical fixings with washers are normally used to secure both the insulation and waterproof membranes. Fixings that penetrate the vapour control layer must be of the self sealing type.

Xtratherm tapered roof insulation TR/ALU is suitable for use under single ply mechanically fixed roof membranes. Xtratherm TR/ALU tapered roof insulation systems have been designed to provide solutions to design issues that arise in new and refurbishment roofs.

Xtratherm TR/ALU systems address most flat roof failures i.e. ponding of rainwater caused by an inability to shed rainwater on the surface whilst providing a high level of thermal insulation performance.

Product Benefits

1 – Xtratherm TR/ALU is faced with a gas-tight foil face. Xtratherm TR/ALU foil faced roof boards are suitable for use below single ply mechanically fixed roof membranes.

Note: TR/ALU is not suitable for applications with built-up bitumen based roofing or mastic asphalt systems.

2 – Xtratherm TR/ALU foil faced insulation boards are suitable for use on roof decks that are subject to maintenance traffic only. Walk ways should be provided on roofs requiring regular pedestrian access. When the roof is complete, protective boarding should be laid if additional site work is to be carried out. The completed roof should not be used for storage of heavy materials or air conditioning plant.

Additional Infomation

A U-value calculation should be carried out at design for minimum or average U-values depending on requirements. In addition a condensation risk analysis must be calculated within the guidance provided in BS 5250 code of practice for control of condensation in buildings.

The fire rating when tested to EN 13501-5 and BS 476 Part 3 ‘External Fire Exposure Roof Test’ will be dependent upon waterproofing system specified.

Xtratherm TR/ALU is the tapered version of FR/ALU. It is faced on both sides with composite gas tight foil facings autohesively bonded to a Polyisocyanurate (PIR) core during manufacture. ALU achieves a BRE Green Guide A+ Rating.

The specification for fixing of Xtratherm roof boards will vary with the location, roof height/width and topographical data, architectural specification should be consulted.

Xtratherm TR/ALU tapered boards should be laid over the vapour control layer with all joints fully supported by the deck. The TR/ALU boards are secured by mechanical fixings with washers. The waterproofing is also mechanically fixed in accordance with the specific manufacturer’s instructions.

Xtratherm TR/ALU tapered boards should be fitted over the vapour control layer that has been laid on a prepared deck that is clear, dry and level without gaps. The TR/ALU boards are secured by mechanical fixings with washers. The waterproofing is also mechanically fixed in accordance with the specific manufacturers instructions.

The facing of Xtratherm TR/ALU should not be considered as temporary waterproofing, when work is interrupted or at the end of each day, a night joint must be made to prevent water penetration. Xtratherm tapered boards should be waterproofed as soon as possible after fixing.

Related case studies

View Case Studies

Interesed in this product? Contact us today


Our related products

View Products

Profiled Roofing

Expanded Polystyrene is non-toxic, non-irritant and odorless, making it completely safe to handle. It can be cut on site using a fine tooth saw or a hot wire cutter. For more information refer to our Safety Data Sheet

View product


The TaperedPlus A1 B.T.P System is an A1 Non-Combustible, Insulation System specifically designed for Balconies, Terraces and Plant Room Roofs.

View product